The patch titled
Subject: afs: fix tracepoint string placement with built-in AFS
has been removed from the -mm tree. Its filename was
afs-fix-tracepoint-string-placement-with-built-in-afs.patch
This patch was dropped because an alternative patch was merged
------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: afs: fix tracepoint string placement with built-in AFS
I was adding custom tracepoint to the kernel, grabbed full F34 kernel
.config, disabled modules and booted whole shebang as VM kernel.
Then did
perf record -a -e ...
It crashed:
general protection fault, probably for non-canonical address 0x435f5346592e4243: 0000 [#1] SMP PTI
CPU: 1 PID: 842 Comm: cat Not tainted 5.12.6+ #26
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
RIP: 0010:t_show+0x22/0xd0
Then reproducer was narrowed to
# cat /sys/kernel/tracing/printk_formats
Original F34 kernel with modules didn't crash.
So I started to disable options and after disabling AFS everything started
working again.
The root cause is that AFS was placing char arrays content into a section
full of _pointers_ to strings with predictable consequences.
Non canonical address 435f5346592e4243 is "CB.YFS_" which came from
CM_NAME macro.
The fix is to create char array and pointer to it separatedly.
Steps to reproduce:
CONFIG_AFS=y
CONFIG_TRACING=y
# cat /sys/kernel/tracing/printk_formats
Link: https://lkml.kernel.org/r/YLAXfvZ+rObEOdc/@localhost.localdomain
Fixes: 8e8d7f13b6d5a9 ("afs: Add some tracepoints")
Signed-off-by: Alexey Dobriyan (SK hynix) <adobriyan@xxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/afs/cmservice.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/afs/cmservice.c~afs-fix-tracepoint-string-placement-with-built-in-afs
+++ a/fs/afs/cmservice.c
@@ -30,8 +30,9 @@ static void SRXAFSCB_TellMeAboutYourself
static int afs_deliver_yfs_cb_callback(struct afs_call *);
#define CM_NAME(name) \
- char afs_SRXCB##name##_name[] __tracepoint_string = \
- "CB." #name
+ const char afs_SRXCB##name##_name[] = "CB." #name; \
+ static const char *_afs_SRXCB##name##_name __tracepoint_string =\
+ afs_SRXCB##name##_name
/*
* CB.CallBack operation type
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
lib-memscan-fixlet.patch
lib-uninline-simple_strtoull.patch
exec-remove-checks-in-__register_bimfmt.patch
