From: Lai Jiangshan jiangshan.ljs@antgroup.com
[ Upstream commit c42b145181aafd59ed31ccd879493389e3ea5a08 ]
In idtentry_vc(), vc_switch_off_ist() determines a safe stack to switch to, off of the IST stack. Annotate the new stack switch with ENCODE_FRAME_POINTER in case UNWINDER_FRAME_POINTER is used.
A stack walk before looks like this:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-rc7+ #2 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dump_stack_lvl dump_stack kernel_exc_vmm_communication asm_exc_vmm_communication ? native_read_msr ? __x2apic_disable.part.0 ? x2apic_setup ? cpu_init ? trap_init ? start_kernel ? x86_64_start_reservations ? x86_64_start_kernel ? secondary_startup_64_no_verify </TASK>
and with the fix, the stack dump is exact:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.18.0-rc7+ #3 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dump_stack_lvl dump_stack kernel_exc_vmm_communication asm_exc_vmm_communication RIP: 0010:native_read_msr Code: ... < snipped regs > ? __x2apic_disable.part.0 x2apic_setup cpu_init trap_init start_kernel x86_64_start_reservations x86_64_start_kernel secondary_startup_64_no_verify </TASK>
[ bp: Test in a SEV-ES guest and rewrite the commit message to explain what exactly this does. ]
Fixes: a13644f3a53d ("x86/entry/64: Add entry code for #VC handler") Signed-off-by: Lai Jiangshan jiangshan.ljs@antgroup.com Signed-off-by: Borislav Petkov bp@suse.de Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lore.kernel.org/r/20220316041612.71357-1-jiangshanlai@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/entry/entry_64.S | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 466df3e50276..f7a0cc261b14 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -499,6 +499,7 @@ SYM_CODE_START(\asmsym) call vc_switch_off_ist movq %rax, %rsp /* Switch to new stack */
+ ENCODE_FRAME_POINTER UNWIND_HINT_REGS
/* Update pt_regs */