[PATCH v6 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL
From: Kees Cook <hidden>
Date: 2014-08-21 16:47:34
Also in:
lkml
On Thu, Aug 21, 2014 at 3:56 AM, AKASHI Takahiro [off-list ref] wrote:
To allow tracer to be able to change/skip a system call by re-writing
a syscall number, there are several approaches:
(1) modify x8 register with ptrace(PTRACE_SETREGSET), and handle this case
later on in syscall_trace_enter(), or
(2) support ptrace(PTRACE_SET_SYSCALL) as on 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
to be visible, especially case of -1, before this function returns in
syscall_trace_enter(), we'd better take (2).
Signed-off-by: AKASHI Takahiro <redacted>Thanks, I like having this on both arm and arm64. I wonder if other archs should add this option too. Reviewed-by: Kees Cook <redacted>
quoted hunk ↗ jump to hunk
--- arch/arm64/include/uapi/asm/ptrace.h | 1 + arch/arm64/kernel/ptrace.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-)diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index 6913643..49c6174 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h@@ -23,6 +23,7 @@ #include <asm/hwcap.h> +#define PTRACE_SET_SYSCALL 23 /* * PSR bitsdiff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 0310811..8876049 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c@@ -1077,7 +1077,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task) long arch_ptrace(struct task_struct *child, long request, unsigned long addr, unsigned long data) { - return ptrace_request(child, request, addr, data); + int ret; + + switch (request) { + case PTRACE_SET_SYSCALL: + task_pt_regs(child)->syscallno = data; + ret = 0; + break; + default: + ret = ptrace_request(child, request, addr, data); + break; + } + + return ret; } enum ptrace_syscall_dir { --1.7.9.5
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