562 lines
17 KiB
C
562 lines
17 KiB
C
/* Profiling of shared libraries.
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Copyright (C) 1997,1998,1999,2000,2001,2002 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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Based on the BSD mcount implementation.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <ldsodefs.h>
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#include <sys/gmon.h>
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#include <sys/gmon_out.h>
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#include <sys/mman.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <atomicity.h>
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/* The LD_PROFILE feature has to be implemented different to the
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normal profiling using the gmon/ functions. The problem is that an
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arbitrary amount of processes simulataneously can be run using
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profiling and all write the results in the same file. To provide
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this mechanism one could implement a complicated mechanism to merge
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the content of two profiling runs or one could extend the file
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format to allow more than one data set. For the second solution we
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would have the problem that the file can grow in size beyond any
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limit and both solutions have the problem that the concurrency of
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writing the results is a big problem.
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Another much simpler method is to use mmap to map the same file in
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all using programs and modify the data in the mmap'ed area and so
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also automatically on the disk. Using the MAP_SHARED option of
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mmap(2) this can be done without big problems in more than one
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file.
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This approach is very different from the normal profiling. We have
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to use the profiling data in exactly the way they are expected to
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be written to disk. But the normal format used by gprof is not usable
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to do this. It is optimized for size. It writes the tags as single
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bytes but this means that the following 32/64 bit values are
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unaligned.
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Therefore we use a new format. This will look like this
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0 1 2 3 <- byte is 32 bit word
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0000 g m o n
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0004 *version* <- GMON_SHOBJ_VERSION
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0008 00 00 00 00
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000c 00 00 00 00
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0010 00 00 00 00
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0014 *tag* <- GMON_TAG_TIME_HIST
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0018 ?? ?? ?? ??
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?? ?? ?? ?? <- 32/64 bit LowPC
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0018+A ?? ?? ?? ??
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?? ?? ?? ?? <- 32/64 bit HighPC
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0018+2*A *histsize*
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001c+2*A *profrate*
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0020+2*A s e c o
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0024+2*A n d s \0
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0028+2*A \0 \0 \0 \0
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002c+2*A \0 \0 \0
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002f+2*A s
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0030+2*A ?? ?? ?? ?? <- Count data
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... ...
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0030+2*A+K ?? ?? ?? ??
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0030+2*A+K *tag* <- GMON_TAG_CG_ARC
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0034+2*A+K *lastused*
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0038+2*A+K ?? ?? ?? ??
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?? ?? ?? ?? <- FromPC#1
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0038+3*A+K ?? ?? ?? ??
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?? ?? ?? ?? <- ToPC#1
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0038+4*A+K ?? ?? ?? ?? <- Count#1
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... ... ...
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0038+(2*(CN-1)+2)*A+(CN-1)*4+K ?? ?? ?? ??
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?? ?? ?? ?? <- FromPC#CGN
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0038+(2*(CN-1)+3)*A+(CN-1)*4+K ?? ?? ?? ??
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?? ?? ?? ?? <- ToPC#CGN
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0038+(2*CN+2)*A+(CN-1)*4+K ?? ?? ?? ?? <- Count#CGN
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We put (for now?) no basic block information in the file since this would
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introduce rase conditions among all the processes who want to write them.
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`K' is the number of count entries which is computed as
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textsize / HISTFRACTION
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`CG' in the above table is the number of call graph arcs. Normally,
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the table is sparse and the profiling code writes out only the those
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entries which are really used in the program run. But since we must
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not extend this table (the profiling file) we'll keep them all here.
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So CN can be executed in advance as
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MINARCS <= textsize*(ARCDENSITY/100) <= MAXARCS
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Now the remaining question is: how to build the data structures we can
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work with from this data. We need the from set and must associate the
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froms with all the associated tos. We will do this by constructing this
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data structures at the program start. To do this we'll simply visit all
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entries in the call graph table and add it to the appropriate list. */
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extern int __profile_frequency (void);
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/* We define a special type to address the elements of the arc table.
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This is basically the `gmon_cg_arc_record' format but it includes
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the room for the tag and it uses real types. */
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struct here_cg_arc_record
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{
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uintptr_t from_pc;
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uintptr_t self_pc;
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uint32_t count;
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} __attribute__ ((packed));
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static struct here_cg_arc_record *data;
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/* Nonzero if profiling is under way. */
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static int running;
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/* This is the number of entry which have been incorporated in the toset. */
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static uint32_t narcs;
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/* This is a pointer to the object representing the number of entries
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currently in the mmaped file. At no point of time this has to be the
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same as NARCS. If it is equal all entries from the file are in our
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lists. */
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static volatile uint32_t *narcsp;
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static volatile uint16_t *kcount;
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static size_t kcountsize;
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struct here_fromstruct
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{
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struct here_cg_arc_record volatile *here;
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uint16_t link;
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};
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static volatile uint16_t *tos;
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static struct here_fromstruct *froms;
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static uint32_t fromlimit;
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static volatile uint32_t fromidx;
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static uintptr_t lowpc;
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static size_t textsize;
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static unsigned int hashfraction;
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static unsigned int log_hashfraction;
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/* Set up profiling data to profile object desribed by MAP. The output
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file is found (or created) in OUTPUT_DIR. */
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void
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internal_function
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_dl_start_profile (struct link_map *map, const char *output_dir)
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{
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char *filename;
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int fd;
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struct stat64 st;
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const ElfW(Phdr) *ph;
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ElfW(Addr) mapstart = ~((ElfW(Addr)) 0);
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ElfW(Addr) mapend = 0;
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struct gmon_hdr gmon_hdr;
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struct gmon_hist_hdr hist_hdr;
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char *hist, *cp;
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size_t idx;
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size_t tossize;
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size_t fromssize;
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uintptr_t highpc;
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struct gmon_hdr *addr = NULL;
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off_t expected_size;
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/* See profil(2) where this is described. */
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int s_scale;
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#define SCALE_1_TO_1 0x10000L
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/* Compute the size of the sections which contain program code. */
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for (ph = map->l_phdr; ph < &map->l_phdr[map->l_phnum]; ++ph)
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if (ph->p_type == PT_LOAD && (ph->p_flags & PF_X))
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{
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ElfW(Addr) start = (ph->p_vaddr & ~(GL(dl_pagesize) - 1));
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ElfW(Addr) end = ((ph->p_vaddr + ph->p_memsz + GL(dl_pagesize) - 1)
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& ~(GL(dl_pagesize) - 1));
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if (start < mapstart)
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mapstart = start;
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if (end > mapend)
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mapend = end;
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}
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/* Now we can compute the size of the profiling data. This is done
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with the same formulars as in `monstartup' (see gmon.c). */
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running = 0;
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lowpc = ROUNDDOWN (mapstart + map->l_addr,
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HISTFRACTION * sizeof (HISTCOUNTER));
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highpc = ROUNDUP (mapend + map->l_addr,
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HISTFRACTION * sizeof (HISTCOUNTER));
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textsize = highpc - lowpc;
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kcountsize = textsize / HISTFRACTION;
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hashfraction = HASHFRACTION;
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if ((HASHFRACTION & (HASHFRACTION - 1)) == 0)
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{
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/* If HASHFRACTION is a power of two, mcount can use shifting
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instead of integer division. Precompute shift amount.
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This is a constant but the compiler cannot compile the
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expression away since the __ffs implementation is not known
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to the compiler. Help the compiler by precomputing the
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usual cases. */
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assert (hashfraction == 2);
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if (sizeof (*froms) == 8)
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log_hashfraction = 4;
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else if (sizeof (*froms) == 16)
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log_hashfraction = 5;
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else
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log_hashfraction = __ffs (hashfraction * sizeof (*froms)) - 1;
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}
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else
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log_hashfraction = -1;
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tossize = textsize / HASHFRACTION;
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fromlimit = textsize * ARCDENSITY / 100;
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if (fromlimit < MINARCS)
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fromlimit = MINARCS;
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if (fromlimit > MAXARCS)
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fromlimit = MAXARCS;
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fromssize = fromlimit * sizeof (struct here_fromstruct);
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expected_size = (sizeof (struct gmon_hdr)
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+ 4 + sizeof (struct gmon_hist_hdr) + kcountsize
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+ 4 + 4 + fromssize * sizeof (struct here_cg_arc_record));
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/* Create the gmon_hdr we expect or write. */
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memset (&gmon_hdr, '\0', sizeof (struct gmon_hdr));
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memcpy (&gmon_hdr.cookie[0], GMON_MAGIC, sizeof (gmon_hdr.cookie));
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*(int32_t *) gmon_hdr.version = GMON_SHOBJ_VERSION;
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/* Create the hist_hdr we expect or write. */
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*(char **) hist_hdr.low_pc = (char *) mapstart;
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*(char **) hist_hdr.high_pc = (char *) mapend;
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*(int32_t *) hist_hdr.hist_size = kcountsize / sizeof (HISTCOUNTER);
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*(int32_t *) hist_hdr.prof_rate = __profile_frequency ();
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if (sizeof (hist_hdr.dimen) >= sizeof ("seconds"))
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{
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memcpy (hist_hdr.dimen, "seconds", sizeof ("seconds"));
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memset (hist_hdr.dimen + sizeof ("seconds"), '\0',
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sizeof (hist_hdr.dimen) - sizeof ("seconds"));
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}
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else
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strncpy (hist_hdr.dimen, "seconds", sizeof (hist_hdr.dimen));
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hist_hdr.dimen_abbrev = 's';
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/* First determine the output name. We write in the directory
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OUTPUT_DIR and the name is composed from the shared objects
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soname (or the file name) and the ending ".profile". */
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filename = (char *) alloca (strlen (output_dir) + 1 + strlen (GL(dl_profile))
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+ sizeof ".profile");
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cp = __stpcpy (filename, output_dir);
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*cp++ = '/';
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__stpcpy (__stpcpy (cp, GL(dl_profile)), ".profile");
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#ifdef O_NOFOLLOW
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# define EXTRA_FLAGS | O_NOFOLLOW
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#else
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# define EXTRA_FLAGS
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#endif
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fd = __open (filename, O_RDWR | O_CREAT EXTRA_FLAGS, DEFFILEMODE);
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if (fd == -1)
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{
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/* We cannot write the profiling data so don't do anything. */
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char buf[400];
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_dl_error_printf ("%s: cannot open file: %s\n", filename,
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__strerror_r (errno, buf, sizeof buf));
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return;
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}
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if (__fxstat64 (_STAT_VER, fd, &st) < 0 || !S_ISREG (st.st_mode))
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{
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/* Not stat'able or not a regular file => don't use it. */
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char buf[400];
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int errnum = errno;
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__close (fd);
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_dl_error_printf ("%s: cannot stat file: %s\n", filename,
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__strerror_r (errnum, buf, sizeof buf));
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return;
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}
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/* Test the size. If it does not match what we expect from the size
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values in the map MAP we don't use it and warn the user. */
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if (st.st_size == 0)
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{
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/* We have to create the file. */
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char buf[GL(dl_pagesize)];
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memset (buf, '\0', GL(dl_pagesize));
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if (__lseek (fd, expected_size & ~(GL(dl_pagesize) - 1), SEEK_SET) == -1)
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{
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char buf[400];
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int errnum;
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cannot_create:
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errnum = errno;
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__close (fd);
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_dl_error_printf ("%s: cannot create file: %s\n", filename,
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__strerror_r (errnum, buf, sizeof buf));
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return;
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}
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if (TEMP_FAILURE_RETRY (__libc_write (fd, buf, (expected_size
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& (GL(dl_pagesize)
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- 1))))
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< 0)
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goto cannot_create;
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}
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else if (st.st_size != expected_size)
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{
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__close (fd);
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wrong_format:
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if (addr != NULL)
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__munmap ((void *) addr, expected_size);
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_dl_error_printf ("%s: file is no correct profile data file for `%s'\n",
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filename, GL(dl_profile));
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return;
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}
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addr = (struct gmon_hdr *) __mmap (NULL, expected_size, PROT_READ|PROT_WRITE,
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MAP_SHARED|MAP_FILE, fd, 0);
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if (addr == (struct gmon_hdr *) MAP_FAILED)
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{
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char buf[400];
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int errnum = errno;
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__close (fd);
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_dl_error_printf ("%s: cannot map file: %s\n", filename,
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__strerror_r (errnum, buf, sizeof buf));
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return;
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}
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/* We don't need the file desriptor anymore. */
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__close (fd);
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/* Pointer to data after the header. */
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hist = (char *) (addr + 1);
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kcount = (uint16_t *) ((char *) hist + sizeof (uint32_t)
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+ sizeof (struct gmon_hist_hdr));
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/* Compute pointer to array of the arc information. */
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narcsp = (uint32_t *) ((char *) kcount + kcountsize + sizeof (uint32_t));
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data = (struct here_cg_arc_record *) ((char *) narcsp + sizeof (uint32_t));
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if (st.st_size == 0)
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{
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/* Create the signature. */
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memcpy (addr, &gmon_hdr, sizeof (struct gmon_hdr));
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*(uint32_t *) hist = GMON_TAG_TIME_HIST;
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memcpy (hist + sizeof (uint32_t), &hist_hdr,
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sizeof (struct gmon_hist_hdr));
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narcsp[-1] = GMON_TAG_CG_ARC;
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}
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else
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{
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/* Test the signature in the file. */
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if (memcmp (addr, &gmon_hdr, sizeof (struct gmon_hdr)) != 0
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|| *(uint32_t *) hist != GMON_TAG_TIME_HIST
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|| memcmp (hist + sizeof (uint32_t), &hist_hdr,
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sizeof (struct gmon_hist_hdr)) != 0
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|| narcsp[-1] != GMON_TAG_CG_ARC)
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goto wrong_format;
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}
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/* Allocate memory for the froms data and the pointer to the tos records. */
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tos = (uint16_t *) calloc (tossize + fromssize, 1);
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if (tos == NULL)
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{
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__munmap ((void *) addr, expected_size);
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_dl_fatal_printf ("Out of memory while initializing profiler\n");
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/* NOTREACHED */
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}
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froms = (struct here_fromstruct *) ((char *) tos + tossize);
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fromidx = 0;
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/* Now we have to process all the arc count entries. BTW: it is
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not critical whether the *NARCSP value changes meanwhile. Before
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we enter a new entry in to toset we will check that everything is
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available in TOS. This happens in _dl_mcount.
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Loading the entries in reverse order should help to get the most
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frequently used entries at the front of the list. */
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for (idx = narcs = MIN (*narcsp, fromlimit); idx > 0; )
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{
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size_t to_index;
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size_t newfromidx;
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--idx;
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to_index = (data[idx].self_pc / (hashfraction * sizeof (*tos)));
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newfromidx = fromidx++;
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froms[newfromidx].here = &data[idx];
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froms[newfromidx].link = tos[to_index];
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tos[to_index] = newfromidx;
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}
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/* Setup counting data. */
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if (kcountsize < highpc - lowpc)
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{
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#if 0
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s_scale = ((double) kcountsize / (highpc - lowpc)) * SCALE_1_TO_1;
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#else
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size_t range = highpc - lowpc;
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size_t quot = range / kcountsize;
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if (quot >= SCALE_1_TO_1)
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s_scale = 1;
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else if (quot >= SCALE_1_TO_1 / 256)
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s_scale = SCALE_1_TO_1 / quot;
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else if (range > ULONG_MAX / 256)
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s_scale = (SCALE_1_TO_1 * 256) / (range / (kcountsize / 256));
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else
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s_scale = (SCALE_1_TO_1 * 256) / ((range * 256) / kcountsize);
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#endif
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}
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else
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s_scale = SCALE_1_TO_1;
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/* Start the profiler. */
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__profil ((void *) kcount, kcountsize, lowpc, s_scale);
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/* Turn on profiling. */
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running = 1;
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}
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INTDEF (_dl_start_profile)
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void
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_dl_mcount (ElfW(Addr) frompc, ElfW(Addr) selfpc)
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{
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volatile uint16_t *topcindex;
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size_t i, fromindex;
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struct here_fromstruct *fromp;
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if (! running)
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return;
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/* Compute relative addresses. The shared object can be loaded at
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any address. The value of frompc could be anything. We cannot
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restrict it in any way, just set to a fixed value (0) in case it
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is outside the allowed range. These calls show up as calls from
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<external> in the gprof output. */
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frompc -= lowpc;
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if (frompc >= textsize)
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frompc = 0;
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selfpc -= lowpc;
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if (selfpc >= textsize)
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goto done;
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/* Getting here we now have to find out whether the location was
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already used. If yes we are lucky and only have to increment a
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counter (this also has to be atomic). If the entry is new things
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are getting complicated... */
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/* Avoid integer divide if possible. */
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||
if ((HASHFRACTION & (HASHFRACTION - 1)) == 0)
|
||
i = selfpc >> log_hashfraction;
|
||
else
|
||
i = selfpc / (hashfraction * sizeof (*tos));
|
||
|
||
topcindex = &tos[i];
|
||
fromindex = *topcindex;
|
||
|
||
if (fromindex == 0)
|
||
goto check_new_or_add;
|
||
|
||
fromp = &froms[fromindex];
|
||
|
||
/* We have to look through the chain of arcs whether there is already
|
||
an entry for our arc. */
|
||
while (fromp->here->from_pc != frompc)
|
||
{
|
||
if (fromp->link != 0)
|
||
do
|
||
fromp = &froms[fromp->link];
|
||
while (fromp->link != 0 && fromp->here->from_pc != frompc);
|
||
|
||
if (fromp->here->from_pc != frompc)
|
||
{
|
||
topcindex = &fromp->link;
|
||
|
||
check_new_or_add:
|
||
/* Our entry is not among the entries we read so far from the
|
||
data file. Now see whether we have to update the list. */
|
||
while (narcs != *narcsp && narcs < fromlimit)
|
||
{
|
||
size_t to_index;
|
||
size_t newfromidx;
|
||
to_index = (data[narcs].self_pc
|
||
/ (hashfraction * sizeof (*tos)));
|
||
newfromidx = exchange_and_add (&fromidx, 1) + 1;
|
||
froms[newfromidx].here = &data[narcs];
|
||
froms[newfromidx].link = tos[to_index];
|
||
tos[to_index] = newfromidx;
|
||
atomic_add (&narcs, 1);
|
||
}
|
||
|
||
/* If we still have no entry stop searching and insert. */
|
||
if (*topcindex == 0)
|
||
{
|
||
uint_fast32_t newarc = exchange_and_add (narcsp, 1);
|
||
|
||
/* In rare cases it could happen that all entries in FROMS are
|
||
occupied. So we cannot count this anymore. */
|
||
if (newarc >= fromlimit)
|
||
goto done;
|
||
|
||
*topcindex = exchange_and_add (&fromidx, 1) + 1;
|
||
fromp = &froms[*topcindex];
|
||
|
||
fromp->here = &data[newarc];
|
||
data[newarc].from_pc = frompc;
|
||
data[newarc].self_pc = selfpc;
|
||
data[newarc].count = 0;
|
||
fromp->link = 0;
|
||
atomic_add (&narcs, 1);
|
||
|
||
break;
|
||
}
|
||
|
||
fromp = &froms[*topcindex];
|
||
}
|
||
else
|
||
/* Found in. */
|
||
break;
|
||
}
|
||
|
||
/* Increment the counter. */
|
||
atomic_add (&fromp->here->count, 1);
|
||
|
||
done:
|
||
;
|
||
}
|
||
INTDEF(_dl_mcount)
|