diff options
Diffstat (limited to 'arch/arm64/include/asm/scs.h')
| -rw-r--r-- | arch/arm64/include/asm/scs.h | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h index 8297bccf0784..ff7da1268a52 100644 --- a/arch/arm64/include/asm/scs.h +++ b/arch/arm64/include/asm/scs.h @@ -5,6 +5,7 @@ #ifdef __ASSEMBLY__ #include <asm/asm-offsets.h> +#include <asm/sysreg.h> #ifdef CONFIG_SHADOW_CALL_STACK scs_sp .req x18 @@ -24,6 +25,54 @@ .endm #endif /* CONFIG_SHADOW_CALL_STACK */ + +#else + +#include <linux/scs.h> +#include <asm/cpufeature.h> + +#ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS +static inline bool should_patch_pac_into_scs(void) +{ + u64 reg; + + /* + * We only enable the shadow call stack dynamically if we are running + * on a system that does not implement PAC or BTI. PAC and SCS provide + * roughly the same level of protection, and BTI relies on the PACIASP + * instructions serving as landing pads, preventing us from patching + * those instructions into something else. + */ + reg = read_sysreg_s(SYS_ID_AA64ISAR1_EL1); + if (SYS_FIELD_GET(ID_AA64ISAR1_EL1, APA, reg) | + SYS_FIELD_GET(ID_AA64ISAR1_EL1, API, reg)) + return false; + + reg = read_sysreg_s(SYS_ID_AA64ISAR2_EL1); + if (SYS_FIELD_GET(ID_AA64ISAR2_EL1, APA3, reg)) + return false; + + if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) { + reg = read_sysreg_s(SYS_ID_AA64PFR1_EL1); + if (reg & (0xf << ID_AA64PFR1_EL1_BT_SHIFT)) + return false; + } + return true; +} + +static inline void dynamic_scs_init(void) +{ + if (should_patch_pac_into_scs()) { + pr_info("Enabling dynamic shadow call stack\n"); + static_branch_enable(&dynamic_scs_enabled); + } +} +#else +static inline void dynamic_scs_init(void) {} +#endif + +int scs_patch(const u8 eh_frame[], int size); + #endif /* __ASSEMBLY __ */ #endif /* _ASM_SCS_H */ |