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    SubjectRe: [PATCH 02/46] sysfs: crash debugging
    On Thu, Oct 16, 2008 at 01:40:56PM -0400, Mathieu Desnoyers wrote:
    > * Greg Kroah-Hartman (gregkh@suse.de) wrote:
    > > From: Andrew Morton <akpm@linux-foundation.org>
    > >
    > > Print the name of the last-accessed sysfs file when we oops, to help track
    > > down oopses which occur in sysfs store/read handlers. Because these oopses
    > > tend to not leave any trace of the offending code in the stack traces.
    > >
    > > Cc: Kay Sievers <kay.sievers@vrfy.org>
    > > Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    > > Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    > > ---
    > > arch/x86/kernel/dumpstack_32.c | 2 ++
    > > arch/x86/kernel/dumpstack_64.c | 2 ++
    > > fs/sysfs/file.c | 13 +++++++++++++
    > > include/linux/sysfs.h | 6 ++++++
    > > 4 files changed, 23 insertions(+), 0 deletions(-)
    > >
    > > diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
    > > index 201ee35..1a78180 100644
    > > --- a/arch/x86/kernel/dumpstack_32.c
    > > +++ b/arch/x86/kernel/dumpstack_32.c
    > > @@ -13,6 +13,7 @@
    > > #include <linux/kexec.h>
    > > #include <linux/bug.h>
    > > #include <linux/nmi.h>
    > > +#include <linux/sysfs.h>
    > >
    > > #include <asm/stacktrace.h>
    > >
    > > @@ -343,6 +344,7 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
    > > printk("DEBUG_PAGEALLOC");
    > > #endif
    > > printk("\n");
    > > + sysfs_printk_last_file();
    > > if (notify_die(DIE_OOPS, str, regs, err,
    > > current->thread.trap_no, SIGSEGV) == NOTIFY_STOP)
    > > return 1;
    > > diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
    > > index 086cc81..96a5db7 100644
    > > --- a/arch/x86/kernel/dumpstack_64.c
    > > +++ b/arch/x86/kernel/dumpstack_64.c
    > > @@ -13,6 +13,7 @@
    > > #include <linux/kexec.h>
    > > #include <linux/bug.h>
    > > #include <linux/nmi.h>
    > > +#include <linux/sysfs.h>
    > >
    > > #include <asm/stacktrace.h>
    > >
    > > @@ -489,6 +490,7 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
    > > printk("DEBUG_PAGEALLOC");
    > > #endif
    > > printk("\n");
    > > + sysfs_printk_last_file();
    > > if (notify_die(DIE_OOPS, str, regs, err,
    > > current->thread.trap_no, SIGSEGV) == NOTIFY_STOP)
    > > return 1;
    > > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
    > > index c9e4e50..ce8339c 100644
    > > --- a/fs/sysfs/file.c
    > > +++ b/fs/sysfs/file.c
    > > @@ -19,10 +19,18 @@
    > > #include <linux/poll.h>
    > > #include <linux/list.h>
    > > #include <linux/mutex.h>
    > > +#include <linux/limits.h>
    > > #include <asm/uaccess.h>
    > >
    > > #include "sysfs.h"
    > >
    > > +/* used in crash dumps to help with debugging */
    > > +static char last_sysfs_file[PATH_MAX];
    > > +void sysfs_printk_last_file(void)
    > > +{
    > > + printk(KERN_EMERG "last sysfs file: %s\n", last_sysfs_file);
    > > +}
    > > +
    > > /*
    > > * There's one sysfs_buffer for each open file and one
    > > * sysfs_open_dirent for each sysfs_dirent with one or more open
    > > @@ -328,6 +336,11 @@ static int sysfs_open_file(struct inode *inode, struct file *file)
    > > struct sysfs_buffer *buffer;
    > > struct sysfs_ops *ops;
    > > int error = -EACCES;
    > > + char *p;
    > > +
    > > + p = d_path(&file->f_path, last_sysfs_file, sizeof(last_sysfs_file));
    > > + if (p)
    >
    > if (!IS_ERR(p)) ?
    >
    > > + memmove(last_sysfs_file, p, strlen(p) + 1);
    > >
    >
    > Given we do a strlen() here anyway, shouldn't we just use strcpy ?

    Probably would be good.

    Care to send a patch for both of these?

    thanks,

    greg k-h


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