Implement branch tracing on Linux based on perf_event such that it can be shared
between gdb and gdbserver. gdb/ * common/linux_btrace.h: New file. * common/linux_btrace.c: New file. * Makefile.in (SFILES): Add btrace.c. (HFILES_NO_SRCDIR): Add common/linux-btrace.h. (COMMON_OBS): Add btrace.o. (linux-btrace.o): New rule. gdbserver/ * Makefile.in (SFILES): Add $(srcdir)/common/linux-btrace.c. (linux_btrace_h): New variable. (linux-btrace.o): New rule.
This commit is contained in:
Markus Metzger
parent
1999790bb6
commit
7c97f91ebf
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@ -1,3 +1,12 @@
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2013-03-11 Markus Metzger <markus.t.metzger@intel.com>
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* common/linux_btrace.h: New file.
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* common/linux_btrace.c: New file.
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* Makefile.in (SFILES): Add btrace.c.
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(HFILES_NO_SRCDIR): Add common/linux-btrace.h.
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(COMMON_OBS): Add btrace.o.
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(linux-btrace.o): New rule.
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2013-03-11 Markus Metzger <markus.t.metzger@intel.com>
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* target.h: Include btrace.h.
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@ -835,7 +835,7 @@ gnulib/import/stddef.in.h gnulib/import/inttypes.in.h inline-frame.h skip.h \
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common/common-utils.h common/xml-utils.h common/buffer.h common/ptid.h \
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common/format.h common/host-defs.h utils.h common/queue.h \
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common/linux-osdata.h gdb-dlfcn.h auto-load.h probe.h stap-probe.h \
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gdb_bfd.h sparc-ravenscar-thread.h ppc-ravenscar-thread.h
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gdb_bfd.h sparc-ravenscar-thread.h ppc-ravenscar-thread.h common/linux-btrace.h
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# Header files that already have srcdir in them, or which are in objdir.
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@ -1965,6 +1965,10 @@ vec.o: ${srcdir}/common/vec.c
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$(COMPILE) $(srcdir)/common/vec.c
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$(POSTCOMPILE)
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linux-btrace.o: ${srcdir}/common/linux-btrace.c
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$(COMPILE) $(srcdir)/common/linux-btrace.c
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$(POSTCOMPILE)
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#
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# gdb/tui/ dependencies
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#
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@ -0,0 +1,425 @@
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/* Linux-dependent part of branch trace support for GDB, and GDBserver.
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Copyright (C) 2013 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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#ifdef GDBSERVER
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#include "server.h"
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#else
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#include "defs.h"
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#endif
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#include "linux-btrace.h"
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#include "common-utils.h"
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#include "gdb_assert.h"
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#include "regcache.h"
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#include "gdbthread.h"
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#if HAVE_LINUX_PERF_EVENT_H
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#include <errno.h>
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#include <string.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <sys/mman.h>
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#include <sys/user.h>
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/* A branch trace record in perf_event. */
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struct perf_event_bts
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{
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/* The linear address of the branch source. */
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uint64_t from;
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/* The linear address of the branch destination. */
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uint64_t to;
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};
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/* A perf_event branch trace sample. */
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struct perf_event_sample
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{
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/* The perf_event sample header. */
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struct perf_event_header header;
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/* The perf_event branch tracing payload. */
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struct perf_event_bts bts;
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};
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/* Get the perf_event header. */
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static inline volatile struct perf_event_mmap_page *
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perf_event_header (struct btrace_target_info* tinfo)
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{
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return tinfo->buffer;
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}
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/* Get the size of the perf_event mmap buffer. */
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static inline size_t
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perf_event_mmap_size (const struct btrace_target_info *tinfo)
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{
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/* The branch trace buffer is preceded by a configuration page. */
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return (tinfo->size + 1) * PAGE_SIZE;
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}
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/* Get the size of the perf_event buffer. */
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static inline size_t
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perf_event_buffer_size (struct btrace_target_info* tinfo)
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{
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return tinfo->size * PAGE_SIZE;
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}
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/* Get the start address of the perf_event buffer. */
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static inline const uint8_t *
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perf_event_buffer_begin (struct btrace_target_info* tinfo)
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{
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return ((const uint8_t *) tinfo->buffer) + PAGE_SIZE;
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}
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/* Get the end address of the perf_event buffer. */
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static inline const uint8_t *
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perf_event_buffer_end (struct btrace_target_info* tinfo)
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{
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return perf_event_buffer_begin (tinfo) + perf_event_buffer_size (tinfo);
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}
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/* Check whether an address is in the kernel. */
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static inline int
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perf_event_is_kernel_addr (const struct btrace_target_info *tinfo,
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uint64_t addr)
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{
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uint64_t mask;
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/* If we don't know the size of a pointer, we can't check. Let's assume it's
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not a kernel address in this case. */
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if (tinfo->ptr_bits == 0)
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return 0;
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/* A bit mask for the most significant bit in an address. */
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mask = (uint64_t) 1 << (tinfo->ptr_bits - 1);
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/* Check whether the most significant bit in the address is set. */
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return (addr & mask) != 0;
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}
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/* Check whether a perf event record should be skipped. */
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static inline int
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perf_event_skip_record (const struct btrace_target_info *tinfo,
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const struct perf_event_bts *bts)
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{
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/* The hardware may report branches from kernel into user space. Branches
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from user into kernel space will be suppressed. We filter the former to
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provide a consistent branch trace excluding kernel. */
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return perf_event_is_kernel_addr (tinfo, bts->from);
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}
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/* Perform a few consistency checks on a perf event sample record. This is
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meant to catch cases when we get out of sync with the perf event stream. */
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static inline int
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perf_event_sample_ok (const struct perf_event_sample *sample)
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{
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if (sample->header.type != PERF_RECORD_SAMPLE)
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return 0;
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if (sample->header.size != sizeof (*sample))
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return 0;
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return 1;
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}
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/* Branch trace is collected in a circular buffer [begin; end) as pairs of from
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and to addresses (plus a header).
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Start points into that buffer at the next sample position.
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We read the collected samples backwards from start.
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While reading the samples, we convert the information into a list of blocks.
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For two adjacent samples s1 and s2, we form a block b such that b.begin =
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s1.to and b.end = s2.from.
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In case the buffer overflows during sampling, one sample may have its lower
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part at the end and its upper part at the beginning of the buffer. */
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static VEC (btrace_block_s) *
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perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
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const uint8_t *end, const uint8_t *start)
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{
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VEC (btrace_block_s) *btrace = NULL;
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struct perf_event_sample sample;
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size_t read = 0, size = (end - begin);
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struct btrace_block block = { 0, 0 };
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struct regcache *regcache;
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gdb_assert (begin <= start);
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gdb_assert (start <= end);
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/* The first block ends at the current pc. */
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#ifdef GDBSERVER
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regcache = get_thread_regcache (find_thread_ptid (tinfo->ptid), 1);
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#else
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regcache = get_thread_regcache (tinfo->ptid);
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#endif
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block.end = regcache_read_pc (regcache);
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/* The buffer may contain a partial record as its last entry (i.e. when the
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buffer size is not a multiple of the sample size). */
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read = sizeof (sample) - 1;
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for (; read < size; read += sizeof (sample))
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{
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const struct perf_event_sample *psample;
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/* Find the next perf_event sample in a backwards traversal. */
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start -= sizeof (sample);
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/* If we're still inside the buffer, we're done. */
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if (begin <= start)
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psample = (const struct perf_event_sample *) start;
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else
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{
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int missing;
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/* We're to the left of the ring buffer, we will wrap around and
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reappear at the very right of the ring buffer. */
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missing = (begin - start);
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start = (end - missing);
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/* If the entire sample is missing, we're done. */
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if (missing == sizeof (sample))
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psample = (const struct perf_event_sample *) start;
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else
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{
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uint8_t *stack;
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/* The sample wrapped around. The lower part is at the end and
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the upper part is at the beginning of the buffer. */
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stack = (uint8_t *) &sample;
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/* Copy the two parts so we have a contiguous sample. */
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memcpy (stack, start, missing);
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memcpy (stack + missing, begin, sizeof (sample) - missing);
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psample = &sample;
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}
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}
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if (!perf_event_sample_ok (psample))
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{
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warning (_("Branch trace may be incomplete."));
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break;
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}
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if (perf_event_skip_record (tinfo, &psample->bts))
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continue;
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/* We found a valid sample, so we can complete the current block. */
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block.begin = psample->bts.to;
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VEC_safe_push (btrace_block_s, btrace, &block);
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/* Start the next block. */
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block.end = psample->bts.from;
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}
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return btrace;
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}
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/* See linux-btrace.h. */
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int
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linux_supports_btrace (void)
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{
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return 1;
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}
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/* See linux-btrace.h. */
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struct btrace_target_info *
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linux_enable_btrace (ptid_t ptid)
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{
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struct btrace_target_info *tinfo;
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int pid;
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tinfo = xzalloc (sizeof (*tinfo));
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tinfo->ptid = ptid;
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tinfo->attr.size = sizeof (tinfo->attr);
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tinfo->attr.type = PERF_TYPE_HARDWARE;
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tinfo->attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS;
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tinfo->attr.sample_period = 1;
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/* We sample from and to address. */
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tinfo->attr.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR;
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tinfo->attr.exclude_kernel = 1;
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tinfo->attr.exclude_hv = 1;
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tinfo->attr.exclude_idle = 1;
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tinfo->ptr_bits = 0;
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pid = ptid_get_lwp (ptid);
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if (pid == 0)
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pid = ptid_get_pid (ptid);
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errno = 0;
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tinfo->file = syscall (SYS_perf_event_open, &tinfo->attr, pid, -1, -1, 0);
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if (tinfo->file < 0)
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goto err;
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/* We hard-code the trace buffer size.
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At some later time, we should make this configurable. */
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tinfo->size = 1;
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tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo),
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PROT_READ, MAP_SHARED, tinfo->file, 0);
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if (tinfo->buffer == MAP_FAILED)
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goto err_file;
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return tinfo;
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err_file:
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close (tinfo->file);
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err:
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xfree (tinfo);
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return NULL;
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}
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/* See linux-btrace.h. */
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int
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linux_disable_btrace (struct btrace_target_info *tinfo)
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{
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int errcode;
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errno = 0;
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errcode = munmap (tinfo->buffer, perf_event_mmap_size (tinfo));
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if (errcode != 0)
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return errno;
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close (tinfo->file);
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xfree (tinfo);
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return 0;
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}
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/* Check whether the branch trace has changed. */
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static int
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linux_btrace_has_changed (struct btrace_target_info *tinfo)
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{
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volatile struct perf_event_mmap_page *header = perf_event_header (tinfo);
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return header->data_head != tinfo->data_head;
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}
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/* See linux-btrace.h. */
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VEC (btrace_block_s) *
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linux_read_btrace (struct btrace_target_info *tinfo,
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enum btrace_read_type type)
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{
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VEC (btrace_block_s) *btrace = NULL;
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volatile struct perf_event_mmap_page *header;
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const uint8_t *begin, *end, *start;
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unsigned long data_head, retries = 5;
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size_t buffer_size;
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if (type == btrace_read_new && !linux_btrace_has_changed (tinfo))
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return NULL;
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header = perf_event_header (tinfo);
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buffer_size = perf_event_buffer_size (tinfo);
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/* We may need to retry reading the trace. See below. */
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while (retries--)
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{
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data_head = header->data_head;
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/* If there's new trace, let's read it. */
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if (data_head != tinfo->data_head)
|
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{
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/* Data_head keeps growing; the buffer itself is circular. */
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begin = perf_event_buffer_begin (tinfo);
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start = begin + data_head % buffer_size;
|
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|
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if (data_head <= buffer_size)
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end = start;
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else
|
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end = perf_event_buffer_end (tinfo);
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|
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btrace = perf_event_read_bts (tinfo, begin, end, start);
|
||||
}
|
||||
|
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/* The stopping thread notifies its ptracer before it is scheduled out.
|
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On multi-core systems, the debugger might therefore run while the
|
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kernel might be writing the last branch trace records.
|
||||
|
||||
Let's check whether the data head moved while we read the trace. */
|
||||
if (data_head == header->data_head)
|
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break;
|
||||
}
|
||||
|
||||
tinfo->data_head = data_head;
|
||||
|
||||
return btrace;
|
||||
}
|
||||
|
||||
#else /* !HAVE_LINUX_PERF_EVENT_H */
|
||||
|
||||
/* See linux-btrace.h. */
|
||||
|
||||
int
|
||||
linux_supports_btrace (void)
|
||||
{
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* See linux-btrace.h. */
|
||||
|
||||
struct btrace_target_info *
|
||||
linux_enable_btrace (ptid_t ptid)
|
||||
{
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/* See linux-btrace.h. */
|
||||
|
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int
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linux_disable_btrace (struct btrace_target_info *tinfo)
|
||||
{
|
||||
return ENOSYS;
|
||||
}
|
||||
|
||||
/* See linux-btrace.h. */
|
||||
|
||||
VEC (btrace_block_s) *
|
||||
linux_read_btrace (struct btrace_target_info *tinfo,
|
||||
enum btrace_read_type type)
|
||||
{
|
||||
return NULL;
|
||||
}
|
||||
|
||||
#endif /* !HAVE_LINUX_PERF_EVENT_H */
|
||||
|
|
@ -0,0 +1,77 @@
|
|||
/* Linux-dependent part of branch trace support for GDB, and GDBserver.
|
||||
|
||||
Copyright (C) 2013 Free Software Foundation, Inc.
|
||||
|
||||
Contributed by Intel Corp. <markus.t.metzger@intel.com>
|
||||
|
||||
This file is part of GDB.
|
||||
|
||||
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 3 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, see <http://www.gnu.org/licenses/>. */
|
||||
|
||||
#ifndef LINUX_BTRACE_H
|
||||
#define LINUX_BTRACE_H
|
||||
|
||||
#include "btrace-common.h"
|
||||
#include "config.h"
|
||||
#include "vec.h"
|
||||
#include "ptid.h"
|
||||
#include <stddef.h>
|
||||
#include <stdint.h>
|
||||
|
||||
#if HAVE_LINUX_PERF_EVENT_H
|
||||
# include <linux/perf_event.h>
|
||||
#endif
|
||||
|
||||
/* Branch trace target information per thread. */
|
||||
struct btrace_target_info
|
||||
{
|
||||
#if HAVE_LINUX_PERF_EVENT_H
|
||||
/* The Linux perf_event configuration for collecting the branch trace. */
|
||||
struct perf_event_attr attr;
|
||||
|
||||
/* The ptid of this thread. */
|
||||
ptid_t ptid;
|
||||
|
||||
/* The mmap configuration mapping the branch trace perf_event buffer.
|
||||
|
||||
file .. the file descriptor
|
||||
buffer .. the mmapped memory buffer
|
||||
size .. the buffer's size in pages without the configuration page
|
||||
data_head .. the data head from the last read */
|
||||
int file;
|
||||
void *buffer;
|
||||
size_t size;
|
||||
unsigned long data_head;
|
||||
#endif /* HAVE_LINUX_PERF_EVENT_H */
|
||||
|
||||
/* The size of a pointer in bits for this thread.
|
||||
The information is used to identify kernel addresses in order to skip
|
||||
records from/to kernel space. */
|
||||
int ptr_bits;
|
||||
};
|
||||
|
||||
/* Check whether branch tracing is supported. */
|
||||
extern int linux_supports_btrace (void);
|
||||
|
||||
/* Enable branch tracing for @ptid. */
|
||||
extern struct btrace_target_info *linux_enable_btrace (ptid_t ptid);
|
||||
|
||||
/* Disable branch tracing and deallocate @tinfo. */
|
||||
extern int linux_disable_btrace (struct btrace_target_info *tinfo);
|
||||
|
||||
/* Read branch trace data. */
|
||||
extern VEC (btrace_block_s) *linux_read_btrace (struct btrace_target_info *,
|
||||
enum btrace_read_type);
|
||||
|
||||
#endif /* LINUX_BTRACE_H */
|
||||
|
|
@ -1,3 +1,9 @@
|
|||
2013-03-11 Markus Metzger <markus.t.metzger@intel.com>
|
||||
|
||||
* Makefile.in (SFILES): Add $(srcdir)/common/linux-btrace.c.
|
||||
(linux_btrace_h): New variable.
|
||||
(linux-btrace.o): New rule.
|
||||
|
||||
2013-03-08 Stan Shebs <stan@codesourcery.com>
|
||||
Hafiz Abid Qadeer <abidh@codesourcery.com>
|
||||
|
||||
|
|
|
|||
|
|
@ -155,7 +155,7 @@ SFILES= $(srcdir)/gdbreplay.c $(srcdir)/inferiors.c $(srcdir)/dll.c \
|
|||
$(srcdir)/common/vec.c $(srcdir)/common/gdb_vecs.c \
|
||||
$(srcdir)/common/common-utils.c $(srcdir)/common/xml-utils.c \
|
||||
$(srcdir)/common/linux-osdata.c $(srcdir)/common/ptid.c \
|
||||
$(srcdir)/common/buffer.c
|
||||
$(srcdir)/common/buffer.c $(srcdir)/common/linux-btrace.c
|
||||
|
||||
DEPFILES = @GDBSERVER_DEPFILES@
|
||||
|
||||
|
|
@ -425,6 +425,8 @@ signals_h = $(srcdir)/../../include/gdb/signals.h $(signals_def)
|
|||
ptid_h = $(srcdir)/../common/ptid.h
|
||||
ax_h = $(srcdir)/ax.h
|
||||
agent_h = $(srcdir)/../common/agent.h
|
||||
linux_btrace_h = $(srcdir)/../common/linux-btrace.h \
|
||||
$(srcdir)/../common/btrace-common.h $(vec_h) $(ptid_h)
|
||||
linux_osdata_h = $(srcdir)/../common/linux-osdata.h
|
||||
vec_h = $(srcdir)/../common/vec.h
|
||||
gdb_vecs_h = $(srcdir)/../common/gdb_vecs.h
|
||||
|
|
@ -544,6 +546,9 @@ agent.o: ../common/agent.c
|
|||
$(COMPILE) $<
|
||||
$(POSTCOMPILE)
|
||||
|
||||
linux-btrace.o: ../common/linux-btrace.c $(linux_btrace_h) $(server_h)
|
||||
$(CC) -c $(CPPFLAGS) $(INTERNAL_CFLAGS) $<
|
||||
|
||||
# We build vasprintf with -DHAVE_CONFIG_H because we want that unit to
|
||||
# include our config.h file. Otherwise, some system headers do not get
|
||||
# included, and the compiler emits a warning about implicitly defined
|
||||
|
|
|
|||
Loading…
Reference in New Issue