mainlining shenanigans
59c026c359
When use 'echo c > /proc/sysrq-trigger' to trigger kdump, riscv_crash_save_regs()
will be called to save regs for vmcore, we found "epc" value 00ffffffa5537400
is not a valid kernel virtual address, but is a user virtual address. Other
regs(eg, ra, sp, gp...) are correct kernel virtual address.
Actually 0x00ffffffb0dd9400 is the user mode PC of 'PID: 113 Comm: sh', which
is saved in the task's stack.
[ 21.201701] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #45
[ 21.201979] Hardware name: riscv-virtio,qemu (DT)
[ 21.202160] epc : 00ffffffa5537400 ra : ffffffff80088640 sp : ff20000010333b90
[ 21.202435] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff8032be7c
[ 21.202707] t1 : 0720072007200720 t2 : 30203a7375746174 s0 : ff20000010333cf0
[ 21.202973] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000000001
[ 21.203243] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 28c8f0aeffea4e00
[ 21.203519] a5 : 28c8f0aeffea4e00 a6 : 0000000000000009 a7 : ffffffff8035c9b8
[ 21.203794] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010333b98
[ 21.204062] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80c4a468
[ 21.204331] s8 : 00ffffffef451410 s9 : 0000000000000007 s10: 00aaaaaac0510700
[ 21.204606] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001218f00
[ 21.204876] t5 : ff60000001218000 t6 : ff200000103338b8
[ 21.205079] status: 0000000200000020 badaddr: 0000000000000000 cause: 0000000000000008
With the incorrect PC, the backtrace showed by crash tool as below, the first
stack frame is abnormal,
crash> bt
PID: 113 TASK: ff60000002269600 CPU: 0 COMMAND: "sh"
#0 [ff2000001039bb90] __efistub_.Ldebug_info0 at 00ffffffa5537400 <-- Abnormal
#1 [ff2000001039bcf0] panic at ffffffff806578ba
#2 [ff2000001039bd50] sysrq_reset_seq_param_set at ffffffff8038c030
#3 [ff2000001039bda0] __handle_sysrq at ffffffff8038c5f8
#4 [ff2000001039be00] write_sysrq_trigger at ffffffff8038cad8
#5 [ff2000001039be20] proc_reg_write at ffffffff801b7edc
#6 [ff2000001039be40] vfs_write at ffffffff80152ba6
#7 [ff2000001039be80] ksys_write at ffffffff80152ece
#8 [ff2000001039bed0] sys_write at ffffffff80152f46
With the patch, we can get current kernel mode PC, the output as below,
[ 17.607658] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #42
[ 17.607937] Hardware name: riscv-virtio,qemu (DT)
[ 17.608150] epc : ffffffff800078f8 ra : ffffffff8008862c sp : ff20000010333b90
[ 17.608441] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff8032be68
[ 17.608741] t1 : 0720072007200720 t2 : 666666666666663c s0 : ff20000010333cf0
[ 17.609025] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000000001
[ 17.609320] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 0000000000000000
[ 17.609601] a5 : ff60000001c78000 a6 : 000000000000003c a7 : ffffffff8035c9a4
[ 17.609894] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010333b98
[ 17.610186] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80c4a468
[ 17.610469] s8 : 00ffffffca281410 s9 : 0000000000000007 s10: 00aaaaaab5bb6700
[ 17.610755] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001218f00
[ 17.611041] t5 : ff60000001218000 t6 : ff20000010333988
[ 17.611255] status: 0000000200000020 badaddr: 0000000000000000 cause: 0000000000000008
With the correct PC, the backtrace showed by crash tool as below,
crash> bt
PID: 113 TASK: ff6000000226c200 CPU: 0 COMMAND: "sh"
#0 [ff20000010333b90] riscv_crash_save_regs at ffffffff800078f8 <--- Normal
#1 [ff20000010333cf0] panic at ffffffff806578c6
#2 [ff20000010333d50] sysrq_reset_seq_param_set at ffffffff8038c03c
#3 [ff20000010333da0] __handle_sysrq at ffffffff8038c604
#4 [ff20000010333e00] write_sysrq_trigger at ffffffff8038cae4
#5 [ff20000010333e20] proc_reg_write at ffffffff801b7ee8
#6 [ff20000010333e40] vfs_write at ffffffff80152bb2
#7 [ff20000010333e80] ksys_write at ffffffff80152eda
#8 [ff20000010333ed0] sys_write at ffffffff80152f52
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.