x86/entry/32: Migrate to C exit path

This removes the hybrid asm-and-C implementation of exit work.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eric Paris <eparis@parisplace.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2baa438619ea6c027b40ec9fceacca52f09c74d09.1438378274.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 11 insertions, 51 deletions

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index a3c307ad5ac4..b2909bf8cf70 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -256,14 +256,10 @@ ret_from_intr:
 
 ENTRY(resume_userspace)
         LOCKDEP_SYS_EXIT
-        DISABLE_INTERRUPTS(CLBR_ANY)            # make sure we don't miss an interrupt
-                                                # setting need_resched or sigpending
-                                                # between sampling and the iret
+        DISABLE_INTERRUPTS(CLBR_ANY)
         TRACE_IRQS_OFF
-        movl    TI_flags(%ebp), %ecx
-        andl    $_TIF_WORK_MASK, %ecx           # is there any work to be done on
-                                                # int/exception return?
-        jne     work_pending
+        movl    %esp, %eax
+        call    prepare_exit_to_usermode
         jmp     restore_all
 END(ret_from_exception)
 
@@ -341,7 +337,7 @@ sysenter_after_call:
         TRACE_IRQS_OFF
         movl    TI_flags(%ebp), %ecx
         testl   $_TIF_ALLWORK_MASK, %ecx
-        jnz     syscall_exit_work
+        jnz     syscall_exit_work_irqs_off
 sysenter_exit:
 /* if something modifies registers it must also disable sysexit */
         movl    PT_EIP(%esp), %edx
@@ -377,13 +373,7 @@ syscall_after_call:
         movl    %eax, PT_EAX(%esp)              # store the return value
 syscall_exit:
         LOCKDEP_SYS_EXIT
-        DISABLE_INTERRUPTS(CLBR_ANY)            # make sure we don't miss an interrupt
-                                                # setting need_resched or sigpending
-                                                # between sampling and the iret
-        TRACE_IRQS_OFF
-        movl    TI_flags(%ebp), %ecx
-        testl   $_TIF_ALLWORK_MASK, %ecx        # current->work
-        jnz     syscall_exit_work
+        jmp     syscall_exit_work
 
 restore_all:
         TRACE_IRQS_IRET
@@ -460,35 +450,6 @@ ldt_ss:
 #endif
 ENDPROC(entry_INT80_32)
 
-        # perform work that needs to be done immediately before resumption
-        ALIGN
-work_pending:
-        testb   $_TIF_NEED_RESCHED, %cl
-        jz      work_notifysig
-work_resched:
-        call    schedule
-        LOCKDEP_SYS_EXIT
-        DISABLE_INTERRUPTS(CLBR_ANY)            # make sure we don't miss an interrupt
-                                                # setting need_resched or sigpending
-                                                # between sampling and the iret
-        TRACE_IRQS_OFF
-        movl    TI_flags(%ebp), %ecx
-        andl    $_TIF_WORK_MASK, %ecx           # is there any work to be done other
-                                                # than syscall tracing?
-        jz      restore_all
-        testb   $_TIF_NEED_RESCHED, %cl
-        jnz     work_resched
-
-work_notifysig:                                 # deal with pending signals and
-                                                # notify-resume requests
-        TRACE_IRQS_ON
-        ENABLE_INTERRUPTS(CLBR_NONE)
-        movl    %esp, %eax
-        xorl    %edx, %edx
-        call    do_notify_resume
-        jmp     resume_userspace
-END(work_pending)
-
         # perform syscall exit tracing
         ALIGN
 syscall_trace_entry:
@@ -503,15 +464,14 @@ END(syscall_trace_entry)
 
         # perform syscall exit tracing
         ALIGN
-syscall_exit_work:
-        testl   $_TIF_WORK_SYSCALL_EXIT, %ecx
-        jz      work_pending
+syscall_exit_work_irqs_off:
         TRACE_IRQS_ON
-        ENABLE_INTERRUPTS(CLBR_ANY)             # could let syscall_trace_leave() call
-                                                # schedule() instead
+        ENABLE_INTERRUPTS(CLBR_ANY)
+
+syscall_exit_work:
         movl    %esp, %eax
-        call    syscall_trace_leave
-        jmp     resume_userspace
+        call    syscall_return_slowpath
+        jmp     restore_all
 END(syscall_exit_work)
 
 syscall_fault: