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Subject[PATCH v2 1/3] powerpc: Don't force ENOSYS as error on syscall fail
Date
In certain scenarios - e.g. seccomp filtering with ERRNO as default action -
the system call fails for other reasons than the syscall not being available.
The seccomp filter can be configured to store a user-defined error code on
return from a blacklisted syscall. Don't always set ENOSYS on
do_syscall_trace_enter failure.

v2:
- move setting ENOSYS as errno from the syscall entry assembly to
do_syscall_trace_enter, only in the specific case

Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
---
arch/powerpc/kernel/entry_32.S | 2 +-
arch/powerpc/kernel/entry_64.S | 1 -
arch/powerpc/kernel/ptrace.c | 4 +++-
3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 10a0935..d2c58a3 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -425,7 +425,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
b 1b
#endif /* CONFIG_44x */

-66: li r3,-ENOSYS
+66:
b ret_from_syscall

.globl ret_from_fork
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 194e46d..0111e04 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -269,7 +269,6 @@ syscall_dotrace:
b .Lsyscall_dotrace_cont

syscall_enosys:
- li r3,-ENOSYS
b syscall_exit

syscall_exit_work:
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index f21897b..d82fd0b 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -1775,13 +1775,15 @@ long do_syscall_trace_enter(struct pt_regs *regs)
secure_computing_strict(regs->gpr[0]);

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs)) {
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
* error, but leave the original number in regs->gpr[0].
*/
ret = -1L;
+ syscall_set_return_value(current, regs, -ENOSYS, 0);
+ }

if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->gpr[0]);
--
2.1.4


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