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arm64: do not enforce strict 16 byte alignment to stack pointer 

copy_thread should not be enforcing 16 byte aligment and returning
-EINVAL. Other architectures trap misaligned stack access with SIGBUS
so arm64 should follow this convention, so remove the strict enforcement
check.

For example, currently clone(2) fails with -EINVAL when passing
a misaligned stack and this gives little clue to what is wrong. Instead,
it is arguable that a SIGBUS on the fist access to a misaligned stack
allows one to figure out that it is a misaligned stack issue rather
than trying to figure out why an unconventional (and undocumented)
-EINVAL is being returned.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Colin Ian King 2016-05-11 17:56:54 +01:00 committed by Will Deacon
parent 61462c8a6b
commit e6d9a52543
1 changed files with 0 additions and 3 deletions
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3
arch/arm64/kernel/process.c
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@ -265,9 +265,6 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
if (stack_start) {
if (is_compat_thread(task_thread_info(p)))
childregs->compat_sp = stack_start;
/* 16-byte aligned stack mandatory on AArch64 */
else if (stack_start & 15)
return -EINVAL;
else
childregs->sp = stack_start;
}