| Message ID | 20231130092112.18118-1-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] xen/public: fix flexible array definitions | expand |
Hi Juergen, On 30/11/2023 09:21, Juergen Gross wrote: > --- > V2: > - bump interface version and make change only for new version > (Jan Beulich) > --- > xen/include/public/io/cameraif.h | 2 +- > xen/include/public/io/displif.h | 2 +- > xen/include/public/io/fsif.h | 4 ++-- > xen/include/public/io/pvcalls.h | 2 +- > xen/include/public/io/ring.h | 5 +++-- > xen/include/public/io/sndif.h | 2 +- > xen/include/public/xen-compat.h | 2 +- > xen/include/public/xen.h | 6 ++++++ > 8 files changed, 16 insertions(+), 9 deletions(-) > > diff --git a/xen/include/public/io/cameraif.h b/xen/include/public/io/cameraif.h > index 13763abef9..a389443769 100644 > --- a/xen/include/public/io/cameraif.h > +++ b/xen/include/public/io/cameraif.h > @@ -763,7 +763,7 @@ struct xencamera_buf_create_req { > */ > struct xencamera_page_directory { > grant_ref_t gref_dir_next_page; > - grant_ref_t gref[1]; /* Variable length */ > + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; > }; > > /* > diff --git a/xen/include/public/io/displif.h b/xen/include/public/io/displif.h > index 73d0cbdf15..132c96fa5c 100644 > --- a/xen/include/public/io/displif.h > +++ b/xen/include/public/io/displif.h > @@ -537,7 +537,7 @@ struct xendispl_dbuf_create_req { > > struct xendispl_page_directory { > grant_ref_t gref_dir_next_page; > - grant_ref_t gref[1]; /* Variable length */ > + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; > }; > > /* > diff --git a/xen/include/public/io/fsif.h b/xen/include/public/io/fsif.h > index ec57850233..dcade1c698 100644 > --- a/xen/include/public/io/fsif.h > +++ b/xen/include/public/io/fsif.h > @@ -40,7 +40,7 @@ struct fsif_read_request { > int32_t pad; > uint64_t len; > uint64_t offset; > - grant_ref_t grefs[1]; /* Variable length */ > + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; > }; > > struct fsif_write_request { > @@ -48,7 +48,7 @@ struct fsif_write_request { > int32_t pad; > uint64_t len; > uint64_t offset; > - grant_ref_t grefs[1]; /* Variable length */ > + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; > }; > > struct fsif_stat_request { > diff --git a/xen/include/public/io/pvcalls.h b/xen/include/public/io/pvcalls.h > index 230b0719e3..af0e9abd13 100644 > --- a/xen/include/public/io/pvcalls.h > +++ b/xen/include/public/io/pvcalls.h > @@ -30,7 +30,7 @@ struct pvcalls_data_intf { > uint8_t pad2[52]; > > RING_IDX ring_order; > - grant_ref_t ref[]; > + grant_ref_t ref[XENPV_FLEX_ARRAY_DIM]; I am probably missing something. In the commit message, you suggested that XENPV_FLEX_ARRAY_DIM will use 1 for older interface version for compatibility reason. Yet, if I am not mistaken, [] is not equivalent to [1]. So aren't you effectively breaking the compatibility? Cheers,
On 30/11/2023 9:21 am, Juergen Gross wrote: > Flexible arrays in public headers can be problematic with some > compilers. > > With XEN_FLEX_ARRAY_DIM there is a mechanism available to deal with > this issue, but care must be taken to not change the affected structs > in an incompatible way. > > So bump __XEN_LATEST_INTERFACE_VERSION__ and introduce a new macro > XENPV_FLEX_ARRAY_DIM which will be XENPV_FLEX_ARRAY_DIM with the > interface version being new enough and "1" (the value used today in > the affected headers) when the interface version is an old one. > > Replace the arr[1] instances (this includes the ones seen to be > problematic in recent Linux kernels [1]) with arr[XENPV_FLEX_ARRAY_DIM] > in order to avoid compilation errors. > > [1]: https://bugzilla.kernel.org/show_bug.cgi?id=217693 > > Signed-off-by: Juergen Gross <jgross@suse.com> CHANGELOG please. This change, however it ends up looking, absolutely needs covering. ~Andrew
On 30.11.23 12:33, Julien Grall wrote: > Hi Juergen, > > On 30/11/2023 09:21, Juergen Gross wrote: >> --- >> V2: >> - bump interface version and make change only for new version >> (Jan Beulich) >> --- >> xen/include/public/io/cameraif.h | 2 +- >> xen/include/public/io/displif.h | 2 +- >> xen/include/public/io/fsif.h | 4 ++-- >> xen/include/public/io/pvcalls.h | 2 +- >> xen/include/public/io/ring.h | 5 +++-- >> xen/include/public/io/sndif.h | 2 +- >> xen/include/public/xen-compat.h | 2 +- >> xen/include/public/xen.h | 6 ++++++ >> 8 files changed, 16 insertions(+), 9 deletions(-) >> >> diff --git a/xen/include/public/io/cameraif.h b/xen/include/public/io/cameraif.h >> index 13763abef9..a389443769 100644 >> --- a/xen/include/public/io/cameraif.h >> +++ b/xen/include/public/io/cameraif.h >> @@ -763,7 +763,7 @@ struct xencamera_buf_create_req { >> */ >> struct xencamera_page_directory { >> grant_ref_t gref_dir_next_page; >> - grant_ref_t gref[1]; /* Variable length */ >> + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; >> }; >> /* >> diff --git a/xen/include/public/io/displif.h b/xen/include/public/io/displif.h >> index 73d0cbdf15..132c96fa5c 100644 >> --- a/xen/include/public/io/displif.h >> +++ b/xen/include/public/io/displif.h >> @@ -537,7 +537,7 @@ struct xendispl_dbuf_create_req { >> struct xendispl_page_directory { >> grant_ref_t gref_dir_next_page; >> - grant_ref_t gref[1]; /* Variable length */ >> + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; >> }; >> /* >> diff --git a/xen/include/public/io/fsif.h b/xen/include/public/io/fsif.h >> index ec57850233..dcade1c698 100644 >> --- a/xen/include/public/io/fsif.h >> +++ b/xen/include/public/io/fsif.h >> @@ -40,7 +40,7 @@ struct fsif_read_request { >> int32_t pad; >> uint64_t len; >> uint64_t offset; >> - grant_ref_t grefs[1]; /* Variable length */ >> + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; >> }; >> struct fsif_write_request { >> @@ -48,7 +48,7 @@ struct fsif_write_request { >> int32_t pad; >> uint64_t len; >> uint64_t offset; >> - grant_ref_t grefs[1]; /* Variable length */ >> + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; >> }; >> struct fsif_stat_request { >> diff --git a/xen/include/public/io/pvcalls.h b/xen/include/public/io/pvcalls.h >> index 230b0719e3..af0e9abd13 100644 >> --- a/xen/include/public/io/pvcalls.h >> +++ b/xen/include/public/io/pvcalls.h >> @@ -30,7 +30,7 @@ struct pvcalls_data_intf { >> uint8_t pad2[52]; >> RING_IDX ring_order; >> - grant_ref_t ref[]; >> + grant_ref_t ref[XENPV_FLEX_ARRAY_DIM]; > > I am probably missing something. In the commit message, you suggested that > XENPV_FLEX_ARRAY_DIM will use 1 for older interface version for compatibility > reason. > > Yet, if I am not mistaken, [] is not equivalent to [1]. So aren't you > effectively breaking the compatibility? Oh, thanks for catching this one! I agree, this should be XEN_FLEX_ARRAY_DIM instead. Juergen
On 30.11.2023 10:21, Juergen Gross wrote: > --- a/xen/include/public/xen.h > +++ b/xen/include/public/xen.h > @@ -46,6 +46,12 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t); > #else > #define XEN_FLEX_ARRAY_DIM 1 /* variable size */ > #endif > +/* Some PV I/O interfaces need a compatibility variant. */ > +#if __XEN_INTERFACE_VERSION__ < 0x00041300 > +#define XENPV_FLEX_ARRAY_DIM 1 /* variable size */ > +#else > +#define XENPV_FLEX_ARRAY_DIM XEN_FLEX_ARRAY_DIM > +#endif May I suggest that this live in io/ring.h, for the lack of a better place under io/? Jan
On 30.11.23 14:14, Jan Beulich wrote: > On 30.11.2023 10:21, Juergen Gross wrote: >> --- a/xen/include/public/xen.h >> +++ b/xen/include/public/xen.h >> @@ -46,6 +46,12 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t); >> #else >> #define XEN_FLEX_ARRAY_DIM 1 /* variable size */ >> #endif >> +/* Some PV I/O interfaces need a compatibility variant. */ >> +#if __XEN_INTERFACE_VERSION__ < 0x00041300 >> +#define XENPV_FLEX_ARRAY_DIM 1 /* variable size */ >> +#else >> +#define XENPV_FLEX_ARRAY_DIM XEN_FLEX_ARRAY_DIM >> +#endif > > May I suggest that this live in io/ring.h, for the lack of a better place > under io/? Yes, fine with me. Juergen
On 30.11.23 12:34, Andrew Cooper wrote: > On 30/11/2023 9:21 am, Juergen Gross wrote: >> Flexible arrays in public headers can be problematic with some >> compilers. >> >> With XEN_FLEX_ARRAY_DIM there is a mechanism available to deal with >> this issue, but care must be taken to not change the affected structs >> in an incompatible way. >> >> So bump __XEN_LATEST_INTERFACE_VERSION__ and introduce a new macro >> XENPV_FLEX_ARRAY_DIM which will be XENPV_FLEX_ARRAY_DIM with the >> interface version being new enough and "1" (the value used today in >> the affected headers) when the interface version is an old one. >> >> Replace the arr[1] instances (this includes the ones seen to be >> problematic in recent Linux kernels [1]) with arr[XENPV_FLEX_ARRAY_DIM] >> in order to avoid compilation errors. >> >> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=217693 >> >> Signed-off-by: Juergen Gross <jgross@suse.com> > > CHANGELOG please. This change, however it ends up looking, absolutely > needs covering. Would this be fine: ### Changed + - Changed flexible array definitions in public I/O interface headers to not + use "1" as the number of array elements. Juergen
diff --git a/xen/include/public/io/cameraif.h b/xen/include/public/io/cameraif.h index 13763abef9..a389443769 100644 --- a/xen/include/public/io/cameraif.h +++ b/xen/include/public/io/cameraif.h @@ -763,7 +763,7 @@ struct xencamera_buf_create_req { */ struct xencamera_page_directory { grant_ref_t gref_dir_next_page; - grant_ref_t gref[1]; /* Variable length */ + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; }; /* diff --git a/xen/include/public/io/displif.h b/xen/include/public/io/displif.h index 73d0cbdf15..132c96fa5c 100644 --- a/xen/include/public/io/displif.h +++ b/xen/include/public/io/displif.h @@ -537,7 +537,7 @@ struct xendispl_dbuf_create_req { struct xendispl_page_directory { grant_ref_t gref_dir_next_page; - grant_ref_t gref[1]; /* Variable length */ + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; }; /* diff --git a/xen/include/public/io/fsif.h b/xen/include/public/io/fsif.h index ec57850233..dcade1c698 100644 --- a/xen/include/public/io/fsif.h +++ b/xen/include/public/io/fsif.h @@ -40,7 +40,7 @@ struct fsif_read_request { int32_t pad; uint64_t len; uint64_t offset; - grant_ref_t grefs[1]; /* Variable length */ + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; }; struct fsif_write_request { @@ -48,7 +48,7 @@ struct fsif_write_request { int32_t pad; uint64_t len; uint64_t offset; - grant_ref_t grefs[1]; /* Variable length */ + grant_ref_t grefs[XENPV_FLEX_ARRAY_DIM]; }; struct fsif_stat_request { diff --git a/xen/include/public/io/pvcalls.h b/xen/include/public/io/pvcalls.h index 230b0719e3..af0e9abd13 100644 --- a/xen/include/public/io/pvcalls.h +++ b/xen/include/public/io/pvcalls.h @@ -30,7 +30,7 @@ struct pvcalls_data_intf { uint8_t pad2[52]; RING_IDX ring_order; - grant_ref_t ref[]; + grant_ref_t ref[XENPV_FLEX_ARRAY_DIM]; }; DEFINE_XEN_FLEX_RING(pvcalls); diff --git a/xen/include/public/io/ring.h b/xen/include/public/io/ring.h index 0cae4367be..955fe5a1fc 100644 --- a/xen/include/public/io/ring.h +++ b/xen/include/public/io/ring.h @@ -25,6 +25,7 @@ * and grant_table.h from the Xen public headers. */ +#include "../xen.h" #include "../xen-compat.h" #if __XEN_INTERFACE_VERSION__ < 0x00030208 @@ -110,7 +111,7 @@ struct __name##_sring { \ uint8_t pvt_pad[4]; \ } pvt; \ uint8_t __pad[44]; \ - union __name##_sring_entry ring[1]; /* variable-length */ \ + union __name##_sring_entry ring[XENPV_FLEX_ARRAY_DIM]; \ }; \ \ /* "Front" end's private variables */ \ @@ -479,7 +480,7 @@ struct name##_data_intf { \ uint8_t pad2[56]; \ \ RING_IDX ring_order; \ - grant_ref_t ref[]; \ + grant_ref_t ref[XENPV_FLEX_ARRAY_DIM]; \ }; \ DEFINE_XEN_FLEX_RING(name) diff --git a/xen/include/public/io/sndif.h b/xen/include/public/io/sndif.h index 4234a47c87..cce1459b7b 100644 --- a/xen/include/public/io/sndif.h +++ b/xen/include/public/io/sndif.h @@ -659,7 +659,7 @@ struct xensnd_open_req { struct xensnd_page_directory { grant_ref_t gref_dir_next_page; - grant_ref_t gref[1]; /* Variable length */ + grant_ref_t gref[XENPV_FLEX_ARRAY_DIM]; }; /* diff --git a/xen/include/public/xen-compat.h b/xen/include/public/xen-compat.h index 97fe698498..078b796664 100644 --- a/xen/include/public/xen-compat.h +++ b/xen/include/public/xen-compat.h @@ -10,7 +10,7 @@ #ifndef __XEN_PUBLIC_XEN_COMPAT_H__ #define __XEN_PUBLIC_XEN_COMPAT_H__ -#define __XEN_LATEST_INTERFACE_VERSION__ 0x00040e00 +#define __XEN_LATEST_INTERFACE_VERSION__ 0x00041300 #if defined(__XEN__) || defined(__XEN_TOOLS__) /* Xen is built with matching headers and implements the latest interface. */ diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h index b812a0a324..62c4b04fa2 100644 --- a/xen/include/public/xen.h +++ b/xen/include/public/xen.h @@ -46,6 +46,12 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t); #else #define XEN_FLEX_ARRAY_DIM 1 /* variable size */ #endif +/* Some PV I/O interfaces need a compatibility variant. */ +#if __XEN_INTERFACE_VERSION__ < 0x00041300 +#define XENPV_FLEX_ARRAY_DIM 1 /* variable size */ +#else +#define XENPV_FLEX_ARRAY_DIM XEN_FLEX_ARRAY_DIM +#endif /* Turn a plain number into a C unsigned (long (long)) constant. */ #define __xen_mk_uint(x) x ## U
Flexible arrays in public headers can be problematic with some compilers. With XEN_FLEX_ARRAY_DIM there is a mechanism available to deal with this issue, but care must be taken to not change the affected structs in an incompatible way. So bump __XEN_LATEST_INTERFACE_VERSION__ and introduce a new macro XENPV_FLEX_ARRAY_DIM which will be XENPV_FLEX_ARRAY_DIM with the interface version being new enough and "1" (the value used today in the affected headers) when the interface version is an old one. Replace the arr[1] instances (this includes the ones seen to be problematic in recent Linux kernels [1]) with arr[XENPV_FLEX_ARRAY_DIM] in order to avoid compilation errors. [1]: https://bugzilla.kernel.org/show_bug.cgi?id=217693 Signed-off-by: Juergen Gross <jgross@suse.com> --- V2: - bump interface version and make change only for new version (Jan Beulich) --- xen/include/public/io/cameraif.h | 2 +- xen/include/public/io/displif.h | 2 +- xen/include/public/io/fsif.h | 4 ++-- xen/include/public/io/pvcalls.h | 2 +- xen/include/public/io/ring.h | 5 +++-- xen/include/public/io/sndif.h | 2 +- xen/include/public/xen-compat.h | 2 +- xen/include/public/xen.h | 6 ++++++ 8 files changed, 16 insertions(+), 9 deletions(-)