arch/arm64/include/asm/scs.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_SCS_H
   3 #define _ASM_SCS_H
   4
   5 #ifdef __ASSEMBLY__
   6
   7 #include <asm/asm-offsets.h>
   8 #include <asm/sysreg.h>
   9
  10 #ifdef CONFIG_SHADOW_CALL_STACK
  11         scs_sp  .req    x18
  12
  13         .macro scs_load_current
  14         get_current_task scs_sp
  15         ldr     scs_sp, [scs_sp, #TSK_TI_SCS_SP]
  16         .endm
  17
  18         .macro scs_save tsk
  19         str     scs_sp, [\tsk, #TSK_TI_SCS_SP]
  20         .endm
  21 #else
  22         .macro scs_load_current
  23         .endm
  24
  25         .macro scs_save tsk
  26         .endm
  27 #endif /* CONFIG_SHADOW_CALL_STACK */
  28
  29
  30 #else
  31
  32 #include <linux/scs.h>
  33 #include <asm/cpufeature.h>
  34
  35 #ifdef CONFIG_UNWIND_PATCH_PAC_INTO_SCS
  36 static inline bool should_patch_pac_into_scs(void)
  37 {
  38         u64 reg;
  39
  40         /*
  41          * We only enable the shadow call stack dynamically if we are running
  42          * on a system that does not implement PAC or BTI. PAC and SCS provide
  43          * roughly the same level of protection, and BTI relies on the PACIASP
  44          * instructions serving as landing pads, preventing us from patching
  45          * those instructions into something else.
  46          */
  47         reg = read_sysreg_s(SYS_ID_AA64ISAR1_EL1);
  48         if (SYS_FIELD_GET(ID_AA64ISAR1_EL1, APA, reg) |
  49             SYS_FIELD_GET(ID_AA64ISAR1_EL1, API, reg))
  50                 return false;
  51
  52         reg = read_sysreg_s(SYS_ID_AA64ISAR2_EL1);
  53         if (SYS_FIELD_GET(ID_AA64ISAR2_EL1, APA3, reg))
  54                 return false;
  55
  56         if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) {
  57                 reg = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
  58                 if (reg & (0xf << ID_AA64PFR1_EL1_BT_SHIFT))
  59                         return false;
  60         }
  61         return true;
  62 }
  63
  64 static inline void dynamic_scs_init(void)
  65 {
  66         if (should_patch_pac_into_scs()) {
  67                 pr_info("Enabling dynamic shadow call stack\n");
  68                 static_branch_enable(&dynamic_scs_enabled);
  69         }
  70 }
  71 #else
  72 static inline void dynamic_scs_init(void) {}
  73 #endif
  74
  75 int __pi_scs_patch(const u8 eh_frame[], int size);
  76 asmlinkage void __pi_scs_patch_vmlinux(void);
  77
  78 #endif /* __ASSEMBLY __ */
  79
  80 #endif /* _ASM_SCS_H */