From 39e8701f33d65c7f51d749a5d12a1379065e0926 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 5 Oct 2015 17:48:13 -0700 Subject: [PATCH] x86/entry/32: Open-code return tracking from fork and kthreads syscall_exit is going away, and return tracing is just a function call now, so open-code the two non-syscall 32-bit users. While we're at it, update the big register layout comment. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/a6b3c472fda7cda0e368c3ccd553dea7447dfdd2.1444091585.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/entry/entry_32.S | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index a08ded481aba..36b6beb181f6 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -3,7 +3,7 @@ * * entry_32.S contains the system-call and low-level fault and trap handling routines. * - * Stack layout in 'syscall_exit': + * Stack layout while running C code: * ptrace needs to have all registers on the stack. * If the order here is changed, it needs to be * updated in fork.c:copy_process(), signal.c:do_signal(), @@ -211,7 +211,11 @@ ENTRY(ret_from_fork) popl %eax pushl $0x0202 # Reset kernel eflags popfl - jmp syscall_exit + + /* 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) @@ -224,7 +228,15 @@ ENTRY(ret_from_kernel_thread) movl PT_EBP(%esp), %eax call *PT_EBX(%esp) movl $0, PT_EAX(%esp) - jmp syscall_exit + + /* + * 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. + */ + movl %esp, %eax + call syscall_return_slowpath + jmp restore_all ENDPROC(ret_from_kernel_thread) /*