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[PATCH] x86: Fix check_ist_exit() assertions
- To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Tue, 19 Sep 2023 11:35:14 +0100
- Authentication-results: esa2.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none
- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Tue, 19 Sep 2023 10:35:28 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
The patch adding check_ist_exit() neglected to consider reset_stack_and_jump()
leaving C and entering one of the Xen exit paths. The value in %r12 is stale,
and depending on compiler decisions may not be 0.
This shows up in Gitlab CI for the Clang build:
https://gitlab.com/xen-project/people/andyhhp/xen/-/jobs/5112783827
and in OSSTest for GCC 8:
http://logs.test-lab.xenproject.org/osstest/logs/183045/test-amd64-amd64-xl-qemuu-debianhvm-amd64/serial-pinot0.log
The justification for ensuring ist_exit is accurate in the exit paths still
stands, so zero %r12 in reset_stack_and_jump() to indicate a non-IST exit.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
xen/arch/x86/include/asm/current.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/xen/arch/x86/include/asm/current.h
b/xen/arch/x86/include/asm/current.h
index da5e152a10cc..2ce43e275784 100644
--- a/xen/arch/x86/include/asm/current.h
+++ b/xen/arch/x86/include/asm/current.h
@@ -178,6 +178,7 @@ unsigned long get_stack_dump_bottom (unsigned long sp);
SHADOW_STACK_WORK \
"mov %[stk], %%rsp;" \
CHECK_FOR_LIVEPATCH_WORK \
+ "xor %%r12d, %%r12d;" /* non-IST exit */ \
instr "[fun]" \
: [val] "=&r" (tmp), \
[ssp] "=&r" (tmp) \
base-commit: ea36ac0de27c2a7c847a2a52c3e0f97a45864d81
--
2.30.2
|
