From 1da77581c0559e62b80b27f06f81dad4c7a7a0be Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Mon, 7 Oct 2013 19:31:13 +0000 Subject: [PATCH] don't share per-BFD data if relocations are needed Right now we always share per-BFD data across objfiles, if there is a BFD. This works fine. However, we're going to start sharing more data, and sometimes this data will come directly from sections of the BFD. If such a section has SEC_RELOC set, then the data coming from that section will not be truly sharable -- the section will be program-space-dependent, and re-read by gdb for each objfile. This patch disallows per-BFD sharing in this case. This is a bit "heavy" in that we could in theory examine each bit of shared data for suitability. However, that is more complicated, and SEC_RELOC is rare enough that I think we needn't bother. Note that the "no sharing" case is equivalent to "gdb works as it historically did". That is, the sharing is a new(-ish) optimization. Built and regtested on x86-64 Fedora 18. * gdb_bfd.c (struct gdb_bfd_data) : New fields. (gdb_bfd_requires_relocations): New function. * gdb_bfd.h (gdb_bfd_requires_relocations): Declare. * objfiles.c (get_objfile_bfd_data): Disallow sharing if the BFD needs relocations applied. --- gdb/ChangeLog | 9 +++++++++ gdb/gdb_bfd.c | 31 +++++++++++++++++++++++++++++++ gdb/gdb_bfd.h | 5 +++++ gdb/objfiles.c | 12 ++++++++---- 4 files changed, 53 insertions(+), 4 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 9c3d419..5a10cba 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,12 @@ +2013-10-07 Tom Tromey + + * gdb_bfd.c (struct gdb_bfd_data) : New fields. + (gdb_bfd_requires_relocations): New function. + * gdb_bfd.h (gdb_bfd_requires_relocations): Declare. + * objfiles.c (get_objfile_bfd_data): Disallow sharing if + the BFD needs relocations applied. + 2013-10-07 Pedro Alves PR breakpoints/11568 diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c index 7ba120e..25cee5c 100644 --- a/gdb/gdb_bfd.c +++ b/gdb/gdb_bfd.c @@ -82,6 +82,13 @@ struct gdb_bfd_data /* The mtime of the BFD at the point the cache entry was made. */ time_t mtime; + /* This is true if we have determined whether this BFD has any + sections requiring relocation. */ + unsigned int relocation_computed : 1; + + /* This is true if any section needs relocation. */ + unsigned int needs_relocations : 1; + /* This is true if we have successfully computed the file's CRC. */ unsigned int crc_computed : 1; @@ -634,6 +641,30 @@ gdb_bfd_count_sections (bfd *abfd) return bfd_count_sections (abfd) + 4; } +/* See gdb_bfd.h. */ + +int +gdb_bfd_requires_relocations (bfd *abfd) +{ + struct gdb_bfd_data *gdata = bfd_usrdata (abfd); + + if (gdata->relocation_computed == 0) + { + asection *sect; + + for (sect = abfd->sections; sect != NULL; sect = sect->next) + if ((sect->flags & SEC_RELOC) != 0) + { + gdata->needs_relocations = 1; + break; + } + + gdata->relocation_computed = 1; + } + + return gdata->needs_relocations; +} + /* A callback for htab_traverse that prints a single BFD. */ diff --git a/gdb/gdb_bfd.h b/gdb/gdb_bfd.h index ca2eddc..d28b29e 100644 --- a/gdb/gdb_bfd.h +++ b/gdb/gdb_bfd.h @@ -135,4 +135,9 @@ int gdb_bfd_section_index (bfd *abfd, asection *section); int gdb_bfd_count_sections (bfd *abfd); +/* Return true if any section requires relocations, false + otherwise. */ + +int gdb_bfd_requires_relocations (bfd *abfd); + #endif /* GDB_BFD_H */ diff --git a/gdb/objfiles.c b/gdb/objfiles.c index b10f803..b9bcfd7 100644 --- a/gdb/objfiles.c +++ b/gdb/objfiles.c @@ -137,18 +137,22 @@ get_objfile_bfd_data (struct objfile *objfile, struct bfd *abfd) if (storage == NULL) { - if (abfd != NULL) + /* If the object requires gdb to do relocations, we simply fall + back to not sharing data across users. These cases are rare + enough that this seems reasonable. */ + if (abfd != NULL && !gdb_bfd_requires_relocations (abfd)) { storage = bfd_zalloc (abfd, sizeof (struct objfile_per_bfd_storage)); set_bfd_data (abfd, objfiles_bfd_data, storage); - - /* Look up the gdbarch associated with the BFD. */ - storage->gdbarch = gdbarch_from_bfd (abfd); } else storage = OBSTACK_ZALLOC (&objfile->objfile_obstack, struct objfile_per_bfd_storage); + /* Look up the gdbarch associated with the BFD. */ + if (abfd != NULL) + storage->gdbarch = gdbarch_from_bfd (abfd); + obstack_init (&storage->storage_obstack); storage->filename_cache = bcache_xmalloc (NULL, NULL); storage->macro_cache = bcache_xmalloc (NULL, NULL); -- 2.7.4