linux-kernel - [PATCH v6 04/15] x86/pvh: Use fixed_percpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250123190747.745588-5-brgerst@gmail.com>
Date: Thu, 23 Jan 2025 14:07:36 -0500
From: Brian Gerst <brgerst@...il.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Uros Bizjak <ubizjak@...il.com>,
	Brian Gerst <brgerst@...il.com>
Subject: [PATCH v6 04/15] x86/pvh: Use fixed_percpu_data for early boot GSBASE

Instead of having a private area for the stack canary, use
fixed_percpu_data for GSBASE like the native kernel.

Signed-off-by: Brian Gerst <brgerst@...il.com>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/platform/pvh/head.S | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 4733a5f467b8..fa0072e0ca43 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -173,10 +173,15 @@ SYM_CODE_START(pvh_start_xen)
 1:
 	UNWIND_HINT_END_OF_STACK
 
-	/* Set base address in stack canary descriptor. */
-	mov $MSR_GS_BASE,%ecx
-	leal canary(%rip), %eax
-	xor %edx, %edx
+	/*
+	 * Set up GSBASE.
+	 * Note that, on SMP, the boot cpu uses init data section until
+	 * the per cpu areas are set up.
+	 */
+	movl $MSR_GS_BASE,%ecx
+	leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+	movq %edx, %eax
+	shrq $32, %rdx
 	wrmsr
 
 	/* Call xen_prepare_pvh() via the kernel virtual mapping */
@@ -238,8 +243,6 @@ SYM_DATA_START_LOCAL(gdt_start)
 SYM_DATA_END_LABEL(gdt_start, SYM_L_LOCAL, gdt_end)
 
 	.balign 16
-SYM_DATA_LOCAL(canary, .fill 48, 1, 0)
-
 SYM_DATA_START_LOCAL(early_stack)
 	.fill BOOT_STACK_SIZE, 1, 0
 SYM_DATA_END_LABEL(early_stack, SYM_L_LOCAL, early_stack_end)
-- 
2.47.1