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MN10300: die_if_no_fixup() shouldn't use get_user() as it doesn't call set_fs()

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die_if_no_fixup() shouldn't use get_user() as it doesn't call set_fs() to
indicate that it wants to probe a kernel address.  Instead it should use
probe_kernel_read().

This fixes the problem of gdb seeing SIGILL rather than SIGTRAP when hitting
the KGDB special breakpoint upon SysRq+g being seen.  The problem was that
die_if_no_fixup() was failing to read the opcode of the instruction that caused
the exception, and thus not fixing up the exception.

This caused gdb to get a S04 response to the $? request in its remote protocol
rather than S05 - which would then cause it to continue with $C04 rather than
$c in an attempt to pass the signal onto the inferior process.  The kernel,
however, does not support $Cnn, and so objects by returning an E22 response,
indicating an error.  gdb does not expect this and prints:

	warning: Remote failure reply: E22

and then returns to the gdb command prompt unable to continue.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells 2011-06-06 15:47:14 +01:00 committed by Linus Torvalds
parent 2e65d1f6ee
commit db1c9dfa64
1 changed files with 2 additions and 2 deletions
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4
arch/mn10300/kernel/traps.c
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@ -28,7 +28,7 @@
#include <linux/irq.h> #include <linux/irq.h>
#include <asm/processor.h> #include <asm/processor.h>
#include <asm/system.h> #include <asm/system.h>
#include <asm/uaccess.h> #include <linux/uaccess.h>
#include <asm/io.h> #include <asm/io.h>
#include <asm/atomic.h> #include <asm/atomic.h>
#include <asm/smp.h> #include <asm/smp.h>
@ -156,7 +156,7 @@ int die_if_no_fixup(const char *str, struct pt_regs *regs,
case EXCEP_TRAP: case EXCEP_TRAP:
case EXCEP_UNIMPINS: case EXCEP_UNIMPINS:
if (get_user(opcode, (uint8_t __user *)regs->pc) != 0) if (probe_kernel_read(&opcode, (u8 *)regs->pc, 1) < 0)
break; break;
if (opcode == 0xff) { if (opcode == 0xff) {
if (notify_die(DIE_BREAKPOINT, str, regs, code, 0, 0)) if (notify_die(DIE_BREAKPOINT, str, regs, code, 0, 0))