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arm64: asm: Override SYM_FUNC_START when building the kernel with BTI

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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_x macros is for the
benefit of the macro-generated functions in xen-hypercall.S.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20200506195138.22086-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Brown 2020-05-06 20:51:30 +01:00 committed by Will Deacon
parent 92e2294d87
commit 714a8d02ca
1 changed files with 46 additions and 0 deletions
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46
arch/arm64/include/asm/linkage.h
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@ -4,6 +4,52 @@
#define __ALIGN .align 2
#define __ALIGN_STR ".align 2"
#if defined(CONFIG_ARM64_BTI_KERNEL) && defined(__aarch64__)
/*
* 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.