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Subject[PATCH v6 11/13] arm64: add ptrace regsets for ptrauth key management
Date
Add two new ptrace regsets, which can be used to request and change the
pointer authentication keys of a thread. NT_ARM_PACA_KEYS gives access
to the instruction/data address keys, and NT_ARM_PACG_KEYS to the
generic authentication key.

The regsets are only exposed if the kernel is compiled with
CONFIG_CHECKPOINT_RESTORE=y, as the intended use case is checkpointing
and restoring processes that are using pointer authentication. Normally
applications or debuggers should not need to know the keys (and exposing
the keys is a security risk), so the regsets are not exposed by default.

Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
---
arch/arm64/include/uapi/asm/ptrace.h | 18 +++++++++
arch/arm64/kernel/ptrace.c | 72 ++++++++++++++++++++++++++++++++++++
include/uapi/linux/elf.h | 2 +
3 files changed, 92 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index c2f249bcd829..fafa7f6decf9 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h
@@ -236,6 +236,24 @@ struct user_pac_mask {
__u64 insn_mask;
};

+/* pointer authentication keys (NT_ARM_PACA_KEYS, NT_ARM_PACG_KEYS) */
+
+struct user_pac_address_keys {
+ __u64 apiakey_lo;
+ __u64 apiakey_hi;
+ __u64 apibkey_lo;
+ __u64 apibkey_hi;
+ __u64 apdakey_lo;
+ __u64 apdakey_hi;
+ __u64 apdbkey_lo;
+ __u64 apdbkey_hi;
+};
+
+struct user_pac_generic_keys {
+ __u64 apgakey_lo;
+ __u64 apgakey_hi;
+};
+
#endif /* __ASSEMBLY__ */

#endif /* _UAPI__ASM_PTRACE_H */
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 6c1f63cb6c4e..f18f14c64d1e 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -979,6 +979,56 @@ static int pac_mask_get(struct task_struct *target,

return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &uregs, 0, -1);
}
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static int pac_address_keys_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ void *kbuf, void __user *ubuf)
+{
+ if (!system_supports_address_auth())
+ return -EINVAL;
+
+ return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+ &target->thread_info.keys_user, 0, -1);
+}
+
+static int pac_address_keys_set(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ const void *kbuf, const void __user *ubuf)
+{
+ if (!system_supports_address_auth())
+ return -EINVAL;
+
+ return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread_info.keys_user, 0, -1);
+}
+
+static int pac_generic_keys_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ void *kbuf, void __user *ubuf)
+{
+ if (!system_supports_generic_auth())
+ return -EINVAL;
+
+ return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+ &target->thread_info.keys_user.apga, 0, -1);
+}
+
+static int pac_generic_keys_set(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ const void *kbuf, const void __user *ubuf)
+{
+ if (!system_supports_generic_auth())
+ return -EINVAL;
+
+ return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread_info.keys_user.apga, 0, -1);
+}
+#endif /* CONFIG_CHECKPOINT_RESTORE */
#endif /* CONFIG_ARM64_PTR_AUTH */

enum aarch64_regset {
@@ -995,6 +1045,10 @@ enum aarch64_regset {
#endif
#ifdef CONFIG_ARM64_PTR_AUTH
REGSET_PAC_MASK,
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ REGSET_PACA_KEYS,
+ REGSET_PACG_KEYS,
+#endif
#endif
};

@@ -1074,6 +1128,24 @@ static const struct user_regset aarch64_regsets[] = {
.get = pac_mask_get,
/* this cannot be set dynamically */
},
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ [REGSET_PACA_KEYS] = {
+ .core_note_type = NT_ARM_PACA_KEYS,
+ .n = sizeof(struct user_pac_address_keys) / sizeof(u64),
+ .size = sizeof(u64),
+ .align = sizeof(u64),
+ .get = pac_address_keys_get,
+ .set = pac_address_keys_set,
+ },
+ [REGSET_PACG_KEYS] = {
+ .core_note_type = NT_ARM_PACG_KEYS,
+ .n = sizeof(struct user_pac_generic_keys) / sizeof(u64),
+ .size = sizeof(u64),
+ .align = sizeof(u64),
+ .get = pac_generic_keys_get,
+ .set = pac_generic_keys_set,
+ },
+#endif
#endif
};

diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 3f23273d690c..c1afbc592531 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -421,6 +421,8 @@ typedef struct elf64_shdr {
#define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */
#define NT_ARM_SVE 0x405 /* ARM Scalable Vector Extension registers */
#define NT_ARM_PAC_MASK 0x406 /* ARM pointer authentication code masks */
+#define NT_ARM_PACA_KEYS 0x407 /* ARM pointer authentication address keys */
+#define NT_ARM_PACG_KEYS 0x408 /* ARM pointer authentication generic key */
#define NT_ARC_V2 0x600 /* ARCv2 accumulator/extra registers */
#define NT_VMCOREDD 0x700 /* Vmcore Device Dump Note */
#define NT_MIPS_DSP 0x800 /* MIPS DSP ASE registers */
--
2.11.0
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