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powerpc/kernel: Change the do_syscall_trace_enter() API

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The API for calling do_syscall_trace_enter() is currently sensible
enough, it just returns the (modified) syscall number.

However once we enable seccomp filter it will get more complicated. When
seccomp filter runs, the seccomp kernel code (via SECCOMP_RET_ERRNO), or
a ptracer (via SECCOMP_RET_TRACE), may reject the syscall and *may* or may
*not* set a return value in r3.

That means the assembler that calls do_syscall_trace_enter() can not
blindly return ENOSYS, it needs to only return ENOSYS if a return value
has not already been set.

There is no way to implement that logic with the current API. So change
the do_syscall_trace_enter() API to make it deal with the return code
juggling, and the assembler can then just return whatever return code it
is given.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Michael Ellerman
2015-07-23 20:21:02 +10:00
parent c3525940cc
commit d38374142b
3 changed files with 58 additions and 17 deletions
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4
arch/powerpc/kernel/entry_32.S
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@@ -458,6 +458,10 @@ syscall_dotrace:
lwz r7,GPR7(r1)
lwz r8,GPR8(r1)
REST_NVGPRS(r1)
cmplwi r0,NR_syscalls
/* Return code is already in r3 thanks to do_syscall_trace_enter() */
bge- ret_from_syscall
b syscall_dotrace_cont
syscall_exit_work: