Commit a25bd94964e87b1b93903a822fba5025d995d4da
Committed by
Ingo Molnar
Ingo Molnar
1 parent
6dab27784b
Exists in
master
and in
20 other branches
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>
Showing 2 changed files with 35 additions and 13 deletions Side-by-side Diff
Documentation/kernel-parameters.txt
| ... | ... | @@ -416,8 +416,8 @@ |
| 416 | 416 | [SPARC64] tick |
| 417 | 417 | [X86-64] hpet,tsc |
| 418 | 418 | |
| 419 | - code_bytes [IA32] How many bytes of object code to print in an | |
| 420 | - oops report. | |
| 419 | + code_bytes [IA32/X86_64] How many bytes of object code to print | |
| 420 | + in an oops report. | |
| 421 | 421 | Range: 0 - 8192 |
| 422 | 422 | Default: 64 |
| 423 | 423 |
arch/x86/kernel/traps_64.c
| ... | ... | @@ -74,6 +74,8 @@ |
| 74 | 74 | asmlinkage void machine_check(void); |
| 75 | 75 | asmlinkage void spurious_interrupt_bug(void); |
| 76 | 76 | |
| 77 | +static unsigned int code_bytes = 64; | |
| 78 | + | |
| 77 | 79 | static inline void conditional_sti(struct pt_regs *regs) |
| 78 | 80 | { |
| 79 | 81 | if (regs->flags & X86_EFLAGS_IF) |
| 80 | 82 | |
| 81 | 83 | |
| ... | ... | @@ -459,12 +461,15 @@ |
| 459 | 461 | void show_registers(struct pt_regs *regs) |
| 460 | 462 | { |
| 461 | 463 | int i; |
| 462 | - int in_kernel = !user_mode(regs); | |
| 463 | 464 | unsigned long sp; |
| 464 | 465 | const int cpu = smp_processor_id(); |
| 465 | 466 | struct task_struct *cur = cpu_pda(cpu)->pcurrent; |
| 467 | + u8 *ip; | |
| 468 | + unsigned int code_prologue = code_bytes * 43 / 64; | |
| 469 | + unsigned int code_len = code_bytes; | |
| 466 | 470 | |
| 467 | 471 | sp = regs->sp; |
| 472 | + ip = (u8 *) regs->ip - code_prologue; | |
| 468 | 473 | printk("CPU %d ", cpu); |
| 469 | 474 | __show_regs(regs); |
| 470 | 475 | printk("Process %s (pid: %d, threadinfo %p, task %p)\n", |
| 471 | 476 | |
| 472 | 477 | |
| 473 | 478 | |
| ... | ... | @@ -474,22 +479,28 @@ |
| 474 | 479 | * When in-kernel, we also print out the stack and code at the |
| 475 | 480 | * time of the fault.. |
| 476 | 481 | */ |
| 477 | - if (in_kernel) { | |
| 482 | + if (!user_mode(regs)) { | |
| 483 | + unsigned char c; | |
| 478 | 484 | printk("Stack: "); |
| 479 | 485 | _show_stack(NULL, regs, (unsigned long *)sp, regs->bp); |
| 486 | + printk("\n"); | |
| 480 | 487 | |
| 481 | - printk("\nCode: "); | |
| 482 | - if (regs->ip < PAGE_OFFSET) | |
| 483 | - goto bad; | |
| 484 | - | |
| 485 | - for (i=0; i<20; i++) { | |
| 486 | - unsigned char c; | |
| 487 | - if (__get_user(c, &((unsigned char*)regs->ip)[i])) { | |
| 488 | -bad: | |
| 488 | + printk(KERN_EMERG "Code: "); | |
| 489 | + if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) { | |
| 490 | + /* try starting at RIP */ | |
| 491 | + ip = (u8 *) regs->ip; | |
| 492 | + code_len = code_len - code_prologue + 1; | |
| 493 | + } | |
| 494 | + for (i = 0; i < code_len; i++, ip++) { | |
| 495 | + if (ip < (u8 *)PAGE_OFFSET || | |
| 496 | + probe_kernel_address(ip, c)) { | |
| 489 | 497 | printk(" Bad RIP value."); |
| 490 | 498 | break; |
| 491 | 499 | } |
| 492 | - printk("%02x ", c); | |
| 500 | + if (ip == (u8 *)regs->ip) | |
| 501 | + printk("<%02x> ", c); | |
| 502 | + else | |
| 503 | + printk("%02x ", c); | |
| 493 | 504 | } |
| 494 | 505 | } |
| 495 | 506 | printk("\n"); |
| ... | ... | @@ -1164,4 +1175,15 @@ |
| 1164 | 1175 | return 0; |
| 1165 | 1176 | } |
| 1166 | 1177 | early_param("kstack", kstack_setup); |
| 1178 | + | |
| 1179 | + | |
| 1180 | +static int __init code_bytes_setup(char *s) | |
| 1181 | +{ | |
| 1182 | + code_bytes = simple_strtoul(s, NULL, 0); | |
| 1183 | + if (code_bytes > 8192) | |
| 1184 | + code_bytes = 8192; | |
| 1185 | + | |
| 1186 | + return 1; | |
| 1187 | +} | |
| 1188 | +__setup("code_bytes=", code_bytes_setup); |