The kernel can be caused to crash when making the following syscall
sysmips(MIPS_ATOMIC_SET, [unaligned addr], value, 0);
The latest mips_atomic_set does not use the fixups that are defined
for the ll/sc instructions.
If an unaligned address is passed in we take the exception and
unaligned.c:emulate_load_store_insn ignores the fixups for the
ll/sc and sends a SIGBUS instead, thus causing the kernel to die.
The patch is to make the ll/sc instructions lookup the fixup table
and do them if present.
Also the fixup for the instructions in scall_o32.S appears to be
inappropriate, so the fixup is set to be bad_addr and an -EFAULT
is returned from the syscall.
--- ../sgi-cvs/arch/mips/kernel/unaligned.c Mon Dec 3 10:49:23 2001
+++ arch/mips/kernel/unaligned.c Thu Dec 6 15:07:00 2001
@@ -114,12 +114,14 @@
* These are instructions that a compiler doesn't generate. We
* can assume therefore that the code is MIPS-aware and
* really buggy. Emulating these instructions would break the
- * semantics anyway.
+ * semantics anyway. However, we do want to look at the exception
+ * table to see if we can exit gracefully.
+ goto fault;
* For these instructions the only way to create an address
--- ../sgi-cvs/arch/mips/kernel/scall_o32.S Mon Oct 8 09:56:02 2001
+++ arch/mips/kernel/scall_o32.S Thu Dec 6 15:34:47 2001
@@ -201,7 +201,7 @@
or a0, a0, a1
li v0, -EFAULT
and a0, a0, v1
- bltz a0, 8f
+ bltz a0, bad_address
/* Ok, this is the ll/sc case. World is sane :-) */
@@ -211,8 +211,8 @@
beqz a0, 1b
- PTR 1b, bad_stack
- PTR 2b, bad_stack
+ PTR 1b, bad_address
+ PTR 2b, bad_address
sw a1, 16(sp)
@@ -256,8 +256,9 @@
no_mem: li v0, -ENOMEM
-8: li v0, -EFAULT
-9: jr ra
+ li v0, -EFAULT
+ jr ra