Hi Douglas,
While testing the BTF encoder parallelization work done by
Kui-Feng Lee, I noticed this problem.
The whole tree is at the 'next' branch in my git repo.
Please check and consider providing a Reviewed-by or Acked-by,
Thanks,
- Arnaldo
----
tldr;
gdb pfunct
(gdb) run --compile tcp.o
Program received signal SIGFPE, Arithmetic exception.
0x00007ffff7f18551 in class__fprintf_cacheline_boundary (conf=0x7fffffffda10, offset=0, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:1319
1319 uint32_t cacheline = offset / conf->cacheline_size;
(gdb) bt
#0 0x00007ffff7f18551 in class__fprintf_cacheline_boundary (conf=0x7fffffffda10, offset=0, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:1319
#1 0x00007ffff7f16af2 in class_member__fprintf (member=0x45de10, union_member=false, type=0x45dfb0, cu=0x435a40, conf=0x7fffffffda10, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:869
#2 0x00007ffff7f1717b in struct_member__fprintf (member=0x45de10, type=0x45dfb0, cu=0x435a40, conf=0x7fffffffda10, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:983
#3 0x00007ffff7f1945c in __class__fprintf (class=0x45dcc0, cu=0x435a40, conf=0x7fffffffdbb0, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:1583
#4 0x00007ffff7f1a6bd in tag__fprintf (tag=0x45dcc0, cu=0x435a40, conf=0x7fffffffdc70, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_fprintf.c:1906
#5 0x00007ffff7fbf022 in type__emit (tag=0x45dcc0, cu=0x435a40, prefix=0x0, suffix=0x0, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:333
#6 0x00007ffff7fbed3d in tag__emit_definitions (tag=0x6b21e0, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:265
#7 0x00007ffff7fbef45 in type__emit_definitions (tag=0x6b20c0, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:315
#8 0x00007ffff7fbed15 in tag__emit_definitions (tag=0x6b3b40, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:264
#9 0x00007ffff7fbef45 in type__emit_definitions (tag=0x6b31d0, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:315
#10 0x00007ffff7fbed15 in tag__emit_definitions (tag=0x4cb920, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:264
#11 0x00007ffff7fbef45 in type__emit_definitions (tag=0x4cb7d0, cu=0x435a40, emissions=0x408300 <emissions>, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/dwarves_emit.c:315
#12 0x0000000000403592 in function__emit_type_definitions (func=0x738ad0, cu=0x435a40, fp=0x7ffff7e17520 <_IO_2_1_stdout_>) at /var/home/acme/git/pahole/pfunct.c:353
#13 0x0000000000403670 in function__show (func=0x738ad0, cu=0x435a40) at /var/home/acme/git/pahole/pfunct.c:371
#14 0x00000000004038e9 in cu_function_iterator (cu=0x435a40, cookie=0x0) at /var/home/acme/git/pahole/pfunct.c:404
#15 0x00007ffff7f1296b in cus__for_each_cu (cus=0x4369e0, iterator=0x403869 <cu_function_iterator>, cookie=0x0, filter=0x0) at /var/home/acme/git/pahole/dwarves.c:1919
#16 0x000000000040432a in main (argc=3, argv=0x7fffffffe1f8) at /var/home/acme/git/pahole/pfunct.c:776
(gdb) p conf->cacheline_size
$2 = 0
We need to pass a conf_fprintf pointer to the chain starting with
function__emit_type_definitions(), i.e. dwarves_emit.c needs to receive
the printing configuration instead of, right at type__emit() synthesize
a conf_fprintf without initializing conf_fprintf->cacheline_size which
ends up in a division by zero.
But to fix this quicker just add a helper that checks if it is zero and
uses the conf_fprintf__defaults.cacheline_size field that is being
initialized by all tools via:
dwarves__resolve_cacheline_size(&conf_load, 0);
Fixes: 772725a77d3323c6 ("dwarves_fprintf: Move cacheline_size into struct conf_fprintf")
Cc: Douglas Raillard <douglas.raillard@xxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
dwarves_fprintf.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index c5921d77d326579a..5d4329b718a7f65b 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -148,10 +148,30 @@ static struct conf_fprintf conf_fprintf__defaults = {
const char tabs[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t";
+/*
+ * In dwarves_emit.c we can call type__emit() using a locally setup conf_fprintf for which
+ * the conf->cacheline_size member is not setup and is thus zero, so check for that and
+ * use the default one for that case.
+ *
+ * We really need to make the *_emit*() methods to receive a conf_fprintf pointer for
+ * which conf->cacheline_size is set, all tools call:
+ *
+ * dwarves__resolve_cacheline_size(&conf_load, 0);
+ *
+ * To have a conf_load/conf_fprintf with that resolved, but that is not being passed to
+ * the *_emit*() routines, duh.
+ *
+ * Fixing this properly will entail a series of patches, so to fix this problem
+ * more quickly add this helper.
+ */
+static uint16_t conf_fprintf__cacheline_size(const struct conf_fprintf *conf)
+{
+ return conf->cacheline_size ?: conf_fprintf__defaults.cacheline_size;
+}
size_t tag__nr_cachelines(const struct conf_fprintf *conf, const struct tag *tag, const struct cu *cu)
{
- return (tag__size(tag, cu) + conf->cacheline_size - 1) / conf->cacheline_size;
+ return (tag__size(tag, cu) + conf_fprintf__cacheline_size(conf) - 1) / conf_fprintf__cacheline_size(conf);
}
static const char *tag__accessibility(const struct tag *tag)
@@ -1316,11 +1336,11 @@ static size_t class__fprintf_cacheline_boundary(struct conf_fprintf *conf,
FILE *fp)
{
int indent = conf->indent;
- uint32_t cacheline = offset / conf->cacheline_size;
+ uint32_t cacheline = offset / conf_fprintf__cacheline_size(conf);
size_t printed = 0;
if (cacheline > *conf->cachelinep) {
- const uint32_t cacheline_pos = offset % conf->cacheline_size;
+ const uint32_t cacheline_pos = offset % conf_fprintf__cacheline_size(conf);
const uint32_t cacheline_in_bytes = offset - cacheline_pos;
if (cacheline_pos == 0)
@@ -1762,7 +1782,7 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu,
}
printed += fprintf(fp, " */\n");
}
- cacheline = (cconf.base_offset + type->size) % conf->cacheline_size;
+ cacheline = (cconf.base_offset + type->size) % conf_fprintf__cacheline_size(conf);
if (cacheline != 0)
printed += fprintf(fp, "%.*s/* last cacheline: %u bytes */\n",
cconf.indent, tabs,
--
2.34.1
