[PATCH v5 14/15] gdb: update gnu ifunc resolve

Markus Metzger via Gdb-patches
2022-06-02T14:36:30Z

Update elf_gnu_ifunc_resolve_by_cache() and elf_gnu_ifunc_resolve_by_got()
to use gdbarch_iterate_over_objfiles_in_search_order() in order to
restrict the objfile traversal to the initial namespace.

In order to extend this to other namespaces, we'd need to provide context,
e.g. via an objfile inside that namespace.
---
gdb/elfread.c | 153 ++++++++++++++++++++++++++++----------------------
1 file changed, 87 insertions(+), 66 deletions(-)

diff --git a/gdb/elfread.c b/gdb/elfread.c
index 32cb27c8967..c097d272a49 100644
--- a/gdb/elfread.c
+++ b/gdb/elfread.c
@@ -769,32 +769,42 @@ elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr)
static int
elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p)
{
- for (objfile *objfile : current_program_space->objfiles ())
- {
- htab_t htab;
- struct elf_gnu_ifunc_cache *entry_p;
- void **slot;
-
- htab = elf_objfile_gnu_ifunc_cache_data.get (objfile);
- if (htab == NULL)
- continue;
-
- entry_p = ((struct elf_gnu_ifunc_cache *)
- alloca (sizeof (*entry_p) + strlen (name)));
- strcpy (entry_p->name, name);
-
- slot = htab_find_slot (htab, entry_p, NO_INSERT);
- if (slot == NULL)
- continue;
- entry_p = (struct elf_gnu_ifunc_cache *) *slot;
- gdb_assert (entry_p != NULL);
-
- if (addr_p)
- *addr_p = entry_p->addr;
- return 1;
- }
-
- return 0;
+ int found = 0;
+
+ /* FIXME: we only search the initial namespace.
+
+ To search other namespaces, we would need to provide context, e.g. in
+ form of an objfile in that namespace. */
+ gdbarch_iterate_over_objfiles_in_search_order
+ (target_gdbarch (),
+ [name, &addr_p, &found] (struct objfile *objfile)
+ {
+ htab_t htab;
+ elf_gnu_ifunc_cache *entry_p;
+ void **slot;
+
+ htab = elf_objfile_gnu_ifunc_cache_data.get (objfile);
+ if (htab == NULL)
+ return 0;
+
+ entry_p = ((elf_gnu_ifunc_cache *)
+ alloca (sizeof (*entry_p) + strlen (name)));
+ strcpy (entry_p->name, name);
+
+ slot = htab_find_slot (htab, entry_p, NO_INSERT);
+ if (slot == NULL)
+ return 0;
+ entry_p = (elf_gnu_ifunc_cache *) *slot;
+ gdb_assert (entry_p != NULL);
+
+ if (addr_p)
+ *addr_p = entry_p->addr;
+
+ found = 1;
+ return 1;
+ }, nullptr);
+
+ return found;
}

/* Try to find the target resolved function entry address of a STT_GNU_IFUNC
@@ -810,50 +820,61 @@ elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p)
{
char *name_got_plt;
const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
+ int found = 0;

name_got_plt = (char *) alloca (strlen (name) + got_suffix_len + 1);
sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name);

- for (objfile *objfile : current_program_space->objfiles ())
- {
- bfd *obfd = objfile->obfd;
- struct gdbarch *gdbarch = objfile->arch ();
- struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
- size_t ptr_size = TYPE_LENGTH (ptr_type);
- CORE_ADDR pointer_address, addr;
- asection *plt;
- gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
- struct bound_minimal_symbol msym;
-
- msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
- if (msym.minsym == NULL)
- continue;
- if (msym.minsym->type () != mst_slot_got_plt)
- continue;
- pointer_address = msym.value_address ();
-
- plt = bfd_get_section_by_name (obfd, ".plt");
- if (plt == NULL)
- continue;
-
- if (msym.minsym->size () != ptr_size)
- continue;
- if (target_read_memory (pointer_address, buf, ptr_size) != 0)
- continue;
- addr = extract_typed_address (buf, ptr_type);
- addr = gdbarch_convert_from_func_ptr_addr
- (gdbarch, addr, current_inferior ()->top_target ());
- addr = gdbarch_addr_bits_remove (gdbarch, addr);
-
- if (elf_gnu_ifunc_record_cache (name, addr))
- {
- if (addr_p != NULL)
- *addr_p = addr;
- return 1;
- }
- }
-
- return 0;
+ /* FIXME: we only search the initial namespace.
+
+ To search other namespaces, we would need to provide context, e.g. in
+ form of an objfile in that namespace. */
+ gdbarch_iterate_over_objfiles_in_search_order
+ (target_gdbarch (),
+ [name, name_got_plt, &addr_p, &found] (struct objfile *objfile)
+ {
+ bfd *obfd = objfile->obfd;
+ struct gdbarch *gdbarch = objfile->arch ();
+ type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
+ size_t ptr_size = TYPE_LENGTH (ptr_type);
+ CORE_ADDR pointer_address, addr;
+ asection *plt;
+ gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
+ bound_minimal_symbol msym;
+
+ msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
+ if (msym.minsym == NULL)
+ return 0;
+ if (msym.minsym->type () != mst_slot_got_plt)
+ return 0;
+ pointer_address = msym.value_address ();
+
+ plt = bfd_get_section_by_name (obfd, ".plt");
+ if (plt == NULL)
+ return 0;
+
+ if (msym.minsym->size () != ptr_size)
+ return 0;
+ if (target_read_memory (pointer_address, buf, ptr_size) != 0)
+ return 0;
+ addr = extract_typed_address (buf, ptr_type);
+ addr = gdbarch_convert_from_func_ptr_addr
+ (gdbarch, addr, current_inferior ()->top_target ());
+ addr = gdbarch_addr_bits_remove (gdbarch, addr);
+
+ if (elf_gnu_ifunc_record_cache (name, addr))
+ {
+ if (addr_p != NULL)
+ *addr_p = addr;
+
+ found = 1;
+ return 1;
+ }
+
+ return 0;
+ }, nullptr);
+
+ return found;
}

/* Try to find the target resolved function entry address of a STT_GNU_IFUNC
--
2.35.3