Re: [PATCH 0/5] x86/dumpstack: Cleanups and user opcode bytes Code: section
From: Borislav Petkov
Date: Wed Feb 21 2018 - 12:54:53 EST
On Wed, Feb 21, 2018 at 10:15:53AM +0100, Ingo Molnar wrote:
> That looks really useful!
Ok, lemme run it by Linus too as he probably stares at this part of the
output a *lot* :-)
Combined patch at the end. I'll split it later.
@Linus: also, pls have a look at
https://lkml.kernel.org/r/20180219202826.19797-6-bp@xxxxxxxxx
I've added Code: section to user faults too because there might be
some usefulness in seeing the user opcode bytes when it faults. Some
arguments in the commit message there.
Anyway, here's a 64-bit splat. I'm basically dumping opcode bytes
everytime we dump RIP.
[ 18.304872] sysrq: SysRq : Trigger a crash
[ 18.306961] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 18.310702] IP: sysrq_handle_crash+0x17/0x20
[ 18.312830] PGD 7a972067 P4D 7a972067 PUD 7a351067 PMD 0
[ 18.316431] Oops: 0002 [#1] PREEMPT SMP
[ 18.317219] Modules linked in:
[ 18.317865] CPU: 6 PID: 3681 Comm: bash Not tainted 4.16.0-rc1+ #14
[ 18.319237] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 18.321162] RIP: 0010:sysrq_handle_crash+0x17/0x20
[ 18.322273] RSP: 0018:ffffc90000c23df0 EFLAGS: 00010246
[ 18.322274] Code: eb d1 e8 fd ca b6 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 f6 de bc ff c7 05 84 0d 1a 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 86 df c1 ff fb 66
[ 18.331362] RAX: 0000000000000000 RBX: 0000000000000063 RCX: 0000000000000000
[ 18.332660] RDX: 0000000000000000 RSI: ffffffff81103293 RDI: 0000000000000063
[ 18.333931] RBP: ffffffff82271880 R08: 00000000000001a4 R09: 000000000004a6e8
[ 18.335209] R10: 0000000000000000 R11: 0000000000000000 R12: 000000000000000a
[ 18.336874] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 18.338732] FS: 00007ffff7fdb700(0000) GS:ffff88007ed80000(0000) knlGS:0000000000000000
[ 18.344827] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 18.346395] CR2: 0000000000000000 CR3: 000000007c39e000 CR4: 00000000000406e0
[ 18.348205] Call Trace:
[ 18.348905] __handle_sysrq+0x9e/0x160
[ 18.349835] write_sysrq_trigger+0x2b/0x30
[ 18.350827] proc_reg_write+0x38/0x70
[ 18.351747] __vfs_write+0x36/0x160
[ 18.356573] ? __fd_install+0x69/0x110
[ 18.357516] ? preempt_count_add+0x74/0xb0
[ 18.358509] ? _raw_spin_lock+0x13/0x30
[ 18.359454] ? set_close_on_exec+0x41/0x80
[ 18.360468] ? preempt_count_sub+0xa8/0x100
[ 18.361476] vfs_write+0xc0/0x190
[ 18.362327] SyS_write+0x64/0xe0
[ 18.363162] ? trace_hardirqs_off_thunk+0x1a/0x1c
[ 18.364269] do_syscall_64+0x76/0x140
[ 18.368969] entry_SYSCALL_64_after_hwframe+0x42/0xb7
[ 18.370390] RIP: 0033:0x7ffff74b9620
[ 18.371479] RSP: 002b:00007fffffffe7a8 EFLAGS: 00000246
[ 18.371481] Code: ff 73 01 c3 48 8b 0d 68 98 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d bd f1 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ce 8f 01 00 48 89 04
[ 18.377743] ORIG_RAX: 0000000000000001
[ 18.381942] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007ffff74b9620
[ 18.383212] RDX: 0000000000000002 RSI: 0000000000705408 RDI: 0000000000000001
[ 18.384490] RBP: 0000000000705408 R08: 000000000000000a R09: 00007ffff7fdb700
[ 18.385759] R10: 00007ffff77826a0 R11: 0000000000000246 R12: 00007ffff77842a0
[ 18.387024] R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000
[ 18.388437] RIP: 0010:sysrq_handle_crash+0x17/0x20
[ 18.389550] RSP: 0018:ffffc90000c23df0 EFLAGS: 00010246
[ 18.389550] Code: eb d1 e8 fd ca b6 ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 e8 f6 de bc ff c7 05 84 0d 1a 01 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 c3 0f 1f 44 00 00 e8 86 df c1 ff fb 66
[ 18.398707] CR2: 0000000000000000
[ 18.399864] ---[ end trace e17dc9a4aa5cc4d9 ]---
[ 18.401351] Kernel panic - not syncing: Fatal exception
[ 18.401678] Kernel Offset: disabled
[ 18.408342] ---[ end Kernel panic - not syncing: Fatal exception
32-bit, respectively:
[ 20.992127] sysrq: SysRq : Trigger a crash
[ 20.994364] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 20.997892] IP: sysrq_handle_crash+0x1d/0x30
[ 20.999807] *pde = 00000000
[ 21.000512] Oops: 0002 [#1] PREEMPT SMP
[ 21.007170] Modules linked in:
[ 21.008299] CPU: 4 PID: 2079 Comm: bash Not tainted 4.16.0-rc1+ #18
[ 21.022652] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 21.024480] EIP: sysrq_handle_crash+0x1d/0x30 SS:ESP: 0068:f3f21e8c
[ 21.026929] Code: bf ff eb d6 e8 35 eb b9 ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 d3 dd bf ff c7 05 b4 ba c3 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f
[ 21.037904] EAX: 00000000 EBX: 0000000a ECX: 00000000 EDX: c1505fe0
[ 21.039740] ESI: 00000063 EDI: 00000000 EBP: f3f21e8c ESP: f3f21e8c
[ 21.041575] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[ 21.043233] CR0: 80050033 CR2: 00000000 CR3: 33e6c000 CR4: 000406d0
[ 21.049620] Call Trace:
[ 21.050286] __handle_sysrq+0x93/0x130
[ 21.051167] ? sysrq_filter+0x3c0/0x3c0
[ 21.052053] write_sysrq_trigger+0x27/0x40
[ 21.052977] proc_reg_write+0x4d/0x80
[ 21.053939] ? proc_reg_poll+0x70/0x70
[ 21.055209] __vfs_write+0x38/0x160
[ 21.056433] ? preempt_count_sub+0xa0/0x110
[ 21.057805] ? __fd_install+0x51/0xd0
[ 21.063481] ? __sb_start_write+0x4c/0xc0
[ 21.064811] ? preempt_count_sub+0xa0/0x110
[ 21.066193] vfs_write+0x98/0x180
[ 21.067371] SyS_write+0x4f/0xb0
[ 21.068592] do_fast_syscall_32+0x9e/0x210
[ 21.069946] entry_SYSENTER_32+0x53/0x86
[ 21.071257] EIP: 0xb7fccce9 SS:ESP: 007b:bfa15fc0
[ 21.072733] Code: 55 08 8b 80 64 cd ff ff 85 d2 74 02 89 02 5d c3 8b 04 24 c3 8b 0c 24 c3 8b 1c 24 c3 8b 3c 24 c3 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d 76 00 58 b8 77 00 00 00 cd 80 90 8d
[ 21.081472] EAX: ffffffda EBX: 00000001 ECX: 081e8a08 EDX: 00000002
[ 21.081474] ESI: 00000002 EDI: b7f97d80 EBP: 081e8a08 ESP: bfa15fc0
[ 21.081476] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b
[ 21.081482] EIP: sysrq_handle_crash+0x1d/0x30 SS:ESP: 0068:f3f21e8c
[ 21.081483] Code: bf ff eb d6 e8 35 eb b9 ff 90 8d 74 26 00 0f 1f 44 00 00 55 89 e5 e8 d3 dd bf ff c7 05 b4 ba c3 c1 01 00 00 00 0f ae f8 0f 1f 00 <c6> 05 00 00 00 00 01 5d c3 8d 76 00 8d bc 27 00 00 00 00 0f 1f
[ 21.104318] CR2: 0000000000000000
[ 21.105155] ---[ end trace 7a104a17e091751a ]---
[ 21.106160] Kernel panic - not syncing: Fatal exception
[ 21.106479] Kernel Offset: disabled
[ 21.108329] ---[ end Kernel panic - not syncing: Fatal exception
Combined diff ontop:
---
diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
index 0630eeb18bbc..b6dc698f992a 100644
--- a/arch/x86/include/asm/stacktrace.h
+++ b/arch/x86/include/asm/stacktrace.h
@@ -112,4 +112,5 @@ static inline unsigned long caller_frame_pointer(void)
}
void show_opcodes(u8 *rip, const char *loglvl);
+void show_ip(struct pt_regs *regs, const char *loglvl);
#endif /* _ASM_X86_STACKTRACE_H */
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 3d595e4cf280..b60232d9969b 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -73,14 +73,56 @@ static void printk_stack_address(unsigned long address, int reliable,
printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
}
-void show_opcodes(u8 *rip, const char *loglvl);
+void show_opcodes(u8 *rip, const char *loglvl)
+{
+ unsigned int code_prologue = code_bytes * 43 / OPCODE_BUFSIZE;
+ u8 *ip;
+ int i;
-void show_iret_regs(struct pt_regs *regs)
+ printk("%sCode: ", loglvl);
+
+ ip = (u8 *)rip - code_prologue;
+ if (probe_kernel_read(opcodes, ip, code_bytes)) {
+ pr_cont(" Bad RIP value.\n");
+ return;
+ }
+
+ for (i = 0; i < code_bytes; i++, ip++) {
+ if (ip == (u8 *)rip)
+ pr_cont("<%02x> ", opcodes[i]);
+ else
+ pr_cont("%02x ", opcodes[i]);
+ }
+ pr_cont("\n");
+}
+
+void show_ip(struct pt_regs *regs, const char *loglvl)
{
- printk(KERN_DEFAULT "RIP: %04x:%pS\n", (int)regs->cs, (void *)regs->ip);
- printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss,
+#ifdef CONFIG_X86_32
+ unsigned short ss;
+ unsigned long sp;
+
+ if (user_mode(regs)) {
+ sp = regs->sp;
+ ss = regs->ss;
+ } else {
+ sp = kernel_stack_pointer(regs);
+ savesegment(ss, ss);
+ }
+
+ printk("%sEIP: %pS SS:ESP: %04x:%08lx\n", loglvl, (void *)regs->ip, ss, sp);
+#else
+ printk("%sRIP: %04x:%pS\n", loglvl, (int)regs->cs, (void *)regs->ip);
+ printk("%sRSP: %04x:%016lx EFLAGS: %08lx", loglvl, (int)regs->ss,
regs->sp, regs->flags);
- show_opcodes((u8 *)regs->ip, KERN_DEFAULT);
+#endif
+
+ show_opcodes((u8 *)regs->ip, loglvl);
+}
+
+void show_iret_regs(struct pt_regs *regs)
+{
+ show_ip(regs, KERN_DEFAULT);
}
static void show_regs_if_on_stack(struct stack_info *info, struct pt_regs *regs,
@@ -312,10 +354,6 @@ NOKPROBE_SYMBOL(oops_end);
int __die(const char *str, struct pt_regs *regs, long err)
{
-#ifdef CONFIG_X86_32
- unsigned short ss;
- unsigned long sp;
-#endif
printk(KERN_DEFAULT
"%s: %04lx [#%d]%s%s%s%s%s\n", str, err & 0xffff, ++die_counter,
IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",
@@ -331,20 +369,10 @@ int __die(const char *str, struct pt_regs *regs, long err)
print_modules();
show_regs(regs);
-#ifdef CONFIG_X86_32
- if (user_mode(regs)) {
- sp = regs->sp;
- ss = regs->ss;
- } else {
- sp = kernel_stack_pointer(regs);
- savesegment(ss, ss);
- }
- printk(KERN_EMERG "EIP: %pS SS:ESP: %04x:%08lx\n",
- (void *)regs->ip, ss, sp);
-#else
+
/* Executive summary in case the oops scrolled away */
- printk(KERN_ALERT "RIP: %pS RSP: %016lx\n", (void *)regs->ip, regs->sp);
-#endif
+ show_ip(regs, KERN_EMERG);
+
return 0;
}
NOKPROBE_SYMBOL(__die);
@@ -391,29 +419,6 @@ static int __init code_bytes_setup(char *s)
}
__setup("code_bytes=", code_bytes_setup);
-void show_opcodes(u8 *rip, const char *loglvl)
-{
- unsigned int code_prologue = code_bytes * 43 / OPCODE_BUFSIZE;
- u8 *ip;
- int i;
-
- printk("%sCode: ", loglvl);
-
- ip = (u8 *)rip - code_prologue;
- if (probe_kernel_read(opcodes, ip, code_bytes)) {
- pr_cont(" Bad RIP value.\n");
- return;
- }
-
- for (i = 0; i < code_bytes; i++, ip++) {
- if (ip == (u8 *)rip)
- pr_cont("<%02x> ", opcodes[i]);
- else
- pr_cont("%02x ", opcodes[i]);
- }
- pr_cont("\n");
-}
-
void show_regs(struct pt_regs *regs)
{
bool all = true;
@@ -434,7 +439,5 @@ void show_regs(struct pt_regs *regs)
if (regs->ip < PAGE_OFFSET)
pr_cont(" Bad RIP value.\n");
- else
- show_opcodes((u8 *)regs->ip, KERN_DEFAULT);
}
}
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 5224c6099184..3d1f1226b972 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -76,9 +76,7 @@ void __show_regs(struct pt_regs *regs, int all)
savesegment(gs, gs);
}
- printk(KERN_DEFAULT "EIP: %pS\n", (void *)regs->ip);
- printk(KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n", regs->flags,
- raw_smp_processor_id());
+ show_ip(regs, KERN_DEFAULT);
printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
regs->ax, regs->bx, regs->cx, regs->dx);
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.