On 2022/8/4 12:55, Josh Poimboeuf wrote:
On Wed, Jul 27, 2022 at 11:15:06AM +0800, Chen Zhongjin wrote:
This reverts commit f1d9a2abff66aa8156fbc1493abed468db63ea48.
When CONFIG_GCOV_PROFILE_ALL is enabled, show_stack() and related
functions (e.g. dump_stack) will break for x86 ORC unwinder.
Call Trace:
<TASK>
? dump_stack_lvl+0x83/0xb7
? schedule+0x1/0x190
? dump_stack+0x13/0x1f
? handler_pre0+0x3f/0x53 [kp_unwind]
...
show_trace_log_lvl() searches text address on stack to validate
whether unwind results are reliable. The code:
Hi,
Thanks for the patch. The change itself makes sense, though I'm having
trouble recreating the bug described in the patch description.
I enabled CONFIG_GCOV_PROFILE_ALL and did 'echo l >
/proc/sysrq-trigger', but I got a valid stack trace:
# echo l > /proc/sysrq-trigger
[ 343.916728] sysrq: Show backtrace of all active CPUs
[ 343.917459] NMI backtrace for cpu 2
[ 343.917884] CPU: 2 PID: 1007 Comm: bash Not tainted 5.19.0-rc8+ #68
[ 343.918562] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-1.fc36 04/01/2014
[ 343.919534] Call Trace:
[ 343.919904] <TASK>
[ 343.920226] dump_stack_lvl+0xcc/0x11b
[ 343.920742] dump_stack+0x17/0x24
[ 343.921199] nmi_cpu_backtrace.cold+0xb5/0x10d
[ 343.921795] ? lapic_can_unplug_cpu+0xa0/0xa0
[ 343.922375] nmi_trigger_cpumask_backtrace+0x171/0x200
[ 343.923053] arch_trigger_cpumask_backtrace+0x21/0x30
[ 343.923599] sysrq_handle_showallcpus+0x1f/0x30
[ 343.924104] __handle_sysrq.cold+0x81/0x234
[ 343.924576] write_sysrq_trigger+0x6a/0x90
[ 343.925098] proc_reg_write+0x99/0x120
[ 343.925587] vfs_write+0x16c/0x350
[ 343.926093] ksys_write+0x8c/0x180
[ 343.926597] __x64_sys_write+0x21/0x30
[ 343.927144] do_syscall_64+0x76/0x100
[ 343.927676] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 343.928343] RIP: 0033:0x7f555e8f7b50
[ 343.928822] Code: 73 01 c3 48 8b 0d 38 83 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 79 db 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 1e e3 01 00 48 89 04 24
[ 343.930801] RSP: 002b:00007ffdd20d0978 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 343.931761] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f555e8f7b50
[ 343.932551] RDX: 0000000000000002 RSI: 000055ff471bfe20 RDI: 0000000000000001
[ 343.933347] RBP: 000055ff471bfe20 R08: 00007f555ebc2740 R09: 00007f555f80f700
[ 343.934155] R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000002
[ 343.934962] R13: 0000000000000001 R14: 00007f555ebc15e0 R15: 00007f555ebbd3c0
[ 343.935798] </TASK>
[ 343.936341] Sending NMI from CPU 2 to CPUs 0-1,3:
[ 343.937163] NMI backtrace for cpu 3
[ 343.937167] CPU: 3 PID: 600 Comm: systemd-journal Not tainted 5.19.0-rc8+ #68
Was this with an upstream kernel? Can you share the config and
toolchain versions?
Hi,
My kernel is upstream and config is defconfig with only
CONFIG_GCOV_PROFILE_ALL=y then make menuconfig.
CONFIG_CC_VERSION_TEXT="gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0"
And I got:
[ 29.745728] NMI backtrace for cpu 1
[ 29.745728] CPU: 1 PID: 135 Comm: sh Not tainted
5.19.0-02858-ge2b542100719 #58
[ 29.745728] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.15.0-0-g2dd4b9b3f8404
[ 29.745728] Call Trace:
[ 29.745728] <TASK>
[ 29.745728] ? dump_stack_lvl+0x72/0xa1
[ 29.745728] ? dump_stack+0x13/0x1f
[ 29.745728] ? nmi_cpu_backtrace+0x19f/0x1d0
[ 29.745728] ? lapic_can_unplug_cpu+0xf0/0xf0
[ 29.745728] ? nmi_trigger_cpumask_backtrace+0x15e/0x210
[ 29.745728] ? arch_trigger_cpumask_backtrace+0x18/0x30
[ 29.745728] ? sysrq_handle_showallcpus+0x16/0x30
[ 29.745728] ? __handle_sysrq+0xc4/0x250
[ 29.745728] ? write_sysrq_trigger+0x46/0x60
[ 29.745728] ? proc_reg_write+0xbc/0x120
[ 29.745728] ? preempt_count_add+0x8e/0x130
[ 29.745728] ? vfs_write+0xfe/0x460
[ 29.745728] ? ksys_write+0xdc/0x170
[ 29.745728] ? fpregs_assert_state_consistent+0x2d/0x90
[ 29.745728] ? __x64_sys_write+0x19/0x30
[ 29.745728] ? do_syscall_64+0x3a/0x90
[ 29.745728] ? entry_SYSCALL_64_after_hwframe+0x63/0xcd
[ 29.745728] </TASK>
It also happened with CONFIG_CC_VERSION_TEXT="gcc-8 (Ubuntu
8.4.0-1ubuntu1~18.04) 8.4.0".
I believe disassemble show_stack in vmlinux and if we have:
push %rbp
mov %rsp,%rbp
... (no regs pushed to stack)
callq <show_trace_log_lvl>
This can be reproduced.
Your stacktrace looks just as normal as the one in my commit message
(show_stack is optimized out).
Best,
Chen
