0568462bbf
For the BTS recording format, we sometimes get a FROM->TO record where the FROM address lies in the kernel and the TO address lies in user space at whatever address the user process was resumed. GDB has a heuristic to filter out such records based on looking at the most significant bit in the PC. This works fine for 64-bit systems but it doesn't always work for 32-bit systems. Libraries that are loaded at fairly high addresses might be mistaken for kernel code and branches inside the library are filtered out. Change the heuristic to (again heuristically) try to determine the lowest address in kernel space. Any PC that is smaller than that should be in user space. On today's systems, there should be a symbol "_text" at that address. Read /proc/kallsyms and search for that symbol. It is not guaranteed that /proc/kallsyms is readable on all systems. On 64-bit systems, we fall back to check the most significant bit. On 32-bit systems, we refrain from filtering out addresses. The filtering should really be done by the kernel. And it soon will be: https://lkml.org/lkml/2015/8/31/212. gdb/ * nat/linux-btrace.h (struct btrace_target_info) <ptr_bits>: Remove. * nat/linux-btrace.c: Include filestuff.h and inttypes.h. Remove include of sys/utsname.h. (linux_determine_kernel_ptr_bits): Remove. (linux_determine_kernel_start): New. (perf_event_is_kernel_addr): Remove tinfo argument. Update users. Update check. (perf_event_skip_bts_record): Remove tinfo argument. Update users. (linux_enable_bts, linux_enable_pt): Remove tinfo->ptr_bits initialization. * x86-linux-nat.c (x86_linux_enable_btrace): Remove ptr_bits assignment. gdbserver/ * linux-low.c (linux_low_enable_btrace): Remove. (linux_target_ops): Replace linux_low_enable_btrace with linux_enable_btrace.
124 lines
3.4 KiB
C
124 lines
3.4 KiB
C
/* Linux-dependent part of branch trace support for GDB, and GDBserver.
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Copyright (C) 2013-2015 Free Software Foundation, Inc.
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Contributed by Intel Corp. <markus.t.metzger@intel.com>
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef LINUX_BTRACE_H
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#define LINUX_BTRACE_H
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#include "btrace-common.h"
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#include "vec.h"
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#if HAVE_LINUX_PERF_EVENT_H
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# include <linux/perf_event.h>
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#endif
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struct target_ops;
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#if HAVE_LINUX_PERF_EVENT_H
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/* A Linux perf event buffer. */
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struct perf_event_buffer
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{
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/* The mapped memory. */
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const uint8_t *mem;
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/* The size of the mapped memory in bytes. */
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size_t size;
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/* A pointer to the data_head field for this buffer. */
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volatile __u64 *data_head;
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/* The data_head value from the last read. */
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__u64 last_head;
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};
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/* Branch trace target information for BTS tracing. */
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struct btrace_tinfo_bts
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{
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/* The Linux perf_event configuration for collecting the branch trace. */
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struct perf_event_attr attr;
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/* The perf event file. */
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int file;
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/* The perf event configuration page. */
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volatile struct perf_event_mmap_page *header;
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/* The BTS perf event buffer. */
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struct perf_event_buffer bts;
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};
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/* Branch trace target information for Intel(R) Processor Trace. */
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struct btrace_tinfo_pt
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{
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/* The Linux perf_event configuration for collecting the branch trace. */
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struct perf_event_attr attr;
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/* The perf event file. */
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int file;
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/* The perf event configuration page. */
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volatile struct perf_event_mmap_page *header;
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/* The trace perf event buffer. */
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struct perf_event_buffer pt;
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};
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#endif /* HAVE_LINUX_PERF_EVENT_H */
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/* Branch trace target information per thread. */
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struct btrace_target_info
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{
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/* The ptid of this thread. */
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ptid_t ptid;
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/* The obtained branch trace configuration. */
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struct btrace_config conf;
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#if HAVE_LINUX_PERF_EVENT_H
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/* The branch tracing format specific information. */
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union
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{
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/* CONF.FORMAT == BTRACE_FORMAT_BTS. */
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struct btrace_tinfo_bts bts;
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/* CONF.FORMAT == BTRACE_FORMAT_PT. */
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struct btrace_tinfo_pt pt;
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} variant;
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#endif /* HAVE_LINUX_PERF_EVENT_H */
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};
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/* See to_supports_btrace in target.h. */
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extern int linux_supports_btrace (struct target_ops *, enum btrace_format);
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/* See to_enable_btrace in target.h. */
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extern struct btrace_target_info *
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linux_enable_btrace (ptid_t ptid, const struct btrace_config *conf);
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/* See to_disable_btrace in target.h. */
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extern enum btrace_error linux_disable_btrace (struct btrace_target_info *ti);
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/* See to_read_btrace in target.h. */
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extern enum btrace_error linux_read_btrace (struct btrace_data *btrace,
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struct btrace_target_info *btinfo,
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enum btrace_read_type type);
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/* See to_btrace_conf in target.h. */
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extern const struct btrace_config *
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linux_btrace_conf (const struct btrace_target_info *);
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#endif /* LINUX_BTRACE_H */
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