mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 17:30:02 +00:00
![Prarit Bhargava](/assets/img/avatar_default.png)
rsyslog will display KERN_EMERG messages on a connected terminal. However, these messages are useless/undecipherable for a general user. For example, after a softlockup we get: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Stack: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Call Trace: Message from syslogd@intel-s3e37-04 at Jan 25 14:18:06 ... kernel:Code: ff ff a8 08 75 25 31 d2 48 8d 86 38 e0 ff ff 48 89 d1 0f 01 c8 0f ae f0 48 8b 86 38 e0 ff ff a8 08 75 08 b1 01 4c 89 e0 0f 01 c9 <e8> ea 69 dd ff 4c 29 e8 48 89 c7 e8 0f bc da ff 49 89 c4 49 89 This happens because the printk levels for these messages are incorrect. Only an informational message should be displayed on a terminal. I modified the printk levels for various messages in the kernel and tested the output by using the drivers/misc/lkdtm.c kernel modules (ie, softlockups, panics, hard lockups, etc.) and confirmed that the console output was still the same and that the output to the terminals was correct. For example, in the case of a softlockup we now see the much more informative: Message from syslogd@intel-s3e37-04 at Jan 25 10:18:06 ... BUG: soft lockup - CPU4 stuck for 60s! instead of the above confusing messages. AFAICT, the messages no longer have to be KERN_EMERG. In the most important case of a panic we set console_verbose(). As for the other less severe cases the correct data is output to the console and /var/log/messages. Successfully tested by me using the drivers/misc/lkdtm.c module. Signed-off-by: Prarit Bhargava <prarit@redhat.com> Cc: dzickus@redhat.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1327586134-11926-1-git-send-email-prarit@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
183 lines
4.7 KiB
C
183 lines
4.7 KiB
C
/*
|
|
Generic support for BUG()
|
|
|
|
This respects the following config options:
|
|
|
|
CONFIG_BUG - emit BUG traps. Nothing happens without this.
|
|
CONFIG_GENERIC_BUG - enable this code.
|
|
CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
|
|
the containing struct bug_entry for bug_addr and file.
|
|
CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
|
|
|
|
CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
|
|
(though they're generally always on).
|
|
|
|
CONFIG_GENERIC_BUG is set by each architecture using this code.
|
|
|
|
To use this, your architecture must:
|
|
|
|
1. Set up the config options:
|
|
- Enable CONFIG_GENERIC_BUG if CONFIG_BUG
|
|
|
|
2. Implement BUG (and optionally BUG_ON, WARN, WARN_ON)
|
|
- Define HAVE_ARCH_BUG
|
|
- Implement BUG() to generate a faulting instruction
|
|
- NOTE: struct bug_entry does not have "file" or "line" entries
|
|
when CONFIG_DEBUG_BUGVERBOSE is not enabled, so you must generate
|
|
the values accordingly.
|
|
|
|
3. Implement the trap
|
|
- In the illegal instruction trap handler (typically), verify
|
|
that the fault was in kernel mode, and call report_bug()
|
|
- report_bug() will return whether it was a false alarm, a warning,
|
|
or an actual bug.
|
|
- You must implement the is_valid_bugaddr(bugaddr) callback which
|
|
returns true if the eip is a real kernel address, and it points
|
|
to the expected BUG trap instruction.
|
|
|
|
Jeremy Fitzhardinge <jeremy@goop.org> 2006
|
|
*/
|
|
#include <linux/list.h>
|
|
#include <linux/module.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/bug.h>
|
|
#include <linux/sched.h>
|
|
|
|
extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
|
|
|
|
static inline unsigned long bug_addr(const struct bug_entry *bug)
|
|
{
|
|
#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
|
|
return bug->bug_addr;
|
|
#else
|
|
return (unsigned long)bug + bug->bug_addr_disp;
|
|
#endif
|
|
}
|
|
|
|
#ifdef CONFIG_MODULES
|
|
static LIST_HEAD(module_bug_list);
|
|
|
|
static const struct bug_entry *module_find_bug(unsigned long bugaddr)
|
|
{
|
|
struct module *mod;
|
|
|
|
list_for_each_entry(mod, &module_bug_list, bug_list) {
|
|
const struct bug_entry *bug = mod->bug_table;
|
|
unsigned i;
|
|
|
|
for (i = 0; i < mod->num_bugs; ++i, ++bug)
|
|
if (bugaddr == bug_addr(bug))
|
|
return bug;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
|
|
struct module *mod)
|
|
{
|
|
char *secstrings;
|
|
unsigned int i;
|
|
|
|
mod->bug_table = NULL;
|
|
mod->num_bugs = 0;
|
|
|
|
/* Find the __bug_table section, if present */
|
|
secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
|
|
for (i = 1; i < hdr->e_shnum; i++) {
|
|
if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
|
|
continue;
|
|
mod->bug_table = (void *) sechdrs[i].sh_addr;
|
|
mod->num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Strictly speaking this should have a spinlock to protect against
|
|
* traversals, but since we only traverse on BUG()s, a spinlock
|
|
* could potentially lead to deadlock and thus be counter-productive.
|
|
*/
|
|
list_add(&mod->bug_list, &module_bug_list);
|
|
}
|
|
|
|
void module_bug_cleanup(struct module *mod)
|
|
{
|
|
list_del(&mod->bug_list);
|
|
}
|
|
|
|
#else
|
|
|
|
static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
|
|
{
|
|
return NULL;
|
|
}
|
|
#endif
|
|
|
|
const struct bug_entry *find_bug(unsigned long bugaddr)
|
|
{
|
|
const struct bug_entry *bug;
|
|
|
|
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
|
|
if (bugaddr == bug_addr(bug))
|
|
return bug;
|
|
|
|
return module_find_bug(bugaddr);
|
|
}
|
|
|
|
enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
|
|
{
|
|
const struct bug_entry *bug;
|
|
const char *file;
|
|
unsigned line, warning;
|
|
|
|
if (!is_valid_bugaddr(bugaddr))
|
|
return BUG_TRAP_TYPE_NONE;
|
|
|
|
bug = find_bug(bugaddr);
|
|
|
|
file = NULL;
|
|
line = 0;
|
|
warning = 0;
|
|
|
|
if (bug) {
|
|
#ifdef CONFIG_DEBUG_BUGVERBOSE
|
|
#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
|
|
file = bug->file;
|
|
#else
|
|
file = (const char *)bug + bug->file_disp;
|
|
#endif
|
|
line = bug->line;
|
|
#endif
|
|
warning = (bug->flags & BUGFLAG_WARNING) != 0;
|
|
}
|
|
|
|
if (warning) {
|
|
/* this is a WARN_ON rather than BUG/BUG_ON */
|
|
printk(KERN_WARNING "------------[ cut here ]------------\n");
|
|
|
|
if (file)
|
|
printk(KERN_WARNING "WARNING: at %s:%u\n",
|
|
file, line);
|
|
else
|
|
printk(KERN_WARNING "WARNING: at %p "
|
|
"[verbose debug info unavailable]\n",
|
|
(void *)bugaddr);
|
|
|
|
print_modules();
|
|
show_regs(regs);
|
|
print_oops_end_marker();
|
|
add_taint(BUG_GET_TAINT(bug));
|
|
return BUG_TRAP_TYPE_WARN;
|
|
}
|
|
|
|
printk(KERN_DEFAULT "------------[ cut here ]------------\n");
|
|
|
|
if (file)
|
|
printk(KERN_CRIT "kernel BUG at %s:%u!\n",
|
|
file, line);
|
|
else
|
|
printk(KERN_CRIT "Kernel BUG at %p "
|
|
"[verbose debug info unavailable]\n",
|
|
(void *)bugaddr);
|
|
|
|
return BUG_TRAP_TYPE_BUG;
|
|
}
|