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workaround: gcc v4.8 on 32 bit param. passing bug when -02 opimization used

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gcc -O2 v4.8 on 32 bit architecture is causing a bug in parameter
passing. It does not happen with -01 nor -O0.

The problematic part of the code was strlen use in config.c in
the config_def_check fn and the call for _config_def_check_tree in it:

<snip>
  rplen = strlen(rp);
  if (!_config_def_check_tree(handle, vp, vp + strlen(vp), rp, rp + rplen, CFG_PATH_MAX_LEN - rplen, cn, cmd->cft_def_hash)) ...
</snip>

If compiled with -O0 (correct):

Breakpoint 1, config_def_check (cmd=0x819b050, handle=0x81a04f8) at config/config.c:775
(gdb) p	vp
$1 = 0x8189ee0 <_cfg_path> "config"
(gdb) p	strlen(vp)
$2 = 6
(gdb)
_config_def_check_tree (handle=0x81a04f8, vp=0x8189ee0 <_cfg_path>
"config", pvp=0x8189ee6 <_cfg_path+6> "", rp=0xbfffe1e8 "config",
prp=0xbfffe1ee "", buf_size=58, root=0x81a2568, ht=0x81a65
48) at config/config.c:680
(gdb) p	vp
$4 = 0x8189ee0 <_cfg_path> "config"
(gdb) p	pvp
$5 = 0x8189ee6 <_cfg_path+6> ""

If compiled with -O2 (incorrect):

Breakpoint 1, config_def_check (cmd=cmd@entry=0x8183050, handle=0x81884f8) at config/config.c:775
(gdb) p	vp
$1 = 0x8172fc0 <_cfg_path> "config"
(gdb) p strlen(vp)
$2 = 6
(gdb) p	vp + strlen(vp)
$3 = 0x8172fc6 <_cfg_path+6> ""
(gdb)
_config_def_check_tree (handle=handle@entry=0x81884f8, pvp=0x8172fc7
<_cfg_path+7> "host_list", rp=rp@entry=0xbffff190 "config",
prp=prp@entry=0xbffff196 "", buf_size=buf_size@entry=58, ht=0x
818e548, root=0x818a568, vp=0x8172fc0 <_cfg_path> "config") at
config/config.c:674
(gdb) p	pvp
$4 = 0x8172fc7 <_cfg_path+7> "host_list"

The difference is in passing the "pvp" arg for _config_def_check_tree.
While in the correct case, the value of _cfg_path+6 is passed
(the result of vp + strlen(vp) - see the snippet of the code above),
in the incorrect case, this value is increased by 1 to _cfg_path+7,
hence totally malforming the string that is being processed.

This ends up with incorrect validation check and incorrect warning
messages are issued like:

 "Configuration setting "config/checks" has invalid type. Found integer, expected section."

To workaround this issue, remove the "static" qualifier from the
"static char _cfg_path[CFG_PATH_MAX_LEN]". This causes the optimalizer
to be less aggressive (also shuffling the arg list for
_config_def_check_tree call helps).
This commit is contained in:
Peter Rajnoha 2013-08-09 13:06:17 +02:00
parent 8d3347f70b
commit 2f61478436
2 changed files with 2 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
WHATS_NEW
View File

@ -1,5 +1,6 @@
Version 2.02.100 - Version 2.02.100 -
================================ ================================
Workaround gcc v4.8 -O2 bug causing failures if config/checks=1 (32bit arch).
Verify clvmd message validity before processing and log error if incorrect. Verify clvmd message validity before processing and log error if incorrect.
Fix issue preventing PV creation on mirror LVs Fix issue preventing PV creation on mirror LVs
When converting mirrors, default segtype should be the same unless specified. When converting mirrors, default segtype should be the same unless specified.

2
lib/config/config.c
View File

@ -56,7 +56,7 @@ struct config_source {
} source; } source;
}; };
static char _cfg_path[CFG_PATH_MAX_LEN]; char _cfg_path[CFG_PATH_MAX_LEN];
/* /*
* Map each ID to respective definition of the configuration item. * Map each ID to respective definition of the configuration item.