This regeset is intended to be used to get and set a system call number while tracing. There was some discussion about possible approaches to do so:
(1) modify x8 register with ptrace(PTRACE_SETREGSET) indirectly, and update regs->syscallno later on in syscall_trace_enter(), or (2) define a dedicated regset for this purpose as on s390, or (3) support ptrace(PTRACE_SET_SYSCALL) as on arch/arm
Thinking of the fact that user_pt_regs doesn't expose 'syscallno' to tracer as well as that secure_computing() expects a changed syscall number, especially case of -1, to be visible before this function returns in syscall_trace_enter(), (1) doesn't work well. We will take (2) since it looks much cleaner.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- arch/arm64/kernel/ptrace.c | 35 +++++++++++++++++++++++++++++++++++ include/uapi/linux/elf.h | 1 + 2 files changed, 36 insertions(+)
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 8a4ae8e..f576781 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -551,6 +551,32 @@ static int tls_set(struct task_struct *target, const struct user_regset *regset, return ret; }
+static int system_call_get(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + void *kbuf, void __user *ubuf) +{ + int syscallno = task_pt_regs(target)->syscallno; + + return user_regset_copyout(&pos, &count, &kbuf, &ubuf, + &syscallno, 0, -1); +} + +static int system_call_set(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + int syscallno, ret; + + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &syscallno, 0, -1); + if (ret) + return ret; + + task_pt_regs(target)->syscallno = syscallno; + return ret; +} + enum aarch64_regset { REGSET_GPR, REGSET_FPR, @@ -559,6 +585,7 @@ enum aarch64_regset { REGSET_HW_BREAK, REGSET_HW_WATCH, #endif + REGSET_SYSTEM_CALL, };
static const struct user_regset aarch64_regsets[] = { @@ -608,6 +635,14 @@ static const struct user_regset aarch64_regsets[] = { .set = hw_break_set, }, #endif + [REGSET_SYSTEM_CALL] = { + .core_note_type = NT_ARM_SYSTEM_CALL, + .n = 1, + .size = sizeof(int), + .align = sizeof(int), + .get = system_call_get, + .set = system_call_set, + }, };
static const struct user_regset_view user_aarch64_view = { diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index ea9bf25..71e1d0e 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -397,6 +397,7 @@ typedef struct elf64_shdr { #define NT_ARM_TLS 0x401 /* ARM TLS register */ #define NT_ARM_HW_BREAK 0x402 /* ARM hardware breakpoint registers */ #define NT_ARM_HW_WATCH 0x403 /* ARM hardware watchpoint registers */ +#define NT_ARM_SYSTEM_CALL 0x404 /* ARM system call number */ #define NT_METAG_CBUF 0x500 /* Metag catch buffer registers */ #define NT_METAG_RPIPE 0x501 /* Metag read pipeline state */ #define NT_METAG_TLS 0x502 /* Metag TLS pointer */