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compat: add a compat_need_64bit_alignment_fixup() helper

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Add a helper to check if the calling syscall needs a fixup for
non-natural 64-bit type alignment in the compat ABI.  This will only
return true for i386 syscalls on x86_64.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2020-09-17 09:41:58 +02:00 committed by Al Viro
parent cc7886d25b
commit 527c412519
2 changed files with 10 additions and 0 deletions
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1
arch/x86/include/asm/compat.h
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@ -209,6 +209,7 @@ static inline bool in_compat_syscall(void)
return in_32bit_syscall(); return in_32bit_syscall();
} }
#define in_compat_syscall in_compat_syscall /* override the generic impl */ #define in_compat_syscall in_compat_syscall /* override the generic impl */
#define compat_need_64bit_alignment_fixup in_ia32_syscall
#endif #endif
struct compat_siginfo; struct compat_siginfo;

9
include/linux/compat.h
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@ -932,6 +932,15 @@ static inline bool in_compat_syscall(void) { return false; }
#endif /* CONFIG_COMPAT */ #endif /* CONFIG_COMPAT */
/*
* Some legacy ABIs like the i386 one use less than natural alignment for 64-bit
* types, and will need special compat treatment for that. Most architectures
* don't need that special handling even for compat syscalls.
*/
#ifndef compat_need_64bit_alignment_fixup
#define compat_need_64bit_alignment_fixup() false
#endif
/* /*
* A pointer passed in from user mode. This should not * A pointer passed in from user mode. This should not
* be used for syscall parameters, just declare them * be used for syscall parameters, just declare them