cregit-Linux how code gets into the kernel

Release 4.12 lib/bug.c

Directory: lib
  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:

  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 <> 2006

#define pr_fmt(fmt) fmt

#include <linux/list.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/sched.h>
#include <linux/rculist.h>

extern 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 }


Jan Beulich37100.00%1100.00%

#ifdef CONFIG_MODULES /* Updates are protected by module mutex */ static LIST_HEAD(module_bug_list);
static struct bug_entry *module_find_bug(unsigned long bugaddr) { struct module *mod; struct bug_entry *bug = NULL; rcu_read_lock_sched(); list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { unsigned i; bug = mod->bug_table; for (i = 0; i < mod->num_bugs; ++i, ++bug) if (bugaddr == bug_addr(bug)) goto out; } bug = NULL; out: rcu_read_unlock_sched(); return bug; }


Jeremy Fitzhardinge5663.64%125.00%
Masami Hiramatsu2730.68%125.00%
Jan Beulich33.41%125.00%
Peter Zijlstra22.27%125.00%

void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *mod) { char *secstrings; unsigned int i; lockdep_assert_held(&module_mutex); 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. * Thus, this uses RCU to safely manipulate the bug list, since BUG * must run in non-interruptive state. */ list_add_rcu(&mod->bug_list, &module_bug_list); }


Jeremy Fitzhardinge13493.71%125.00%
Peter Zijlstra64.20%125.00%
Masami Hiramatsu21.40%125.00%
Linus Torvalds10.70%125.00%

void module_bug_cleanup(struct module *mod) { lockdep_assert_held(&module_mutex); list_del_rcu(&mod->bug_list); }


Jeremy Fitzhardinge1770.83%133.33%
Peter Zijlstra625.00%133.33%
Masami Hiramatsu14.17%133.33%

static inline struct bug_entry *module_find_bug(unsigned long bugaddr) { return NULL; }


Jeremy Fitzhardinge16100.00%1100.00%

struct bug_entry *find_bug(unsigned long bugaddr) { 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); }


Jeremy Fitzhardinge4493.62%150.00%
Jan Beulich36.38%150.00%

enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs) { struct bug_entry *bug; const char *file; unsigned line, warning, once, done; 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; once = (bug->flags & BUGFLAG_ONCE) != 0; done = (bug->flags & BUGFLAG_DONE) != 0; if (warning && once) { if (done) return BUG_TRAP_TYPE_WARN; /* * Since this is the only store, concurrency is not an issue. */ bug->flags |= BUGFLAG_DONE; } } if (warning) { /* this is a WARN_ON rather than BUG/BUG_ON */ __warn(file, line, (void *)bugaddr, BUG_GET_TAINT(bug), regs, NULL); return BUG_TRAP_TYPE_WARN; } printk(KERN_DEFAULT "------------[ cut here ]------------\n"); if (file) pr_crit("kernel BUG at %s:%u!\n", file, line); else pr_crit("Kernel BUG at %p [verbose debug info unavailable]\n", (void *)bugaddr); return BUG_TRAP_TYPE_BUG; }


Jeremy Fitzhardinge13458.01%19.09%
Peter Zijlstra5021.65%19.09%
Jan Beulich208.66%19.09%
Anton Blanchard62.60%19.09%
Heiko Carstens52.16%19.09%
Josh Poimboeuf52.16%19.09%
Ben Hutchings41.73%19.09%
Fabian Frederick31.30%19.09%
Paul Mundt20.87%19.09%
Prarit Bhargava10.43%19.09%
Rusty Russell10.43%19.09%

Overall Contributors

Jeremy Fitzhardinge43268.03%16.25%
Jan Beulich6410.08%16.25%
Peter Zijlstra6410.08%212.50%
Masami Hiramatsu304.72%16.25%
Fabian Frederick101.57%16.25%
Heiko Carstens81.26%16.25%
Anton Blanchard60.94%16.25%
Josh Poimboeuf50.79%16.25%
Paul Mundt50.79%16.25%
Ben Hutchings40.63%16.25%
Ingo Molnar30.47%16.25%
Rusty Russell20.31%212.50%
Linus Torvalds10.16%16.25%
Prarit Bhargava10.16%16.25%
Directory: lib
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