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authorAl Viro <viro@zeniv.linux.org.uk>2012-04-30 18:24:46 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2012-06-01 13:01:51 -0400
commit44fbbb3dc687c9709a6f2236197316e5c79ab1eb (patch)
treed3c995b1cb7e3f9ac5af09b8d78f6c839a65f35a
parent29bf5dd895219e5111099908040aecfc1509f9bb (diff)
downloadlinux-sh-44fbbb3dc687c9709a6f2236197316e5c79ab1eb.tar.gz
x86: get rid of calling do_notify_resume() when returning to kernel mode
If we end up calling do_notify_resume() with !user_mode(refs), it does nothing (do_signal() explicitly bails out and we can't get there with TIF_NOTIFY_RESUME in such situations). Then we jump to resume_userspace_sig, which rechecks the same thing and bails out to resume_kernel, thus breaking the loop. It's easier and cheaper to check *before* calling do_notify_resume() and bail out to resume_kernel immediately. And kill the check in do_signal()... Note that on amd64 we can't get there with !user_mode() at all - asm glue takes care of that. Acked-and-reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--arch/x86/kernel/entry_32.S13
-rw-r--r--arch/x86/kernel/signal.c10
2 files changed, 10 insertions, 13 deletions
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 01ccf9b71473..623f28837476 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -316,7 +316,6 @@ ret_from_exception:
preempt_stop(CLBR_ANY)
ret_from_intr:
GET_THREAD_INFO(%ebp)
-resume_userspace_sig:
#ifdef CONFIG_VM86
movl PT_EFLAGS(%esp), %eax # mix EFLAGS and CS
movb PT_CS(%esp), %al
@@ -615,9 +614,13 @@ work_notifysig: # deal with pending signals and
# vm86-space
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
+ movb PT_CS(%esp), %bl
+ andb $SEGMENT_RPL_MASK, %bl
+ cmpb $USER_RPL, %bl
+ jb resume_kernel
xorl %edx, %edx
call do_notify_resume
- jmp resume_userspace_sig
+ jmp resume_userspace
ALIGN
work_notifysig_v86:
@@ -630,9 +633,13 @@ work_notifysig_v86:
#endif
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
+ movb PT_CS(%esp), %bl
+ andb $SEGMENT_RPL_MASK, %bl
+ cmpb $USER_RPL, %bl
+ jb resume_kernel
xorl %edx, %edx
call do_notify_resume
- jmp resume_userspace_sig
+ jmp resume_userspace
END(work_pending)
# perform syscall exit tracing
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index e8a89374d356..21af737053aa 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -737,16 +737,6 @@ static void do_signal(struct pt_regs *regs)
siginfo_t info;
int signr;
- /*
- * We want the common case to go fast, which is why we may in certain
- * cases get here from kernel mode. Just return without doing anything
- * if so.
- * X86_32: vm86 regs switched out by assembly code before reaching
- * here, so testing against kernel CS suffices.
- */
- if (!user_mode(regs))
- return;
-
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
/* Whee! Actually deliver the signal. */