On Thu, Dec 26, 2024 at 11:21:59PM +0800, Celeste Liu wrote:
>
> On 2024-12-26 21:35, Dmitry V. Levin wrote:
> > On Thu, Dec 26, 2024 at 06:52:52PM +0800, Celeste Liu wrote:
> >> This test checks that orig_a0 allows a syscall argument to be modified,
> >> and that changing a0 does not change the syscall argument.
> >>
> >> Co-developed-by: Quan Zhou <zhouquan@xxxxxxxxxxx>
> >> Signed-off-by: Quan Zhou <zhouquan@xxxxxxxxxxx>
> >> Co-developed-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> >> Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> >> Reviewed-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
> >> Signed-off-by: Celeste Liu <uwu@xxxxxxxxxxxxxxxxx>
> > [...]
> >> diff --git a/tools/testing/selftests/riscv/abi/ptrace.c b/tools/testing/selftests/riscv/abi/ptrace.c
> >> new file mode 100644
> >> index 0000000000000000000000000000000000000000..023695352215bb5de3f91c1a6f5ea3b4f9373ff9
> >> --- /dev/null
> >> +++ b/tools/testing/selftests/riscv/abi/ptrace.c
> > [...]
> >> + if (ptrace(PTRACE_GET_SYSCALL_INFO, pid, PTRACE_SYSCALL_INFO_ENTRY, &syscall_info_entry))
> >> + perr_and_exit("failed to get syscall info of entry\n");
> >> + result->orig_a0 = syscall_info_entry->entry.args[0];
> >> + if (ptrace(PTRACE_GET_SYSCALL_INFO, pid, PTRACE_SYSCALL_INFO_EXIT, &syscall_info_exit))
> >> + perr_and_exit("failed to get syscall info of exit\n");
> >> + result->a0 = syscall_info_exit->exit.rval;
> >
> > I'm sorry but this is not how PTRACE_GET_SYSCALL_INFO should be used.
> >
> > PTRACE_GET_SYSCALL_INFO operation takes a pointer and a size,
> > and in this example instead of size you pass constants 1 and 2, which
> > essentially means that both syscall_info_entry->entry.args[0] and
> > syscall_info_exit->exit.rval are not going to be assigned
> > and would just contain some garbage from the stack.
> >
> > Also, PTRACE_GET_SYSCALL_INFO operation returns the number of bytes
> > available to be written by the kernel, which is always nonzero on any
> > PTRACE_GET_SYSCALL_INFO-capable kernel. In other words, this example
> > will always end up with perr_and_exit() call.
> >
> > I wonder how this test was tested before the submission.
>
> Oops... It seems I forget sync the code to test board so it runs with the old code...
> The code is completely not tested...
> I'm so sorry for my mistake.
>
> I will correct it and test it carefully later...
It would be great to get this into 6.14. Let me know if you would like
any help!
- Charlie
>
> >
> >
>
