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authorJosh Poimboeuf <[email protected]>2020-04-25 05:03:02 -0500
committerIngo Molnar <[email protected]>2020-04-25 12:22:27 +0200
commit1fb143634a38095b641a3a21220774799772dc4c (patch)
tree449ca969c81e2fd11704062bef4bb0b640d9e3f8
parent06a9750edcffa808494d56da939085c35904e618 (diff)
x86/entry/64: Fix unwind hints in kernel exit path
In swapgs_restore_regs_and_return_to_usermode, after the stack is switched to the trampoline stack, the existing UNWIND_HINT_REGS hint is no longer valid, which can result in the following ORC unwinder warning: WARNING: can't dereference registers at 000000003aeb0cdd for ip swapgs_restore_regs_and_return_to_usermode+0x93/0xa0 For full correctness, we could try to add complicated unwind hints so the unwinder could continue to find the registers, but when when it's this close to kernel exit, unwind hints aren't really needed anymore and it's fine to just use an empty hint which tells the unwinder to stop. For consistency, also move the UNWIND_HINT_EMPTY in entry_SYSCALL_64_after_hwframe to a similar location. Fixes: 3e3b9293d392 ("x86/entry/64: Return to userspace from the trampoline stack") Reported-by: Vince Weaver <[email protected]> Reported-by: Dave Jones <[email protected]> Reported-by: Dr. David Alan Gilbert <[email protected]> Reported-by: Joe Mario <[email protected]> Reported-by: Jann Horn <[email protected]> Reported-by: Linus Torvalds <[email protected]> Reviewed-by: Miroslav Benes <[email protected]> Signed-off-by: Josh Poimboeuf <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: https://lore.kernel.org/r/60ea8f562987ed2d9ace2977502fe481c0d7c9a0.1587808742.git.jpoimboe@redhat.com
-rw-r--r--arch/x86/entry/entry_64.S3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 0e9504fabe52..6b0d679efd6b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -249,7 +249,6 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
*/
syscall_return_via_sysret:
/* rcx and r11 are already restored (see code above) */
- UNWIND_HINT_EMPTY
POP_REGS pop_rdi=0 skip_r11rcx=1
/*
@@ -258,6 +257,7 @@ syscall_return_via_sysret:
*/
movq %rsp, %rdi
movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
+ UNWIND_HINT_EMPTY
pushq RSP-RDI(%rdi) /* RSP */
pushq (%rdi) /* RDI */
@@ -637,6 +637,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
*/
movq %rsp, %rdi
movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
+ UNWIND_HINT_EMPTY
/* Copy the IRET frame to the trampoline stack. */
pushq 6*8(%rdi) /* SS */