[PATCH 05/20] signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT

Eric W. Biederman
2021-10-20T17:44:57Z

When an instruction to save or restore a register from the stack fails
in _save_fp_context or _restore_fp_context return with -EFAULT. This
change was made to r2300_fpu.S[1] but it looks like it got lost with
the introduction of EX2[2]. This is also what the other implementation
of _save_fp_context and _restore_fp_context in r4k_fpu.S does, and
what is needed for the callers to be able to handle the error.

Furthermore calling do_exit(SIGSEGV) from bad_stack is wrong because
it does not terminate the entire process it just terminates a single
thread.

As the changed code was the only caller of arch/mips/kernel/syscall.c:bad_stack
remove the problematic and now unused helper function.

Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Maciej Rozycki <macro@orcam.me.uk>
Cc: linux-mips@vger.kernel.org
[1] 35938a00ba86 ("MIPS: Fix ISA I FP sigcontext access violation handling")
[2] f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout")
Fixes: f92722dc4545 ("MIPS: Correct MIPS I FP sigcontext layout")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
arch/mips/kernel/r2300_fpu.S | 4 ++--
arch/mips/kernel/syscall.c | 9 ---------
2 files changed, 2 insertions(+), 11 deletions(-)

diff --git a/arch/mips/kernel/r2300_fpu.S b/arch/mips/kernel/r2300_fpu.S
index 12e58053544f..cbf6db98cfb3 100644
--- a/arch/mips/kernel/r2300_fpu.S
+++ b/arch/mips/kernel/r2300_fpu.S
@@ -29,8 +29,8 @@
#define EX2(a,b) \
9: a,##b; \
.section __ex_table,"a"; \
- PTR 9b,bad_stack; \
- PTR 9b+4,bad_stack; \
+ PTR 9b,fault; \
+ PTR 9b+4,fault; \
.previous

.set mips1
diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 2afa3eef486a..5512cd586e6e 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -240,12 +240,3 @@ SYSCALL_DEFINE3(cachectl, char *, addr, int, nbytes, int, op)
{
return -ENOSYS;
}
-
-/*
- * If we ever come here the user sp is bad. Zap the process right away.
- * Due to the bad stack signaling wouldn't work.
- */
-asmlinkage void bad_stack(void)
-{
- do_exit(SIGSEGV);
-}
--
2.20.1