dwarves/gobuffer.c
Petr Vandrovec 88674f0395 gobuffer: Do not crash on object without any public symbols
pahole -J .tmp_linux.btf during Linux build process always crashes
on my system.

Problem is that when gobuffer is initialized via gobuffer__init(),
it is in state where 'index' (AKA its size) is set to 1, but
'entries' is NULL.

State corrects itself if 'gobuffer__add()' is invoked, as that
will allocate buffer (even if added len == 0).  But if __add()
is never invoked because only anonymous symbols are present,
one ends up with gobuffer that crashes gobuffer__copy.

Instead of allocating single-byte buffer always I opted for
checking if gobuffer entries is NULL before use in copy and
compress - gobuffer__init() would need prototype change to
report malloc failures, and it seems unnecessary to allocate
memory always - even if file does not have any symbols after
all.

(gdb) bt
 #0  __memmove_sse2_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:287
 #1  0x00007f2f2c1ec2ee in btf_elf__encode (btfe=0x5654e31e2e30, flags=flags@entry=0 '\000') at libbtf.c:750
 #2  0x00007f2f2c1e9af0 in btf_encoder__encode () at btf_encoder.c:164
 #3  0x00005654e2407599 in main (argc=3, argv=0x7ffcd8783f18) at pahole.c:1344
(gdb) frame 1
 #1  0x00007f2f2c1ec2ee in btf_elf__encode (btfe=0x5654e31e2e30, flags=flags@entry=0 '\000') at libbtf.c:750
750             gobuffer__copy(btfe->strings, btf_elf__nohdr_data(btfe) + hdr->str_off);
(gdb) print btfe->strings
$1 = (struct gobuffer *) 0x5654e31db2c8
(gdb) print *btfe->strings
$2 = {entries = 0x0, nr_entries = 0, index = 1, allocated_size = 0}
(gdb) print btfe->types
$3 = {entries = 0x5654e31e2ef0 "", nr_entries = 1, index = 16, allocated_size = 8192}
(gdb) x /16bx btfe->types.entries
0x5654e31e2ef0: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x01
0x5654e31e2ef8: 0x04    0x00    0x00    0x00    0x20    0x00    0x00    0x00

Signed-off-by: Petr Vandrovec <petr@vmware.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-01-17 13:54:15 -03:00

144 lines
2.8 KiB
C

/*
SPDX-License-Identifier: GPL-2.0-only
Copyright (C) 2008 Arnaldo Carvalho de Melo <acme@redhat.com>
Grow only buffer, add entries but never delete
*/
#include "gobuffer.h"
#include <search.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <zlib.h>
#include <errno.h>
#include "dutil.h"
#define GOBUFFER__BCHUNK (8 * 1024)
#define GOBUFFER__ZCHUNK (8 * 1024)
void gobuffer__init(struct gobuffer *gb)
{
gb->entries = NULL;
gb->nr_entries = gb->allocated_size = 0;
/* 0 == NULL */
gb->index = 1;
}
struct gobuffer *gobuffer__new(void)
{
struct gobuffer *gb = malloc(sizeof(*gb));
if (gb != NULL)
gobuffer__init(gb);
return gb;
}
void __gobuffer__delete(struct gobuffer *gb)
{
free(gb->entries);
}
void gobuffer__delete(struct gobuffer *gb)
{
__gobuffer__delete(gb);
free(gb);
}
void *gobuffer__ptr(const struct gobuffer *gb, unsigned int s)
{
return s ? gb->entries + s : NULL;
}
int gobuffer__allocate(struct gobuffer *gb, unsigned int len)
{
const unsigned int rc = gb->index;
const unsigned int index = gb->index + len;
if (index >= gb->allocated_size) {
unsigned int allocated_size = (gb->allocated_size +
GOBUFFER__BCHUNK);
if (allocated_size < index)
allocated_size = index + GOBUFFER__BCHUNK;
char *entries = realloc(gb->entries, allocated_size);
if (entries == NULL)
return -ENOMEM;
gb->allocated_size = allocated_size;
gb->entries = entries;
}
gb->index = index;
return rc;
}
int gobuffer__add(struct gobuffer *gb, const void *s, unsigned int len)
{
const int rc = gobuffer__allocate(gb, len);
if (rc >= 0) {
++gb->nr_entries;
memcpy(gb->entries + rc, s, len);
}
return rc;
}
void gobuffer__copy(const struct gobuffer *gb, void *dest)
{
if (gb->entries) {
memcpy(dest, gb->entries, gobuffer__size(gb));
} else {
/* gobuffer__size will be 0 or 1. */
memcpy(dest, "", gobuffer__size(gb));
}
}
const void *gobuffer__compress(struct gobuffer *gb, unsigned int *size)
{
z_stream z = {
.zalloc = Z_NULL,
.zfree = Z_NULL,
.opaque = Z_NULL,
.avail_in = gobuffer__size(gb),
.next_in = (Bytef *)(gobuffer__entries(gb) ? : ""),
};
void *bf = NULL;
unsigned int bf_size = 0;
if (deflateInit(&z, Z_BEST_COMPRESSION) != Z_OK)
goto out_free;
do {
const unsigned int new_bf_size = bf_size + GOBUFFER__ZCHUNK;
void *nbf = realloc(bf, new_bf_size);
if (nbf == NULL)
goto out_close_and_free;
bf = nbf;
z.avail_out = GOBUFFER__ZCHUNK;
z.next_out = (Bytef *)bf + bf_size;
bf_size = new_bf_size;
if (deflate(&z, Z_FINISH) == Z_STREAM_ERROR)
goto out_close_and_free;
} while (z.avail_out == 0);
deflateEnd(&z);
*size = bf_size - z.avail_out;
out:
return bf;
out_close_and_free:
deflateEnd(&z);
out_free:
free(bf);
bf = NULL;
goto out;
}