diff options
author | Gary Benson <gbenson@redhat.com> | 2014-06-19 14:46:38 +0100 |
---|---|---|
committer | Gary Benson <gbenson@redhat.com> | 2014-06-20 14:06:48 +0100 |
commit | 125f8a3ddedd413a2290dae011f0bed9ffc78278 (patch) | |
tree | d9755566364119d825f6ee87229983c7a8d68e46 /gdb/nat/linux-btrace.c | |
parent | 42995dbda646ff0291a36f83a7f1a9f45e3fda8a (diff) | |
download | fsf-binutils-gdb-125f8a3ddedd413a2290dae011f0bed9ffc78278.zip fsf-binutils-gdb-125f8a3ddedd413a2290dae011f0bed9ffc78278.tar.gz fsf-binutils-gdb-125f8a3ddedd413a2290dae011f0bed9ffc78278.tar.bz2 |
Move shared native target specific code to gdb/nat
https://sourceware.org/gdb/wiki/Common describes the following
directory structure:
gdb/nat/
Native target backend files. Code that interfaces with the
host debug API. E.g., ptrace code, Windows debug API code,
procfs code should go here.
gdb/target/
Host-independent, target vector specific code (target_ops).
gdb/common/
All other shared code.
This commit moves all native target backend files currently in
gdb/common to gdb/nat.
gdb/
2014-06-20 Gary Benson <gbenson@redhat.com>
* common/gdb_thread_db.h: Moved to nat. All includes updated.
* common/glibc_thread_db.h: Likewise.
* common/i386-cpuid.h: Likewise.
* common/i386-gcc-cpuid.h: Likewise.
* common/linux-btrace.h: Likewise.
* common/linux-osdata.h: Likewise.
* common/linux-procfs.h: Likewise.
* common/linux-ptrace.h: Likewise.
* common/mips-linux-watch.h: Likewise.
* common/linux-btrace.c: Moved to nat.
* common/linux-osdata.c: Likewise.
* common/linux-procfs.c: Likewise.
* common/linux-ptrace.c: Likewise.
* common/mips-linux-watch.c: Likewise.
* nat/gdb_thread_db.h: Moved from common.
* nat/glibc_thread_db.h: Likewise.
* nat/i386-cpuid.h: Likewise.
* nat/i386-gcc-cpuid.h: Likewise.
* nat/linux-btrace.c: Likewise.
* nat/linux-btrace.h: Likewise.
* nat/linux-osdata.c: Likewise.
* nat/linux-osdata.h: Likewise.
* nat/linux-procfs.c: Likewise.
* nat/linux-procfs.h: Likewise.
* nat/linux-ptrace.c: Likewise.
* nat/linux-ptrace.h: Likewise.
* nat/mips-linux-watch.c: Likewise.
* nat/mips-linux-watch.h: Likewise.
* Makefile.in (HFILES_NO_SRCDIR): Reflect new locations.
(object file files): Reordered.
* gdb/copyright.py (EXCLUDE_LIST): Reflect new location
of glibc_thread_db.h.
gdb/gdbserver/
2014-06-20 Gary Benson <gbenson@redhat.com>
* Makefile.in (SFILES): Update locations for files moved
from common to nat.
(object file files): Reordered.
gdb/testsuite/
2014-06-20 Gary Benson <gbenson@redhat.com>
* gdb.arch/i386-avx.exp: Fix include file location.
* gdb.arch/i386-sse.exp: Likewise.
Diffstat (limited to 'gdb/nat/linux-btrace.c')
-rw-r--r-- | gdb/nat/linux-btrace.c | 634 |
1 files changed, 634 insertions, 0 deletions
diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c new file mode 100644 index 0000000..188220b --- /dev/null +++ b/gdb/nat/linux-btrace.c @@ -0,0 +1,634 @@ +/* Linux-dependent part of branch trace support for GDB, and GDBserver. + + Copyright (C) 2013-2014 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/>. */ + +#ifdef GDBSERVER +#include "server.h" +#else +#include "defs.h" +#endif + +#include "linux-btrace.h" +#include "common-utils.h" +#include "gdb_assert.h" +#include "regcache.h" +#include "gdbthread.h" +#include "gdb_wait.h" +#include "i386-cpuid.h" + +#ifdef HAVE_SYS_SYSCALL_H +#include <sys/syscall.h> +#endif + +#if HAVE_LINUX_PERF_EVENT_H && defined(SYS_perf_event_open) + +#include <errno.h> +#include <string.h> +#include <stdint.h> +#include <unistd.h> +#include <sys/mman.h> +#include <sys/user.h> +#include <sys/ptrace.h> +#include <sys/types.h> +#include <signal.h> + +/* A branch trace record in perf_event. */ +struct perf_event_bts +{ + /* The linear address of the branch source. */ + uint64_t from; + + /* The linear address of the branch destination. */ + uint64_t to; +}; + +/* A perf_event branch trace sample. */ +struct perf_event_sample +{ + /* The perf_event sample header. */ + struct perf_event_header header; + + /* The perf_event branch tracing payload. */ + struct perf_event_bts bts; +}; + +/* Get the perf_event header. */ + +static inline volatile struct perf_event_mmap_page * +perf_event_header (struct btrace_target_info* tinfo) +{ + return tinfo->buffer; +} + +/* Get the size of the perf_event mmap 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; +} + +/* Get the size of the perf_event buffer. */ + +static inline size_t +perf_event_buffer_size (struct btrace_target_info* tinfo) +{ + return tinfo->size * PAGE_SIZE; +} + +/* Get the start address of the perf_event buffer. */ + +static inline const uint8_t * +perf_event_buffer_begin (struct btrace_target_info* tinfo) +{ + return ((const uint8_t *) tinfo->buffer) + PAGE_SIZE; +} + +/* Get the end address of the perf_event buffer. */ + +static inline const uint8_t * +perf_event_buffer_end (struct btrace_target_info* tinfo) +{ + return perf_event_buffer_begin (tinfo) + perf_event_buffer_size (tinfo); +} + +/* Check whether an address is in the kernel. */ + +static inline int +perf_event_is_kernel_addr (const struct btrace_target_info *tinfo, + uint64_t addr) +{ + uint64_t mask; + + /* If we don't know the size of a pointer, we can't check. Let's assume it's + not a kernel address in this case. */ + if (tinfo->ptr_bits == 0) + return 0; + + /* A bit mask for the most significant bit in an address. */ + mask = (uint64_t) 1 << (tinfo->ptr_bits - 1); + + /* Check whether the most significant bit in the address is set. */ + return (addr & mask) != 0; +} + +/* Check whether a perf event record should be skipped. */ + +static inline int +perf_event_skip_record (const struct btrace_target_info *tinfo, + const struct perf_event_bts *bts) +{ + /* The hardware may report branches from kernel into user space. Branches + from user into kernel space will be suppressed. We filter the former to + provide a consistent branch trace excluding kernel. */ + return perf_event_is_kernel_addr (tinfo, bts->from); +} + +/* Perform a few consistency checks on a perf event sample record. This is + meant to catch cases when we get out of sync with the perf event stream. */ + +static inline int +perf_event_sample_ok (const struct perf_event_sample *sample) +{ + if (sample->header.type != PERF_RECORD_SAMPLE) + return 0; + + if (sample->header.size != sizeof (*sample)) + return 0; + + return 1; +} + +/* Branch trace is collected in a circular buffer [begin; end) as pairs of from + and to addresses (plus a 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, one sample may have its lower + part at the end and its upper part at the beginning of the buffer. */ + +static VEC (btrace_block_s) * +perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin, + const uint8_t *end, const uint8_t *start, size_t size) +{ + VEC (btrace_block_s) *btrace = NULL; + struct perf_event_sample sample; + size_t read = 0; + struct btrace_block block = { 0, 0 }; + struct regcache *regcache; + + gdb_assert (begin <= start); + gdb_assert (start <= end); + + /* The first block ends at the current pc. */ +#ifdef GDBSERVER + regcache = get_thread_regcache (find_thread_ptid (tinfo->ptid), 1); +#else + regcache = get_thread_regcache (tinfo->ptid); +#endif + block.end = regcache_read_pc (regcache); + + /* The buffer may contain a partial record as its last entry (i.e. when the + buffer size is not a multiple 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 in a backwards traversal. */ + start -= sizeof (sample); + + /* If we're still inside the buffer, we're done. */ + if (begin <= start) + psample = (const struct perf_event_sample *) start; + else + { + int missing; + + /* We're to the left of the ring buffer, we will wrap around and + reappear at the very right of the ring buffer. */ + + missing = (begin - start); + start = (end - missing); + + /* If the entire sample is missing, we're done. */ + if (missing == sizeof (sample)) + psample = (const struct perf_event_sample *) start; + else + { + uint8_t *stack; + + /* The sample wrapped around. The lower part is at the end and + the upper part is at the beginning of the buffer. */ + stack = (uint8_t *) &sample; + + /* Copy the two parts so we have a contiguous sample. */ + memcpy (stack, start, missing); + memcpy (stack + missing, begin, sizeof (sample) - missing); + + psample = &sample; + } + } + + if (!perf_event_sample_ok (psample)) + { + warning (_("Branch trace may be incomplete.")); + 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; + + VEC_safe_push (btrace_block_s, btrace, &block); + + /* Start the next block. */ + block.end = psample->bts.from; + } + + /* Push the last block (i.e. the first one of inferior execution), as well. + We don't know where it ends, but we know where it starts. If we're + reading delta trace, we can fill in the start address later on. + Otherwise we will prune it. */ + block.begin = 0; + VEC_safe_push (btrace_block_s, btrace, &block); + + return btrace; +} + +/* Check whether the kernel supports branch tracing. */ + +static int +kernel_supports_btrace (void) +{ + struct perf_event_attr attr; + pid_t child, pid; + int status, file; + + errno = 0; + child = fork (); + switch (child) + { + case -1: + warning (_("test branch tracing: cannot fork: %s."), strerror (errno)); + return 0; + + case 0: + status = ptrace (PTRACE_TRACEME, 0, NULL, NULL); + if (status != 0) + { + warning (_("test branch tracing: cannot PTRACE_TRACEME: %s."), + strerror (errno)); + _exit (1); + } + + status = raise (SIGTRAP); + if (status != 0) + { + warning (_("test branch tracing: cannot raise SIGTRAP: %s."), + strerror (errno)); + _exit (1); + } + + _exit (1); + + default: + pid = waitpid (child, &status, 0); + if (pid != child) + { + warning (_("test branch tracing: bad pid %ld, error: %s."), + (long) pid, strerror (errno)); + return 0; + } + + if (!WIFSTOPPED (status)) + { + warning (_("test branch tracing: expected stop. status: %d."), + status); + return 0; + } + + memset (&attr, 0, sizeof (attr)); + + attr.type = PERF_TYPE_HARDWARE; + attr.config = PERF_COUNT_HW_BRANCH_INSTRUCTIONS; + attr.sample_period = 1; + attr.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR; + attr.exclude_kernel = 1; + attr.exclude_hv = 1; + attr.exclude_idle = 1; + + file = syscall (SYS_perf_event_open, &attr, child, -1, -1, 0); + if (file >= 0) + close (file); + + kill (child, SIGKILL); + ptrace (PTRACE_KILL, child, NULL, NULL); + + pid = waitpid (child, &status, 0); + if (pid != child) + { + warning (_("test branch tracing: bad pid %ld, error: %s."), + (long) pid, strerror (errno)); + if (!WIFSIGNALED (status)) + warning (_("test branch tracing: expected killed. status: %d."), + status); + } + + return (file >= 0); + } +} + +/* Check whether an Intel cpu supports branch tracing. */ + +static int +intel_supports_btrace (void) +{ + unsigned int cpuid, model, family; + + if (!i386_cpuid (1, &cpuid, NULL, NULL, NULL)) + return 0; + + family = (cpuid >> 8) & 0xf; + model = (cpuid >> 4) & 0xf; + + switch (family) + { + case 0x6: + model += (cpuid >> 12) & 0xf0; + + switch (model) + { + case 0x1a: /* Nehalem */ + case 0x1f: + case 0x1e: + case 0x2e: + case 0x25: /* Westmere */ + case 0x2c: + case 0x2f: + case 0x2a: /* Sandy Bridge */ + case 0x2d: + case 0x3a: /* Ivy Bridge */ + + /* AAJ122: LBR, BTM, or BTS records may have incorrect branch + "from" information afer an EIST transition, T-states, C1E, or + Adaptive Thermal Throttling. */ + return 0; + } + } + + return 1; +} + +/* Check whether the cpu supports branch tracing. */ + +static int +cpu_supports_btrace (void) +{ + unsigned int ebx, ecx, edx; + + if (!i386_cpuid (0, NULL, &ebx, &ecx, &edx)) + return 0; + + if (ebx == signature_INTEL_ebx && ecx == signature_INTEL_ecx + && edx == signature_INTEL_edx) + return intel_supports_btrace (); + + /* Don't know about others. Let's assume they do. */ + return 1; +} + +/* See linux-btrace.h. */ + +int +linux_supports_btrace (struct target_ops *ops) +{ + static int cached; + + if (cached == 0) + { + if (!kernel_supports_btrace ()) + cached = -1; + else if (!cpu_supports_btrace ()) + cached = -1; + else + cached = 1; + } + + return cached > 0; +} + +/* See linux-btrace.h. */ + +struct btrace_target_info * +linux_enable_btrace (ptid_t ptid) +{ + struct btrace_target_info *tinfo; + int pid, pg; + + tinfo = xzalloc (sizeof (*tinfo)); + tinfo->ptid = ptid; + + 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 == 0) + pid = ptid_get_pid (ptid); + + errno = 0; + tinfo->file = syscall (SYS_perf_event_open, &tinfo->attr, pid, -1, -1, 0); + if (tinfo->file < 0) + goto err; + + /* We try to allocate as much buffer as we can get. + We could allow the user to specify the size of the buffer, but then + we'd leave this search for the maximum buffer size to him. */ + for (pg = 4; pg >= 0; --pg) + { + /* The number of pages we request needs to be a power of two. */ + tinfo->size = 1 << pg; + tinfo->buffer = mmap (NULL, perf_event_mmap_size (tinfo), + PROT_READ, MAP_SHARED, tinfo->file, 0); + if (tinfo->buffer == MAP_FAILED) + continue; + + return tinfo; + } + + /* We were not able to allocate any buffer. */ + close (tinfo->file); + + err: + xfree (tinfo); + return NULL; +} + +/* See linux-btrace.h. */ + +enum btrace_error +linux_disable_btrace (struct btrace_target_info *tinfo) +{ + int errcode; + + errno = 0; + errcode = munmap (tinfo->buffer, perf_event_mmap_size (tinfo)); + if (errcode != 0) + return BTRACE_ERR_UNKNOWN; + + close (tinfo->file); + xfree (tinfo); + + return BTRACE_ERR_NONE; +} + +/* Check whether the branch trace has changed. */ + +static int +linux_btrace_has_changed (struct btrace_target_info *tinfo) +{ + volatile struct perf_event_mmap_page *header = perf_event_header (tinfo); + + return header->data_head != tinfo->data_head; +} + +/* See linux-btrace.h. */ + +enum btrace_error +linux_read_btrace (VEC (btrace_block_s) **btrace, + struct btrace_target_info *tinfo, + enum btrace_read_type type) +{ + volatile struct perf_event_mmap_page *header; + const uint8_t *begin, *end, *start; + unsigned long data_head, data_tail, retries = 5; + size_t buffer_size, size; + + /* For delta reads, we return at least the partial last block containing + the current PC. */ + if (type == BTRACE_READ_NEW && !linux_btrace_has_changed (tinfo)) + return BTRACE_ERR_NONE; + + header = perf_event_header (tinfo); + buffer_size = perf_event_buffer_size (tinfo); + data_tail = tinfo->data_head; + + /* We may need to retry reading the trace. See below. */ + while (retries--) + { + data_head = header->data_head; + + /* Delete any leftover trace from the previous iteration. */ + VEC_free (btrace_block_s, *btrace); + + if (type == BTRACE_READ_DELTA) + { + /* Determine the number of bytes to read and check for buffer + overflows. */ + + /* Check for data head overflows. We might be able to recover from + those but they are very unlikely and it's not really worth the + effort, I think. */ + if (data_head < data_tail) + return BTRACE_ERR_OVERFLOW; + + /* If the buffer is smaller than the trace delta, we overflowed. */ + size = data_head - data_tail; + if (buffer_size < size) + return BTRACE_ERR_OVERFLOW; + } + else + { + /* Read the entire buffer. */ + size = buffer_size; + + /* Adjust the size if the buffer has not overflowed, yet. */ + if (data_head < size) + size = 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); + + *btrace = perf_event_read_bts (tinfo, begin, end, start, size); + + /* 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; + + /* Prune the incomplete last block (i.e. the first one of inferior execution) + if we're not doing a delta read. There is no way of filling in its zeroed + BEGIN element. */ + if (!VEC_empty (btrace_block_s, *btrace) && type != BTRACE_READ_DELTA) + VEC_pop (btrace_block_s, *btrace); + + return BTRACE_ERR_NONE; +} + +#else /* !HAVE_LINUX_PERF_EVENT_H */ + +/* See linux-btrace.h. */ + +int +linux_supports_btrace (struct target_ops *ops) +{ + return 0; +} + +/* See linux-btrace.h. */ + +struct btrace_target_info * +linux_enable_btrace (ptid_t ptid) +{ + return NULL; +} + +/* See linux-btrace.h. */ + +enum btrace_error +linux_disable_btrace (struct btrace_target_info *tinfo) +{ + return BTRACE_ERR_NOT_SUPPORTED; +} + +/* See linux-btrace.h. */ + +enum btrace_error +linux_read_btrace (VEC (btrace_block_s) **btrace, + struct btrace_target_info *tinfo, + enum btrace_read_type type) +{ + return BTRACE_ERR_NOT_SUPPORTED; +} + +#endif /* !HAVE_LINUX_PERF_EVENT_H */ |