Commit 945fb68f authored Sep 04, 2014 by AKASHI Takahiro Committed by Ruchi Kandoi Feb 04, 2015

arm64: ptrace: add PTRACE_SET_SYSCALL



Note: This patch is from v6 of Takahiro's proposed
"arm64: add seccomp support" patchset (leecam@google.com)

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 <takahiro.akashi@linaro.org>

parent a77185d6

arch/arm64/include/uapi/asm/ptrace.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -23,6 +23,7 @@

		#include <asm/hwcap.h>

		#define PTRACE_SET_SYSCALL 23

		/*
		* PSR bits

arch/arm64/kernel/ptrace.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -1082,7 +1082,19 @@ 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 {