On Fri, 2003-01-03 at 05:46, Ralf Baechle wrote:
> On Fri, Jan 03, 2003 at 02:29:22AM -0800, Pete Popov wrote:
>
> > The changes betwen rev 1.23 and 1.24 in unaligned.c, to replace
> > check_axs() with verify_area(), causes any unaligned access from within
> > a kernel module to crash. access_ok() returns -EFAULT as the
> > __access_mask is 0xffffffff so __access_ok evaluates to > 0. It's too
> > late for me to look into it any further but perhaps the problem will be
> > obvious to someone else. I'm not sure what get_fs() should return in
> > this case (again, the access is from within a kernel module) but it
> > returns 0xffffffff.
>
> The address error handler should do something like:
>
> mm_segment_t seg;
>
> seg = get_fs();
> if (!user_mode(regs))
> set_fs(KERNEL_DS);
>
> ... usual unaligned stuff goes here ...
>
> set_fs(seg);
Thanks! The patch below works. I had a test case plus a pcmcia driver that was
crashing, and now they both pass.
--- linux-2.4-head/arch/mips/kernel/unaligned.c Thu Dec 26 21:35:00 2002
+++ linux-2.4-dev/arch/mips/kernel/unaligned.c Sat Jan 4 12:21:06 2003
@@ -98,6 +98,11 @@
union mips_instruction insn;
unsigned long value, fixup;
unsigned int res;
+ mm_segment_t seg;
+
+ seg = get_fs();
+ if (!user_mode(regs))
+ set_fs(KERNEL_DS);
regs->regs[0] = 0;
/*
@@ -458,6 +463,7 @@
unaligned_instructions++;
#endif
+ set_fs(seg);
return;
fault:
@@ -469,24 +475,28 @@
printk(KERN_DEBUG "%s: Forwarding exception at [<%lx>] (%lx)\n",
current->comm, regs->cp0_epc, new_epc);
regs->cp0_epc = new_epc;
+ set_fs(seg);
return;
}
die_if_kernel ("Unhandled kernel unaligned access", regs);
send_sig(SIGSEGV, current, 1);
+ set_fs(seg);
return;
sigbus:
die_if_kernel("Unhandled kernel unaligned access", regs);
send_sig(SIGBUS, current, 1);
+ set_fs(seg);
return;
sigill:
die_if_kernel("Unhandled kernel unaligned access or invalid instruction", regs);
send_sig(SIGILL, current, 1);
+ set_fs(seg);
return;
}
