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-rw-r--r--arch/x86/entry/entry_32.S68
1 files changed, 52 insertions, 16 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 0b56666e6039..b75a8bcd2d23 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -204,34 +204,70 @@
POP_GS_EX
.endm
+/*
+ * %eax: prev task
+ * %edx: next task
+ */
+ENTRY(__switch_to_asm)
+ /*
+ * Save callee-saved registers
+ * This must match the order in struct inactive_task_frame
+ */
+ pushl %ebp
+ pushl %ebx
+ pushl %edi
+ pushl %esi
+
+ /* switch stack */
+ movl %esp, TASK_threadsp(%eax)
+ movl TASK_threadsp(%edx), %esp
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+ movl TASK_stack_canary(%edx), %ebx
+ movl %ebx, PER_CPU_VAR(stack_canary)+stack_canary_offset
+#endif
+
+ /* restore callee-saved registers */
+ popl %esi
+ popl %edi
+ popl %ebx
+ popl %ebp
+
+ jmp __switch_to
+END(__switch_to_asm)
+
+/*
+ * A newly forked process directly context switches into this address.
+ *
+ * eax: prev task we switched from
+ * ebx: kernel thread func (NULL for user thread)
+ * edi: kernel thread arg
+ */
ENTRY(ret_from_fork)
pushl %eax
call schedule_tail
popl %eax
+ testl %ebx, %ebx
+ jnz 1f /* kernel threads are uncommon */
+
+2:
/* When we fork, we trace the syscall return in the child, too. */
movl %esp, %eax
call syscall_return_slowpath
jmp restore_all
-END(ret_from_fork)
-
-ENTRY(ret_from_kernel_thread)
- pushl %eax
- call schedule_tail
- popl %eax
- movl PT_EBP(%esp), %eax
- call *PT_EBX(%esp)
- movl $0, PT_EAX(%esp)
+ /* kernel thread */
+1: movl %edi, %eax
+ call *%ebx
/*
- * Kernel threads return to userspace as if returning from a syscall.
- * We should check whether anything actually uses this path and, if so,
- * consider switching it over to ret_from_fork.
+ * A kernel thread is allowed to return here after successfully
+ * calling do_execve(). Exit to userspace to complete the execve()
+ * syscall.
*/
- movl %esp, %eax
- call syscall_return_slowpath
- jmp restore_all
-ENDPROC(ret_from_kernel_thread)
+ movl $0, PT_EAX(%esp)
+ jmp 2b
+END(ret_from_fork)
/*
* Return to user mode is not as complex as all this looks,