| Date | Fri, 9 Oct 2015 06:12:24 -0700 | From | tip-bot for Andy Lutomirski <> | Subject | [tip:x86/asm] x86/entry/32: Open-code return tracking from fork and kthreads |
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Commit-ID: 39e8701f33d65c7f51d749a5d12a1379065e0926 Gitweb: http://git.kernel.org/tip/39e8701f33d65c7f51d749a5d12a1379065e0926 Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Mon, 5 Oct 2015 17:48:13 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Fri, 9 Oct 2015 09:41:10 +0200
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 <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/a6b3c472fda7cda0e368c3ccd553dea7447dfdd2.1444091585.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- 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 a08ded4..36b6beb 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) /*
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