diff options
Diffstat (limited to 'arch/x86/entry/entry_32.S')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 68 |
1 files changed, 52 insertions, 16 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 64d29a3ad376..21b352a11b49 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -205,34 +205,70 @@ 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, |