Mike Frysinger wrote:
On Wednesday 12 December 2007, Carmelo AMOROSO wrote:
while running more tests on this (indeed never used dladdr in the past),
which tests ? our dl tests certainly dont have the coverage anywhere close to
what i wish they did ...
-mike
Hello,
based on the patch from Nickolai, here you can find a comprehensive
patch to fix
dladdr function.
With the current implementation, the invocation of dladdr((void *) 1,
&dlinfo)
will fill dlinfo.dli_fname with the name of the application itself and
dlinfo.dli_fbase with 0 (the current value of tpnt->loadaddr for the
main app).
The patch solves this adding a new field into the struct elf_resolve
named DL_LOADADDR_TYPE mapaddr.
For shared objects, mapaddr has exactly the same value as loadaddr,
while for the
main app it contains the address of the first PT_LOAD segmented loaded.
loadaddr will keep it's value and will used exactly as is (as a in
memory offset
with respect to relative addresses from ELF sections).
While in the DL_ADDR_IN_LOADADDR macro, the new field mapaddr needs to
be used.
I hope I was clear enough in my explanation ;-)
Any comments are welcome.
Cheers,
Carmelo
This patch solves a problem in dladdr caused by the wrong value
of elf_resolve.loadaddr for the main application.
Signed-off-by: Filippo Arcidiacono <[EMAIL PROTECTED]>
Signed-off-by: Carmelo Amoroso <[EMAIL PROTECTED]>
Index: ldso/ldso/ldso.c
===================================================================
--- ldso/ldso/ldso.c (revision 20834)
+++ ldso/ldso/ldso.c (working copy)
@@ -135,6 +135,7 @@
char **argv
DL_GET_READY_TO_RUN_EXTRA_PARMS)
{
+ DL_LOADADDR_TYPE app_loadaddr = NULL;
ElfW(Phdr) *ppnt;
ElfW(Dyn) *dpnt;
char *lpntstr;
@@ -276,6 +277,9 @@
relro_addr = ppnt->p_vaddr;
relro_size = ppnt->p_memsz;
}
+ if (!app_loadaddr && (ppnt->p_type == PT_LOAD)) {
+ app_loadaddr = ppnt->p_vaddr;
+ }
if (ppnt->p_type == PT_DYNAMIC) {
dpnt = (ElfW(Dyn) *) DL_RELOC_ADDR(app_tpnt->loadaddr,
ppnt->p_vaddr);
_dl_parse_dynamic_info(dpnt, app_tpnt->dynamic_info,
debug_addr, app_tpnt->loadaddr);
@@ -322,6 +326,7 @@
_dl_symbol_tables = rpnt = (struct dyn_elf *)
_dl_malloc(sizeof(struct dyn_elf));
_dl_memset(rpnt, 0, sizeof(struct dyn_elf));
rpnt->dyn = _dl_loaded_modules;
+ app_tpnt->mapaddr = app_loadaddr;
app_tpnt->rtld_flags = unlazy | RTLD_GLOBAL;
app_tpnt->usage_count++;
app_tpnt->symbol_scope = _dl_symbol_tables;
Index: ldso/include/dl-defs.h
===================================================================
--- ldso/include/dl-defs.h (revision 20834)
+++ ldso/include/dl-defs.h (working copy)
@@ -168,8 +168,8 @@
*/
#ifndef DL_ADDR_IN_LOADADDR
# define DL_ADDR_IN_LOADADDR(ADDR, TPNT, TFROM) \
- ((void*)(TPNT)->loadaddr < (void*)(ADDR) \
- && (!(TFROM) || (TFROM)->loadaddr < (TPNT)->loadaddr))
+ ((void*)(TPNT)->mapaddr < (void*)(ADDR) \
+ && (!(TFROM) || (TFROM)->mapaddr < (TPNT)->mapaddr))
#endif
/* This is called from dladdr() to give targets that use function descriptors
Index: ldso/include/dl-hash.h
===================================================================
--- ldso/include/dl-hash.h (revision 20834)
+++ ldso/include/dl-hash.h (working copy)
@@ -34,6 +34,8 @@
struct elf_resolve * next;
struct elf_resolve * prev;
/* Nothing after this address is used by gdb. */
+
+ DL_LOADADDR_TYPE mapaddr; /* Address at which ELF segments (either main
app and DSO) are mapped into */
enum {elf_lib, elf_executable,program_interpreter, loaded_file} libtype;
struct dyn_elf * symbol_scope;
unsigned short usage_count;
Index: ldso/libdl/libdl.c
===================================================================
--- ldso/libdl/libdl.c (revision 20834)
+++ ldso/libdl/libdl.c (working copy)
@@ -739,13 +739,40 @@
char *strtab;
ElfW(Sym) *symtab;
unsigned int hn, si, sn, sf;
- ElfW(Addr) sa;
+ ElfW(Addr) sa = 0;
- sa = 0;
+ /* Set the info for the object the address lies in */
+ __info->dli_fname = pelf->libname;
+ __info->dli_fbase = (void *)(pelf->mapaddr);
+
symtab = (ElfW(Sym) *) (pelf->dynamic_info[DT_SYMTAB]);
strtab = (char *) (pelf->dynamic_info[DT_STRTAB]);
sf = sn = 0;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ if (pelf->l_gnu_bitmask) {
+ for (hn = 0; hn < pelf->nbucket; hn++) {
+ si = pelf->l_gnu_buckets[hn];
+ if (!si)
+ continue;
+
+ const Elf32_Word *hasharr =
&pelf->l_gnu_chain_zero[si];
+ do {
+ ElfW(Addr) symbol_addr;
+
+ symbol_addr = (ElfW(Addr))
pelf->loadaddr + symtab[si].st_value;
+ if (symbol_addr <=
(ElfW(Addr))__address && (!sf || sa < symbol_addr)) {
+ sa = symbol_addr;
+ sn = si;
+ sf = 1;
+ }
+ _dl_if_debug_print("Symbol \"%s\" at
%p\n",
+ strtab
+ symtab[si].st_name, symbol_addr);
+ ++si;
+ } while ((*hasharr++ & 1u) == 0);
+ }
+ } else
+#endif
for (hn = 0; hn < pelf->nbucket; hn++) {
for (si = pelf->elf_buckets[hn]; si; si =
pelf->chains[si]) {
ElfW(Addr) symbol_addr;
@@ -763,10 +790,14 @@
}
if (sf) {
- __info->dli_fname = pelf->libname;
- __info->dli_fbase = (void *)
DL_LOADADDR_BASE(pelf->loadaddr);
+ /* A nearest symbol has been found; fill the entries */
__info->dli_sname = strtab + symtab[sn].st_name;
__info->dli_saddr = (void *)sa;
+ } else {
+ /* No symbol found, fill entries with NULL value,
+ only the containing object will be returned. */
+ __info->dli_sname = NULL;
+ __info->dli_saddr = NULL;
}
return 1;
}
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