m68k: Check syscall_trace_enter() return code

[ Upstream commit 2ca8a1de44 ]

Check return code of syscall_trace_enter(), and skip syscall
if -1. Return code will be left at what had been set by
ptrace or seccomp (in regs->d0).

No regression seen in testing with strace on ARAnyM.

Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20230112035529.13521-2-schmitzmic@gmail.com
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/m68k/68000/entry.S

@@ -45,6 +45,8 @@ do_trace:
 	jbsr	syscall_trace_enter
 	RESTORE_SWITCH_STACK
 	addql	#4,%sp
+	addql	#1,%d0
+	jeq	ret_from_exception
 	movel	%sp@(PT_OFF_ORIG_D0),%d1
 	movel	#-ENOSYS,%d0
 	cmpl	#NR_syscalls,%d1

arch/m68k/coldfire/entry.S

@@ -90,6 +90,8 @@ ENTRY(system_call)
 	jbsr	syscall_trace_enter
 	RESTORE_SWITCH_STACK
 	addql	#4,%sp
+	addql	#1,%d0
+	jeq	ret_from_exception
 	movel	%d3,%a0
 	jbsr	%a0@
 	movel	%d0,%sp@(PT_OFF_D0)		/* save the return value */

arch/m68k/kernel/entry.S

@@ -184,9 +184,12 @@ do_trace_entry:
 	jbsr	syscall_trace
 	RESTORE_SWITCH_STACK
 	addql	#4,%sp
+	addql	#1,%d0			| optimization for cmpil #-1,%d0
+	jeq	ret_from_syscall
 	movel	%sp@(PT_OFF_ORIG_D0),%d0
 	cmpl	#NR_syscalls,%d0
 	jcs	syscall
+	jra	ret_from_syscall
 badsys:
 	movel	#-ENOSYS,%sp@(PT_OFF_D0)
 	jra	ret_from_syscall