Hi guys: Very for the sorry for disturbs, this is a test for local git send email setup and sent by mistake. Please ignore this. Regards Zengtao > -----邮件原件----- > 发件人: Zengtao (B) > 发送时间: 2021年6月22日 14:52 > 收件人: Zengtao (B) <prime.zeng@xxxxxxxxxxxxx> > 抄送: Alexey Dobriyan <adobriyan@xxxxxxxxx>; Andi Kleen <andi@xxxxxxxxxxxxxx>; > David Howells <dhowells@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx>; Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > 主题: [PATCH] afs: fix tracepoint string placement with built-in AFS > > From: Alexey Dobriyan <adobriyan@xxxxxxxxx> > > 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> > Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > --- > fs/afs/cmservice.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/afs/cmservice.c b/fs/afs/cmservice.c > index d3c6bb22c5f4..d39c63b13d9f 100644 > --- a/fs/afs/cmservice.c > +++ b/fs/afs/cmservice.c > @@ -30,8 +30,9 @@ static void SRXAFSCB_TellMeAboutYourself(struct > work_struct *); > 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 > -- > 2.30.0
