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authorRoland McGrath <roland@redhat.com>2008-06-23 23:41:12 -0400
committerRoland McGrath <roland@redhat.com>2008-07-23 20:43:36 -0400
commit15e8f348db372dec21229fda5d52ae6ee7e64666 (patch)
tree73afc044ef5b4e29a893e98afee2fe794938aeb3 /arch/x86/kernel/entry_64.S
parent20b7997e8abdf338dcc27fb4f1333c4973a7f113 (diff)
x86_64: remove bogus optimization in sysret_signal
This short-circuit path in sysret_signal looks wrong to me. AFAICT, in practice the branch is never taken--and if it were, it would go wrong. To wit, try loading a module whose init function does set_thread_flag(TIF_IRET), and see insmod crash (presumably with a wrong user stack pointer). This is because the FIXUP_TOP_OF_STACK work hasn't been done yet when we jump around the call to ptregscall_common and get to int_with_check--where it expects the user RSP,SS,CS and EFLAGS to have been stored by FIXUP_TOP_OF_STACK. I don't think it's normally possible to get to sysret_signal with no _TIF_DO_NOTIFY_MASK bits set anyway, so these two instructions are already superfluous. If it ever did happen, it is harmless to call do_notify_resume with nothing for it to do. Signed-off-by: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
-rw-r--r--arch/x86/kernel/entry_64.S6
1 files changed, 1 insertions, 5 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8410e26f4183..a169225869cc 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -402,16 +402,12 @@ sysret_careful:
402sysret_signal: 402sysret_signal:
403 TRACE_IRQS_ON 403 TRACE_IRQS_ON
404 ENABLE_INTERRUPTS(CLBR_NONE) 404 ENABLE_INTERRUPTS(CLBR_NONE)
405 testl $_TIF_DO_NOTIFY_MASK,%edx
406 jz 1f
407
408 /* Really a signal */
409 /* edx: work flags (arg3) */ 405 /* edx: work flags (arg3) */
410 leaq do_notify_resume(%rip),%rax 406 leaq do_notify_resume(%rip),%rax
411 leaq -ARGOFFSET(%rsp),%rdi # &pt_regs -> arg1 407 leaq -ARGOFFSET(%rsp),%rdi # &pt_regs -> arg1
412 xorl %esi,%esi # oldset -> arg2 408 xorl %esi,%esi # oldset -> arg2
413 call ptregscall_common 409 call ptregscall_common
4141: movl $_TIF_WORK_MASK,%edi 410 movl $_TIF_WORK_MASK,%edi
415 /* Use IRET because user could have changed frame. This 411 /* Use IRET because user could have changed frame. This
416 works because ptregscall_common has called FIXUP_TOP_OF_STACK. */ 412 works because ptregscall_common has called FIXUP_TOP_OF_STACK. */
417 DISABLE_INTERRUPTS(CLBR_NONE) 413 DISABLE_INTERRUPTS(CLBR_NONE)