mirror of https://gitee.com/openkylin/linux.git
f474c28fbc
powerpc hardware triggers watchpoint before executing the instruction.
To make trigger-after-execute behavior, kernel emulates the
instruction. If the instruction is 'load something into non-volatile
register', exception handler should restore emulated register state
while returning back, otherwise there will be register state
corruption. eg, adding a watchpoint on a list can corrput the list:
# cat /proc/kallsyms | grep kthread_create_list
c00000000121c8b8 d kthread_create_list
Add watchpoint on kthread_create_list->prev:
# perf record -e mem:0xc00000000121c8c0
Run some workload such that new kthread gets invoked. eg, I just
logged out from console:
list_add corruption. next->prev should be prev (c000000001214e00), \
but was c00000000121c8b8. (next=c00000000121c8b8).
WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0
CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69
...
NIP __list_add_valid+0xb4/0xc0
LR __list_add_valid+0xb0/0xc0
Call Trace:
__list_add_valid+0xb0/0xc0 (unreliable)
__kthread_create_on_node+0xe0/0x260
kthread_create_on_node+0x34/0x50
create_worker+0xe8/0x260
worker_thread+0x444/0x560
kthread+0x160/0x1a0
ret_from_kernel_thread+0x5c/0x70
List corruption happened because it uses 'load into non-volatile
register' instruction:
Snippet from __kthread_create_on_node:
c000000000136be8: addis r29,r2,-19
c000000000136bec: ld r29,31424(r29)
if (!__list_add_valid(new, prev, next))
c000000000136bf0: mr r3,r30
c000000000136bf4: mr r5,r28
c000000000136bf8: mr r4,r29
c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8>
Register state from WARN_ON():
GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075
GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000
GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa
GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00
GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370
GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000
GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628
GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0
Watchpoint hit at 0xc000000000136bec.
addis r29,r2,-19
=> r29 = 0xc000000001344e00 + (-19 << 16)
=> r29 = 0xc000000001214e00
ld r29,31424(r29)
=> r29 = *(0xc000000001214e00 + 31424)
=> r29 = *(0xc00000000121c8c0)
0xc00000000121c8c0 is where we placed a watchpoint and thus this
instruction was emulated by emulate_step. But because handle_dabr_fault
did not restore emulated register state, r29 still contains stale
value in above register state.
Fixes:
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|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| 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 | ||
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.