This is a note to let you know that I've just added the patch titled
x86/entry/64: Fix unwind hints in __switch_to_asm()
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-entry-64-fix-unwind-hints-in-__switch_to_asm.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 96c64806b4bf35f5edb465cafa6cec490e424a30 Mon Sep 17 00:00:00 2001
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Sat, 25 Apr 2020 05:03:03 -0500
Subject: x86/entry/64: Fix unwind hints in __switch_to_asm()
From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
commit 96c64806b4bf35f5edb465cafa6cec490e424a30 upstream.
UNWIND_HINT_FUNC has some limitations: specifically, it doesn't reset
all the registers to undefined. This causes objtool to get confused
about the RBP push in __switch_to_asm(), resulting in bad ORC data.
While __switch_to_asm() does do some stack magic, it's otherwise a
normal callable-from-C function, so just annotate it as a function,
which makes objtool happy and allows it to produces the correct hints
automatically.
Fixes: 8c1f75587a18 ("x86/entry/64: Add unwind hint annotations")
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Jones <dsj@xxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Link: https://lore.kernel.org/r/03d0411920d10f7418f2e909210d8e9a3b2ab081.1587808742.git.jpoimboe@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/entry_64.S | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -279,8 +279,7 @@ SYM_CODE_END(entry_SYSCALL_64)
* %rdi: prev task
* %rsi: next task
*/
-SYM_CODE_START(__switch_to_asm)
- UNWIND_HINT_FUNC
+SYM_FUNC_START(__switch_to_asm)
/*
* Save callee-saved registers
* This must match the order in inactive_task_frame
@@ -321,7 +320,7 @@ SYM_CODE_START(__switch_to_asm)
popq %rbp
jmp __switch_to
-SYM_CODE_END(__switch_to_asm)
+SYM_FUNC_END(__switch_to_asm)
/*
* A newly forked process directly context switches into this address.
Patches currently in stable-queue which might be from jpoimboe@xxxxxxxxxx are
queue-5.6/x86-entry-64-fix-unwind-hints-in-kernel-exit-path.patch
queue-5.6/x86-unwind-orc-don-t-skip-the-first-frame-for-inactive-tasks.patch
queue-5.6/x86-unwind-orc-prevent-unwinding-before-orc-initialization.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-__switch_to_asm.patch
queue-5.6/x86-unwind-orc-fix-error-path-for-bad-orc-entry-type.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-rewind_stack_do_exit.patch
queue-5.6/x86-unwind-orc-fix-premature-unwind-stoppage-due-to-iret-frames.patch
queue-5.6/x86-entry-64-fix-unwind-hints-in-register-clearing-code.patch
queue-5.6/objtool-fix-stack-offset-tracking-for-indirect-cfas.patch
queue-5.6/kvm-vmx-explicitly-clear-rflags.cf-and-rflags.zf-in-vm-exit-rsb-path.patch
