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x86: add the "print code before the trapping instruction" feature to 64 bit 

The 32 bit x86 tree has a very useful feature that prints the Code: line
for the code even before the trapping instrution (and the start of the
trapping instruction is then denoted with a <>). Unfortunately, the 64 bit
x86 tree does not yet have this feature, making diagnosing backtraces harder
than needed.

This patch adds this feature in the same was as the 32 bit tree has
(including the same kernel boot parameter), and including a bugfix
to make the code use probe_kernel_address() rarther than a buggy (deadlocking)
__get_user.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Arjan van de Ven 2008-01-30 13:33:08 +01:00 committed by Ingo Molnar
parent 6dab27784b
commit a25bd94964
2 changed files with 35 additions and 13 deletions
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4
Documentation/kernel-parameters.txt
View File

@ -416,8 +416,8 @@ and is between 256 and 4096 characters. It is defined in the file
[SPARC64] tick
[X86-64] hpet,tsc
code_bytes [IA32] How many bytes of object code to print in an
oops report.
code_bytes [IA32/X86_64] How many bytes of object code to print
in an oops report.
Range: 0 - 8192
Default: 64

44
arch/x86/kernel/traps_64.c
View File

@ -74,6 +74,8 @@ asmlinkage void alignment_check(void);
asmlinkage void machine_check(void);
asmlinkage void spurious_interrupt_bug(void);
static unsigned int code_bytes = 64;
static inline void conditional_sti(struct pt_regs *regs)
{
if (regs->flags & X86_EFLAGS_IF)
@ -459,12 +461,15 @@ EXPORT_SYMBOL(dump_stack);
void show_registers(struct pt_regs *regs)
{
int i;
int in_kernel = !user_mode(regs);
unsigned long sp;
const int cpu = smp_processor_id();
struct task_struct *cur = cpu_pda(cpu)->pcurrent;
u8 *ip;
unsigned int code_prologue = code_bytes * 43 / 64;
unsigned int code_len = code_bytes;
sp = regs->sp;
ip = (u8 *) regs->ip - code_prologue;
printk("CPU %d ", cpu);
__show_regs(regs);
printk("Process %s (pid: %d, threadinfo %p, task %p)\n",
@ -474,22 +479,28 @@ void show_registers(struct pt_regs *regs)
* When in-kernel, we also print out the stack and code at the
* time of the fault..
*/
if (in_kernel) {
if (!user_mode(regs)) {
unsigned char c;
printk("Stack: ");
_show_stack(NULL, regs, (unsigned long *)sp, regs->bp);
printk("\n");
printk("\nCode: ");
if (regs->ip < PAGE_OFFSET)
goto bad;
for (i=0; i<20; i++) {
unsigned char c;
if (__get_user(c, &((unsigned char*)regs->ip)[i])) {
bad:
printk(KERN_EMERG "Code: ");
if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
/* try starting at RIP */
ip = (u8 *) regs->ip;
code_len = code_len - code_prologue + 1;
}
for (i = 0; i < code_len; i++, ip++) {
if (ip < (u8 *)PAGE_OFFSET ||
probe_kernel_address(ip, c)) {
printk(" Bad RIP value.");
break;
}
printk("%02x ", c);
if (ip == (u8 *)regs->ip)
printk("<%02x> ", c);
else
printk("%02x ", c);
}
}
printk("\n");
@ -1164,3 +1175,14 @@ static int __init kstack_setup(char *s)
return 0;
}
early_param("kstack", kstack_setup);
static int __init code_bytes_setup(char *s)
{
code_bytes = simple_strtoul(s, NULL, 0);
if (code_bytes > 8192)
code_bytes = 8192;
return 1;
}
__setup("code_bytes=", code_bytes_setup);