MIPS: scall: Always run the seccomp syscall filters
The MIPS syscall handler code used to return -ENOSYS on invalid
syscalls. Whilst this is expected, it caused problems for seccomp
filters because the said filters never had the change to run since
the code returned -ENOSYS before triggering them. This caused
problems on the chromium testsuite for filters looking for invalid
syscalls. This has now changed and the seccomp filters are always
run even if the syscall is invalid. We return -ENOSYS once we
return from the seccomp filters. Moreover, similar codepaths have
been merged in the process which simplifies somewhat the overall
syscall code.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11236/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index d06e30c..65a74e4 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -36,16 +36,8 @@
lw t1, PT_EPC(sp) # skip syscall on return
subu v0, v0, __NR_O32_Linux # check syscall number
- sltiu t0, v0, __NR_O32_Linux_syscalls + 1
addiu t1, 4 # skip to next instruction
sw t1, PT_EPC(sp)
- beqz t0, illegal_syscall
-
- sll t0, v0, 2
- la t1, sys_call_table
- addu t1, t0
- lw t2, (t1) # syscall routine
- beqz t2, illegal_syscall
sw a3, PT_R26(sp) # save a3 for syscall restarting
@@ -96,6 +88,16 @@
li t1, _TIF_WORK_SYSCALL_ENTRY
and t0, t1
bnez t0, syscall_trace_entry # -> yes
+syscall_common:
+ sltiu t0, v0, __NR_O32_Linux_syscalls + 1
+ beqz t0, illegal_syscall
+
+ sll t0, v0, 2
+ la t1, sys_call_table
+ addu t1, t0
+ lw t2, (t1) # syscall routine
+
+ beqz t2, illegal_syscall
jalr t2 # Do The Real Thing (TM)
@@ -116,7 +118,7 @@
syscall_trace_entry:
SAVE_STATIC
- move s0, t2
+ move s0, v0
move a0, sp
/*
@@ -129,27 +131,18 @@
1: jal syscall_trace_enter
- bltz v0, 2f # seccomp failed? Skip syscall
+ bltz v0, 1f # seccomp failed? Skip syscall
- move t0, s0
+ move v0, s0 # restore syscall
+
RESTORE_STATIC
lw a0, PT_R4(sp) # Restore argument registers
lw a1, PT_R5(sp)
lw a2, PT_R6(sp)
lw a3, PT_R7(sp)
- jalr t0
+ j syscall_common
- li t0, -EMAXERRNO - 1 # error?
- sltu t0, t0, v0
- sw t0, PT_R7(sp) # set error flag
- beqz t0, 1f
-
- lw t1, PT_R2(sp) # syscall number
- negu v0 # error
- sw t1, PT_R0(sp) # save it for syscall restarting
-1: sw v0, PT_R2(sp) # result
-
-2: j syscall_exit
+1: j syscall_exit
/* ------------------------------------------------------------------------ */