[git commit] ldso: Add runtime prelink support
Filippo Arcidiacono
filippo.arcidiacono at st.com
Fri Jul 1 07:49:47 UTC 2011
commit: http://git.uclibc.org/uClibc/commit/?id=a33796043bdef5345bc00a528c942f91a87af8e9
branch: http://git.uclibc.org/uClibc/commit/?id=refs/heads/master
Added runtime prelink support to be able to run a prelinked
application; at process startup only the conflicts will be relocated.
This speed up the startup time.
Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono at st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso at st.com>
---
Makerules | 9 ++++++
extra/Configs/Config.in | 11 +++++++
ldso/include/dl-elf.h | 43 +++++++++++++++++++++++++++--
ldso/ldso/Makefile.in | 8 +++++
ldso/ldso/dl-elf.c | 9 +++++-
ldso/ldso/dl-hash.c | 4 +++
ldso/ldso/dl-startup.c | 33 +++++++++++++++++++---
ldso/ldso/ldso.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++
8 files changed, 177 insertions(+), 9 deletions(-)
diff --git a/Makerules b/Makerules
index 2e9ca05..435ccfd 100644
--- a/Makerules
+++ b/Makerules
@@ -294,6 +294,15 @@ endef
cmd_hcompile.u = $(HOSTCC) $(filter-out $(PHONY),$^) $(DEPS-$(notdir $@)) -o $@ $(BUILD_LDFLAGS) $(BUILD_LDFLAGS-$(notdir $(^D))) $(BUILD_LDFLAGS-$(notdir $@)) $(BUILD_CFLAGS) $(BUILD_CFLAGS-$(notdir $(^D))) $(BUILD_CFLAGS-$(notdir $@))
cmd_hcompile.o = $(HOSTCC) $(filter-out $(PHONY),$<) $(DEPS-$(notdir $@)) -c -o $@ $(BUILD_CFLAGS) $(BUILD_CFLAGS-$(notdir $(^D))) $(BUILD_CFLAGS-$(notdir $@))
+define create-lds
+ $(Q)$(RM) $@.lds
+ $(Q)$(CC) -nostdlib -nostartfiles -shared -Wl,-z,combreloc \
+ -Wl,-z,relro -Wl,--hash-style=gnu -Wl,-z,defs \
+ -Wl,--verbose 2>&1 | LC_ALL=C \
+ sed -e '/^=========/,/^=========/!d;/^=========/d' \
+ -e 's/\. = .* + SIZEOF_HEADERS;/& _begin = . - SIZEOF_HEADERS;/' > $@.lds
+endef
+
define link.so
$(Q)$(RM) $@ $@.$(2) $(dir $@)$(1)
@$(disp_ld)
diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in
index 9721186..801669a 100644
--- a/extra/Configs/Config.in
+++ b/extra/Configs/Config.in
@@ -359,6 +359,17 @@ config LDSO_STANDALONE_SUPPORT
capabilities to uClibc dynamic linker, as well useful for testing an
updated version of the dynamic linker without breaking the system.
+config LDSO_PRELINK_SUPPORT
+ bool "Dynamic linker prelink support"
+ depends on HAVE_SHARED
+ default n
+ select LDSO_STANDALONE_SUPPORT
+ help
+ The dynamic linker can be used in stand-alone mode by the prelink tool
+ for prelinking ELF shared libraries and binaries to speed up startup
+ time. It also is able to load and handle prelinked libraries and
+ binaries at runtime.
+
config UCLIBC_STATIC_LDCONFIG
bool "Link ldconfig statically"
depends on HAVE_SHARED
diff --git a/ldso/include/dl-elf.h b/ldso/include/dl-elf.h
index 3e85864..40c88b9 100644
--- a/ldso/include/dl-elf.h
+++ b/ldso/include/dl-elf.h
@@ -85,24 +85,47 @@ extern void _dl_protect_relro (struct elf_resolve *l);
#endif
/* OS and/or GNU dynamic extensions */
+
+#define OS_NUM_BASE 1 /* for DT_RELOCCOUNT */
+
#ifdef __LDSO_GNU_HASH_SUPPORT__
-# define OS_NUM 2 /* for DT_RELOCCOUNT and DT_GNU_HASH entries */
+# define OS_NUM_GNU_HASH 1 /* for DT_GNU_HASH entry */
+#else
+# define OS_NUM_GNU_HASH 0
+#endif
+
+#ifdef __LDSO_PRELINK_SUPPORT__
+# define OS_NUM_PRELINK 6 /* for DT_GNU_PRELINKED entry */
#else
-# define OS_NUM 1 /* for DT_RELOCCOUNT entry */
+# define OS_NUM_PRELINK 0
#endif
+#define OS_NUM (OS_NUM_BASE + OS_NUM_GNU_HASH + OS_NUM_PRELINK)
+
#ifndef ARCH_DYNAMIC_INFO
/* define in arch specific code, if needed */
# define ARCH_NUM 0
#endif
-#define DYNAMIC_SIZE (DT_NUM+OS_NUM+ARCH_NUM)
+#define DYNAMIC_SIZE (DT_NUM + OS_NUM + ARCH_NUM)
/* Keep ARCH specific entries into dynamic section at the end of the array */
#define DT_RELCONT_IDX (DYNAMIC_SIZE - OS_NUM - ARCH_NUM)
#ifdef __LDSO_GNU_HASH_SUPPORT__
/* GNU hash comes just after the relocation count */
# define DT_GNU_HASH_IDX (DT_RELCONT_IDX + 1)
+#else
+# define DT_GNU_HASH_IDX DT_RELCONT_IDX
+#endif
+
+#ifdef __LDSO_PRELINK_SUPPORT__
+/* GNU prelink comes just after the GNU hash if present */
+#define DT_GNU_PRELINKED_IDX (DT_GNU_HASH_IDX + 1)
+#define DT_GNU_CONFLICT_IDX (DT_GNU_HASH_IDX + 2)
+#define DT_GNU_CONFLICTSZ_IDX (DT_GNU_HASH_IDX + 3)
+#define DT_GNU_LIBLIST_IDX (DT_GNU_HASH_IDX + 4)
+#define DT_GNU_LIBLISTSZ_IDX (DT_GNU_HASH_IDX + 5)
+#define DT_CHECKSUM_IDX (DT_GNU_HASH_IDX + 6)
#endif
extern unsigned int _dl_parse_dynamic_info(ElfW(Dyn) *dpnt, unsigned long dynamic_info[],
@@ -151,6 +174,20 @@ unsigned int __dl_parse_dynamic_info(ElfW(Dyn) *dpnt, unsigned long dynamic_info
if (dpnt->d_tag == DT_GNU_HASH)
dynamic_info[DT_GNU_HASH_IDX] = dpnt->d_un.d_ptr;
#endif
+#ifdef __LDSO_PRELINK_SUPPORT__
+ if (dpnt->d_tag == DT_GNU_PRELINKED)
+ dynamic_info[DT_GNU_PRELINKED_IDX] = dpnt->d_un.d_val;
+ if (dpnt->d_tag == DT_GNU_CONFLICT)
+ dynamic_info[DT_GNU_CONFLICT_IDX] = dpnt->d_un.d_ptr;
+ if (dpnt->d_tag == DT_GNU_CONFLICTSZ)
+ dynamic_info[DT_GNU_CONFLICTSZ_IDX] = dpnt->d_un.d_val;
+ if (dpnt->d_tag == DT_GNU_LIBLIST)
+ dynamic_info[DT_GNU_LIBLIST_IDX] = dpnt->d_un.d_ptr;
+ if (dpnt->d_tag == DT_GNU_LIBLISTSZ)
+ dynamic_info[DT_GNU_LIBLISTSZ_IDX] = dpnt->d_un.d_val;
+ if (dpnt->d_tag == DT_CHECKSUM)
+ dynamic_info[DT_CHECKSUM_IDX] = dpnt->d_un.d_val;
+#endif
}
#ifdef ARCH_DYNAMIC_INFO
else {
diff --git a/ldso/ldso/Makefile.in b/ldso/ldso/Makefile.in
index e71ae15..c9dcebd 100644
--- a/ldso/ldso/Makefile.in
+++ b/ldso/ldso/Makefile.in
@@ -62,8 +62,16 @@ ldso-y := $($(UCLIBC_LDSO_NAME)_OBJS:.o=.oS)
lib-so-y += $(ldso)
objclean-y += CLEAN_ldso/ldso
+ifeq ($(LDSO_PRELINK_SUPPORT),y)
+# Use a specific linker script for ld.so
+LDFLAGS-$(UCLIBC_LDSO_NAME).so += -T $(ldso:.$(ABI_VERSION)=).lds
+endif
+
$(ldso): $(ldso:.$(ABI_VERSION)=)
$(ldso:.$(ABI_VERSION)=): $($(UCLIBC_LDSO_NAME)_OUT)/$(UCLIBC_LDSO_NAME)_so.a
+ifeq ($(LDSO_PRELINK_SUPPORT),y)
+ $(call create-lds)
+endif
$(call link.so,$(ldso_FULL_NAME),$(ABI_VERSION))
$($(UCLIBC_LDSO_NAME)_OUT)/$(UCLIBC_LDSO_NAME)_so.a: $(ldso-y)
diff --git a/ldso/ldso/dl-elf.c b/ldso/ldso/dl-elf.c
index a8ccc5e..9625f5a 100644
--- a/ldso/ldso/dl-elf.c
+++ b/ldso/ldso/dl-elf.c
@@ -343,7 +343,7 @@ struct elf_resolve *_dl_load_elf_shared_library(int secure,
size_t relro_size = 0;
struct stat st;
uint32_t *p32;
- DL_LOADADDR_TYPE lib_loadaddr;
+ DL_LOADADDR_TYPE lib_loadaddr = 0;
DL_INIT_LOADADDR_EXTRA_DECLS
libaddr = 0;
@@ -880,7 +880,12 @@ int _dl_fixup(struct dyn_elf *rpnt, struct r_scope_elem *scope, int now_flag)
relative_count = tpnt->dynamic_info[DT_RELCONT_IDX];
if (relative_count) { /* Optimize the XX_RELATIVE relocations if possible */
reloc_size -= relative_count * sizeof(ELF_RELOC);
- elf_machine_relative(tpnt->loadaddr, reloc_addr, relative_count);
+ if (tpnt->loadaddr
+#ifdef __LDSO_PRELINK_SUPPORT__
+ || (!tpnt->dynamic_info[DT_GNU_PRELINKED_IDX])
+#endif
+ )
+ elf_machine_relative(tpnt->loadaddr, reloc_addr, relative_count);
reloc_addr += relative_count * sizeof(ELF_RELOC);
}
goof += _dl_parse_relocation_information(rpnt, scope,
diff --git a/ldso/ldso/dl-hash.c b/ldso/ldso/dl-hash.c
index 2e2111f..f0683c6 100644
--- a/ldso/ldso/dl-hash.c
+++ b/ldso/ldso/dl-hash.c
@@ -145,7 +145,11 @@ struct elf_resolve *_dl_add_elf_hash_table(const char *libname,
hash_addr += tpnt->nbucket;
tpnt->chains = hash_addr;
}
+#ifdef __LDSO_PRELINK_SUPPORT__
+ tpnt->loadaddr = dynamic_info[DT_GNU_PRELINKED_IDX] ? 0 : loadaddr;
+#else
tpnt->loadaddr = loadaddr;
+#endif
tpnt->mapaddr = DL_RELOC_ADDR(loadaddr, 0);
for (i = 0; i < DYNAMIC_SIZE; i++)
tpnt->dynamic_info[i] = dynamic_info[i];
diff --git a/ldso/ldso/dl-startup.c b/ldso/ldso/dl-startup.c
index feffa78..4799846 100644
--- a/ldso/ldso/dl-startup.c
+++ b/ldso/ldso/dl-startup.c
@@ -94,6 +94,11 @@
/* Pull in all the arch specific stuff */
#include "dl-startup.h"
+#ifdef __LDSO_PRELINK_SUPPORT__
+/* These defined magically in the linker script. */
+extern char _begin[] attribute_hidden;
+#endif
+
/* Static declarations */
static int (*_dl_elf_main) (int, char **, char **);
@@ -164,11 +169,26 @@ DL_START(unsigned long args)
aux_dat += 2;
}
- /* locate the ELF header. We need this done as soon as possible
- * (esp since SEND_STDERR() needs this on some platforms... */
+ /*
+ * Locate the dynamic linker ELF header. We need this done as soon as
+ * possible (esp since SEND_STDERR() needs this on some platforms...
+ */
+
+#ifdef __LDSO_PRELINK_SUPPORT__
+ /*
+ * The `_begin' symbol created by the linker script points to ld.so ELF
+ * We use it if the kernel is not passing a valid address through the auxvt.
+ */
+
+ if (!auxvt[AT_BASE].a_un.a_val)
+ auxvt[AT_BASE].a_un.a_val = (Elf32_Addr) &_begin;
+ /* Note: if the dynamic linker itself is prelinked, the load_addr is 0 */
+ DL_INIT_LOADADDR_BOOT(load_addr, elf_machine_load_address());
+#else
if (!auxvt[AT_BASE].a_un.a_val)
auxvt[AT_BASE].a_un.a_val = elf_machine_load_address();
DL_INIT_LOADADDR_BOOT(load_addr, auxvt[AT_BASE].a_un.a_val);
+#endif
header = (ElfW(Ehdr) *) auxvt[AT_BASE].a_un.a_val;
/* Check the ELF header to make sure everything looks ok. */
@@ -183,7 +203,7 @@ DL_START(unsigned long args)
_dl_exit(0);
}
SEND_EARLY_STDERR_DEBUG("ELF header=");
- SEND_ADDRESS_STDERR_DEBUG(DL_LOADADDR_BASE(load_addr), 1);
+ SEND_ADDRESS_STDERR_DEBUG(DL_LOADADDR_BASE(header), 1);
/* Locate the global offset table. Since this code must be PIC
* we can take advantage of the magic offset register, if we
@@ -258,7 +278,12 @@ DL_START(unsigned long args)
if (!indx && relative_count) {
rel_size -= relative_count * sizeof(ELF_RELOC);
- elf_machine_relative(load_addr, rel_addr, relative_count);
+ if (load_addr
+#ifdef __LDSO_PRELINK_SUPPORT__
+ || !tpnt->dynamic_info[DT_GNU_PRELINKED_IDX]
+#endif
+ )
+ elf_machine_relative(load_addr, rel_addr, relative_count);
rel_addr += relative_count * sizeof(ELF_RELOC);
}
diff --git a/ldso/ldso/ldso.c b/ldso/ldso/ldso.c
index 4a7b639..b056f8a 100644
--- a/ldso/ldso/ldso.c
+++ b/ldso/ldso/ldso.c
@@ -61,6 +61,7 @@ void (*_dl_free_function) (void *p) = NULL;
char *_dl_trace_prelink = NULL; /* Library for prelinking trace */
struct elf_resolve *_dl_trace_prelink_map = NULL; /* Library module for prelinking trace */
bool _dl_verbose = true; /* On by default */
+bool prelinked = false;
#endif
static int _dl_secure = 1; /* Are we dealing with setuid stuff? */
@@ -1189,8 +1190,75 @@ of this helper program; chances are you did not intend to run this program.\n\
_dl_exit(-1);
_dl_exit(0);
}
+
+ if (_dl_loaded_modules->dynamic_info[DT_GNU_LIBLIST_IDX]) {
+ ElfW(Lib) *liblist, *liblistend;
+ struct elf_resolve **r_list, **r_listend, *l;
+ const char *strtab = (const char *)_dl_loaded_modules->dynamic_info[DT_STRTAB];
+
+ _dl_assert (_dl_loaded_modules->dynamic_info[DT_GNU_LIBLISTSZ_IDX] != 0);
+ liblist = (ElfW(Lib) *) _dl_loaded_modules->dynamic_info[DT_GNU_LIBLIST_IDX];
+ liblistend = (ElfW(Lib) *)
+ ((char *) liblist + _dl_loaded_modules->dynamic_info[DT_GNU_LIBLISTSZ_IDX]);
+ r_list = _dl_loaded_modules->symbol_scope.r_list;
+ r_listend = r_list + nscope_elem;
+
+ for (; r_list < r_listend && liblist < liblistend; r_list++) {
+ l = *r_list;
+
+ if (l == _dl_loaded_modules)
+ continue;
+
+ /* If the library is not mapped where it should, fail. */
+ if (l->loadaddr)
+ break;
+
+ /* Next, check if checksum matches. */
+ if (l->dynamic_info[DT_CHECKSUM_IDX] == 0 ||
+ l->dynamic_info[DT_CHECKSUM_IDX] != liblist->l_checksum)
+ break;
+
+ if (l->dynamic_info[DT_GNU_PRELINKED_IDX] == 0 ||
+ (l->dynamic_info[DT_GNU_PRELINKED_IDX] != liblist->l_time_stamp))
+ break;
+
+ if (_dl_strcmp(strtab + liblist->l_name, _dl_get_last_path_component(l->libname)) != 0)
+ break;
+
+ ++liblist;
+ }
+
+
+ if (r_list == r_listend && liblist == liblistend)
+ prelinked = true;
+
+ }
+
+ _dl_debug_early ("\nprelink checking: %s\n", prelinked ? "ok" : "failed");
+
+ if (prelinked) {
+ if (_dl_loaded_modules->dynamic_info[DT_GNU_CONFLICT_IDX]) {
+ ELF_RELOC *conflict;
+ unsigned long conflict_size;
+
+ _dl_assert (_dl_loaded_modules->dynamic_info[DT_GNU_CONFLICTSZ_IDX] != 0);
+ conflict = (ELF_RELOC *) _dl_loaded_modules->dynamic_info[DT_GNU_CONFLICT_IDX];
+ conflict_size = _dl_loaded_modules->dynamic_info[DT_GNU_CONFLICTSZ_IDX];
+ _dl_parse_relocation_information(_dl_symbol_tables, global_scope,
+ (unsigned long) conflict, conflict_size);
+ }
+
+ /* Mark all the objects so we know they have been already relocated. */
+ for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
+ tpnt->init_flag |= RELOCS_DONE;
+ if (tpnt->relro_size)
+ _dl_protect_relro (tpnt);
+ }
+ } else
#endif
+ {
+
_dl_debug_early("Beginning relocation fixups\n");
#ifdef __mips__
@@ -1215,6 +1283,7 @@ of this helper program; chances are you did not intend to run this program.\n\
if (tpnt->relro_size)
_dl_protect_relro (tpnt);
}
+ } /* not prelinked */
#if defined(USE_TLS) && USE_TLS
if (!was_tls_init_tp_called && _dl_tls_max_dtv_idx > 0)
--
1.7.3.4
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