The following commit has been merged into the x86/cpu branch of tip:
Commit-ID: f220125b999b2c9694149c6bda2798d8096f47ed
Gitweb: https://git.kernel.org/tip/f220125b999b2c9694149c6bda2798d8096f47ed
Author: Borislav Petkov (AMD) <bp@xxxxxxxxx>
AuthorDate: Mon, 15 May 2023 16:07:26 +02:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Wed, 17 May 2023 12:14:21 +02:00
x86/retbleed: Add __x86_return_thunk alignment checks
Add a linker assertion and compute the 0xcc padding dynamically so that
__x86_return_thunk is always cacheline-aligned. Leave the SYM_START()
macro in as the untraining doesn't need ENDBR annotations anyway.
Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230515140726.28689-1-bp@xxxxxxxxx
---
arch/x86/kernel/vmlinux.lds.S | 4 ++++
arch/x86/lib/retpoline.S | 2 +-
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 25f1552..03c885d 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -508,4 +508,8 @@ INIT_PER_CPU(irq_stack_backing_store);
"fixed_percpu_data is not at start of per-cpu area");
#endif
+#ifdef CONFIG_RETHUNK
+. = ASSERT((__x86_return_thunk & 0x3f) == 0, "__x86_return_thunk not cacheline-aligned");
+#endif
+
#endif /* CONFIG_X86_64 */
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index b3b1e37..3fd066d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -143,7 +143,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
* from re-poisioning the BTB prediction.
*/
.align 64
- .skip 63, 0xcc
+ .skip 64 - (__x86_return_thunk - zen_untrain_ret), 0xcc
SYM_START(zen_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
ANNOTATE_NOENDBR
/*
|