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Re: [RFC updated PATCHES] Bug Translator 3016 : Error accessing members of anonymous structs / unions
Hi Masami,
Thanks for letting me know..
It pointed me to an incorrect pointer reference that I had
overlooked...Its funny why this was never uncovered in all test-runs I
had on x86 & x86_64 :-)
Here's the updated patch...with this, your test script correctly throws
a semantic error instead of causing SEGV.
Masami Hiramatsu wrote:
Hi Prerna,
Prerna Saxena wrote:
Agree, but making "die_mem" as the 6th arg will disturb the call flow.
This is because in each recursive call, the 6th arg is overwritten by
a die which is pointed to by DW_AT_type attribute of the original
attr_mem. If die_mem is re-used as 6th arg instead of a new variable,
the old contents of die (in the parent recursive call) will also be
lost as both die & die_mem point to the same location, (whose
contents would be overwritten). This is not a problem if search in a
branch has succeeded-- but in case a search path fails and a new
branch needs to be tried, this will deem it impossible.
I agree with your concern about "temp_die_2" being local memory on
the stack which may be reused, so I've fixed it by copying the
contents of "temp_die_2" to "die_mem" in case of a successful match.
This should take care of memory errors.
Hmm, you seems right, but the below command still cause SEGV.
$ stap -e 'probe
module("libsas").function("sas_ex_revalidate_domain"){print($port_dev->ex_dev->children)}'
-vp2
Pass 1: parsed user script and 45 library script(s) in
370usr/30sys/404real ms.
Segmentation fault
Would you run above command for testing & debugging?
Thank you,
Thanks & regards,
--
Prerna Saxena
Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India
Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Index: systemtap/tapsets.cxx
===================================================================
--- systemtap.orig/tapsets.cxx
+++ systemtap/tapsets.cxx
@@ -1866,7 +1866,15 @@ struct dwflpp
{
Dwarf_Die *die = vardie;
Dwarf_Die struct_die;
+ Dwarf_Attribute temp_attr;
+
unsigned i = 0;
+
+ static unsigned int func_call_level ;
+ static unsigned int dwarf_error_flag ; // indicates current error is dwarf error
+ static unsigned int dwarf_error_count ; // keeps track of no of dwarf errors
+ static semantic_error saved_dwarf_error("");
+
while (i < components.size())
{
/* XXX: This would be desirable, but we don't get the target_symbol token,
@@ -1924,9 +1932,7 @@ struct dwflpp
switch (dwarf_child (die, die_mem))
{
case 1: /* No children. */
- throw semantic_error ("empty struct "
- + string (dwarf_diename_integrate (die) ?: "<anonymous>"));
- break;
+ return NULL;
case -1: /* Error. */
default: /* Shouldn't happen */
throw semantic_error (string (typetag == DW_TAG_union_type ? "union" : "struct")
@@ -1941,14 +1947,60 @@ struct dwflpp
while (dwarf_tag (die) != DW_TAG_member
|| ({ const char *member = dwarf_diename_integrate (die);
member == NULL || string(member) != components[i].second; }))
+ {
+ if ( dwarf_diename (die) == NULL ) // handling Anonymous structs/unions
+ {
+ Dwarf_Die temp_die = *die;
+ Dwarf_Die temp_die_2;
+
+ try
+ {
+ if (!dwarf_attr_integrate (&temp_die, DW_AT_type, &temp_attr))
+ {
+ dwarf_error_flag ++ ;
+ dwarf_error_count ++;
+ throw semantic_error(" Error in obtaining type attribute for "+ string(dwarf_diename(&temp_die)?:"<anonymous>"));
+ }
+
+ if ( !dwarf_formref_die (&temp_attr, &temp_die))
+ {
+ dwarf_error_flag ++ ;
+ dwarf_error_count ++;
+ throw semantic_error(" Error in decoding DW_AT_type attribute for " + string(dwarf_diename(&temp_die)?:"<anonymous>"));
+ }
+
+ func_call_level ++ ;
+
+ Dwarf_Die *result_die = translate_components(pool, tail, pc, components, &temp_die, &temp_die_2, &temp_attr );
+
+ func_call_level -- ;
+
+ if (result_die != NULL)
+ {
+ memcpy(die_mem, &temp_die_2, sizeof(Dwarf_Die));
+ memcpy(attr_mem, &temp_attr, sizeof(Dwarf_Attribute));
+ return die_mem;
+ }
+ }
+ catch (const semantic_error& e)
+ {
+ if ( !dwarf_error_flag ) //not a dwarf error
+ throw;
+ else
+ {
+ dwarf_error_flag = 0 ;
+ saved_dwarf_error = e ;
+ }
+ }
+ }
if (dwarf_siblingof (die, die_mem) != 0)
- {
- stringstream alternatives;
- print_members (&struct_die, alternatives);
- throw semantic_error ("field '" + components[i].second
- + "' not found (alternatives:"
- + alternatives.str () + ")");
- }
+ {
+ if ( func_call_level == 0 && dwarf_error_count ) // this is parent call & a dwarf error has been reported in a branch somewhere
+ throw semantic_error( saved_dwarf_error );
+ else
+ return NULL;
+ }
+ }
if (dwarf_attr_integrate (die, DW_AT_data_member_location,
attr_mem) == NULL)
@@ -2230,6 +2282,8 @@ struct dwflpp
Dwarf_Die die_mem, *die = NULL;
die = translate_components (&pool, &tail, pc, components,
&vardie, &die_mem, &attr_mem);
+ if(!die)
+ throw semantic_error("Translation failure");
/* Translate the assignment part, either
x = $foo->bar->baz[NN]
@@ -2297,6 +2351,8 @@ struct dwflpp
Dwarf_Die die_mem, *die = NULL;
die = translate_components (&pool, &tail, pc, components,
vardie, &die_mem, &attr_mem);
+ if(!die)
+ throw semantic_error("Translation Failure");
/* Translate the assignment part, either
x = $return->bar->baz[NN]
Signed-off-by : Prerna Saxena <prerna@linux.vnet.ibm.com>
Index: systemtap/tapsets.cxx
===================================================================
--- systemtap.orig/tapsets.cxx
+++ systemtap/tapsets.cxx
@@ -1845,9 +1845,33 @@ struct dwflpp
// Output each sibling's name to 'o'.
while (dwarf_tag (die) == DW_TAG_member)
{
- const char *member = (dwarf_diename_integrate (die) ?: "<anonymous>");
+ const char *member = dwarf_diename_integrate (die) ;
+
+ if ( member != NULL )
+
+ o << " " << member;
+
+ else
+ {
+ Dwarf_Die temp_die = *die;
+ Dwarf_Attribute temp_attr ;
+
+ if (!dwarf_attr_integrate (&temp_die, DW_AT_type, &temp_attr))
+ {
+ clog<<"\n Error in obtaining type attribute for "
+ <<(dwarf_diename(&temp_die)?:"<anonymous>");
+ return ;
+ }
+
+ if ( ! dwarf_formref_die (&temp_attr,&temp_die))
+ {
+ clog<<"\n Error in decoding type attribute for "
+ <<(dwarf_diename(&temp_die)?:"<anonymous>");
+ return ;
+ }
+ print_members(&temp_die,o);
- o << " " << member;
+ }
if (dwarf_siblingof (die, &die_mem) != 0)
break;
@@ -2283,7 +2307,12 @@ struct dwflpp
die = translate_components (&pool, &tail, pc, components,
&vardie, &die_mem, &attr_mem);
if(!die)
- throw semantic_error("Translation failure");
+ {
+ die = dwarf_formref_die (&attr_mem, &vardie);
+ stringstream alternatives;
+ print_members(die,alternatives);
+ throw semantic_error("Translation failure : \n ALTERNATIVES [ " + alternatives.str() + " ] \n");
+ }
/* Translate the assignment part, either
x = $foo->bar->baz[NN]
@@ -2352,7 +2381,13 @@ struct dwflpp
die = translate_components (&pool, &tail, pc, components,
vardie, &die_mem, &attr_mem);
if(!die)
- throw semantic_error("Translation Failure");
+ {
+ die = dwarf_formref_die (&attr_mem, vardie);
+ stringstream alternatives;
+ print_members(die,alternatives);
+ throw semantic_error("Translation failure : \n ALTERNATIVES [ " + alternatives.str() + " ] \n");
+ }
+
/* Translate the assignment part, either
x = $return->bar->baz[NN]