diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2017-05-23 10:37:29 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-24 09:05:16 +0200 |
| commit | ebd574994c63164d538a197172157318f58ac647 (patch) | |
| tree | 0016f12f367965af38a23c8d8c84cfad2dd9ea8f /arch/x86/entry/entry_64.S | |
| parent | 3780578761921f094179c6289072a74b2228c602 (diff) | |
Revert "x86/entry: Fix the end of the stack for newly forked tasks"
Petr Mladek reported the following warning when loading the livepatch
sample module:
WARNING: CPU: 1 PID: 3699 at arch/x86/kernel/stacktrace.c:132 save_stack_trace_tsk_reliable+0x133/0x1a0
...
Call Trace:
__schedule+0x273/0x820
schedule+0x36/0x80
kthreadd+0x305/0x310
? kthread_create_on_cpu+0x80/0x80
? icmp_echo.part.32+0x50/0x50
ret_from_fork+0x2c/0x40
That warning means the end of the stack is no longer recognized as such
for newly forked tasks. The problem was introduced with the following
commit:
ff3f7e2475bb ("x86/entry: Fix the end of the stack for newly forked tasks")
... which was completely misguided. It only partially fixed the
reported issue, and it introduced another bug in the process. None of
the other entry code saves the frame pointer before calling into C code,
so it doesn't make sense for ret_from_fork to do so either.
Contrary to what I originally thought, the original issue wasn't related
to newly forked tasks. It was actually related to ftrace. When entry
code calls into a function which then calls into an ftrace handler, the
stack frame looks different than normal.
The original issue will be fixed in the unwinder, in a subsequent patch.
Reported-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: live-patching@vger.kernel.org
Fixes: ff3f7e2475bb ("x86/entry: Fix the end of the stack for newly forked tasks")
Link: http://lkml.kernel.org/r/f350760f7e82f0750c8d1dd093456eb212751caa.1495553739.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry/entry_64.S')
| -rw-r--r-- | arch/x86/entry/entry_64.S | 11 |
1 files changed, 4 insertions, 7 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 607d72c4a485..4a4c0834f965 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -36,7 +36,6 @@ #include <asm/smap.h> #include <asm/pgtable_types.h> #include <asm/export.h> -#include <asm/frame.h> #include <linux/err.h> .code64 @@ -406,19 +405,17 @@ END(__switch_to_asm) * r12: kernel thread arg */ ENTRY(ret_from_fork) - FRAME_BEGIN /* help unwinder find end of stack */ movq %rax, %rdi - call schedule_tail /* rdi: 'prev' task parameter */ + call schedule_tail /* rdi: 'prev' task parameter */ - testq %rbx, %rbx /* from kernel_thread? */ - jnz 1f /* kernel threads are uncommon */ + testq %rbx, %rbx /* from kernel_thread? */ + jnz 1f /* kernel threads are uncommon */ 2: - leaq FRAME_OFFSET(%rsp),%rdi /* pt_regs pointer */ + movq %rsp, %rdi call syscall_return_slowpath /* returns with IRQs disabled */ TRACE_IRQS_ON /* user mode is traced as IRQS on */ SWAPGS - FRAME_END jmp restore_regs_and_iret 1: |