| Message ID | alpine.DEB.2.22.394.2404031806510.2245130@ubuntu-linux-20-04-desktop (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v3] docs/misra: document the expected sizes of integer types | expand |
Hi Stefano, > On 4 Apr 2024, at 03:12, Stefano Stabellini <sstabellini@kernel.org> wrote: > > Xen makes assumptions about the size of integer types on the various > architectures. Document these assumptions. > > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> > --- > Changes in v3: > - add links to System V, AAPCS32 and AAPCS64 > > --- > docs/misra/C-language-toolchain.rst | 69 +++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/docs/misra/C-language-toolchain.rst b/docs/misra/C-language-toolchain.rst > index b7c2000992..84b21992bc 100644 > --- a/docs/misra/C-language-toolchain.rst > +++ b/docs/misra/C-language-toolchain.rst > @@ -480,4 +480,73 @@ The table columns are as follows: > - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. > > > +Sizes of Integer types > +______________________ > + > +Xen expects System V ABI on x86_64: > + https://gitlab.com/x86-psABIs/x86-64-ABI > + > +Xen expects AAPCS32 on ARMv8-A AArch32: > + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst > + > +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: > + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst We still support armv7 somehow so we should add something for it here. > + > +A summary table of data types, sizes and alignment is below: > + > +.. list-table:: > + :widths: 10 10 10 45 > + :header-rows: 1 > + > + * - Type > + - Size > + - Alignment > + - Architectures > + > + * - char > + - 8 bits > + - 8 bits > + - all architectures > + > + * - short > + - 16 bits > + - 16 bits > + - all architectures > + > + * - int > + - 32 bits > + - 32 bits > + - all architectures > + > + * - long > + - 32 bits > + - 32 bits > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) Same here armv7 should be mentioned. > + > + * - long > + - 64 bits > + - 64 bits > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > + > + * - long long > + - 64-bit > + - 32-bit > + - x86_32 > + > + * - long long > + - 64-bit > + - 64-bit > + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 Should this be all architecture except x86_32 ? > + > + * - pointer > + - 32-bit > + - 32-bit > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) Armv7 missing here. > + > + * - pointer > + - 64-bit > + - 64-bit > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > + > + > END OF DOCUMENT. > -- > 2.25.1 > Cheers Bertrand
On 04.04.2024 03:12, Stefano Stabellini wrote: > --- a/docs/misra/C-language-toolchain.rst > +++ b/docs/misra/C-language-toolchain.rst > @@ -480,4 +480,73 @@ The table columns are as follows: > - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. > > > +Sizes of Integer types > +______________________ > + > +Xen expects System V ABI on x86_64: > + https://gitlab.com/x86-psABIs/x86-64-ABI > + > +Xen expects AAPCS32 on ARMv8-A AArch32: > + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst > + > +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: > + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst > + > +A summary table of data types, sizes and alignment is below: > + > +.. list-table:: > + :widths: 10 10 10 45 > + :header-rows: 1 > + > + * - Type > + - Size > + - Alignment > + - Architectures > + > + * - char > + - 8 bits > + - 8 bits > + - all architectures This one _may_ be acceptable, but already feels like going too far. > + * - short > + - 16 bits > + - 16 bits > + - all architectures > + > + * - int > + - 32 bits > + - 32 bits > + - all architectures These two I continue to disagree with. The values are minimum required ones. Even if code changes may be needed (Misra already helps us here by stopping undue mixing of e.g. unsigned int and uint32_t in at least some situations), there's no inherent requirement in Xen for such restrictions. > + * - long > + - 32 bits > + - 32 bits > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > + > + * - long > + - 64 bits > + - 64 bits > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > + > + * - long long > + - 64-bit > + - 32-bit > + - x86_32 > + > + * - long long > + - 64-bit > + - 64-bit > + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 Along the lines of the above, simply saying "64-bit architectures" here is too generic. Whereas for long (above) and ... > + * - pointer > + - 32-bit > + - 32-bit > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > + > + * - pointer > + - 64-bit > + - 64-bit > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) ... pointers I agree (and the special mentioning of the architectures in parentheses could even be omitted imo). To summarize, my counter proposal: * - char - at least 8 bits - equaling size - all architectures * - char - 8 bits - 8 bits - x86, ARM, RISC-V, PPC * - short - at least 16 bits - equaling size - all architectures * - short - 16 bits - 16 bits - x86, ARM, RISC-V, PPC * - int - at least 32 bits - equaling size - all architectures * - int - 32 bits - 32 bits - x86, ARM, RISC-V, PPC * - long - 32 bits - 32 bits - 32-bit architectures * - long - 64 bits - 64 bits - 64-bit architectures * - long long - 64-bit - 32-bit - x86_32 * - long long - 64-bit - 64-bit - x86_64, ARMv8-A AArch64, RV64, PPC64, ARMv8-A AArch32, ARMv8-R AArch32 * - pointer - 32-bit - 32-bit - 32-bit architectures * - pointer - 64-bit - 64-bit - 64-bit architectures Eventually, by properly decoupling pointers from longs (via using {,u}intptr_t appropriately), the restrictions on "long" could also be lifted. Note that the generic requirements on char and short also are imposed by C99. It may therefore not be necessary to state them explicitly, but rather refer to that standard (just like you're now referencing the SysV psABI-s). Jan
On Thu, 4 Apr 2024, Jan Beulich wrote: > On 04.04.2024 03:12, Stefano Stabellini wrote: > > --- a/docs/misra/C-language-toolchain.rst > > +++ b/docs/misra/C-language-toolchain.rst > > @@ -480,4 +480,73 @@ The table columns are as follows: > > - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. > > > > > > +Sizes of Integer types > > +______________________ > > + > > +Xen expects System V ABI on x86_64: > > + https://gitlab.com/x86-psABIs/x86-64-ABI > > + > > +Xen expects AAPCS32 on ARMv8-A AArch32: > > + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst > > + > > +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: > > + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst > > + > > +A summary table of data types, sizes and alignment is below: > > + > > +.. list-table:: > > + :widths: 10 10 10 45 > > + :header-rows: 1 > > + > > + * - Type > > + - Size > > + - Alignment > > + - Architectures > > + > > + * - char > > + - 8 bits > > + - 8 bits > > + - all architectures > > This one _may_ be acceptable, but already feels like going too far. > > > + * - short > > + - 16 bits > > + - 16 bits > > + - all architectures > > + > > + * - int > > + - 32 bits > > + - 32 bits > > + - all architectures > > These two I continue to disagree with. The values are minimum required ones. The purpose of the document docs/misra/C-language-toolchain.rst is to describe the reference safety-supported configuration. In a way, this document is similar to SUPPORT.md but for safety instead of security. Here, we need to write down the stable configuration, the one everyone is aligned and convinced should work correctly. Now, let's say that I believe you and agree with you that it should be possible to support int as 64-bit. This configuration is not tested. If I can draw a comparison, it would be similar to ask for XSM to be security supported while in fact is marked as experimental in SUPPORT.md. If you want, taking inspiration from SUPPORT.md, we can have a "supported" column and a "experimental" column. In the experimental column we can write down "at least 32-bit" or "32-bit or larger". > Even if code changes may be needed (Misra already helps us here by stopping > undue mixing of e.g. unsigned int and uint32_t in at least some situations), > there's no inherent requirement in Xen for such restrictions. I hope that my comparison with XSM and SUPPORT.md helps explain why we need to clarify the safety supported configuration with the values we actually validate Xen with. Your goal is to write down what should work with Xen, which is also OK but it is a different goal. It is OK to say that we aim for Xen to also work with other configurations too, and list them. That was not my intention, but I can expand the scope if you request. > > + * - long > > + - 32 bits > > + - 32 bits > > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > > + > > + * - long > > + - 64 bits > > + - 64 bits > > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > > + > > + * - long long > > + - 64-bit > > + - 32-bit > > + - x86_32 > > + > > + * - long long > > + - 64-bit > > + - 64-bit > > + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 > > Along the lines of the above, simply saying "64-bit architectures" here > is too generic. Whereas for long (above) and ... > > > + * - pointer > > + - 32-bit > > + - 32-bit > > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > > + > > + * - pointer > > + - 64-bit > > + - 64-bit > > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > > ... pointers I agree (and the special mentioning of the architectures > in parentheses could even be omitted imo). To summarize, my counter > proposal: > > * - char > - at least 8 bits this > - equaling size > - all architectures > > * - char > - 8 bits > - 8 bits > - x86, ARM, RISC-V, PPC > > * - short > - at least 16 bits and this > - equaling size > - all architectures > > * - short > - 16 bits > - 16 bits > - x86, ARM, RISC-V, PPC > > * - int > - at least 32 bits and this, more below > - equaling size > - all architectures > > * - int > - 32 bits > - 32 bits > - x86, ARM, RISC-V, PPC > > * - long > - 32 bits > - 32 bits > - 32-bit architectures > > * - long > - 64 bits > - 64 bits > - 64-bit architectures > > * - long long > - 64-bit > - 32-bit > - x86_32 > > * - long long > - 64-bit > - 64-bit > - x86_64, ARMv8-A AArch64, RV64, PPC64, ARMv8-A AArch32, ARMv8-R AArch32 > > * - pointer > - 32-bit > - 32-bit > - 32-bit architectures > > * - pointer > - 64-bit > - 64-bit > - 64-bit architectures > > Eventually, by properly decoupling pointers from longs (via using {,u}intptr_t > appropriately), the restrictions on "long" could also be lifted. > > Note that the generic requirements on char and short also are imposed by C99. > It may therefore not be necessary to state them explicitly, but rather refer > to that standard (just like you're now referencing the SysV psABI-s). I am OK with the above, except for the three instances of "at least". As mentioned earlier, we need to specify the supported and validated configuration. If you want we can also add another field to express what we aim at getting Xen to work with, but it should be separate.
On Thu, 4 Apr 2024, Bertrand Marquis wrote: > Hi Stefano, > > > On 4 Apr 2024, at 03:12, Stefano Stabellini <sstabellini@kernel.org> wrote: > > > > Xen makes assumptions about the size of integer types on the various > > architectures. Document these assumptions. > > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> > > --- > > Changes in v3: > > - add links to System V, AAPCS32 and AAPCS64 > > > > --- > > docs/misra/C-language-toolchain.rst | 69 +++++++++++++++++++++++++++++ > > 1 file changed, 69 insertions(+) > > > > diff --git a/docs/misra/C-language-toolchain.rst b/docs/misra/C-language-toolchain.rst > > index b7c2000992..84b21992bc 100644 > > --- a/docs/misra/C-language-toolchain.rst > > +++ b/docs/misra/C-language-toolchain.rst > > @@ -480,4 +480,73 @@ The table columns are as follows: > > - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. > > > > > > +Sizes of Integer types > > +______________________ > > + > > +Xen expects System V ABI on x86_64: > > + https://gitlab.com/x86-psABIs/x86-64-ABI > > + > > +Xen expects AAPCS32 on ARMv8-A AArch32: > > + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst > > + > > +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: > > + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst > > We still support armv7 somehow so we should add something for it here. > > > + > > +A summary table of data types, sizes and alignment is below: > > + > > +.. list-table:: > > + :widths: 10 10 10 45 > > + :header-rows: 1 > > + > > + * - Type > > + - Size > > + - Alignment > > + - Architectures > > + > > + * - char > > + - 8 bits > > + - 8 bits > > + - all architectures > > + > > + * - short > > + - 16 bits > > + - 16 bits > > + - all architectures > > + > > + * - int > > + - 32 bits > > + - 32 bits > > + - all architectures > > + > > + * - long > > + - 32 bits > > + - 32 bits > > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > > Same here armv7 should be mentioned. > > > + > > + * - long > > + - 64 bits > > + - 64 bits > > + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > > + > > + * - long long > > + - 64-bit > > + - 32-bit > > + - x86_32 > > + > > + * - long long > > + - 64-bit > > + - 64-bit > > + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 > > Should this be all architecture except x86_32 ? yes > > + > > + * - pointer > > + - 32-bit > > + - 32-bit > > + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > > Armv7 missing here. What is the formal name I should use for it here? ARMv7 AArch32 ?
On 05.04.2024 01:56, Stefano Stabellini wrote: > On Thu, 4 Apr 2024, Jan Beulich wrote: >> On 04.04.2024 03:12, Stefano Stabellini wrote: >>> --- a/docs/misra/C-language-toolchain.rst >>> +++ b/docs/misra/C-language-toolchain.rst >>> @@ -480,4 +480,73 @@ The table columns are as follows: >>> - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. >>> >>> >>> +Sizes of Integer types >>> +______________________ >>> + >>> +Xen expects System V ABI on x86_64: >>> + https://gitlab.com/x86-psABIs/x86-64-ABI >>> + >>> +Xen expects AAPCS32 on ARMv8-A AArch32: >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst >>> + >>> +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst >>> + >>> +A summary table of data types, sizes and alignment is below: >>> + >>> +.. list-table:: >>> + :widths: 10 10 10 45 >>> + :header-rows: 1 >>> + >>> + * - Type >>> + - Size >>> + - Alignment >>> + - Architectures >>> + >>> + * - char >>> + - 8 bits >>> + - 8 bits >>> + - all architectures >> >> This one _may_ be acceptable, but already feels like going too far. >> >>> + * - short >>> + - 16 bits >>> + - 16 bits >>> + - all architectures >>> + >>> + * - int >>> + - 32 bits >>> + - 32 bits >>> + - all architectures >> >> These two I continue to disagree with. The values are minimum required ones. > > The purpose of the document docs/misra/C-language-toolchain.rst is to > describe the reference safety-supported configuration. In a way, this > document is similar to SUPPORT.md but for safety instead of security. > > Here, we need to write down the stable configuration, the one everyone > is aligned and convinced should work correctly. > > Now, let's say that I believe you and agree with you that it should be > possible to support int as 64-bit. This configuration is not tested. If > I can draw a comparison, it would be similar to ask for XSM to be > security supported while in fact is marked as experimental in > SUPPORT.md. > > If you want, taking inspiration from SUPPORT.md, we can have a > "supported" column and a "experimental" column. In the experimental > column we can write down "at least 32-bit" or "32-bit or larger". > > >> Even if code changes may be needed (Misra already helps us here by stopping >> undue mixing of e.g. unsigned int and uint32_t in at least some situations), >> there's no inherent requirement in Xen for such restrictions. > > I hope that my comparison with XSM and SUPPORT.md helps explain why we > need to clarify the safety supported configuration with the values we > actually validate Xen with. > > Your goal is to write down what should work with Xen, which is also OK > but it is a different goal. It is OK to say that we aim for Xen to also > work with other configurations too, and list them. That was not my > intention, but I can expand the scope if you request. To achieve just your goal, would you then please replace all instances of "all architectures" and "all <N>-bit architectures" by an enumeration of the specific ones, as you have it elsewhere? This would then allow architectures I'm thinking about without impacting your goal. FTAOD ... >>> + * - long >>> + - 32 bits >>> + - 32 bits >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) >>> + >>> + * - long >>> + - 64 bits >>> + - 64 bits >>> + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) >>> + >>> + * - long long >>> + - 64-bit >>> + - 32-bit >>> + - x86_32 >>> + >>> + * - long long >>> + - 64-bit >>> + - 64-bit >>> + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 >> >> Along the lines of the above, simply saying "64-bit architectures" here >> is too generic. Whereas for long (above) and ... >> >>> + * - pointer >>> + - 32-bit >>> + - 32-bit >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) >>> + >>> + * - pointer >>> + - 64-bit >>> + - 64-bit >>> + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) >> >> ... pointers I agree (and the special mentioning of the architectures >> in parentheses could even be omitted imo). To summarize, my counter >> proposal: ... this counter proposal already specifically addressed that aspect, by e.g. ... >> * - char >> - at least 8 bits > > this > >> - equaling size >> - all architectures >> >> * - char >> - 8 bits >> - 8 bits >> - x86, ARM, RISC-V, PPC ... having two sections here: One to address your goal, and one to address mine. My further suggestion further up merely would mean dropping the generic parts (for imo no good reason). Jan >> * - short >> - at least 16 bits > > and this > >> - equaling size >> - all architectures >> >> * - short >> - 16 bits >> - 16 bits >> - x86, ARM, RISC-V, PPC >> >> * - int >> - at least 32 bits > > and this, more below > > >> - equaling size >> - all architectures >> >> * - int >> - 32 bits >> - 32 bits >> - x86, ARM, RISC-V, PPC >> >> * - long >> - 32 bits >> - 32 bits >> - 32-bit architectures >> >> * - long >> - 64 bits >> - 64 bits >> - 64-bit architectures >> >> * - long long >> - 64-bit >> - 32-bit >> - x86_32 >> >> * - long long >> - 64-bit >> - 64-bit >> - x86_64, ARMv8-A AArch64, RV64, PPC64, ARMv8-A AArch32, ARMv8-R AArch32 >> >> * - pointer >> - 32-bit >> - 32-bit >> - 32-bit architectures >> >> * - pointer >> - 64-bit >> - 64-bit >> - 64-bit architectures >> >> Eventually, by properly decoupling pointers from longs (via using {,u}intptr_t >> appropriately), the restrictions on "long" could also be lifted. >> >> Note that the generic requirements on char and short also are imposed by C99. >> It may therefore not be necessary to state them explicitly, but rather refer >> to that standard (just like you're now referencing the SysV psABI-s). > > I am OK with the above, except for the three instances of "at least". As > mentioned earlier, we need to specify the supported and validated > configuration. If you want we can also add another field to express what > we aim at getting Xen to work with, but it should be separate.
Hi Stefano, > On 5 Apr 2024, at 01:57, Stefano Stabellini <sstabellini@kernel.org> wrote: > > On Thu, 4 Apr 2024, Bertrand Marquis wrote: >> Hi Stefano, >> >>> On 4 Apr 2024, at 03:12, Stefano Stabellini <sstabellini@kernel.org> wrote: >>> >>> Xen makes assumptions about the size of integer types on the various >>> architectures. Document these assumptions. >>> >>> Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> >>> --- >>> Changes in v3: >>> - add links to System V, AAPCS32 and AAPCS64 >>> >>> --- >>> docs/misra/C-language-toolchain.rst | 69 +++++++++++++++++++++++++++++ >>> 1 file changed, 69 insertions(+) >>> >>> diff --git a/docs/misra/C-language-toolchain.rst b/docs/misra/C-language-toolchain.rst >>> index b7c2000992..84b21992bc 100644 >>> --- a/docs/misra/C-language-toolchain.rst >>> +++ b/docs/misra/C-language-toolchain.rst >>> @@ -480,4 +480,73 @@ The table columns are as follows: >>> - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. >>> >>> >>> +Sizes of Integer types >>> +______________________ >>> + >>> +Xen expects System V ABI on x86_64: >>> + https://gitlab.com/x86-psABIs/x86-64-ABI >>> + >>> +Xen expects AAPCS32 on ARMv8-A AArch32: >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst >>> + >>> +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst >> >> We still support armv7 somehow so we should add something for it here. >> >>> + >>> +A summary table of data types, sizes and alignment is below: >>> + >>> +.. list-table:: >>> + :widths: 10 10 10 45 >>> + :header-rows: 1 >>> + >>> + * - Type >>> + - Size >>> + - Alignment >>> + - Architectures >>> + >>> + * - char >>> + - 8 bits >>> + - 8 bits >>> + - all architectures >>> + >>> + * - short >>> + - 16 bits >>> + - 16 bits >>> + - all architectures >>> + >>> + * - int >>> + - 32 bits >>> + - 32 bits >>> + - all architectures >>> + >>> + * - long >>> + - 32 bits >>> + - 32 bits >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) >> >> Same here armv7 should be mentioned. >> >>> + >>> + * - long >>> + - 64 bits >>> + - 64 bits >>> + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) >>> + >>> + * - long long >>> + - 64-bit >>> + - 32-bit >>> + - x86_32 >>> + >>> + * - long long >>> + - 64-bit >>> + - 64-bit >>> + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 >> >> Should this be all architecture except x86_32 ? > > yes > >>> + >>> + * - pointer >>> + - 32-bit >>> + - 32-bit >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) >> >> Armv7 missing here. > > What is the formal name I should use for it here? ARMv7 AArch32 ? Armv7-A (no need to specify anything more as it was 32bit only). Cheers Bertrand
On Fri, 5 Apr 2024, Jan Beulich wrote: > On 05.04.2024 01:56, Stefano Stabellini wrote: > > On Thu, 4 Apr 2024, Jan Beulich wrote: > >> On 04.04.2024 03:12, Stefano Stabellini wrote: > >>> --- a/docs/misra/C-language-toolchain.rst > >>> +++ b/docs/misra/C-language-toolchain.rst > >>> @@ -480,4 +480,73 @@ The table columns are as follows: > >>> - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. > >>> > >>> > >>> +Sizes of Integer types > >>> +______________________ > >>> + > >>> +Xen expects System V ABI on x86_64: > >>> + https://gitlab.com/x86-psABIs/x86-64-ABI > >>> + > >>> +Xen expects AAPCS32 on ARMv8-A AArch32: > >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst > >>> + > >>> +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: > >>> + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst > >>> + > >>> +A summary table of data types, sizes and alignment is below: > >>> + > >>> +.. list-table:: > >>> + :widths: 10 10 10 45 > >>> + :header-rows: 1 > >>> + > >>> + * - Type > >>> + - Size > >>> + - Alignment > >>> + - Architectures > >>> + > >>> + * - char > >>> + - 8 bits > >>> + - 8 bits > >>> + - all architectures > >> > >> This one _may_ be acceptable, but already feels like going too far. > >> > >>> + * - short > >>> + - 16 bits > >>> + - 16 bits > >>> + - all architectures > >>> + > >>> + * - int > >>> + - 32 bits > >>> + - 32 bits > >>> + - all architectures > >> > >> These two I continue to disagree with. The values are minimum required ones. > > > > The purpose of the document docs/misra/C-language-toolchain.rst is to > > describe the reference safety-supported configuration. In a way, this > > document is similar to SUPPORT.md but for safety instead of security. > > > > Here, we need to write down the stable configuration, the one everyone > > is aligned and convinced should work correctly. > > > > Now, let's say that I believe you and agree with you that it should be > > possible to support int as 64-bit. This configuration is not tested. If > > I can draw a comparison, it would be similar to ask for XSM to be > > security supported while in fact is marked as experimental in > > SUPPORT.md. > > > > If you want, taking inspiration from SUPPORT.md, we can have a > > "supported" column and a "experimental" column. In the experimental > > column we can write down "at least 32-bit" or "32-bit or larger". > > > > > >> Even if code changes may be needed (Misra already helps us here by stopping > >> undue mixing of e.g. unsigned int and uint32_t in at least some situations), > >> there's no inherent requirement in Xen for such restrictions. > > > > I hope that my comparison with XSM and SUPPORT.md helps explain why we > > need to clarify the safety supported configuration with the values we > > actually validate Xen with. > > > > Your goal is to write down what should work with Xen, which is also OK > > but it is a different goal. It is OK to say that we aim for Xen to also > > work with other configurations too, and list them. That was not my > > intention, but I can expand the scope if you request. > > To achieve just your goal, would you then please replace all instances > of "all architectures" and "all <N>-bit architectures" by an enumeration > of the specific ones, as you have it elsewhere? This would then allow > architectures I'm thinking about without impacting your goal. FTAOD ... Yes, I am fine with that > >>> + * - long > >>> + - 32 bits > >>> + - 32 bits > >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > >>> + > >>> + * - long > >>> + - 64 bits > >>> + - 64 bits > >>> + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > >>> + > >>> + * - long long > >>> + - 64-bit > >>> + - 32-bit > >>> + - x86_32 > >>> + > >>> + * - long long > >>> + - 64-bit > >>> + - 64-bit > >>> + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 > >> > >> Along the lines of the above, simply saying "64-bit architectures" here > >> is too generic. Whereas for long (above) and ... > >> > >>> + * - pointer > >>> + - 32-bit > >>> + - 32-bit > >>> + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) > >>> + > >>> + * - pointer > >>> + - 64-bit > >>> + - 64-bit > >>> + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) > >> > >> ... pointers I agree (and the special mentioning of the architectures > >> in parentheses could even be omitted imo). To summarize, my counter > >> proposal: > > ... this counter proposal already specifically addressed that aspect, by > e.g. ... > > >> * - char > >> - at least 8 bits > > > > this > > > >> - equaling size > >> - all architectures > >> > >> * - char > >> - 8 bits > >> - 8 bits > >> - x86, ARM, RISC-V, PPC > > ... having two sections here: One to address your goal, and one to > address mine. My further suggestion further up merely would mean > dropping the generic parts (for imo no good reason). I don't mind having two sections, one for my goal and one for yours. However, I am a bit unsure how to word the generic part in a way that is clear and unambiguous, so I'll keep only the explicitly listed architectures in the next version (following your suggestion further up.) > >> * - short > >> - at least 16 bits > > > > and this > > > >> - equaling size > >> - all architectures > >> > >> * - short > >> - 16 bits > >> - 16 bits > >> - x86, ARM, RISC-V, PPC > >> > >> * - int > >> - at least 32 bits > > > > and this, more below > > > > > >> - equaling size > >> - all architectures > >> > >> * - int > >> - 32 bits > >> - 32 bits > >> - x86, ARM, RISC-V, PPC > >> > >> * - long > >> - 32 bits > >> - 32 bits > >> - 32-bit architectures > >> > >> * - long > >> - 64 bits > >> - 64 bits > >> - 64-bit architectures > >> > >> * - long long > >> - 64-bit > >> - 32-bit > >> - x86_32 > >> > >> * - long long > >> - 64-bit > >> - 64-bit > >> - x86_64, ARMv8-A AArch64, RV64, PPC64, ARMv8-A AArch32, ARMv8-R AArch32 > >> > >> * - pointer > >> - 32-bit > >> - 32-bit > >> - 32-bit architectures > >> > >> * - pointer > >> - 64-bit > >> - 64-bit > >> - 64-bit architectures > >> > >> Eventually, by properly decoupling pointers from longs (via using {,u}intptr_t > >> appropriately), the restrictions on "long" could also be lifted. > >> > >> Note that the generic requirements on char and short also are imposed by C99. > >> It may therefore not be necessary to state them explicitly, but rather refer > >> to that standard (just like you're now referencing the SysV psABI-s). > > > > I am OK with the above, except for the three instances of "at least". As > > mentioned earlier, we need to specify the supported and validated > > configuration. If you want we can also add another field to express what > > we aim at getting Xen to work with, but it should be separate. >
diff --git a/docs/misra/C-language-toolchain.rst b/docs/misra/C-language-toolchain.rst index b7c2000992..84b21992bc 100644 --- a/docs/misra/C-language-toolchain.rst +++ b/docs/misra/C-language-toolchain.rst @@ -480,4 +480,73 @@ The table columns are as follows: - See Section "4.13 Preprocessing Directives" of GCC_MANUAL and Section "11.1 Implementation-defined behavior" of CPP_MANUAL. +Sizes of Integer types +______________________ + +Xen expects System V ABI on x86_64: + https://gitlab.com/x86-psABIs/x86-64-ABI + +Xen expects AAPCS32 on ARMv8-A AArch32: + https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst + +Xen expects AAPCS64 LP64 on ARMv8-A AArch64: + https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst + +A summary table of data types, sizes and alignment is below: + +.. list-table:: + :widths: 10 10 10 45 + :header-rows: 1 + + * - Type + - Size + - Alignment + - Architectures + + * - char + - 8 bits + - 8 bits + - all architectures + + * - short + - 16 bits + - 16 bits + - all architectures + + * - int + - 32 bits + - 32 bits + - all architectures + + * - long + - 32 bits + - 32 bits + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) + + * - long + - 64 bits + - 64 bits + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) + + * - long long + - 64-bit + - 32-bit + - x86_32 + + * - long long + - 64-bit + - 64-bit + - 64-bit architectures, ARMv8-A AArch32, ARMv8-R AArch32 + + * - pointer + - 32-bit + - 32-bit + - 32-bit architectures (x86_32, ARMv8-A AArch32, ARMv8-R AArch32) + + * - pointer + - 64-bit + - 64-bit + - 64-bit architectures (x86_64, ARMv8-A AArch64, RV64, PPC64) + + END OF DOCUMENT.
Xen makes assumptions about the size of integer types on the various architectures. Document these assumptions. Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com> --- Changes in v3: - add links to System V, AAPCS32 and AAPCS64 --- docs/misra/C-language-toolchain.rst | 69 +++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+)