From 93c1800b3799f17375989b0daf76497dd3e80922 Mon Sep 17 00:00:00 2001
From: David Kaplan <david.kaplan@amd.com>
Date: Sun, 2 Jun 2024 13:19:09 -0500
Subject: [PATCH] x86/kexec: Fix bug with call depth tracking
The call to cc_platform_has() triggers a fault and system crash if call depth
tracking is active because the GS segment has been reset by load_segments() and
GS_BASE is now 0 but call depth tracking uses per-CPU variables to operate.
Call cc_platform_has() earlier in the function when GS is still valid.
[ bp: Massage. ]
Fixes: 5d8213864ade ("x86/retbleed: Add SKL return thunk")
Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20240603083036.637-1-bp@kernel.org
---
arch/x86/kernel/machine_kexec_64.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index b180d8e497c31..cc0f7f70b17ba 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -295,8 +295,15 @@ void machine_kexec_cleanup(struct kimage *image)
void machine_kexec(struct kimage *image)
{
unsigned long page_list[PAGES_NR];
- void *control_page;
+ unsigned int host_mem_enc_active;
int save_ftrace_enabled;
+ void *control_page;
+
+ /*
+ * This must be done before load_segments() since if call depth tracking
+ * is used then GS must be valid to make any function calls.
+ */
+ host_mem_enc_active = cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT);
#ifdef CONFIG_KEXEC_JUMP
if (image->preserve_context)
@@ -358,7 +365,7 @@ void machine_kexec(struct kimage *image)
(unsigned long)page_list,
image->start,
image->preserve_context,
- cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT));
+ host_mem_enc_active);
#ifdef CONFIG_KEXEC_JUMP
if (image->preserve_context)
--
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