c533ffe04d
When the runtime collects a stack trace to associate it with some
profiling event (mem alloc, mutex, etc) there is a skip count passed
to runtime.Callers (or equivalent) to skip some known count of frames
in order to get to the "interesting" frame corresponding to the
profile event. Now that the profiling mechanism uses lazy fixup (when
removing compiler artifacts like thunks, morestack calls etc), we also
need to move the frame skipping logic after the fixup, so as to insure
that the skip count isn't thrown off by these artifacts.
Fixes golang/go#32290.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/179740
From-SVN: r271892
318 lines
9.0 KiB
C
318 lines
9.0 KiB
C
/* go-callers.c -- get callers for Go.
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Copyright 2012 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file. */
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#include "config.h"
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#include "backtrace.h"
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#include "runtime.h"
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#include "array.h"
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/* This is set to non-zero when calling backtrace_full. This is used
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to avoid getting hanging on a recursive lock in dl_iterate_phdr on
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older versions of glibc when a SIGPROF signal arrives while
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collecting a backtrace. */
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uint32 __go_runtime_in_callers;
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/* Argument passed to callback function. */
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struct callers_data
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{
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Location *locbuf;
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int skip;
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int index;
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int max;
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int keep_thunks;
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};
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/* Callback function for backtrace_full. Just collect the locations.
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Return zero to continue, non-zero to stop. */
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static int
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callback (void *data, uintptr_t pc, const char *filename, int lineno,
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const char *function)
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{
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struct callers_data *arg = (struct callers_data *) data;
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Location *loc;
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/* Skip split stack functions. */
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if (function != NULL)
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{
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const char *p;
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p = function;
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if (__builtin_strncmp (p, "___", 3) == 0)
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++p;
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if (__builtin_strncmp (p, "__morestack_", 12) == 0)
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return 0;
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}
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else if (filename != NULL)
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{
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const char *p;
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p = strrchr (filename, '/');
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if (p == NULL)
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p = filename;
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if (__builtin_strncmp (p, "/morestack.S", 12) == 0)
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return 0;
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}
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/* Skip thunks and recover functions. There is no equivalent to
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these functions in the gc toolchain, so returning them here means
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significantly different results for runtime.Caller(N). See also
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similar code in runtime/mprof.go that strips out such functions
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for block/mutex/memory profiles. */
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if (function != NULL && !arg->keep_thunks)
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{
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const char *p;
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p = function + __builtin_strlen (function);
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while (p > function && p[-1] >= '0' && p[-1] <= '9')
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--p;
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if (p - function > 7 && __builtin_strncmp (p - 7, "..thunk", 7) == 0)
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return 0;
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if (p - function > 3 && __builtin_strcmp (p - 3, "..r") == 0)
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return 0;
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if (p - function > 6 && __builtin_strncmp (p - 6, "..stub", 6) == 0)
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return 0;
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}
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if (arg->skip > 0)
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{
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--arg->skip;
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return 0;
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}
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loc = &arg->locbuf[arg->index];
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/* On the call to backtrace_full the pc value was most likely
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decremented if there was a normal call, since the pc referred to
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the instruction where the call returned and not the call itself.
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This was done so that the line number referred to the call
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instruction. To make sure the actual pc from the call stack is
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used, it is incremented here.
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In the case of a signal, the pc was not decremented by
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backtrace_full but still incremented here. That doesn't really
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hurt anything since the line number is right and the pc refers to
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the same instruction. */
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loc->pc = pc + 1;
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/* The libbacktrace library says that these strings might disappear,
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but with the current implementation they won't. We can't easily
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allocate memory here, so for now assume that we can save a
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pointer to the strings. */
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loc->filename = runtime_gostringnocopy ((const byte *) filename);
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loc->function = runtime_gostringnocopy ((const byte *) function);
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loc->lineno = lineno;
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++arg->index;
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/* There is no point to tracing past certain runtime functions.
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Stopping the backtrace here can avoid problems on systems that
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don't provide proper unwind information for makecontext, such as
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Solaris (http://gcc.gnu.org/PR52583 comment #21). */
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if (function != NULL)
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{
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if (__builtin_strcmp (function, "makecontext") == 0)
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return 1;
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if (filename != NULL)
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{
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const char *p;
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p = strrchr (filename, '/');
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if (p == NULL)
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p = filename;
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if (__builtin_strcmp (p, "/proc.c") == 0)
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{
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if (__builtin_strcmp (function, "runtime_mstart") == 0)
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return 1;
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}
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else if (__builtin_strcmp (p, "/proc.go") == 0)
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{
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if (__builtin_strcmp (function, "runtime.kickoff") == 0
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|| __builtin_strcmp (function, "runtime.main") == 0)
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return 1;
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}
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}
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}
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return arg->index >= arg->max;
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}
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/* Syminfo callback. */
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void
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__go_syminfo_fnname_callback (void *data,
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uintptr_t pc __attribute__ ((unused)),
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const char *symname,
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uintptr_t address __attribute__ ((unused)),
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uintptr_t size __attribute__ ((unused)))
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{
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String* strptr = (String*) data;
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if (symname != NULL)
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*strptr = runtime_gostringnocopy ((const byte *) symname);
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}
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/* Error callback. */
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static void
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error_callback (void *data __attribute__ ((unused)),
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const char *msg, int errnum)
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{
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if (errnum == -1)
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{
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/* No debug info available. Carry on as best we can. */
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return;
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}
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if (errnum != 0)
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runtime_printf ("%s errno %d\n", msg, errnum);
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runtime_throw (msg);
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}
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/* Return whether we are already collecting a stack trace. This is
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called from the signal handler. */
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bool alreadyInCallers(void)
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__attribute__ ((no_split_stack));
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bool alreadyInCallers(void)
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__asm__ (GOSYM_PREFIX "runtime.alreadyInCallers");
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bool
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alreadyInCallers()
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{
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return runtime_atomicload(&__go_runtime_in_callers) > 0;
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}
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/* Gather caller PC's. */
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int32
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runtime_callers (int32 skip, Location *locbuf, int32 m, bool keep_thunks)
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{
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struct callers_data data;
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struct backtrace_state* state;
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int32 i;
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data.locbuf = locbuf;
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data.skip = skip + 1;
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data.index = 0;
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data.max = m;
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data.keep_thunks = keep_thunks;
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runtime_xadd (&__go_runtime_in_callers, 1);
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state = __go_get_backtrace_state ();
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backtrace_full (state, 0, callback, error_callback, &data);
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runtime_xadd (&__go_runtime_in_callers, -1);
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/* For some reason GCC sometimes loses the name of a thunk function
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at the top of the stack. If we are skipping thunks, skip that
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one too. */
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if (!keep_thunks
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&& data.index > 2
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&& locbuf[data.index - 2].function.len == 0
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&& locbuf[data.index - 1].function.str != NULL
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&& __builtin_strcmp ((const char *) locbuf[data.index - 1].function.str,
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"runtime.kickoff") == 0)
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{
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locbuf[data.index - 2] = locbuf[data.index - 1];
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--data.index;
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}
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/* Try to use backtrace_syminfo to fill in any missing function
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names. This can happen when tracing through an object which has
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no debug info; backtrace_syminfo will look at the symbol table to
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get the name. This should only happen when tracing through code
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that is not written in Go and is not part of libgo. */
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for (i = 0; i < data.index; ++i)
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{
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if (locbuf[i].function.len == 0 && locbuf[i].pc != 0)
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backtrace_syminfo (state, locbuf[i].pc, __go_syminfo_fnname_callback,
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error_callback, &locbuf[i].function);
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}
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return data.index;
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}
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intgo Callers (intgo, struct __go_open_array)
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__asm__ (GOSYM_PREFIX "runtime.Callers");
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intgo
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Callers (intgo skip, struct __go_open_array pc)
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{
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Location *locbuf;
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int ret;
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int i;
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/* Note that calling mallocgc here assumes that we are not going to
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store any allocated Go pointers in the slice. */
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locbuf = (Location *) runtime_mallocgc (pc.__count * sizeof (Location),
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nil, false);
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/* In the Go 1 release runtime.Callers has an off-by-one error,
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which we can not correct because it would break backward
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compatibility. Normally we would add 1 to SKIP here, but we
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don't so that we are compatible. */
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ret = runtime_callers (skip, locbuf, pc.__count, false);
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for (i = 0; i < ret; i++)
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((uintptr *) pc.__values)[i] = locbuf[i].pc;
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return ret;
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}
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struct callersRaw_data
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{
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uintptr* pcbuf;
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int index;
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int max;
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};
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// Callback function for backtrace_simple. Just collect pc's.
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// Return zero to continue, non-zero to stop.
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static int callback_raw (void *data, uintptr_t pc)
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{
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struct callersRaw_data *arg = (struct callersRaw_data *) data;
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/* On the call to backtrace_simple the pc value was most likely
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decremented if there was a normal call, since the pc referred to
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the instruction where the call returned and not the call itself.
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This was done so that the line number referred to the call
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instruction. To make sure the actual pc from the call stack is
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used, it is incremented here.
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In the case of a signal, the pc was not decremented by
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backtrace_full but still incremented here. That doesn't really
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hurt anything since the line number is right and the pc refers to
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the same instruction. */
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arg->pcbuf[arg->index] = pc + 1;
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arg->index++;
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return arg->index >= arg->max;
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}
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/* runtime_callersRaw is similar to runtime_callers() above, but
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it returns raw PC values as opposed to file/func/line locations. */
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int32
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runtime_callersRaw (uintptr *pcbuf, int32 m)
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{
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struct callersRaw_data data;
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struct backtrace_state* state;
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data.pcbuf = pcbuf;
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data.index = 0;
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data.max = m;
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runtime_xadd (&__go_runtime_in_callers, 1);
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state = __go_get_backtrace_state ();
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backtrace_simple (state, 0, callback_raw, error_callback, &data);
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runtime_xadd (&__go_runtime_in_callers, -1);
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return data.index;
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}
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