From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30566 invoked by alias); 10 May 2012 15:17:53 -0000 Received: (qmail 30124 invoked by uid 22791); 10 May 2012 15:17:44 -0000 X-SWARE-Spam-Status: No, hits=-7.7 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,RCVD_IN_DNSWL_HI,RCVD_IN_HOSTKARMA_W,TW_CP,TW_XZ,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mga01.intel.com (HELO mga01.intel.com) (192.55.52.88) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 10 May 2012 15:17:28 +0000 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP; 10 May 2012 08:16:24 -0700 X-ExtLoop1: 1 Received: from swsutil001.isw.intel.com ([10.237.237.11]) by fmsmga002.fm.intel.com with ESMTP; 10 May 2012 08:16:22 -0700 Received: from ulslx001.iul.intel.com (ulslx001.iul.intel.com [172.28.207.63]) by swsutil001.isw.intel.com (8.13.6/8.13.6/MailSET/Hub) with ESMTP id q4AFGLqb021810; Thu, 10 May 2012 16:16:22 +0100 Received: from ulslx001.iul.intel.com (localhost [127.0.0.1]) by ulslx001.iul.intel.com with ESMTP id q4AFGLNU025503; Thu, 10 May 2012 17:16:21 +0200 Received: (from mmetzger@localhost) by ulslx001.iul.intel.com with id q4AFGLKx025499; Thu, 10 May 2012 17:16:21 +0200 From: markus.t.metzger@intel.com To: gdb-patches@sourceware.org Cc: markus.t.metzger@gmail.com, Markus Metzger Subject: [PATCH 08/16] linux, btrace: perf_event based branch tracing Date: Thu, 10 May 2012 15:17:00 -0000 Message-Id: <1336662810-21937-9-git-send-email-markus.t.metzger@intel.com> In-Reply-To: <1336662810-21937-1-git-send-email-markus.t.metzger@intel.com> References: <1336662810-21937-1-git-send-email-markus.t.metzger@intel.com> X-IsSubscribed: yes Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org X-SW-Source: 2012-05/txt/msg00358.txt.bz2 From: Markus Metzger Implement branch tracing on Linux based on perf_event such taht it can be shared between gdb and gdbserver. The actual btrace target ops will be implemented on top. 2012-05-10 Markus Metzger gdb/common/ * linux_btrace.h: New file * linux_btrace.c: New file gdb/ * Makefile.in: Add linux-btrace rules gdb/gdbserver/ * Makefile.in: Add linux-btrace rules --- gdb/Makefile.in | 7 +- gdb/common/linux-btrace.c | 368 +++++++++++++++++++++++++++++++++++++++++++++ gdb/common/linux-btrace.h | 76 +++++++++ gdb/gdbserver/Makefile.in | 6 +- 4 files changed, 455 insertions(+), 2 deletions(-) create mode 100644 gdb/common/linux-btrace.c create mode 100644 gdb/common/linux-btrace.h diff --git a/gdb/Makefile.in b/gdb/Makefile.in index 5fa7c12..b3fdd4f 100644 --- a/gdb/Makefile.in +++ b/gdb/Makefile.in @@ -826,7 +826,8 @@ gnulib/import/extra/snippet/arg-nonnull.h gnulib/import/extra/snippet/c++defs.h gnulib/import/extra/snippet/warn-on-use.h \ gnulib/import/stddef.in.h gnulib/import/inttypes.in.h inline-frame.h skip.h \ common/common-utils.h common/xml-utils.h common/buffer.h common/ptid.h \ -common/linux-osdata.h gdb-dlfcn.h auto-load.h probe.h stap-probe.h +common/linux-osdata.h gdb-dlfcn.h auto-load.h probe.h stap-probe.h \ +common/linux-btrace.h # Header files that already have srcdir in them, or which are in objdir. @@ -1930,6 +1931,10 @@ vec.o: ${srcdir}/common/vec.c $(COMPILE) $(srcdir)/common/vec.c $(POSTCOMPILE) +linux-btrace.o: ${srcdir}/common/linux-btrace.c + $(COMPILE) $(srcdir)/common/linux-btrace.c + $(POSTCOMPILE) + # # gdb/tui/ dependencies # diff --git a/gdb/common/linux-btrace.c b/gdb/common/linux-btrace.c new file mode 100644 index 0000000..76bca75 --- /dev/null +++ b/gdb/common/linux-btrace.c @@ -0,0 +1,368 @@ +/* Linux-dependent part of branch trace support for GDB, and GDBserver. + + Copyright (C) 2012 Free Software Foundation, Inc. + + Contributed by Intel Corp. + + 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 . */ + +#include "linux-btrace.h" +#include "common-utils.h" +#include + +#if HAVE_LINUX_PERF_EVENT_H + +#include +#include +#include +#include +#include + +typedef unsigned char byte; + +/* A branch trace record in perf_event. */ +struct perf_event_bts +{ + unsigned long long from; + unsigned long long to; +}; + +/* A perf_event branch trace sample. */ +struct perf_event_sample +{ + struct perf_event_header header; + struct perf_event_bts bts; +}; + +static inline volatile struct perf_event_mmap_page * +perf_event_header (struct btrace_target_info* tinfo) +{ + return tinfo->buffer; +} + +static inline size_t +perf_event_mmap_size (const struct btrace_target_info *tinfo) +{ + /* The branch trace buffer is preceded by a configuration page. */ + return ((tinfo->size + 1) * PAGE_SIZE); +} + +static inline size_t +perf_event_buffer_size (struct btrace_target_info* tinfo) +{ + return (tinfo->size * PAGE_SIZE); +} + +static inline const byte * +perf_event_buffer_begin (struct btrace_target_info* tinfo) +{ + return ((const byte *) tinfo->buffer) + PAGE_SIZE; +} + +static inline const byte * +perf_event_buffer_end (struct btrace_target_info* tinfo) +{ + return perf_event_buffer_begin (tinfo) + perf_event_buffer_size (tinfo); +} + +static inline int +perf_event_skip_record (struct btrace_target_info* tinfo, + const struct perf_event_bts *bts) +{ + if (tinfo->ptr_bits) + { + int shift = tinfo->ptr_bits - 1; + + /* Branch trace records branches from kernel space to user space. */ + if (bts->from & (1ull << shift)) + return 1; + + /* Branch trace records branches from user space to kernel space. */ + if (bts->to & (1ull << shift)) + return 1; + } + + return 0; +} + +static inline int +perf_event_check_sample (const struct perf_event_sample *sample) +{ + if (sample->header.type != PERF_RECORD_SAMPLE) + return EINVAL; + + if (sample->header.size != sizeof (*sample)) + return EINVAL; + + return 0; +} + +/* Branch trace is collected in a circular buffer [begin; end) as pairs of from + and to addresses (plus some header). + + Start points into that buffer at the next sample position. + We read the collected samples backwards from start. + + While reading the samples, we convert the information into a list of blocks. + For two adjacent samples s1 and s2, we form a block b such that b.begin = + s1.to and b.end = s2.from. + + In case the buffer overflows during sampling, samples may be split. */ +static int +perf_event_read_bts (struct btrace_target_info* tinfo, + const byte *begin, const byte *end, const byte *start, + int (*fun) (struct linux_btrace_block *, void *), + void *arg) +{ + struct perf_event_sample sample; + int read = 0, size = (end - begin), errcode = 0; + struct linux_btrace_block block = { 0, 0 }; + + if (start < begin) + return EINVAL; + + if (end < start) + return EINVAL; + + /* The buffer may contain a partial record as its last entry (i.e. when the + buffer size is not a mulitple of the sample size). */ + read = sizeof (sample) - 1; + + for (; read < size; read += sizeof (sample)) + { + const struct perf_event_sample *psample; + + /* Find the next perf_event sample. */ + start -= sizeof (sample); + if (begin <= start) + psample = (const struct perf_event_sample *) start; + else + { + int missing = (begin - start); + start = (end - missing); + + if (missing == sizeof (sample)) + psample = (const struct perf_event_sample *) start; + else + { + byte *stack = (byte *) &sample; + + memcpy (stack, start, missing); + memcpy (stack + missing, begin, sizeof (sample) - missing); + + psample = &sample; + } + } + + errcode = perf_event_check_sample (psample); + if (errcode) + break; + + if (perf_event_skip_record (tinfo, &(psample->bts))) + continue; + + /* We found a valid sample, so we can complete the current block. */ + block.begin = psample->bts.to; + + errcode = (*fun) (&block, arg); + if (errcode) + break; + + /* Start the next block. */ + block.end = psample->bts.from; + } + + return errcode; +} + +int +linux_supports_btrace (void) +{ + return 1; +} + +int +linux_btrace_has_changed (struct btrace_target_info *tinfo) +{ + volatile struct perf_event_mmap_page *header = perf_event_header (tinfo); + if (!header) + return 0; + + return (header->data_head != tinfo->data_head); +} + +struct btrace_target_info * +linux_enable_btrace (ptid_t ptid) +{ + struct btrace_target_info *tinfo; + int pid; + + tinfo = xzalloc (sizeof (*tinfo)); + if (!tinfo) + { + errno = ENOMEM; + return NULL; + } + + tinfo->attr.size = sizeof (tinfo->attr); + + tinfo->attr.type = PERF_TYPE_HARDWARE; + tinfo->attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS; + tinfo->attr.sample_period = 1; + + /* We sample from and to address. */ + tinfo->attr.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR; + + tinfo->attr.exclude_kernel = 1; + tinfo->attr.exclude_hv = 1; + tinfo->attr.exclude_idle = 1; + + tinfo->ptr_bits = 0; + + pid = ptid_get_lwp (ptid); + if (!pid) + pid = ptid_get_pid (ptid); + + tinfo->file = syscall (SYS_perf_event_open, &(tinfo->attr), pid, -1, -1, 0); + if (tinfo->file < 0) + goto err; + + /* We hard-code the trace buffer size. + At some later time, we should make this configurable. */ + tinfo->size = 1; + tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo), + PROT_READ, MAP_SHARED, tinfo->file, 0); + if (tinfo->buffer == MAP_FAILED) + goto err_file; + + return tinfo; + +err_file: + close (tinfo->file); + +err: + xfree (tinfo); + return NULL; +} + +int +linux_disable_btrace (struct btrace_target_info *tinfo) +{ + int errcode; + + if (!tinfo) + return -EINVAL; + + errcode = munmap (tinfo->buffer, perf_event_mmap_size (tinfo)); + if (errcode) + return errno; + + close (tinfo->file); + xfree (tinfo); + + return 0; +} + +int +linux_read_btrace (struct btrace_target_info *tinfo, + int (*fun) (struct linux_btrace_block *, void *), + void *arg) +{ + volatile struct perf_event_mmap_page *header; + const byte *begin, *end, *start; + unsigned long data_head, retries = 5; + size_t buffer_size; + int errcode = 0; + + if (!tinfo) + return EINVAL; + + header = perf_event_header (tinfo); + if (!header) + return ENOSYS; + + buffer_size = perf_event_buffer_size (tinfo); + + /* We may need to retry reading the trace. See below. */ + while (retries--) + { + data_head = header->data_head; + + /* If there new trace, let's read it. */ + if (data_head != tinfo->data_head) + { + /* Data_head keeps growing; the buffer itself is circular. */ + begin = perf_event_buffer_begin (tinfo); + start = begin + (data_head % buffer_size); + + if (data_head <= buffer_size) + end = start; + else + end = perf_event_buffer_end (tinfo); + + errcode = perf_event_read_bts (tinfo, begin, end, start, fun, arg); + } + + /* The stopping thread notifies its ptracer before it is scheduled out. + On multi-core systems, the debugger might therefore run while the + 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) + break; + } + + tinfo->data_head = data_head; + + return errcode; +} + +#else /* HAVE_LINUX_PERF_EVENT_H */ + +int +linux_supports_btrace (void) +{ + return 0; +} + +int +linux_btrace_has_changed (struct btrace_target_info *tinfo) +{ + return 0; +} + +struct btrace_target_info * +linux_enable_btrace (ptid_t ptid) +{ + errno = ENOSYS; + return NULL; +} + +int +linux_disable_btrace (struct btrace_target_info *tinfo) +{ + return ENOSYS; +} + +int +linux_read_btrace (struct btrace_target_info *tinfo, + int (*fun) (struct linux_btrace_block *, void *), + void *arg) +{ + return ENOSYS; +} + +#endif /* HAVE_LINUX_PERF_EVENT_H */ diff --git a/gdb/common/linux-btrace.h b/gdb/common/linux-btrace.h new file mode 100644 index 0000000..22f435a --- /dev/null +++ b/gdb/common/linux-btrace.h @@ -0,0 +1,76 @@ +/* Linux-dependent part of branch trace support for GDB, and GDBserver. + + Copyright (C) 2012 Free Software Foundation, Inc. + + Contributed by Intel Corp. + + 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 . */ + +#ifndef LINUX_BTRACE_H +#define LINUX_BTRACE_H + +#include "config.h" +#include "ptid.h" +#include + +#if HAVE_LINUX_PERF_EVENT_H +# include +#endif + +/* A branch trace block on linux. + GDB and GDBserver don't agree on the definition of CORE_ADDR. In order to + allow sharing the perf_event access code, we stick to unsigned long long; + that's also what perf_event delivers. */ +struct linux_btrace_block +{ + unsigned long long begin; + unsigned long long end; +}; + +/* 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 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; +}; + +extern int linux_supports_btrace (void); +extern struct btrace_target_info *linux_enable_btrace (ptid_t); +extern int linux_disable_btrace (struct btrace_target_info *); +extern int linux_btrace_has_changed (struct btrace_target_info *); +extern int linux_read_btrace (struct btrace_target_info *, + int (*) (struct linux_btrace_block *, void *), + void *); + +#endif /* LINUX_BTRACE_H */ diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in index 50786d5..1f256de 100644 --- a/gdb/gdbserver/Makefile.in +++ b/gdb/gdbserver/Makefile.in @@ -139,7 +139,7 @@ SFILES= $(srcdir)/gdbreplay.c $(srcdir)/inferiors.c $(srcdir)/dll.c \ $(srcdir)/common/vec.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@ @@ -408,6 +408,7 @@ 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 linux_osdata_h = $(srcdir)/../common/linux-osdata.h vec_h = $(srcdir)/../common/vec.h # Since everything must include server.h, we make that depend on @@ -514,6 +515,9 @@ buffer.o: ../common/buffer.c $(server_h) agent.o: ../common/agent.c $(server_h) $(agent_h) $(CC) -c $(CPPFLAGS) $(INTERNAL_CFLAGS) $< -DGDBSERVER +linux-btrace.o: ../common/linux-btrace.c $(linux_btrace_h) $(server_h) + $(CC) -c $(CPPFLAGS) $(INTERNAL_CFLAGS) $< -DGDBSERVER + # 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 -- 1.7.1