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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_SCS_H
#define _ASM_SCS_H
#ifdef __ASSEMBLY__
#include <asm/asm-offsets.h>
#include <asm/sysreg.h>
#ifdef CONFIG_SHADOW_CALL_STACK
scs_sp .req x18
.macro scs_load_current
get_current_task scs_sp
ldr scs_sp, [scs_sp, #TSK_TI_SCS_SP]
.endm
.macro scs_save tsk
str scs_sp, [\tsk, #TSK_TI_SCS_SP]
.endm
#else
.macro scs_load_current
.endm
.macro scs_save tsk
.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 */
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