| Message ID | 20240430110922.15052-3-luca.fancellu@arm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | Fix MISRA regression about flexible array member not at the end | expand |
On 30.04.2024 13:09, Luca Fancellu wrote: > --- a/xen/arch/arm/include/asm/setup.h > +++ b/xen/arch/arm/include/asm/setup.h > @@ -64,18 +64,20 @@ struct membank { > }; > > struct membanks { > - unsigned int nr_banks; > - unsigned int max_banks; > + __struct_group(membanks_hdr, common, , > + unsigned int nr_banks; > + unsigned int max_banks; > + ); > struct membank bank[]; > }; I'm afraid I can't spot why __struct_group() is needed here. Why would just one of the two more straightforward struct membanks { struct membanks_hdr { unsigned int nr_banks; unsigned int max_banks; ); struct membank bank[]; }; struct membanks { struct membanks_hdr { unsigned int nr_banks; unsigned int max_banks; ) common; struct membank bank[]; }; not do? (Perhaps the latter, seeing that you need the field name in ... > struct meminfo { > - struct membanks common; > + struct membanks_hdr common; > struct membank bank[NR_MEM_BANKS]; > }; > > struct shared_meminfo { > - struct membanks common; > + struct membanks_hdr common; > struct membank bank[NR_SHMEM_BANKS]; > struct shmem_membank_extra extra[NR_SHMEM_BANKS]; > }; > @@ -166,25 +168,25 @@ extern domid_t max_init_domid; > > static inline struct membanks *bootinfo_get_mem(void) > { > - return &bootinfo.mem.common; > + return container_of(&bootinfo.mem.common, struct membanks, common); > } ... container_of() uses.) Jan
On 2024-04-30 13:09, Luca Fancellu wrote: > Commit 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory > bank structures") introduced a MISRA regression for Rule 1.1 because a > flexible array member is introduced in the middle of a struct, > furthermore > this is using a GCC extension that is going to be deprecated in GCC 14 > and > a warning to identify such cases will be present > (-Wflex-array-member-not-at-end) to identify such cases. > > In order to fix this issue, use the macro __struct_group to create a > structure 'struct membanks_hdr' which will hold the common data among > structures using the 'struct membanks' interface. > > Modify the 'struct shared_meminfo' and 'struct meminfo' to use this new > structure, effectively removing the flexible array member from the > middle > of the structure and modify the code accessing the .common field to use > the macro container_of to maintain the functionality of the interface. > > Given this change, container_of needs to be supplied with a type and so > the macro 'kernel_info_get_mem' inside arm/include/asm/kernel.h can't > be > an option since it uses const and non-const types for struct membanks, > so > introduce two static inline, one of which will keep the const > qualifier. > > Given the complexity of the interface, which carries a lot of benefit > but > on the other hand could be prone to developer confusion if the access > is > open-coded, introduce two static inline helper for the > 'struct kernel_info' .shm_mem member and get rid the open-coding > shm_mem.common access. > > Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory > bank structures") > Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> > --- > xen/arch/arm/acpi/domain_build.c | 2 +- > xen/arch/arm/domain_build.c | 6 +++--- > xen/arch/arm/include/asm/kernel.h | 11 ++++++++++- > xen/arch/arm/include/asm/setup.h | 18 ++++++++++-------- > xen/arch/arm/include/asm/static-shmem.h | 12 ++++++++++++ > xen/arch/arm/static-shmem.c | 19 +++++++++---------- > 6 files changed, 45 insertions(+), 23 deletions(-) > From a MISRA perspective the regression on R1.1 is resolved (see [1]). [1] https://gitlab.com/xen-project/patchew/xen/-/jobs/6748211368
Hi Jan, > On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: > > On 30.04.2024 13:09, Luca Fancellu wrote: >> --- a/xen/arch/arm/include/asm/setup.h >> +++ b/xen/arch/arm/include/asm/setup.h >> @@ -64,18 +64,20 @@ struct membank { >> }; >> >> struct membanks { >> - unsigned int nr_banks; >> - unsigned int max_banks; >> + __struct_group(membanks_hdr, common, , >> + unsigned int nr_banks; >> + unsigned int max_banks; >> + ); >> struct membank bank[]; >> }; > > I'm afraid I can't spot why __struct_group() is needed here. Why would just > one of the two more straightforward > > struct membanks { > struct membanks_hdr { > unsigned int nr_banks; > unsigned int max_banks; > ); > struct membank bank[]; > }; > At the first sight I thought this solution could have worked, however GCC brought me back down to earth remembering me that flexible array members can’t be left alone in an empty structure: /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] 70 | }; | ^ /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members 71 | struct membank bank[]; | ^~~~ [...] Cheers, Luca
On 01.05.2024 08:57, Luca Fancellu wrote: > Hi Jan, > >> On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: >> >> On 30.04.2024 13:09, Luca Fancellu wrote: >>> --- a/xen/arch/arm/include/asm/setup.h >>> +++ b/xen/arch/arm/include/asm/setup.h >>> @@ -64,18 +64,20 @@ struct membank { >>> }; >>> >>> struct membanks { >>> - unsigned int nr_banks; >>> - unsigned int max_banks; >>> + __struct_group(membanks_hdr, common, , >>> + unsigned int nr_banks; >>> + unsigned int max_banks; >>> + ); >>> struct membank bank[]; >>> }; >> >> I'm afraid I can't spot why __struct_group() is needed here. Why would just >> one of the two more straightforward >> >> struct membanks { >> struct membanks_hdr { >> unsigned int nr_banks; >> unsigned int max_banks; >> ); >> struct membank bank[]; >> }; >> > > At the first sight I thought this solution could have worked, however GCC brought me back down to earth > remembering me that flexible array members can’t be left alone in an empty structure: > > /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] > 70 | }; > | ^ > /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members > 71 | struct membank bank[]; > | ^~~~ > [...] Since for patch 1 you looked at Linux'es uapi/linux/stddef.h, the solution to this lies there, in __DECLARE_FLEX_ARRAY(). Alongside or instead of borrowing __struct_group(), we could consider borrowing this as well. Or open-code it just here, for the time being (perhaps my preference). Yet it's not clear to me that doing so will actually be enough to make things work for you. Jan
> On 2 May 2024, at 07:14, Jan Beulich <jbeulich@suse.com> wrote: > > On 01.05.2024 08:57, Luca Fancellu wrote: >> Hi Jan, >> >>> On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: >>> >>> On 30.04.2024 13:09, Luca Fancellu wrote: >>>> --- a/xen/arch/arm/include/asm/setup.h >>>> +++ b/xen/arch/arm/include/asm/setup.h >>>> @@ -64,18 +64,20 @@ struct membank { >>>> }; >>>> >>>> struct membanks { >>>> - unsigned int nr_banks; >>>> - unsigned int max_banks; >>>> + __struct_group(membanks_hdr, common, , >>>> + unsigned int nr_banks; >>>> + unsigned int max_banks; >>>> + ); >>>> struct membank bank[]; >>>> }; >>> >>> I'm afraid I can't spot why __struct_group() is needed here. Why would just >>> one of the two more straightforward >>> >>> struct membanks { >>> struct membanks_hdr { >>> unsigned int nr_banks; >>> unsigned int max_banks; >>> ); >>> struct membank bank[]; >>> }; >>> >> >> At the first sight I thought this solution could have worked, however GCC brought me back down to earth >> remembering me that flexible array members can’t be left alone in an empty structure: >> >> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] >> 70 | }; >> | ^ >> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members >> 71 | struct membank bank[]; >> | ^~~~ >> [...] > > Since for patch 1 you looked at Linux'es uapi/linux/stddef.h, the solution > to this lies there, in __DECLARE_FLEX_ARRAY(). Alongside or instead of > borrowing __struct_group(), we could consider borrowing this as well. Or > open-code it just here, for the time being (perhaps my preference). Yet > it's not clear to me that doing so will actually be enough to make things > work for you. I looked also into __DECLARE_FLEX_ARRAY(), but then decided __struct_group() was enough for my purpose, can I ask the technical reasons why it would be your preference? Is there something in that construct that is a concern for you?
On 02.05.2024 08:33, Luca Fancellu wrote: > > >> On 2 May 2024, at 07:14, Jan Beulich <jbeulich@suse.com> wrote: >> >> On 01.05.2024 08:57, Luca Fancellu wrote: >>> Hi Jan, >>> >>>> On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: >>>> >>>> On 30.04.2024 13:09, Luca Fancellu wrote: >>>>> --- a/xen/arch/arm/include/asm/setup.h >>>>> +++ b/xen/arch/arm/include/asm/setup.h >>>>> @@ -64,18 +64,20 @@ struct membank { >>>>> }; >>>>> >>>>> struct membanks { >>>>> - unsigned int nr_banks; >>>>> - unsigned int max_banks; >>>>> + __struct_group(membanks_hdr, common, , >>>>> + unsigned int nr_banks; >>>>> + unsigned int max_banks; >>>>> + ); >>>>> struct membank bank[]; >>>>> }; >>>> >>>> I'm afraid I can't spot why __struct_group() is needed here. Why would just >>>> one of the two more straightforward >>>> >>>> struct membanks { >>>> struct membanks_hdr { >>>> unsigned int nr_banks; >>>> unsigned int max_banks; >>>> ); >>>> struct membank bank[]; >>>> }; >>>> >>> >>> At the first sight I thought this solution could have worked, however GCC brought me back down to earth >>> remembering me that flexible array members can’t be left alone in an empty structure: >>> >>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] >>> 70 | }; >>> | ^ >>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members >>> 71 | struct membank bank[]; >>> | ^~~~ >>> [...] >> >> Since for patch 1 you looked at Linux'es uapi/linux/stddef.h, the solution >> to this lies there, in __DECLARE_FLEX_ARRAY(). Alongside or instead of >> borrowing __struct_group(), we could consider borrowing this as well. Or >> open-code it just here, for the time being (perhaps my preference). Yet >> it's not clear to me that doing so will actually be enough to make things >> work for you. > > I looked also into __DECLARE_FLEX_ARRAY(), but then decided __struct_group() > was enough for my purpose, can I ask the technical reasons why it would be your > preference? Is there something in that construct that is a concern for you? I don't like either construct very much, but of the two __DECLARE_FLEX_ARRAY() looks slightly more "natural" for what is wanted and how it's done. __struct_group() introducing twice the (effectively) same structure feels pretty odd, for now at least. It's not even entirely clear to me whether there aren't pitfalls, seeing that the C spec differentiates named and unnamed struct fields in a few cases. For __DECLARE_FLEX_ARRAY(), otoh, I can't presently see any reason to suspect possible corner cases. Yet as said before - I'm not sure __DECLARE_FLEX_ARRAY() alone would be enough for what you want to achieve. Jan
> On 2 May 2024, at 07:43, Jan Beulich <jbeulich@suse.com> wrote: > > On 02.05.2024 08:33, Luca Fancellu wrote: >> >> >>> On 2 May 2024, at 07:14, Jan Beulich <jbeulich@suse.com> wrote: >>> >>> On 01.05.2024 08:57, Luca Fancellu wrote: >>>> Hi Jan, >>>> >>>>> On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: >>>>> >>>>> On 30.04.2024 13:09, Luca Fancellu wrote: >>>>>> --- a/xen/arch/arm/include/asm/setup.h >>>>>> +++ b/xen/arch/arm/include/asm/setup.h >>>>>> @@ -64,18 +64,20 @@ struct membank { >>>>>> }; >>>>>> >>>>>> struct membanks { >>>>>> - unsigned int nr_banks; >>>>>> - unsigned int max_banks; >>>>>> + __struct_group(membanks_hdr, common, , >>>>>> + unsigned int nr_banks; >>>>>> + unsigned int max_banks; >>>>>> + ); >>>>>> struct membank bank[]; >>>>>> }; >>>>> >>>>> I'm afraid I can't spot why __struct_group() is needed here. Why would just >>>>> one of the two more straightforward >>>>> >>>>> struct membanks { >>>>> struct membanks_hdr { >>>>> unsigned int nr_banks; >>>>> unsigned int max_banks; >>>>> ); >>>>> struct membank bank[]; >>>>> }; >>>>> >>>> >>>> At the first sight I thought this solution could have worked, however GCC brought me back down to earth >>>> remembering me that flexible array members can’t be left alone in an empty structure: >>>> >>>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] >>>> 70 | }; >>>> | ^ >>>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members >>>> 71 | struct membank bank[]; >>>> | ^~~~ >>>> [...] >>> >>> Since for patch 1 you looked at Linux'es uapi/linux/stddef.h, the solution >>> to this lies there, in __DECLARE_FLEX_ARRAY(). Alongside or instead of >>> borrowing __struct_group(), we could consider borrowing this as well. Or >>> open-code it just here, for the time being (perhaps my preference). Yet >>> it's not clear to me that doing so will actually be enough to make things >>> work for you. >> >> I looked also into __DECLARE_FLEX_ARRAY(), but then decided __struct_group() >> was enough for my purpose, can I ask the technical reasons why it would be your >> preference? Is there something in that construct that is a concern for you? > > I don't like either construct very much, but of the two __DECLARE_FLEX_ARRAY() > looks slightly more "natural" for what is wanted and how it's done. > __struct_group() introducing twice the (effectively) same structure feels > pretty odd, for now at least. It's not even entirely clear to me whether there > aren't pitfalls, seeing that the C spec differentiates named and unnamed > struct fields in a few cases. For __DECLARE_FLEX_ARRAY(), otoh, I can't > presently see any reason to suspect possible corner cases. > > Yet as said before - I'm not sure __DECLARE_FLEX_ARRAY() alone would be enough > for what you want to achieve. Mmm yes, I think I would still have problems because container_of wants a named member, so __DECLARE_FLEX_ARRAY() doesn’t help much alone, if I’m not missing something obvious. If you believe however that importing __struct_group() only for this instance is not enough to justify its presence in the codebase, I could open-code it, provided that maintainers are ok with that. In any case it would be used soon also for other architectures using bootinfo.
On 02.05.2024 10:13, Luca Fancellu wrote: > > >> On 2 May 2024, at 07:43, Jan Beulich <jbeulich@suse.com> wrote: >> >> On 02.05.2024 08:33, Luca Fancellu wrote: >>> >>> >>>> On 2 May 2024, at 07:14, Jan Beulich <jbeulich@suse.com> wrote: >>>> >>>> On 01.05.2024 08:57, Luca Fancellu wrote: >>>>> Hi Jan, >>>>> >>>>>> On 30 Apr 2024, at 12:37, Jan Beulich <jbeulich@suse.com> wrote: >>>>>> >>>>>> On 30.04.2024 13:09, Luca Fancellu wrote: >>>>>>> --- a/xen/arch/arm/include/asm/setup.h >>>>>>> +++ b/xen/arch/arm/include/asm/setup.h >>>>>>> @@ -64,18 +64,20 @@ struct membank { >>>>>>> }; >>>>>>> >>>>>>> struct membanks { >>>>>>> - unsigned int nr_banks; >>>>>>> - unsigned int max_banks; >>>>>>> + __struct_group(membanks_hdr, common, , >>>>>>> + unsigned int nr_banks; >>>>>>> + unsigned int max_banks; >>>>>>> + ); >>>>>>> struct membank bank[]; >>>>>>> }; >>>>>> >>>>>> I'm afraid I can't spot why __struct_group() is needed here. Why would just >>>>>> one of the two more straightforward >>>>>> >>>>>> struct membanks { >>>>>> struct membanks_hdr { >>>>>> unsigned int nr_banks; >>>>>> unsigned int max_banks; >>>>>> ); >>>>>> struct membank bank[]; >>>>>> }; >>>>>> >>>>> >>>>> At the first sight I thought this solution could have worked, however GCC brought me back down to earth >>>>> remembering me that flexible array members can’t be left alone in an empty structure: >>>>> >>>>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:70:6: error: declaration does not declare anything [-Werror] >>>>> 70 | }; >>>>> | ^ >>>>> /data_sdc/lucfan01/gitlab_mickledore_xen/xen/xen/arch/arm/include/asm/setup.h:71:20: error: flexible array member in a struct with no named members >>>>> 71 | struct membank bank[]; >>>>> | ^~~~ >>>>> [...] >>>> >>>> Since for patch 1 you looked at Linux'es uapi/linux/stddef.h, the solution >>>> to this lies there, in __DECLARE_FLEX_ARRAY(). Alongside or instead of >>>> borrowing __struct_group(), we could consider borrowing this as well. Or >>>> open-code it just here, for the time being (perhaps my preference). Yet >>>> it's not clear to me that doing so will actually be enough to make things >>>> work for you. >>> >>> I looked also into __DECLARE_FLEX_ARRAY(), but then decided __struct_group() >>> was enough for my purpose, can I ask the technical reasons why it would be your >>> preference? Is there something in that construct that is a concern for you? >> >> I don't like either construct very much, but of the two __DECLARE_FLEX_ARRAY() >> looks slightly more "natural" for what is wanted and how it's done. >> __struct_group() introducing twice the (effectively) same structure feels >> pretty odd, for now at least. It's not even entirely clear to me whether there >> aren't pitfalls, seeing that the C spec differentiates named and unnamed >> struct fields in a few cases. For __DECLARE_FLEX_ARRAY(), otoh, I can't >> presently see any reason to suspect possible corner cases. >> >> Yet as said before - I'm not sure __DECLARE_FLEX_ARRAY() alone would be enough >> for what you want to achieve. > > Mmm yes, I think I would still have problems because container_of wants a named member, > so __DECLARE_FLEX_ARRAY() doesn’t help much alone, if I’m not missing something obvious. > If you believe however that importing __struct_group() only for this instance is not enough to justify > its presence in the codebase, I could open-code it, provided that maintainers are ok with that. I'm afraid I've even more strongly against open-coding. If you can get an ack from another maintainer for the introduction of struct_group(), that would still allow it to go in. I didn't NAK the change, I merely have reservations. > In any case it would be used soon also for other architectures using bootinfo. Oh, would it? Jan
> >> In any case it would be used soon also for other architectures using bootinfo. > > Oh, would it? PPC people have plans on putting that interface in common: https://patchwork.kernel.org/project/xen-devel/patch/451705505ff7f80ec66c78cc2830196fa6e4090c.1712893887.git.sanastasio@raptorengineering.com/
On 02.05.2024 12:12, Luca Fancellu wrote: >>> In any case it would be used soon also for other architectures using bootinfo. >> >> Oh, would it? > > PPC people have plans on putting that interface in common: I'm aware, but ... > https://patchwork.kernel.org/project/xen-devel/patch/451705505ff7f80ec66c78cc2830196fa6e4090c.1712893887.git.sanastasio@raptorengineering.com/ ... I can't spot any flexible array members in this patch. Jan
> On 2 May 2024, at 11:30, Jan Beulich <jbeulich@suse.com> wrote: > > On 02.05.2024 12:12, Luca Fancellu wrote: >>>> In any case it would be used soon also for other architectures using bootinfo. >>> >>> Oh, would it? >> >> PPC people have plans on putting that interface in common: > > I'm aware, but ... > >> https://patchwork.kernel.org/project/xen-devel/patch/451705505ff7f80ec66c78cc2830196fa6e4090c.1712893887.git.sanastasio@raptorengineering.com/ > > ... I can't spot any flexible array members in this patch. I guess v5 of that patch will have that, because it would be rebased on the latest state of xen/arch/arm/include/asm/setup.h, moving that interface in xen/include/xen/bootfdt.h, in order to use part of the code taken out from xen/arch/arm/setup.c and put in xen/common/device-tree/bootinfo.c
On Tue, 30 Apr 2024, Luca Fancellu wrote: > Commit 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory > bank structures") introduced a MISRA regression for Rule 1.1 because a > flexible array member is introduced in the middle of a struct, furthermore > this is using a GCC extension that is going to be deprecated in GCC 14 and > a warning to identify such cases will be present > (-Wflex-array-member-not-at-end) to identify such cases. > > In order to fix this issue, use the macro __struct_group to create a > structure 'struct membanks_hdr' which will hold the common data among > structures using the 'struct membanks' interface. > > Modify the 'struct shared_meminfo' and 'struct meminfo' to use this new > structure, effectively removing the flexible array member from the middle > of the structure and modify the code accessing the .common field to use > the macro container_of to maintain the functionality of the interface. > > Given this change, container_of needs to be supplied with a type and so > the macro 'kernel_info_get_mem' inside arm/include/asm/kernel.h can't be > an option since it uses const and non-const types for struct membanks, so > introduce two static inline, one of which will keep the const qualifier. > > Given the complexity of the interface, which carries a lot of benefit but > on the other hand could be prone to developer confusion if the access is > open-coded, introduce two static inline helper for the > 'struct kernel_info' .shm_mem member and get rid the open-coding > shm_mem.common access. > > Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory bank structures") > Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> > --- > xen/arch/arm/acpi/domain_build.c | 2 +- > xen/arch/arm/domain_build.c | 6 +++--- > xen/arch/arm/include/asm/kernel.h | 11 ++++++++++- > xen/arch/arm/include/asm/setup.h | 18 ++++++++++-------- > xen/arch/arm/include/asm/static-shmem.h | 12 ++++++++++++ > xen/arch/arm/static-shmem.c | 19 +++++++++---------- > 6 files changed, 45 insertions(+), 23 deletions(-) > > diff --git a/xen/arch/arm/acpi/domain_build.c b/xen/arch/arm/acpi/domain_build.c > index ed895dd8f926..2ce75543d004 100644 > --- a/xen/arch/arm/acpi/domain_build.c > +++ b/xen/arch/arm/acpi/domain_build.c > @@ -451,7 +451,7 @@ static int __init estimate_acpi_efi_size(struct domain *d, > struct acpi_table_rsdp *rsdp_tbl; > struct acpi_table_header *table; > > - efi_size = estimate_efi_size(kernel_info_get_mem(kinfo)->nr_banks); > + efi_size = estimate_efi_size(kernel_info_get_mem_const(kinfo)->nr_banks); > > acpi_size = ROUNDUP(sizeof(struct acpi_table_fadt), 8); > acpi_size += ROUNDUP(sizeof(struct acpi_table_stao), 8); > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c > index 0784e4c5e315..f6550809cfdf 100644 > --- a/xen/arch/arm/domain_build.c > +++ b/xen/arch/arm/domain_build.c > @@ -805,7 +805,7 @@ int __init make_memory_node(const struct kernel_info *kinfo, int addrcells, > * static shared memory banks need to be listed as /memory node, so when > * this function is handling the normal memory, add the banks. > */ > - if ( mem == kernel_info_get_mem(kinfo) ) > + if ( mem == kernel_info_get_mem_const(kinfo) ) > shm_mem_node_fill_reg_range(kinfo, reg, &nr_cells, addrcells, > sizecells); > > @@ -884,7 +884,7 @@ static int __init find_unallocated_memory(const struct kernel_info *kinfo, > { > const struct membanks *mem = bootinfo_get_mem(); > const struct membanks *mem_banks[] = { > - kernel_info_get_mem(kinfo), > + kernel_info_get_mem_const(kinfo), > bootinfo_get_reserved_mem(), > #ifdef CONFIG_STATIC_SHM > bootinfo_get_shmem(), > @@ -1108,7 +1108,7 @@ static int __init find_domU_holes(const struct kernel_info *kinfo, > uint64_t bankend; > const uint64_t bankbase[] = GUEST_RAM_BANK_BASES; > const uint64_t banksize[] = GUEST_RAM_BANK_SIZES; > - const struct membanks *kinfo_mem = kernel_info_get_mem(kinfo); > + const struct membanks *kinfo_mem = kernel_info_get_mem_const(kinfo); > int res = -ENOENT; > > for ( i = 0; i < GUEST_RAM_BANKS; i++ ) > diff --git a/xen/arch/arm/include/asm/kernel.h b/xen/arch/arm/include/asm/kernel.h > index 16a2bfc01e27..7e6e3c82a477 100644 > --- a/xen/arch/arm/include/asm/kernel.h > +++ b/xen/arch/arm/include/asm/kernel.h > @@ -80,7 +80,16 @@ struct kernel_info { > }; > }; > > -#define kernel_info_get_mem(kinfo) (&(kinfo)->mem.common) > +static inline struct membanks *kernel_info_get_mem(struct kernel_info *kinfo) > +{ > + return container_of(&kinfo->mem.common, struct membanks, common); > +} > + > +static inline const struct membanks * > +kernel_info_get_mem_const(const struct kernel_info *kinfo) > +{ > + return container_of(&kinfo->mem.common, const struct membanks, common); > +} > > #ifdef CONFIG_STATIC_SHM > #define KERNEL_INFO_SHM_MEM_INIT .shm_mem.common.max_banks = NR_SHMEM_BANKS, > diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h > index 28fb659fe946..61c15806a7c4 100644 > --- a/xen/arch/arm/include/asm/setup.h > +++ b/xen/arch/arm/include/asm/setup.h > @@ -64,18 +64,20 @@ struct membank { > }; > > struct membanks { > - unsigned int nr_banks; > - unsigned int max_banks; > + __struct_group(membanks_hdr, common, , > + unsigned int nr_banks; > + unsigned int max_banks; > + ); > struct membank bank[]; > }; > > struct meminfo { > - struct membanks common; > + struct membanks_hdr common; > struct membank bank[NR_MEM_BANKS]; > }; > > struct shared_meminfo { > - struct membanks common; > + struct membanks_hdr common; > struct membank bank[NR_SHMEM_BANKS]; > struct shmem_membank_extra extra[NR_SHMEM_BANKS]; > }; > @@ -166,25 +168,25 @@ extern domid_t max_init_domid; > > static inline struct membanks *bootinfo_get_mem(void) > { > - return &bootinfo.mem.common; > + return container_of(&bootinfo.mem.common, struct membanks, common); > } > > static inline struct membanks *bootinfo_get_reserved_mem(void) > { > - return &bootinfo.reserved_mem.common; > + return container_of(&bootinfo.reserved_mem.common, struct membanks, common); > } > > #ifdef CONFIG_ACPI > static inline struct membanks *bootinfo_get_acpi(void) > { > - return &bootinfo.acpi.common; > + return container_of(&bootinfo.acpi.common, struct membanks, common); > } > #endif > > #ifdef CONFIG_STATIC_SHM > static inline struct membanks *bootinfo_get_shmem(void) > { > - return &bootinfo.shmem.common; > + return container_of(&bootinfo.shmem.common, struct membanks, common); > } > > static inline struct shmem_membank_extra *bootinfo_get_shmem_extra(void) > diff --git a/xen/arch/arm/include/asm/static-shmem.h b/xen/arch/arm/include/asm/static-shmem.h > index 3b6569e5703f..806ee41cfc37 100644 > --- a/xen/arch/arm/include/asm/static-shmem.h > +++ b/xen/arch/arm/include/asm/static-shmem.h > @@ -45,6 +45,18 @@ int make_shm_resv_memory_node(const struct kernel_info *kinfo, int addrcells, > void shm_mem_node_fill_reg_range(const struct kernel_info *kinfo, __be32 *reg, > int *nr_cells, int addrcells, int sizecells); > > +static inline struct membanks * > +kernel_info_get_shm_mem(struct kernel_info *kinfo) > +{ > + return container_of(&kinfo->shm_mem.common, struct membanks, common); > +} > + > +static inline const struct membanks * > +kernel_info_get_shm_mem_const(const struct kernel_info *kinfo) > +{ > + return container_of(&kinfo->shm_mem.common, const struct membanks, common); > +} > + > #else /* !CONFIG_STATIC_SHM */ > > /* Worst case /memory node reg element: (addrcells + sizecells) */ > diff --git a/xen/arch/arm/static-shmem.c b/xen/arch/arm/static-shmem.c > index 09f474ec6050..78881dd1d3f7 100644 > --- a/xen/arch/arm/static-shmem.c > +++ b/xen/arch/arm/static-shmem.c > @@ -172,16 +172,16 @@ static int __init assign_shared_memory(struct domain *d, > } > > static int __init > -append_shm_bank_to_domain(struct shared_meminfo *kinfo_shm_mem, paddr_t start, > +append_shm_bank_to_domain(struct kernel_info *kinfo, paddr_t start, > paddr_t size, const char *shm_id) > { > - struct membanks *shm_mem = &kinfo_shm_mem->common; > + struct membanks *shm_mem = kernel_info_get_shm_mem(kinfo); > struct shmem_membank_extra *shm_mem_extra; > > if ( shm_mem->nr_banks >= shm_mem->max_banks ) > return -ENOMEM; > > - shm_mem_extra = &kinfo_shm_mem->extra[shm_mem->nr_banks]; > + shm_mem_extra = &kinfo->shm_mem.extra[shm_mem->nr_banks]; > > shm_mem->bank[shm_mem->nr_banks].start = start; > shm_mem->bank[shm_mem->nr_banks].size = size; > @@ -289,8 +289,7 @@ int __init process_shm(struct domain *d, struct kernel_info *kinfo, > * Record static shared memory region info for later setting > * up shm-node in guest device tree. > */ > - ret = append_shm_bank_to_domain(&kinfo->shm_mem, gbase, psize, > - shm_id); > + ret = append_shm_bank_to_domain(kinfo, gbase, psize, shm_id); > if ( ret ) > return ret; > } > @@ -301,7 +300,7 @@ int __init process_shm(struct domain *d, struct kernel_info *kinfo, > int __init make_shm_resv_memory_node(const struct kernel_info *kinfo, > int addrcells, int sizecells) > { > - const struct membanks *mem = &kinfo->shm_mem.common; > + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); > void *fdt = kinfo->fdt; > unsigned int i = 0; > int res = 0; > @@ -517,7 +516,7 @@ int __init process_shm_node(const void *fdt, int node, uint32_t address_cells, > int __init make_resv_memory_node(const struct kernel_info *kinfo, int addrcells, > int sizecells) > { > - const struct membanks *mem = &kinfo->shm_mem.common; > + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); > void *fdt = kinfo->fdt; > int res = 0; > /* Placeholder for reserved-memory\0 */ > @@ -579,7 +578,7 @@ void __init init_sharedmem_pages(void) > int __init remove_shm_from_rangeset(const struct kernel_info *kinfo, > struct rangeset *rangeset) > { > - const struct membanks *shm_mem = &kinfo->shm_mem.common; > + const struct membanks *shm_mem = kernel_info_get_shm_mem_const(kinfo); > unsigned int i; > > /* Remove static shared memory regions */ > @@ -607,7 +606,7 @@ int __init remove_shm_from_rangeset(const struct kernel_info *kinfo, > int __init remove_shm_holes_for_domU(const struct kernel_info *kinfo, > struct membanks *ext_regions) > { > - const struct membanks *shm_mem = &kinfo->shm_mem.common; > + const struct membanks *shm_mem = kernel_info_get_shm_mem_const(kinfo); > struct rangeset *guest_holes; > unsigned int i; > paddr_t start; > @@ -673,7 +672,7 @@ void __init shm_mem_node_fill_reg_range(const struct kernel_info *kinfo, > __be32 *reg, int *nr_cells, > int addrcells, int sizecells) > { > - const struct membanks *mem = &kinfo->shm_mem.common; > + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); > unsigned int i; > __be32 *cells; > > -- > 2.34.1 >
> On 2 May 2024, at 19:35, Stefano Stabellini <sstabellini@kernel.org> wrote: > > On Tue, 30 Apr 2024, Luca Fancellu wrote: >> Commit 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory >> bank structures") introduced a MISRA regression for Rule 1.1 because a >> flexible array member is introduced in the middle of a struct, furthermore >> this is using a GCC extension that is going to be deprecated in GCC 14 and >> a warning to identify such cases will be present >> (-Wflex-array-member-not-at-end) to identify such cases. >> >> In order to fix this issue, use the macro __struct_group to create a >> structure 'struct membanks_hdr' which will hold the common data among >> structures using the 'struct membanks' interface. >> >> Modify the 'struct shared_meminfo' and 'struct meminfo' to use this new >> structure, effectively removing the flexible array member from the middle >> of the structure and modify the code accessing the .common field to use >> the macro container_of to maintain the functionality of the interface. >> >> Given this change, container_of needs to be supplied with a type and so >> the macro 'kernel_info_get_mem' inside arm/include/asm/kernel.h can't be >> an option since it uses const and non-const types for struct membanks, so >> introduce two static inline, one of which will keep the const qualifier. >> >> Given the complexity of the interface, which carries a lot of benefit but >> on the other hand could be prone to developer confusion if the access is >> open-coded, introduce two static inline helper for the >> 'struct kernel_info' .shm_mem member and get rid the open-coding >> shm_mem.common access. >> >> Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory bank structures") >> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> > > Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Hi Stefano, Thanks! Is it possible to add, eventually on commit, this tag? Reported-by: Nicola Vetrini <nicola.vetrini@bugseng.com>
diff --git a/xen/arch/arm/acpi/domain_build.c b/xen/arch/arm/acpi/domain_build.c index ed895dd8f926..2ce75543d004 100644 --- a/xen/arch/arm/acpi/domain_build.c +++ b/xen/arch/arm/acpi/domain_build.c @@ -451,7 +451,7 @@ static int __init estimate_acpi_efi_size(struct domain *d, struct acpi_table_rsdp *rsdp_tbl; struct acpi_table_header *table; - efi_size = estimate_efi_size(kernel_info_get_mem(kinfo)->nr_banks); + efi_size = estimate_efi_size(kernel_info_get_mem_const(kinfo)->nr_banks); acpi_size = ROUNDUP(sizeof(struct acpi_table_fadt), 8); acpi_size += ROUNDUP(sizeof(struct acpi_table_stao), 8); diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c index 0784e4c5e315..f6550809cfdf 100644 --- a/xen/arch/arm/domain_build.c +++ b/xen/arch/arm/domain_build.c @@ -805,7 +805,7 @@ int __init make_memory_node(const struct kernel_info *kinfo, int addrcells, * static shared memory banks need to be listed as /memory node, so when * this function is handling the normal memory, add the banks. */ - if ( mem == kernel_info_get_mem(kinfo) ) + if ( mem == kernel_info_get_mem_const(kinfo) ) shm_mem_node_fill_reg_range(kinfo, reg, &nr_cells, addrcells, sizecells); @@ -884,7 +884,7 @@ static int __init find_unallocated_memory(const struct kernel_info *kinfo, { const struct membanks *mem = bootinfo_get_mem(); const struct membanks *mem_banks[] = { - kernel_info_get_mem(kinfo), + kernel_info_get_mem_const(kinfo), bootinfo_get_reserved_mem(), #ifdef CONFIG_STATIC_SHM bootinfo_get_shmem(), @@ -1108,7 +1108,7 @@ static int __init find_domU_holes(const struct kernel_info *kinfo, uint64_t bankend; const uint64_t bankbase[] = GUEST_RAM_BANK_BASES; const uint64_t banksize[] = GUEST_RAM_BANK_SIZES; - const struct membanks *kinfo_mem = kernel_info_get_mem(kinfo); + const struct membanks *kinfo_mem = kernel_info_get_mem_const(kinfo); int res = -ENOENT; for ( i = 0; i < GUEST_RAM_BANKS; i++ ) diff --git a/xen/arch/arm/include/asm/kernel.h b/xen/arch/arm/include/asm/kernel.h index 16a2bfc01e27..7e6e3c82a477 100644 --- a/xen/arch/arm/include/asm/kernel.h +++ b/xen/arch/arm/include/asm/kernel.h @@ -80,7 +80,16 @@ struct kernel_info { }; }; -#define kernel_info_get_mem(kinfo) (&(kinfo)->mem.common) +static inline struct membanks *kernel_info_get_mem(struct kernel_info *kinfo) +{ + return container_of(&kinfo->mem.common, struct membanks, common); +} + +static inline const struct membanks * +kernel_info_get_mem_const(const struct kernel_info *kinfo) +{ + return container_of(&kinfo->mem.common, const struct membanks, common); +} #ifdef CONFIG_STATIC_SHM #define KERNEL_INFO_SHM_MEM_INIT .shm_mem.common.max_banks = NR_SHMEM_BANKS, diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h index 28fb659fe946..61c15806a7c4 100644 --- a/xen/arch/arm/include/asm/setup.h +++ b/xen/arch/arm/include/asm/setup.h @@ -64,18 +64,20 @@ struct membank { }; struct membanks { - unsigned int nr_banks; - unsigned int max_banks; + __struct_group(membanks_hdr, common, , + unsigned int nr_banks; + unsigned int max_banks; + ); struct membank bank[]; }; struct meminfo { - struct membanks common; + struct membanks_hdr common; struct membank bank[NR_MEM_BANKS]; }; struct shared_meminfo { - struct membanks common; + struct membanks_hdr common; struct membank bank[NR_SHMEM_BANKS]; struct shmem_membank_extra extra[NR_SHMEM_BANKS]; }; @@ -166,25 +168,25 @@ extern domid_t max_init_domid; static inline struct membanks *bootinfo_get_mem(void) { - return &bootinfo.mem.common; + return container_of(&bootinfo.mem.common, struct membanks, common); } static inline struct membanks *bootinfo_get_reserved_mem(void) { - return &bootinfo.reserved_mem.common; + return container_of(&bootinfo.reserved_mem.common, struct membanks, common); } #ifdef CONFIG_ACPI static inline struct membanks *bootinfo_get_acpi(void) { - return &bootinfo.acpi.common; + return container_of(&bootinfo.acpi.common, struct membanks, common); } #endif #ifdef CONFIG_STATIC_SHM static inline struct membanks *bootinfo_get_shmem(void) { - return &bootinfo.shmem.common; + return container_of(&bootinfo.shmem.common, struct membanks, common); } static inline struct shmem_membank_extra *bootinfo_get_shmem_extra(void) diff --git a/xen/arch/arm/include/asm/static-shmem.h b/xen/arch/arm/include/asm/static-shmem.h index 3b6569e5703f..806ee41cfc37 100644 --- a/xen/arch/arm/include/asm/static-shmem.h +++ b/xen/arch/arm/include/asm/static-shmem.h @@ -45,6 +45,18 @@ int make_shm_resv_memory_node(const struct kernel_info *kinfo, int addrcells, void shm_mem_node_fill_reg_range(const struct kernel_info *kinfo, __be32 *reg, int *nr_cells, int addrcells, int sizecells); +static inline struct membanks * +kernel_info_get_shm_mem(struct kernel_info *kinfo) +{ + return container_of(&kinfo->shm_mem.common, struct membanks, common); +} + +static inline const struct membanks * +kernel_info_get_shm_mem_const(const struct kernel_info *kinfo) +{ + return container_of(&kinfo->shm_mem.common, const struct membanks, common); +} + #else /* !CONFIG_STATIC_SHM */ /* Worst case /memory node reg element: (addrcells + sizecells) */ diff --git a/xen/arch/arm/static-shmem.c b/xen/arch/arm/static-shmem.c index 09f474ec6050..78881dd1d3f7 100644 --- a/xen/arch/arm/static-shmem.c +++ b/xen/arch/arm/static-shmem.c @@ -172,16 +172,16 @@ static int __init assign_shared_memory(struct domain *d, } static int __init -append_shm_bank_to_domain(struct shared_meminfo *kinfo_shm_mem, paddr_t start, +append_shm_bank_to_domain(struct kernel_info *kinfo, paddr_t start, paddr_t size, const char *shm_id) { - struct membanks *shm_mem = &kinfo_shm_mem->common; + struct membanks *shm_mem = kernel_info_get_shm_mem(kinfo); struct shmem_membank_extra *shm_mem_extra; if ( shm_mem->nr_banks >= shm_mem->max_banks ) return -ENOMEM; - shm_mem_extra = &kinfo_shm_mem->extra[shm_mem->nr_banks]; + shm_mem_extra = &kinfo->shm_mem.extra[shm_mem->nr_banks]; shm_mem->bank[shm_mem->nr_banks].start = start; shm_mem->bank[shm_mem->nr_banks].size = size; @@ -289,8 +289,7 @@ int __init process_shm(struct domain *d, struct kernel_info *kinfo, * Record static shared memory region info for later setting * up shm-node in guest device tree. */ - ret = append_shm_bank_to_domain(&kinfo->shm_mem, gbase, psize, - shm_id); + ret = append_shm_bank_to_domain(kinfo, gbase, psize, shm_id); if ( ret ) return ret; } @@ -301,7 +300,7 @@ int __init process_shm(struct domain *d, struct kernel_info *kinfo, int __init make_shm_resv_memory_node(const struct kernel_info *kinfo, int addrcells, int sizecells) { - const struct membanks *mem = &kinfo->shm_mem.common; + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); void *fdt = kinfo->fdt; unsigned int i = 0; int res = 0; @@ -517,7 +516,7 @@ int __init process_shm_node(const void *fdt, int node, uint32_t address_cells, int __init make_resv_memory_node(const struct kernel_info *kinfo, int addrcells, int sizecells) { - const struct membanks *mem = &kinfo->shm_mem.common; + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); void *fdt = kinfo->fdt; int res = 0; /* Placeholder for reserved-memory\0 */ @@ -579,7 +578,7 @@ void __init init_sharedmem_pages(void) int __init remove_shm_from_rangeset(const struct kernel_info *kinfo, struct rangeset *rangeset) { - const struct membanks *shm_mem = &kinfo->shm_mem.common; + const struct membanks *shm_mem = kernel_info_get_shm_mem_const(kinfo); unsigned int i; /* Remove static shared memory regions */ @@ -607,7 +606,7 @@ int __init remove_shm_from_rangeset(const struct kernel_info *kinfo, int __init remove_shm_holes_for_domU(const struct kernel_info *kinfo, struct membanks *ext_regions) { - const struct membanks *shm_mem = &kinfo->shm_mem.common; + const struct membanks *shm_mem = kernel_info_get_shm_mem_const(kinfo); struct rangeset *guest_holes; unsigned int i; paddr_t start; @@ -673,7 +672,7 @@ void __init shm_mem_node_fill_reg_range(const struct kernel_info *kinfo, __be32 *reg, int *nr_cells, int addrcells, int sizecells) { - const struct membanks *mem = &kinfo->shm_mem.common; + const struct membanks *mem = kernel_info_get_shm_mem_const(kinfo); unsigned int i; __be32 *cells;
Commit 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory bank structures") introduced a MISRA regression for Rule 1.1 because a flexible array member is introduced in the middle of a struct, furthermore this is using a GCC extension that is going to be deprecated in GCC 14 and a warning to identify such cases will be present (-Wflex-array-member-not-at-end) to identify such cases. In order to fix this issue, use the macro __struct_group to create a structure 'struct membanks_hdr' which will hold the common data among structures using the 'struct membanks' interface. Modify the 'struct shared_meminfo' and 'struct meminfo' to use this new structure, effectively removing the flexible array member from the middle of the structure and modify the code accessing the .common field to use the macro container_of to maintain the functionality of the interface. Given this change, container_of needs to be supplied with a type and so the macro 'kernel_info_get_mem' inside arm/include/asm/kernel.h can't be an option since it uses const and non-const types for struct membanks, so introduce two static inline, one of which will keep the const qualifier. Given the complexity of the interface, which carries a lot of benefit but on the other hand could be prone to developer confusion if the access is open-coded, introduce two static inline helper for the 'struct kernel_info' .shm_mem member and get rid the open-coding shm_mem.common access. Fixes: 2209c1e35b47 ("xen/arm: Introduce a generic way to access memory bank structures") Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> --- xen/arch/arm/acpi/domain_build.c | 2 +- xen/arch/arm/domain_build.c | 6 +++--- xen/arch/arm/include/asm/kernel.h | 11 ++++++++++- xen/arch/arm/include/asm/setup.h | 18 ++++++++++-------- xen/arch/arm/include/asm/static-shmem.h | 12 ++++++++++++ xen/arch/arm/static-shmem.c | 19 +++++++++---------- 6 files changed, 45 insertions(+), 23 deletions(-)