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d5d8d3d0d4
kdb_printf_lock does not prevent other CPUs from entering the critical
section because it is ignored when KDB_STATE_PRINTF_LOCK is set.
The problematic situation might look like:
CPU0 CPU1
vkdb_printf()
if (!KDB_STATE(PRINTF_LOCK))
KDB_STATE_SET(PRINTF_LOCK);
spin_lock_irqsave(&kdb_printf_lock, flags);
vkdb_printf()
if (!KDB_STATE(PRINTF_LOCK))
BANG: The PRINTF_LOCK state is set and CPU1 is entering the critical
section without spinning on the lock.
The problem is that the code tries to implement locking using two state
variables that are not handled atomically. Well, we need a custom
locking because we want to allow reentering the critical section on the
very same CPU.
Let's use solution from Petr Zijlstra that was proposed for a similar
scenario, see
https://lkml.kernel.org/r/20161018171513.734367391@infradead.org
This patch uses the same trick with cmpxchg(). The only difference is
that we want to handle only recursion from the same context and
therefore we disable interrupts.
In addition, KDB_STATE_PRINTF_LOCK is removed. In fact, we are not able
to set it a non-racy way.
Link: http://lkml.kernel.org/r/1480412276-16690-3-git-send-email-pmladek@suse.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
261 lines
9.4 KiB
C
261 lines
9.4 KiB
C
#ifndef _KDBPRIVATE_H
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#define _KDBPRIVATE_H
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/*
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* Kernel Debugger Architecture Independent Private Headers
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (c) 2000-2004 Silicon Graphics, Inc. All Rights Reserved.
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* Copyright (c) 2009 Wind River Systems, Inc. All Rights Reserved.
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*/
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#include <linux/kgdb.h>
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#include "../debug_core.h"
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/* Kernel Debugger Command codes. Must not overlap with error codes. */
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#define KDB_CMD_GO (-1001)
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#define KDB_CMD_CPU (-1002)
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#define KDB_CMD_SS (-1003)
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#define KDB_CMD_KGDB (-1005)
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/* Internal debug flags */
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#define KDB_DEBUG_FLAG_BP 0x0002 /* Breakpoint subsystem debug */
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#define KDB_DEBUG_FLAG_BB_SUMM 0x0004 /* Basic block analysis, summary only */
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#define KDB_DEBUG_FLAG_AR 0x0008 /* Activation record, generic */
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#define KDB_DEBUG_FLAG_ARA 0x0010 /* Activation record, arch specific */
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#define KDB_DEBUG_FLAG_BB 0x0020 /* All basic block analysis */
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#define KDB_DEBUG_FLAG_STATE 0x0040 /* State flags */
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#define KDB_DEBUG_FLAG_MASK 0xffff /* All debug flags */
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#define KDB_DEBUG_FLAG_SHIFT 16 /* Shift factor for dbflags */
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#define KDB_DEBUG(flag) (kdb_flags & \
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(KDB_DEBUG_FLAG_##flag << KDB_DEBUG_FLAG_SHIFT))
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#define KDB_DEBUG_STATE(text, value) if (KDB_DEBUG(STATE)) \
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kdb_print_state(text, value)
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#if BITS_PER_LONG == 32
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#define KDB_PLATFORM_ENV "BYTESPERWORD=4"
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#define kdb_machreg_fmt "0x%lx"
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#define kdb_machreg_fmt0 "0x%08lx"
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#define kdb_bfd_vma_fmt "0x%lx"
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#define kdb_bfd_vma_fmt0 "0x%08lx"
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#define kdb_elfw_addr_fmt "0x%x"
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#define kdb_elfw_addr_fmt0 "0x%08x"
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#define kdb_f_count_fmt "%d"
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#elif BITS_PER_LONG == 64
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#define KDB_PLATFORM_ENV "BYTESPERWORD=8"
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#define kdb_machreg_fmt "0x%lx"
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#define kdb_machreg_fmt0 "0x%016lx"
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#define kdb_bfd_vma_fmt "0x%lx"
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#define kdb_bfd_vma_fmt0 "0x%016lx"
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#define kdb_elfw_addr_fmt "0x%x"
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#define kdb_elfw_addr_fmt0 "0x%016x"
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#define kdb_f_count_fmt "%ld"
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#endif
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/*
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* KDB_MAXBPT describes the total number of breakpoints
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* supported by this architecure.
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*/
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#define KDB_MAXBPT 16
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/* Symbol table format returned by kallsyms. */
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typedef struct __ksymtab {
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unsigned long value; /* Address of symbol */
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const char *mod_name; /* Module containing symbol or
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* "kernel" */
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unsigned long mod_start;
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unsigned long mod_end;
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const char *sec_name; /* Section containing symbol */
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unsigned long sec_start;
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unsigned long sec_end;
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const char *sym_name; /* Full symbol name, including
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* any version */
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unsigned long sym_start;
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unsigned long sym_end;
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} kdb_symtab_t;
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extern int kallsyms_symbol_next(char *prefix_name, int flag);
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extern int kallsyms_symbol_complete(char *prefix_name, int max_len);
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/* Exported Symbols for kernel loadable modules to use. */
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extern int kdb_getarea_size(void *, unsigned long, size_t);
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extern int kdb_putarea_size(unsigned long, void *, size_t);
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/*
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* Like get_user and put_user, kdb_getarea and kdb_putarea take variable
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* names, not pointers. The underlying *_size functions take pointers.
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*/
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#define kdb_getarea(x, addr) kdb_getarea_size(&(x), addr, sizeof((x)))
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#define kdb_putarea(addr, x) kdb_putarea_size(addr, &(x), sizeof((x)))
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extern int kdb_getphysword(unsigned long *word,
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unsigned long addr, size_t size);
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extern int kdb_getword(unsigned long *, unsigned long, size_t);
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extern int kdb_putword(unsigned long, unsigned long, size_t);
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extern int kdbgetularg(const char *, unsigned long *);
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extern int kdbgetu64arg(const char *, u64 *);
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extern char *kdbgetenv(const char *);
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extern int kdbgetaddrarg(int, const char **, int*, unsigned long *,
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long *, char **);
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extern int kdbgetsymval(const char *, kdb_symtab_t *);
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extern int kdbnearsym(unsigned long, kdb_symtab_t *);
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extern void kdbnearsym_cleanup(void);
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extern char *kdb_strdup(const char *str, gfp_t type);
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extern void kdb_symbol_print(unsigned long, const kdb_symtab_t *, unsigned int);
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/* Routine for debugging the debugger state. */
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extern void kdb_print_state(const char *, int);
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extern int kdb_state;
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#define KDB_STATE_KDB 0x00000001 /* Cpu is inside kdb */
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#define KDB_STATE_LEAVING 0x00000002 /* Cpu is leaving kdb */
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#define KDB_STATE_CMD 0x00000004 /* Running a kdb command */
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#define KDB_STATE_KDB_CONTROL 0x00000008 /* This cpu is under
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* kdb control */
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#define KDB_STATE_HOLD_CPU 0x00000010 /* Hold this cpu inside kdb */
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#define KDB_STATE_DOING_SS 0x00000020 /* Doing ss command */
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#define KDB_STATE_SSBPT 0x00000080 /* Install breakpoint
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* after one ss, independent of
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* DOING_SS */
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#define KDB_STATE_REENTRY 0x00000100 /* Valid re-entry into kdb */
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#define KDB_STATE_SUPPRESS 0x00000200 /* Suppress error messages */
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#define KDB_STATE_PAGER 0x00000400 /* pager is available */
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#define KDB_STATE_GO_SWITCH 0x00000800 /* go is switching
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* back to initial cpu */
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#define KDB_STATE_WAIT_IPI 0x00002000 /* Waiting for kdb_ipi() NMI */
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#define KDB_STATE_RECURSE 0x00004000 /* Recursive entry to kdb */
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#define KDB_STATE_IP_ADJUSTED 0x00008000 /* Restart IP has been
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* adjusted */
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#define KDB_STATE_GO1 0x00010000 /* go only releases one cpu */
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#define KDB_STATE_KEYBOARD 0x00020000 /* kdb entered via
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* keyboard on this cpu */
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#define KDB_STATE_KEXEC 0x00040000 /* kexec issued */
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#define KDB_STATE_DOING_KGDB 0x00080000 /* kgdb enter now issued */
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#define KDB_STATE_KGDB_TRANS 0x00200000 /* Transition to kgdb */
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#define KDB_STATE_ARCH 0xff000000 /* Reserved for arch
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* specific use */
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#define KDB_STATE(flag) (kdb_state & KDB_STATE_##flag)
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#define KDB_STATE_SET(flag) ((void)(kdb_state |= KDB_STATE_##flag))
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#define KDB_STATE_CLEAR(flag) ((void)(kdb_state &= ~KDB_STATE_##flag))
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extern int kdb_nextline; /* Current number of lines displayed */
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typedef struct _kdb_bp {
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unsigned long bp_addr; /* Address breakpoint is present at */
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unsigned int bp_free:1; /* This entry is available */
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unsigned int bp_enabled:1; /* Breakpoint is active in register */
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unsigned int bp_type:4; /* Uses hardware register */
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unsigned int bp_installed:1; /* Breakpoint is installed */
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unsigned int bp_delay:1; /* Do delayed bp handling */
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unsigned int bp_delayed:1; /* Delayed breakpoint */
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unsigned int bph_length; /* HW break length */
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} kdb_bp_t;
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#ifdef CONFIG_KGDB_KDB
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extern kdb_bp_t kdb_breakpoints[/* KDB_MAXBPT */];
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/* The KDB shell command table */
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typedef struct _kdbtab {
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char *cmd_name; /* Command name */
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kdb_func_t cmd_func; /* Function to execute command */
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char *cmd_usage; /* Usage String for this command */
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char *cmd_help; /* Help message for this command */
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short cmd_minlen; /* Minimum legal # command
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* chars required */
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kdb_cmdflags_t cmd_flags; /* Command behaviour flags */
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} kdbtab_t;
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extern int kdb_bt(int, const char **); /* KDB display back trace */
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/* KDB breakpoint management functions */
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extern void kdb_initbptab(void);
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extern void kdb_bp_install(struct pt_regs *);
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extern void kdb_bp_remove(void);
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typedef enum {
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KDB_DB_BPT, /* Breakpoint */
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KDB_DB_SS, /* Single-step trap */
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KDB_DB_SSBPT, /* Single step over breakpoint */
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KDB_DB_NOBPT /* Spurious breakpoint */
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} kdb_dbtrap_t;
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extern int kdb_main_loop(kdb_reason_t, kdb_reason_t,
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int, kdb_dbtrap_t, struct pt_regs *);
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/* Miscellaneous functions and data areas */
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extern int kdb_grepping_flag;
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#define KDB_GREPPING_FLAG_SEARCH 0x8000
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extern char kdb_grep_string[];
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#define KDB_GREP_STRLEN 256
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extern int kdb_grep_leading;
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extern int kdb_grep_trailing;
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extern char *kdb_cmds[];
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extern unsigned long kdb_task_state_string(const char *);
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extern char kdb_task_state_char (const struct task_struct *);
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extern unsigned long kdb_task_state(const struct task_struct *p,
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unsigned long mask);
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extern void kdb_ps_suppressed(void);
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extern void kdb_ps1(const struct task_struct *p);
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extern void kdb_print_nameval(const char *name, unsigned long val);
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extern void kdb_send_sig_info(struct task_struct *p, struct siginfo *info);
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extern void kdb_meminfo_proc_show(void);
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extern char *kdb_getstr(char *, size_t, const char *);
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extern void kdb_gdb_state_pass(char *buf);
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/* Defines for kdb_symbol_print */
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#define KDB_SP_SPACEB 0x0001 /* Space before string */
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#define KDB_SP_SPACEA 0x0002 /* Space after string */
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#define KDB_SP_PAREN 0x0004 /* Parenthesis around string */
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#define KDB_SP_VALUE 0x0008 /* Print the value of the address */
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#define KDB_SP_SYMSIZE 0x0010 /* Print the size of the symbol */
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#define KDB_SP_NEWLINE 0x0020 /* Newline after string */
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#define KDB_SP_DEFAULT (KDB_SP_VALUE|KDB_SP_PAREN)
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#define KDB_TSK(cpu) kgdb_info[cpu].task
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#define KDB_TSKREGS(cpu) kgdb_info[cpu].debuggerinfo
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extern struct task_struct *kdb_curr_task(int);
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#define kdb_task_has_cpu(p) (task_curr(p))
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/* Simplify coexistence with NPTL */
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#define kdb_do_each_thread(g, p) do_each_thread(g, p)
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#define kdb_while_each_thread(g, p) while_each_thread(g, p)
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#define GFP_KDB (in_interrupt() ? GFP_ATOMIC : GFP_KERNEL)
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extern void *debug_kmalloc(size_t size, gfp_t flags);
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extern void debug_kfree(void *);
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extern void debug_kusage(void);
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extern void kdb_set_current_task(struct task_struct *);
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extern struct task_struct *kdb_current_task;
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#ifdef CONFIG_KDB_KEYBOARD
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extern void kdb_kbd_cleanup_state(void);
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#else /* ! CONFIG_KDB_KEYBOARD */
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#define kdb_kbd_cleanup_state()
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#endif /* ! CONFIG_KDB_KEYBOARD */
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#ifdef CONFIG_MODULES
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extern struct list_head *kdb_modules;
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#endif /* CONFIG_MODULES */
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extern char kdb_prompt_str[];
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#define KDB_WORD_SIZE ((int)sizeof(unsigned long))
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#endif /* CONFIG_KGDB_KDB */
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#endif /* !_KDBPRIVATE_H */
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