Re: [PATCH v2] signals, pkeys: make si_pkey 32 bits

From: Ingo Molnar
Date: Mon Feb 29 2016 - 02:57:43 EST



* Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:

> In order to prevent a change of alignment of the _sifields union in the
> siginfo structure on (some) 32 bit platforms and an ABI breakage, we
> change the type of _pkey to unsigned int. If more bits are needed in
> the future, a second unsigned int could be added.
>
> Fixes: cd0ea35ff551 ("signals, pkeys: Notify userspace about protection key faults")
> Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> ---
> arch/ia64/include/uapi/asm/siginfo.h | 2 +-
> arch/mips/include/uapi/asm/siginfo.h | 2 +-
> include/uapi/asm-generic/siginfo.h | 2 +-
> 3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/ia64/include/uapi/asm/siginfo.h b/arch/ia64/include/uapi/asm/siginfo.h
> index 0151cfab929d..19e7db0c9453 100644
> --- a/arch/ia64/include/uapi/asm/siginfo.h
> +++ b/arch/ia64/include/uapi/asm/siginfo.h
> @@ -70,7 +70,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
> - u64 _pkey;
> + unsigned int _pkey;
> };
> } _sigfault;
>
> diff --git a/arch/mips/include/uapi/asm/siginfo.h b/arch/mips/include/uapi/asm/siginfo.h
> index 6f4edf0d794c..3cc14f4a5936 100644
> --- a/arch/mips/include/uapi/asm/siginfo.h
> +++ b/arch/mips/include/uapi/asm/siginfo.h
> @@ -93,7 +93,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
> - u64 _pkey;
> + unsigned int _pkey;
> };
> } _sigfault;
>
> diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
> index 90384d55225b..f4459dc3d31b 100644
> --- a/include/uapi/asm-generic/siginfo.h
> +++ b/include/uapi/asm-generic/siginfo.h
> @@ -98,7 +98,7 @@ typedef struct siginfo {
> void __user *_upper;
> } _addr_bnd;
> /* used when si_code=SEGV_PKUERR */
> - u64 _pkey;
> + unsigned int _pkey;
> };
> } _sigfault;
>

Please use the standard ABI integer type pattern: __u32.

The advantage of only using __[su][8|16|32|64] integer types is that it's
"obvious" at a glance that an ABI is bitness-invariant.

For example include/uapi/linux/perf_event.h only uses such ABI-safe types, and
arch/x86/include/uapi is using these types 95%+ of the time.

( The various struct siginfo definitions should probably be harmonized as well,
but in a separate patch. )

Thanks,

Ingo