[PATCH 5.4 334/389] nios2: add force_successful_syscall_return()

Greg Kroah-Hartman
2022-08-23T11:59:40Z

From: Al Viro <viro@zeniv.linux.org.uk>

commit fd0c153daad135d0ec1a53c5dbe6936a724d6ae1 upstream.

If we use the ancient SysV syscall ABI, we'd better have tell the
kernel how to claim that a negative return value is a success.
Use ->orig_r2 for that - it's inaccessible via ptrace, so it's
a fair game for changes and it's normally[*] non-negative on return
from syscall. Set to -1; syscall is not going to be restart-worthy
by definition, so we won't interfere with that use either.

[*] the only exception is rt_sigreturn(), where we skip the entire
messing with r1/r2 anyway.

Fixes: 82ed08dd1b0e ("nios2: Exception handling")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/nios2/include/asm/ptrace.h | 2 ++
arch/nios2/kernel/entry.S | 6 ++++++
2 files changed, 8 insertions(+)

--- a/arch/nios2/include/asm/ptrace.h
+++ b/arch/nios2/include/asm/ptrace.h
@@ -74,6 +74,8 @@ extern void show_regs(struct pt_regs *);
((struct pt_regs *)((unsigned long)current_thread_info() + THREAD_SIZE)\
- 1)

+#define force_successful_syscall_return() (current_pt_regs()->orig_r2 = -1)
+
int do_syscall_trace_enter(void);
void do_syscall_trace_exit(void);
#endif /* __ASSEMBLY__ */
--- a/arch/nios2/kernel/entry.S
+++ b/arch/nios2/kernel/entry.S
@@ -213,6 +213,9 @@ local_restart:
translate_rc_and_ret:
movi r1, 0
bge r2, zero, 3f
+ ldw r1, PT_ORIG_R2(sp)
+ addi r1, r1, 1
+ beq r1, zero, 3f
sub r2, zero, r2
movi r1, 1
3:
@@ -276,6 +279,9 @@ traced_system_call:
translate_rc_and_ret2:
movi r1, 0
bge r2, zero, 4f
+ ldw r1, PT_ORIG_R2(sp)
+ addi r1, r1, 1
+ beq r1, zero, 4f
sub r2, zero, r2
movi r1, 1
4: