/* 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);
asmlinkage void scs_patch_vmlinux(void);

#endif /* __ASSEMBLY __ */

#endif /* _ASM_SCS_H */