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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-15 00:34:10 +08:00
linux-next/lib/bug.c
Linus Torvalds 5336377d62 modules: Fix module_bug_list list corruption race
With all the recent module loading cleanups, we've minimized the code
that sits under module_mutex, fixing various deadlocks and making it
possible to do most of the module loading in parallel.

However, that whole conversion totally missed the rather obscure code
that adds a new module to the list for BUG() handling.  That code was
doubly obscure because (a) the code itself lives in lib/bugs.c (for
dubious reasons) and (b) it gets called from the architecture-specific
"module_finalize()" rather than from generic code.

Calling it from arch-specific code makes no sense what-so-ever to begin
with, and is now actively wrong since that code isn't protected by the
module loading lock any more.

So this commit moves the "module_bug_{finalize,cleanup}()" calls away
from the arch-specific code, and into the generic code - and in the
process protects it with the module_mutex so that the list operations
are now safe.

Future fixups:
 - move the module list handling code into kernel/module.c where it
   belongs.
 - get rid of 'module_bug_list' and just use the regular list of modules
   (called 'modules' - imagine that) that we already create and maintain
   for other reasons.

Reported-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-05 11:29:27 -07:00

184 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_EMERG "------------[ 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;
}