x86-32, vdso: On system call restart after SYSENTER, use int $0x80

When we enter a 32-bit system call via SYSENTER or SYSCALL, we shuffle
the arguments to match the int $0x80 calling convention.  This was
probably a design mistake, but it's what it is now.  This causes
errors if the system call as to be restarted.

For SYSENTER, we have to invoke the instruction from the vdso as the
return address is hardcoded.  Accordingly, we can simply replace the
jump in the vdso with an int $0x80 instruction and use the slower
entry point for a post-restart.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/CA%2B55aFztZ=r5wa0x26KJQxvZOaQq8s2v3u50wCyJcA-Sc4g8gQ@mail.gmail.com
Cc: <stable@kernel.org>

diff --git a/arch/x86/vdso/vdso32/sysenter.S b/arch/x86/vdso/vdso32/sysenter.S
index e2800affa754d66d8ac3533f25834f0412ec9aee..e354bceee0e0490d29940736b9716f5b2be32d62 100644 (file)
--- a/arch/x86/vdso/vdso32/sysenter.S
+++ b/arch/x86/vdso/vdso32/sysenter.S
@@ -43,7 +43,7 @@ __kernel_vsyscall:
        .space 7,0x90
 
        /* 14: System call restart point is here! (SYSENTER_RETURN-2) */
-       jmp .Lenter_kernel
+       int $0x80
        /* 16: System call normal return point is here! */
 VDSO32_SYSENTER_RETURN:        /* Symbol used by sysenter.c via vdso32-syms.h */
        pop %ebp