From 40f0933d51f4cba26a5c009a26bb230f4514c1b6 Mon Sep 17 00:00:00 2001 From: Roland McGrath <roland@redhat.com> Date: Thu, 28 Feb 2008 19:57:07 -0800 Subject: x86: ia32 syscall restart fix The code to restart syscalls after signals depends on checking for a negative orig_ax, and for particular negative -ERESTART* values in ax. These fields are 64 bits and for a 32-bit task they get zero-extended. The syscall restart behavior is lost, a regression from a native 32-bit kernel and from 64-bit tasks' behavior. This patch fixes the problem by doing sign-extension where it matters. For orig_ax, the only time the value should be -1 but winds up as 0x0ffffffff is via a 32-bit ptrace call. So the patch changes ptrace to sign-extend the 32-bit orig_eax value when it's stored; it doesn't change the checks on orig_ax, though it uses the new current_syscall() inline to better document the subtle importance of the used of signedness there. The ax value is stored a lot of ways and it seems hard to get them all sign-extended at their origins. So for that, we use the current_syscall_ret() to sign-extend it only for 32-bit tasks at the time of the -ERESTART* comparisons. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> --- arch/x86/kernel/ptrace.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/ptrace.c') diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 8f64abe699f..d5904eef1d3 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1055,10 +1055,17 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value) R32(esi, si); R32(ebp, bp); R32(eax, ax); - R32(orig_eax, orig_ax); R32(eip, ip); R32(esp, sp); + case offsetof(struct user32, regs.orig_eax): + /* + * Sign-extend the value so that orig_eax = -1 + * causes (long)orig_ax < 0 tests to fire correctly. + */ + regs->orig_ax = (long) (s32) value; + break; + case offsetof(struct user32, regs.eflags): return set_flags(child, value); -- cgit v1.2.3-70-g09d2