Re: [patch] Speed up find_pc_section

Paul Pluzhnikov
2009-09-11T01:30:10Z

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On Thu, Sep 10, 2009 at 11:29 AM, Joel Brobecker <brobecker@adacore.com> wrote:

>> I am not sure calling complaint rather than warning is really the right
>> thing here: complaints are silent unless the user explicitly turns them on,
>> and overlapping sections indicate a real problem of some sort.
>
> I still think we should use a complaint in this case.

Adjusted patch attached.

Thanks,
--
Paul Pluzhnikov

2009-09-10 Paul Pluzhnikov <ppluzhnikov@google.com>

* objfiles.c (qsort_cmp): Remove asserts.
(insert_section_p, filter_debuginfo_sections): New function.
(filter_overlapping_sections): Likewise.
(update_section_map): Adjust.

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Index: objfiles.c
===================================================================
RCS file: /cvs/src/src/gdb/objfiles.c,v
retrieving revision 1.94
diff -u -p -u -r1.94 objfiles.c
--- objfiles.c 27 Aug 2009 21:56:38 -0000 1.94
+++ objfiles.c 11 Sep 2009 01:25:48 -0000
@@ -51,6 +51,7 @@
#include "arch-utils.h"
#include "exec.h"
#include "observer.h"
+#include "complaints.h"

/* Prototypes for local functions */

@@ -802,15 +803,9 @@ qsort_cmp (const void *a, const void *b)
const CORE_ADDR sect2_addr = obj_section_addr (sect2);

if (sect1_addr < sect2_addr)
- {
- gdb_assert (obj_section_endaddr (sect1) <= sect2_addr);
- return -1;
- }
+ return -1;
else if (sect1_addr > sect2_addr)
- {
- gdb_assert (sect1_addr >= obj_section_endaddr (sect2));
- return 1;
- }
+ return 1;

return 0;
}
@@ -835,12 +830,135 @@ preferred_obj_section (struct obj_sectio
return b;
}

-/* Update PMAP, PMAP_SIZE with non-TLS sections from all objfiles. */
+/* Return 1 if SECTION should be inserted into the section map.
+ We want to insert only non-overlay and non-TLS section. */
+
+static int
+insert_section_p (const struct bfd *abfd,
+ const struct bfd_section *section)
+{
+ const bfd_vma lma = bfd_section_lma (abfd, section);
+
+ if (lma != 0 && lma != bfd_section_vma (abfd, section)
+ && (bfd_get_file_flags (abfd) & BFD_IN_MEMORY) == 0)
+ /* This is an overlay section. IN_MEMORY check is needed to avoid
+ discarding sections from the "system supplied DSO" (aka vdso)
+ on Linux. */
+ return 0;
+ if ((bfd_get_section_flags (abfd, section) & SEC_THREAD_LOCAL) != 0)
+ /* This is a TLS section. */
+ return 0;
+
+ return 1;
+}
+
+/* Filter out overlapping sections where one section came from the real
+ objfile, and the other from a separate debuginfo file.
+ Return the size of table after redundant sections have been eliminated. */
+
+static int
+filter_debuginfo_sections (struct obj_section **map, int map_size)
+{
+ int i, j;
+
+ for (i = 0, j = 0; i < map_size - 1; i++)
+ {
+ struct obj_section *const sect1 = map[i];
+ struct obj_section *const sect2 = map[i + 1];
+ const struct objfile *const objfile1 = sect1->objfile;
+ const struct objfile *const objfile2 = sect2->objfile;
+ const CORE_ADDR sect1_addr = obj_section_addr (sect1);
+ const CORE_ADDR sect2_addr = obj_section_addr (sect2);
+
+ if (sect1_addr == sect2_addr
+ && (objfile1->separate_debug_objfile == objfile2
+ || objfile2->separate_debug_objfile == objfile1))
+ {
+ map[j++] = preferred_obj_section (sect1, sect2);
+ ++i;
+ }
+ else
+ map[j++] = sect1;
+ }
+
+ if (i < map_size)
+ map[j++] = map[i];
+
+ /* The map should not have shrunk to less than half the original size. */
+ gdb_assert (map_size / 2 <= j);
+
+ return j;
+}
+
+/* Filter out overlapping sections, issuing a warning if any are found.
+ Overlapping sections could really be overlay sections which we didn't
+ classify as such in insert_section_p, or we could be dealing with a
+ corrupt binary. */
+
+static int
+filter_overlapping_sections (struct obj_section **map, int map_size)
+{
+ int i, j;
+
+ for (i = 0, j = 0; i < map_size - 1; )
+ {
+ int k;
+
+ map[j++] = map[i];
+ for (k = i + 1; k < map_size; k++)
+ {
+ struct obj_section *const sect1 = map[i];
+ struct obj_section *const sect2 = map[k];
+ const CORE_ADDR sect1_addr = obj_section_addr (sect1);
+ const CORE_ADDR sect2_addr = obj_section_addr (sect2);
+ const CORE_ADDR sect1_endaddr = obj_section_endaddr (sect1);
+
+ gdb_assert (sect1_addr <= sect2_addr);
+
+ if (sect1_endaddr <= sect2_addr)
+ break;
+ else
+ {
+ /* We have an overlap. Report it. */
+
+ struct objfile *const objf1 = sect1->objfile;
+ struct objfile *const objf2 = sect2->objfile;
+
+ const struct bfd *const abfd1 = objf1->obfd;
+ const struct bfd *const abfd2 = objf2->obfd;
+
+ const struct bfd_section *const bfds1 = sect1->the_bfd_section;
+ const struct bfd_section *const bfds2 = sect2->the_bfd_section;
+
+ const CORE_ADDR sect2_endaddr = obj_section_endaddr (sect2);
+
+ struct gdbarch *const gdbarch = get_objfile_arch (objf1);
+
+ complaint (&symfile_complaints,
+ _("Unexpected overlap between "
+ "section `%s' from `%s' [%s, %s) and "
+ "section `%s' from `%s' [%s, %s)"),
+ bfd_section_name (abfd1, bfds1), objf1->name,
+ paddress (gdbarch, sect1_addr),
+ paddress (gdbarch, sect1_endaddr),
+ bfd_section_name (abfd2, bfds2), objf2->name,
+ paddress (gdbarch, sect2_addr),
+ paddress (gdbarch, sect2_endaddr));
+ }
+ }
+ i = k;
+ }
+ return map_size;
+}
+
+
+/* Update PMAP, PMAP_SIZE with sections from all objfiles, excluding any
+ TLS, overlay and overlapping sections. */

static void
update_section_map (struct obj_section ***pmap, int *pmap_size)
{
- int map_size, i, j;
+ int alloc_size, map_size, i;
struct obj_section *s, **map;
struct objfile *objfile;

@@ -849,55 +967,27 @@ update_section_map (struct obj_section *
map = *pmap;
xfree (map);

-#define insert_p(objf, sec) \
- ((bfd_get_section_flags ((objf)->obfd, (sec)->the_bfd_section) \
- & SEC_THREAD_LOCAL) == 0)
-
- map_size = 0;
+ alloc_size = 0;
ALL_OBJSECTIONS (objfile, s)
- if (insert_p (objfile, s))
- map_size += 1;
+ if (insert_section_p (objfile->obfd, s->the_bfd_section))
+ alloc_size += 1;

- map = xmalloc (map_size * sizeof (*map));
+ map = xmalloc (alloc_size * sizeof (*map));

i = 0;
ALL_OBJSECTIONS (objfile, s)
- if (insert_p (objfile, s))
+ if (insert_section_p (objfile->obfd, s->the_bfd_section))
map[i++] = s;

-#undef insert_p
-
- qsort (map, map_size, sizeof (*map), qsort_cmp);
-
- /* With separate debuginfo files, we may have up to two (almost)
- identical copies of some obj_sections in the map.
- Filter out duplicates. */
- for (i = 0, j = 0; i < map_size; ++i)
- {
- struct obj_section *sect1 = map[i];
- struct obj_section *sect2 = (i + 1 < map_size) ? map[i + 1] : NULL;
-
- if (sect2 == NULL
- || obj_section_addr (sect1) != obj_section_addr (sect2))
- map[j++] = sect1;
- else
- {
- map[j++] = preferred_obj_section (sect1, sect2);
- ++i;
- }
- }
-
- if (j < map_size)
- {
- /* Some duplicates were eliminated.
- The new size shouldn't be less than half of the original. */
- gdb_assert (map_size / 2 <= j);
- map_size = j;
-
- map = xrealloc (map, map_size * sizeof (*map)); /* Trim excess space. */
- }
+ qsort (map, alloc_size, sizeof (*map), qsort_cmp);
+ map_size = filter_debuginfo_sections(map, alloc_size);
+ map_size = filter_overlapping_sections(map, map_size);
+
+ if (map_size < alloc_size)
+ /* Some sections were eliminated. Trim excess space. */
+ map = xrealloc (map, map_size * sizeof (*map));
else
- gdb_assert (j == map_size);
+ gdb_assert (alloc_size == map_size);

*pmap = map;
*pmap_size = map_size;