Hi Wilson,
Wilson Callan wrote:
I've been seeing an occasional Illegal Instruction exception on the 5235
coldfire and found that its due to arch/m68knommu/kernel/signal.c which
has an empty push_cache(). I'm using a 100ms ITIMER so there are many
opportunities for this bug.
You cannot put instructions in memory and expect the processor to run
them without flushing the instruction cache. To fix this i've recoded
the return from the user space signal handler to not use instructions on
the stack. Doing it this way is more straight forward and doesnt
require a cache flush (which creates inefficient memory access).
If you dont choose to integrate this patch, also note that there most
likely a bug in setup_rt_frame() where it dangerously goes ahead and
puts machine code on the stack. the 0x4600 instruction is not a "not.l
d0" instruction as the comment suggests.
Here is a slightly reworked version.
It corrects the assembler ret_from_user_rt_signal code so that
it is setting the correct system call number. It also removes the
now dead push_cache() function.
Regards
Greg
------------------------------------------------------------------------
Greg Ungerer -- Chief Software Dude EMAIL: [EMAIL PROTECTED]
Secure Computing Corporation PHONE: +61 7 3435 2888
825 Stanley St, FAX: +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia WEB: http://www.SnapGear.com
--- linux-2.6.x/arch/m68knommu/kernel/signal.c 28 Aug 2007 06:31:25 -0000 1.21
+++ linux-2.6.x/arch/m68knommu/kernel/signal.c 12 Mar 2008 06:48:44 -0000
@@ -51,6 +51,8 @@
#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
+void ret_from_user_signal(void);
+void ret_from_user_rt_signal(void);
asmlinkage int do_signal(sigset_t *oldset, struct pt_regs *regs);
/*
@@ -539,10 +541,6 @@
return err;
}
-static inline void push_cache (unsigned long vaddr)
-{
-}
-
static inline void *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size)
{
@@ -586,16 +584,11 @@
err |= copy_to_user (&frame->sc, &context, sizeof(context));
/* Set up to return from userspace. */
- err |= __put_user(frame->retcode, &frame->pretcode);
- /* moveq #,d0; trap #0 */
- err |= __put_user(0x70004e40 + (__NR_sigreturn << 16),
- (long *)(frame->retcode));
+ err |= __put_user((void *) ret_from_user_signal, &frame->pretcode);
if (err)
goto give_sigsegv;
- push_cache ((unsigned long) &frame->retcode);
-
/* Set up registers for signal handler */
wrusp ((unsigned long) frame);
regs->pc = (unsigned long) ka->sa.sa_handler;
@@ -655,17 +648,11 @@
err |= copy_to_user (&frame->uc.uc_sigmask, set, sizeof(*set));
/* Set up to return from userspace. */
- err |= __put_user(frame->retcode, &frame->pretcode);
- /* moveq #,d0; notb d0; trap #0 */
- err |= __put_user(0x70004600 + ((__NR_rt_sigreturn ^ 0xff) << 16),
- (long *)(frame->retcode + 0));
- err |= __put_user(0x4e40, (short *)(frame->retcode + 4));
+ err |= __put_user((void *) ret_from_user_rt_signal, &frame->pretcode);
if (err)
goto give_sigsegv;
- push_cache ((unsigned long) &frame->retcode);
-
/* Set up registers for signal handler */
wrusp ((unsigned long) frame);
regs->pc = (unsigned long) ka->sa.sa_handler;
--- linux-2.6.x/arch/m68knommu/kernel/entry.S 11 Oct 2006 07:07:41 -0000 1.5
+++ linux-2.6.x/arch/m68knommu/kernel/entry.S 12 Mar 2008 06:48:49 -0000
@@ -32,6 +32,7 @@
#include <asm/segment.h>
#include <asm/asm-offsets.h>
#include <asm/entry.h>
+#include <asm/unistd.h>
.text
@@ -140,3 +141,11 @@
RESTORE_SWITCH_STACK
rts
+ENTRY(ret_from_user_signal)
+ moveq #__NR_sigreturn,%d0
+ trap #0
+
+ENTRY(ret_from_user_rt_signal)
+ move #__NR_rt_sigreturn,%d0
+ trap #0
+
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