breakpoints.c

/*
 * This file is part of ltrace.
 * Copyright (C) 2006,2007,2011,2012 Petr Machata, Red Hat Inc.
 * Copyright (C) 2009 Juan Cespedes
 * Copyright (C) 1998,2001,2002,2003,2007,2008,2009 Juan Cespedes
 * Copyright (C) 2006 Ian Wienand
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include "config.h"

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef __powerpc__
#include <sys/ptrace.h>
#endif

#include "backend.h"
#include "breakpoint.h"
#include "debug.h"
#include "library.h"
#include "ltrace-elf.h"
#include "proc.h"

#ifndef ARCH_HAVE_TRANSLATE_ADDRESS
int
arch_translate_address_dyn(struct Process *proc,
		       arch_addr_t addr, arch_addr_t *ret)
{
	*ret = addr;
	return 0;
}

struct ltelf;
int
arch_translate_address(struct ltelf *lte,
		       arch_addr_t addr, arch_addr_t *ret)
{
	*ret = addr;
	return 0;
}
#endif

void
breakpoint_on_hit(struct breakpoint *bp, struct Process *proc)
{
	assert(bp != NULL);
	if (bp->cbs != NULL && bp->cbs->on_hit != NULL)
		(bp->cbs->on_hit)(bp, proc);
}

void
breakpoint_on_continue(struct breakpoint *bp, struct Process *proc)
{
	assert(bp != NULL);
	if (bp->cbs != NULL && bp->cbs->on_continue != NULL)
		(bp->cbs->on_continue)(bp, proc);
	else
		continue_after_breakpoint(proc, bp);
}

void
breakpoint_on_retract(struct breakpoint *bp, struct Process *proc)
{
	assert(bp != NULL);
	if (bp->cbs != NULL && bp->cbs->on_retract != NULL)
		(bp->cbs->on_retract)(bp, proc);
}

/*****************************************************************************/

struct breakpoint *
address2bpstruct(Process *proc, void *addr)
{
	assert(proc != NULL);
	assert(proc->breakpoints != NULL);
	assert(proc->leader == proc);
	debug(DEBUG_FUNCTION, "address2bpstruct(pid=%d, addr=%p)", proc->pid, addr);
	return dict_find_entry(proc->breakpoints, addr);
}

#ifndef ARCH_HAVE_BREAKPOINT_DATA
int
arch_breakpoint_init(struct Process *proc, struct breakpoint *sbp)
{
	return 0;
}

void
arch_breakpoint_destroy(struct breakpoint *sbp)
{
}

int
arch_breakpoint_clone(struct breakpoint *retp, struct breakpoint *sbp)
{
	return 0;
}
#endif

static void
breakpoint_init_base(struct breakpoint *bp, struct Process *proc,
		     arch_addr_t addr, struct library_symbol *libsym)
{
	bp->cbs = NULL;
	bp->addr = addr;
	memset(bp->orig_value, 0, sizeof(bp->orig_value));
	bp->enabled = 0;
	bp->libsym = libsym;
}

/* On second thought, I don't think we need PROC.  All the translation
 * (arch_translate_address in particular) should be doable using
 * static lookups of various sections in the ELF file.  We shouldn't
 * need process for anything.  */
int
breakpoint_init(struct breakpoint *bp, struct Process *proc,
		arch_addr_t addr, struct library_symbol *libsym)
{
	breakpoint_init_base(bp, proc, addr, libsym);
	return arch_breakpoint_init(proc, bp);
}

void
breakpoint_set_callbacks(struct breakpoint *bp, struct bp_callbacks *cbs)
{
	if (bp->cbs != NULL)
		assert(bp->cbs == NULL);
	bp->cbs = cbs;
}

void
breakpoint_destroy(struct breakpoint *bp)
{
	if (bp == NULL)
		return;
	arch_breakpoint_destroy(bp);
}

struct find_symbol_data {
	struct library_symbol *old_libsym;
	struct library_symbol *found_libsym;
};

static enum callback_status
find_sym_in_lib(struct Process *proc, struct library *lib, void *u)
{
	struct find_symbol_data *fs = u;
	fs->found_libsym
		= library_each_symbol(lib, NULL, library_symbol_equal_cb,
				      fs->old_libsym);
	return fs->found_libsym != NULL ? CBS_STOP : CBS_CONT;
}

int
breakpoint_clone(struct breakpoint *retp, struct Process *new_proc,
		 struct breakpoint *bp, struct Process *old_proc)
{
	/* Find library and symbol that this breakpoint was linked to.  */
	struct library_symbol *libsym = bp->libsym;
	struct library *lib = NULL;
	if (libsym != NULL) {
		struct find_symbol_data f_data = {
			.old_libsym = libsym,
		};
		lib = proc_each_library(old_proc, NULL,
					find_sym_in_lib, &f_data);
		assert(lib != NULL);
		libsym = f_data.found_libsym;
	}

	/* LIB and LIBSYM now hold the new library and symbol that
	 * correspond to the original breakpoint.  Now we can do the
	 * clone itself.  */
	breakpoint_init_base(retp, new_proc, bp->addr, libsym);
	memcpy(retp->orig_value, bp->orig_value, sizeof(bp->orig_value));
	retp->enabled = bp->enabled;
	if (arch_breakpoint_clone(retp, bp) < 0)
		return -1;
	breakpoint_set_callbacks(retp, bp->cbs);
	return 0;
}

int
breakpoint_turn_on(struct breakpoint *bp, struct Process *proc)
{
	bp->enabled++;
	if (bp->enabled == 1) {
		assert(proc->pid != 0);
		enable_breakpoint(proc, bp);
	}
	return 0;
}

int
breakpoint_turn_off(struct breakpoint *bp, struct Process *proc)
{
	bp->enabled--;
	if (bp->enabled == 0)
		disable_breakpoint(proc, bp);
	assert(bp->enabled >= 0);
	return 0;
}

struct breakpoint *
insert_breakpoint(struct Process *proc, void *addr,
		  struct library_symbol *libsym)
{
	Process *leader = proc->leader;

	/* Only the group leader should be getting the breakpoints and
	 * thus have ->breakpoint initialized.  */
	assert(leader != NULL);
	assert(leader->breakpoints != NULL);

	debug(DEBUG_FUNCTION, "insert_breakpoint(pid=%d, addr=%p, symbol=%s)",
	      proc->pid, addr, libsym ? libsym->name : "NULL");

	assert(addr != 0);

	/* XXX what we need to do instead is have a list of
	 * breakpoints that are enabled at this address.  The
	 * following works if every breakpoint is the same and there's
	 * no extra data, but that doesn't hold anymore.  For now it
	 * will suffice, about the only realistic case where we need
	 * to have more than one breakpoint per address is return from
	 * a recursive library call.  */
	struct breakpoint *sbp = dict_find_entry(leader->breakpoints, addr);
	if (sbp == NULL) {
		sbp = malloc(sizeof(*sbp));
		if (sbp == NULL
		    || breakpoint_init(sbp, proc, addr, libsym) < 0) {
			free(sbp);
			return NULL;
		}
		if (proc_add_breakpoint(leader, sbp) < 0) {
		fail:
			breakpoint_destroy(sbp);
			free(sbp);
			return NULL;
		}
	}

	if (breakpoint_turn_on(sbp, proc) < 0) {
		proc_remove_breakpoint(leader, sbp);
		goto fail;
	}

	return sbp;
}

void
delete_breakpoint(Process *proc, void *addr)
{
	debug(DEBUG_FUNCTION, "delete_breakpoint(pid=%d, addr=%p)", proc->pid, addr);

	Process * leader = proc->leader;
	assert(leader != NULL);

	struct breakpoint *sbp = dict_find_entry(leader->breakpoints, addr);
	assert(sbp != NULL);
	/* This should only happen on out-of-memory conditions. */
	if (sbp == NULL)
		return;

	if (breakpoint_turn_off(sbp, proc) < 0) {
		fprintf(stderr, "Couldn't turn off the breakpoint %s@%p\n",
			breakpoint_name(sbp), sbp->addr);
		return;
	}
	if (sbp->enabled == 0) {
		proc_remove_breakpoint(leader, sbp);
		breakpoint_destroy(sbp);
		free(sbp);
	}
}

const char *
breakpoint_name(const struct breakpoint *bp)
{
	assert(bp != NULL);
	return bp->libsym != NULL ? bp->libsym->name : NULL;
}

struct library *
breakpoint_library(const struct breakpoint *bp)
{
	assert(bp != NULL);
	return bp->libsym != NULL ? bp->libsym->lib : NULL;
}

static void
enable_bp_cb(void *addr, void *sbp, void *proc)
{
	debug(DEBUG_FUNCTION, "enable_bp_cb(pid=%d)", ((Process *)proc)->pid);
	if (((struct breakpoint *)sbp)->enabled)
		enable_breakpoint(proc, sbp);
}

void
enable_all_breakpoints(Process *proc)
{
	debug(DEBUG_FUNCTION, "enable_all_breakpoints(pid=%d)", proc->pid);

	debug(1, "Enabling breakpoints for pid %u...", proc->pid);
	if (proc->breakpoints) {
		dict_apply_to_all(proc->breakpoints, enable_bp_cb,
				  proc);
	}
}

static void
disable_bp_cb(void *addr, void *sbp, void *proc)
{
	debug(DEBUG_FUNCTION, "disable_bp_cb(pid=%d)", ((Process *)proc)->pid);
	if (((struct breakpoint *)sbp)->enabled)
		disable_breakpoint(proc, sbp);
}

void
disable_all_breakpoints(Process *proc) {
	debug(DEBUG_FUNCTION, "disable_all_breakpoints(pid=%d)", proc->pid);
	assert(proc->leader == proc);
	dict_apply_to_all(proc->breakpoints, disable_bp_cb, proc);
}

/* XXX This is not currently properly supported.  On clone, this is
 * just sliced.  Hopefully at the point that clone is done, this
 * breakpoint is not necessary anymore.  If this use case ends up
 * being important, we need to add a clone and destroy callbacks to
 * breakpoints, and we should also probably drop arch_breakpoint_data
 * so that we don't end up with two different customization mechanisms
 * for one structure.  */
struct entry_breakpoint {
	struct breakpoint super;
	arch_addr_t dyn_addr;
};

static void
entry_breakpoint_on_hit(struct breakpoint *a, struct Process *proc)
{
	struct entry_breakpoint *bp = (void *)a;
	if (proc == NULL || proc->leader == NULL)
		return;
	arch_addr_t dyn_addr = bp->dyn_addr;
	delete_breakpoint(proc, bp->super.addr);
	linkmap_init(proc, dyn_addr);
	arch_dynlink_done(proc);
}

int
entry_breakpoint_init(struct Process *proc,
		      struct entry_breakpoint *bp, arch_addr_t addr,
		      struct library *lib)
{
	int err;
	if ((err = breakpoint_init(&bp->super, proc, addr, NULL)) < 0)
		return err;

	static struct bp_callbacks entry_callbacks = {
		.on_hit = entry_breakpoint_on_hit,
	};
	bp->super.cbs = &entry_callbacks;
	bp->dyn_addr = lib->dyn_addr;
	return 0;
}

int
breakpoints_init(Process *proc)
{
	debug(DEBUG_FUNCTION, "breakpoints_init(pid=%d)", proc->pid);

	/* XXX breakpoint dictionary should be initialized
	 * outside.  Here we just put in breakpoints.  */
	assert(proc->breakpoints != NULL);

	/* Only the thread group leader should hold the breakpoints.  */
	assert(proc->leader == proc);

	/* N.B. the following used to be conditional on this, and
	 * maybe it still needs to be.  */
	assert(proc->filename != NULL);

	struct library *lib = ltelf_read_main_binary(proc, proc->filename);
	struct entry_breakpoint *entry_bp = NULL;
	int bp_state = 0;
	int result = -1;
	switch (lib != NULL) {
	fail:
		switch (bp_state) {
		case 2:
			proc_remove_library(proc, lib);
			proc_remove_breakpoint(proc, &entry_bp->super);
		case 1:
			breakpoint_destroy(&entry_bp->super);
		}
		library_destroy(lib);
		free(entry_bp);
	case 0:
		return result;
	}

	entry_bp = malloc(sizeof(*entry_bp));
	if (entry_bp == NULL
	    || (entry_breakpoint_init(proc, entry_bp,
				      lib->entry, lib)) < 0) {
		fprintf(stderr,
			"Couldn't initialize entry breakpoint for PID %d.\n"
			"Some tracing events may be missed.\n", proc->pid);
		free(entry_bp);

	} else {
		++bp_state;

		if ((result = proc_add_breakpoint(proc, &entry_bp->super)) < 0)
			goto fail;
		++bp_state;

		if ((result = breakpoint_turn_on(&entry_bp->super, proc)) < 0)
			goto fail;
	}
	proc_add_library(proc, lib);

	proc->callstack_depth = 0;
	return 0;
}