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From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org
Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
	Keith Packard <keithpac@amazon.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Marc Zyngier <maz@kernel.org>
Subject: [PATCH v6 4/8] ARM: entry: avoid clobbering R9 in IRQ handler
Date: Tue, 25 Jan 2022 10:14:49 +0100	[thread overview]
Message-ID: <20220125091453.1475246-5-ardb@kernel.org> (raw)
In-Reply-To: <20220125091453.1475246-1-ardb@kernel.org>

Avoid using R9 in the IRQ handler code, as the entry code uses it for
tsk, and expects it to remain untouched between the IRQ entry and exit
code.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm/kernel/entry-armv.S | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index b58bda51e4b8..038aabb6578f 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -38,11 +38,10 @@
 #ifdef CONFIG_UNWINDER_ARM
 	mov	fpreg, sp		@ Preserve original SP
 #else
-	mov	r8, fp			@ Preserve original FP
-	mov	r9, sp			@ Preserve original SP
+	mov	r7, fp			@ Preserve original FP
+	mov	r8, sp			@ Preserve original SP
 #endif
 	ldr_this_cpu sp, irq_stack_ptr, r2, r3
-
 	.if	\from_user == 0
 UNWIND(	.setfp	fpreg, sp		)
 	@
@@ -82,8 +81,8 @@ UNWIND(	.setfp	fpreg, sp		)
 #ifdef CONFIG_UNWINDER_ARM
 	mov	sp, fpreg		@ Restore original SP
 #else
-	mov	fp, r8			@ Restore original FP
-	mov	sp, r9			@ Restore original SP
+	mov	fp, r7			@ Restore original FP
+	mov	sp, r8			@ Restore original SP
 #endif // CONFIG_UNWINDER_ARM
 #endif // CONFIG_IRQSTACKS
 	.endm
-- 
2.30.2


WARNING: multiple messages have this Message-ID (diff)
From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org
Cc: linux-hardening@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
	Keith Packard <keithpac@amazon.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Marc Zyngier <maz@kernel.org>
Subject: [PATCH v6 4/8] ARM: entry: avoid clobbering R9 in IRQ handler
Date: Tue, 25 Jan 2022 10:14:49 +0100	[thread overview]
Message-ID: <20220125091453.1475246-5-ardb@kernel.org> (raw)
In-Reply-To: <20220125091453.1475246-1-ardb@kernel.org>

Avoid using R9 in the IRQ handler code, as the entry code uses it for
tsk, and expects it to remain untouched between the IRQ entry and exit
code.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm/kernel/entry-armv.S | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index b58bda51e4b8..038aabb6578f 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -38,11 +38,10 @@
 #ifdef CONFIG_UNWINDER_ARM
 	mov	fpreg, sp		@ Preserve original SP
 #else
-	mov	r8, fp			@ Preserve original FP
-	mov	r9, sp			@ Preserve original SP
+	mov	r7, fp			@ Preserve original FP
+	mov	r8, sp			@ Preserve original SP
 #endif
 	ldr_this_cpu sp, irq_stack_ptr, r2, r3
-
 	.if	\from_user == 0
 UNWIND(	.setfp	fpreg, sp		)
 	@
@@ -82,8 +81,8 @@ UNWIND(	.setfp	fpreg, sp		)
 #ifdef CONFIG_UNWINDER_ARM
 	mov	sp, fpreg		@ Restore original SP
 #else
-	mov	fp, r8			@ Restore original FP
-	mov	sp, r9			@ Restore original SP
+	mov	fp, r7			@ Restore original FP
+	mov	sp, r8			@ Restore original SP
 #endif // CONFIG_UNWINDER_ARM
 #endif // CONFIG_IRQSTACKS
 	.endm
-- 
2.30.2


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2022-01-25  9:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-25  9:14 [PATCH v6 0/8] ARM vmap'ed and IRQ stacks roundup Ard Biesheuvel
2022-01-25  9:14 ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 1/8] ARM: mm: switch to swapper_pg_dir early for vmap'ed stack Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 2/8] ARM: assembler: define a Kconfig symbol for group relocation support Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 3/8] ARM: smp: elide HWCAP_TLS checks or __entry_task updates on SMP+v6 Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` Ard Biesheuvel [this message]
2022-01-25  9:14   ` [PATCH v6 4/8] ARM: entry: avoid clobbering R9 in IRQ handler Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 5/8] ARM: mm: make vmalloc_seq handling SMP safe Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 6/8] ARM: iop: make iop_handle_irq() static Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 7/8] ARM: drop pointless SMP check on secondary startup path Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25  9:14 ` [PATCH v6 8/8] ARM: make get_current() and __my_cpu_offset() __always_inline Ard Biesheuvel
2022-01-25  9:14   ` Ard Biesheuvel
2022-01-25 20:48   ` Nick Desaulniers
2022-01-25 20:48     ` Nick Desaulniers

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