From: Mark Brown <broonie@kernel•org>
To: Catalin Marinas <catalin.marinas@arm•com>, Will Deacon <will@kernel•org>
Cc: Mark Brown <broonie@kernel•org>,
Kees Cook <keescook@chromium•org>,
linux-arm-kernel@lists•infradead.org
Subject: [PATCH 2/5] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI
Date: Fri, 27 Mar 2020 19:21:04 +0000 [thread overview]
Message-ID: <20200327192107.18394-3-broonie@kernel.org> (raw)
In-Reply-To: <20200327192107.18394-1-broonie@kernel.org>
When the kernel is built for BTI override SYM_FUNC_START and related macros
to add a BTI landing pad to the start of all global functions, ensuring that
they are BTI safe. The ; at the end of the BTI_C macro is for the benefit of
the macro-generated functions in xen-hypercall.S.
Signed-off-by: Mark Brown <broonie@kernel•org>
---
arch/arm64/include/asm/linkage.h | 46 ++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h
index ebee3113a62f..d8d5b0f77216 100644
--- a/arch/arm64/include/asm/linkage.h
+++ b/arch/arm64/include/asm/linkage.h
@@ -4,6 +4,52 @@
#define __ALIGN .align 2
#define __ALIGN_STR ".align 2"
+#ifdef CONFIG_ARM64_BTI_KERNEL
+
+/*
+ * Since current versions of gas reject the BTI instruction unless we
+ * set the architecture version to v8.5 we use the hint instruction
+ * instead.
+ */
+#define BTI_C hint 34 ;
+#define BTI_J hint 36 ;
+
+/*
+ * When using in-kernel BTI we need to ensure that assembly functions
+ * have suitable annotations. Override SYM_FUNC_START to insert a BTI
+ * landing pad at the start of everything.
+ */
+#define SYM_FUNC_START(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) \
+ BTI_C
+
+#define SYM_FUNC_START_NOALIGN(name) \
+ SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE) \
+ BTI_C
+
+#define SYM_FUNC_START_LOCAL(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN) \
+ BTI_C
+
+#define SYM_FUNC_START_LOCAL_NOALIGN(name) \
+ SYM_START(name, SYM_L_LOCAL, SYM_A_NONE) \
+ BTI_C
+
+#define SYM_FUNC_START_WEAK(name) \
+ SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN) \
+ BTI_C
+
+#define SYM_FUNC_START_WEAK_NOALIGN(name) \
+ SYM_START(name, SYM_L_WEAK, SYM_A_NONE) \
+ BTI_C
+
+#define SYM_INNER_LABEL(name, linkage) \
+ .type name SYM_T_NONE ASM_NL \
+ SYM_ENTRY(name, linkage, SYM_A_NONE) \
+ BTI_J
+
+#endif
+
/*
* Annotate a function as position independent, i.e., safe to be called before
* the kernel virtual mapping is activated.
--
2.20.1
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next prev parent reply other threads:[~2020-03-27 19:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-27 19:21 [PATCH 0/5] arm64: Initial BTI kernel support Mark Brown
2020-03-27 19:21 ` [PATCH 1/5] arm64: bti: Support building kernel C code using BTI Mark Brown
2020-03-28 21:14 ` Kees Cook
2020-03-30 11:33 ` Mark Brown
2020-03-30 18:06 ` Kees Cook
2020-03-31 15:21 ` Mark Brown
2020-03-27 19:21 ` Mark Brown [this message]
2020-03-27 19:21 ` [PATCH 3/5] arm64: Set GP bit in kernel page tables to enable BTI for the kernel Mark Brown
2020-03-27 19:21 ` [PATCH 4/5] arm64: mm: Mark module text as guarded pages Mark Brown
2020-03-27 19:21 ` [PATCH 5/5] arm64: bti: Provide Kconfig for kernel mode BTI Mark Brown
2020-03-28 21:19 ` Kees Cook
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