I found that these tests:
make check-gdb RUNTESTFLAGS="--target_board=cc-with-gdb-index gdb.base/maint.exp"
make check-gdb RUNTESTFLAGS="--target_board=cc-with-debug-names gdb.base/maint.exp"
were causing GDB to segfault. It turns out that this test runs this
command:
maint print psymbols -pc main /path/to/some/file
which tries to lookup the partial_symtab for 'main'. The problem is
that there is no partial_symtab for 'main' as we are using the
.gdb_index or .debug_names instead of partial_symtabs.
What happens is that maintenance_print_symbols calls
find_pc_sect_psymtab, which looks for the partial_symtab in the
objfile's objfile->partial_symtabs->psymtabs_addrmap.
This is a problem because when we are using the indexes
psymtabs_addrmap is reused to hold things other than partial_symtabs,
this can be seen in dwarf2read.c in create_addrmap_from_index and
create_addrmap_from_aranges. If we then lookup in psymtabs_addrmap we
end up returning a pointer to something that isn't really a
partial_symtab, after which everything goes wrong.
Initially I simply added a check at the start of find_pc_sect_psymtab
that the objfile had some partial_symtabs, like:
if (objfile->partial_symtabs->psymtabs == NULL)
return NULL;
Figuring that if there were no partial_symtabs at all then this
function should always return NULL, however, this caused a failure in
the test gdb.python/py-event.exp which I didn't dig into too deeply,
but seems to be that in this tests there are initially no psymtabs,
but the second part of find_pc_sect_psymtab does manage to read some
in from somewhere, with the check I added the test fails as we
returned NULL here and this caused GDB to load in the full symtabs
earlier than was expected.
Instead I chose to guard only the access to psymtabs_addrmap with a
check that the function has some psymtabs. This allows my original
tests to pass, and the py-event.exp test to pass too.
Now, a good argument can be made that we simply should never call
find_pc_sect_psymtab on an objfile that is using indexes instead of
partial_symtabs. I did consider this approach, we could easily add an
assert into find_pc_sect_psymtab that if we find a partial_symtab in
psymtabs_addrmap then the psymtabs pointer must be non-null. The
responsibility would then be on the user of find_pc_sect_psymtab to
ensure that the objfile being checked is suitable. In the end I
didn't take this approach as the check in find_pc_sect_psymtab is
cheap and this ensures that any future miss-uses of the function will
not cause problems.
I also extended the comment on psymtabs_addrmap to indicate that it
holds more than just partial_symtabs as this was not at all clear from
the original comment, and caused me some confusion when I was
initially debugging this problem.
gdb/ChangeLog:
* psymtab.c (find_pc_sect_psymtab): Move baseaddr local into more
inner scope, add check that the objfile has psymtabs before
checking psymtabs_addrmap.
* psymtab.h (psymtab_storage) <psymtabs_addrmap>: Extend comment.
+2019-09-12 Andrew Burgess <andrew.burgess@embecosm.com>
+
+ * psymtab.c (find_pc_sect_psymtab): Move baseaddr local into more
+ inner scope, add check that the objfile has psymtabs before
+ checking psymtabs_addrmap.
+ * psymtab.h (psymtab_storage) <psymtabs_addrmap>: Extend comment.
+
2019-09-12 Philippe Waroquiers <philippe.waroquiers@skynet.be>
* NEWS: Announce that Ada task names are now shown at more places,
struct obj_section *section,
struct bound_minimal_symbol msymbol)
{
- CORE_ADDR baseaddr = ANOFFSET (objfile->section_offsets,
- SECT_OFF_TEXT (objfile));
-
- /* Try just the PSYMTABS_ADDRMAP mapping first as it has better granularity
- than the later used TEXTLOW/TEXTHIGH one. */
-
- if (objfile->partial_symtabs->psymtabs_addrmap != NULL)
+ /* Try just the PSYMTABS_ADDRMAP mapping first as it has better
+ granularity than the later used TEXTLOW/TEXTHIGH one. However, we need
+ to take care as the PSYMTABS_ADDRMAP can hold things other than partial
+ symtabs in some cases.
+
+ This function should only be called for objfiles that are using partial
+ symtabs, not for objfiles that are using indexes (.gdb_index or
+ .debug_names), however 'maintenance print psymbols' calls this function
+ directly for all objfiles. If we assume that PSYMTABS_ADDRMAP contains
+ partial symtabs then we will end up returning a pointer to an object
+ that is not a partial_symtab, which doesn't end well. */
+
+ if (objfile->partial_symtabs->psymtabs != NULL
+ && objfile->partial_symtabs->psymtabs_addrmap != NULL)
{
+ CORE_ADDR baseaddr = ANOFFSET (objfile->section_offsets,
+ SECT_OFF_TEXT (objfile));
+
struct partial_symtab *pst
= ((struct partial_symtab *)
addrmap_find (objfile->partial_symtabs->psymtabs_addrmap,
/* Map addresses to the entries of PSYMTABS. It would be more efficient to
have a map per the whole process but ADDRMAP cannot selectively remove
its items during FREE_OBJFILE. This mapping is already present even for
- PARTIAL_SYMTABs which still have no corresponding full SYMTABs read. */
+ PARTIAL_SYMTABs which still have no corresponding full SYMTABs read.
+
+ The DWARF parser reuses this addrmap to store things other than
+ psymtabs in the cases where debug information is being read from, for
+ example, the .debug-names section. */
struct addrmap *psymtabs_addrmap = nullptr;
projects / binutils-gdb.git / commitdiff