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SubjectRe: [PATCH v8 5/7] powerpc/64: make buildable without CONFIG_COMPAT
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Le 12/09/2019 à 19:26, Michal Suchanek a écrit :
> There are numerous references to 32bit functions in generic and 64bit
> code so ifdef them out.
>
> Signed-off-by: Michal Suchanek <msuchanek@suse.de>
> ---
> v2:
> - fix 32bit ifdef condition in signal.c
> - simplify the compat ifdef condition in vdso.c - 64bit is redundant
> - simplify the compat ifdef condition in callchain.c - 64bit is redundant
> v3:
> - use IS_ENABLED and maybe_unused where possible
> - do not ifdef declarations
> - clean up Makefile
> v4:
> - further makefile cleanup
> - simplify is_32bit_task conditions
> - avoid ifdef in condition by using return
> v5:
> - avoid unreachable code on 32bit
> - make is_current_64bit constant on !COMPAT
> - add stub perf_callchain_user_32 to avoid some ifdefs
> v6:
> - consolidate current_is_64bit
> v7:
> - remove leftover perf_callchain_user_32 stub from previous series version
> v8:
> - fix build again - too trigger-happy with stub removal
> - remove a vdso.c hunk that causes warning according to kbuild test robot
> ---
> arch/powerpc/include/asm/thread_info.h | 4 +--
> arch/powerpc/kernel/Makefile | 7 ++---
> arch/powerpc/kernel/entry_64.S | 2 ++
> arch/powerpc/kernel/signal.c | 3 +-
> arch/powerpc/kernel/syscall_64.c | 6 ++--
> arch/powerpc/kernel/vdso.c | 3 +-
> arch/powerpc/perf/callchain.c | 39 ++++++++++++++------------
> 7 files changed, 33 insertions(+), 31 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> index 8e1d0195ac36..c128d8a48ea3 100644
> --- a/arch/powerpc/include/asm/thread_info.h
> +++ b/arch/powerpc/include/asm/thread_info.h
> @@ -144,10 +144,10 @@ static inline bool test_thread_local_flags(unsigned int flags)
> return (ti->local_flags & flags) != 0;
> }
>
> -#ifdef CONFIG_PPC64
> +#ifdef CONFIG_COMPAT
> #define is_32bit_task() (test_thread_flag(TIF_32BIT))
> #else
> -#define is_32bit_task() (1)
> +#define is_32bit_task() (IS_ENABLED(CONFIG_PPC32))
> #endif
>
> #if defined(CONFIG_PPC64)

[...]

> +static inline int current_is_64bit(void)
> +{
> + if (!IS_ENABLED(CONFIG_COMPAT))
> + return IS_ENABLED(CONFIG_PPC64);
> + /*
> + * We can't use test_thread_flag() here because we may be on an
> + * interrupt stack, and the thread flags don't get copied over
> + * from the thread_info on the main stack to the interrupt stack.
> + */
> + return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
> +}


Since at least commit ed1cd6deb013 ("powerpc: Activate
CONFIG_THREAD_INFO_IN_TASK")
[https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ed1cd6d]
the above comment is wrong and current_is_64bit() is equivalent to
!is_32bit_task()

See https://github.com/linuxppc/issues/issues/275

Christophe

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