Patch from Stefan Allius:

        - Invert all FORCE_SHAREABLE_TEXT_SEGMENTS checks.
	- Define FORCE_SHAREABLE_TEXT_SEGMENTS in the Makefile,
	  so it can be configured by the config system.
	- linuxelf.h inspects that we don't combine FORCE_SHAREABLE_TEXT_SEGMENTS
	  and SVR4_BUGCOMPAT
	- Add a new config option for FORCE_SHAREABLE_TEXT_SEGMENTS

7 files changed, 36 insertions, 10 deletions

diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in
index 99f60dfff..3b5fcf1f5 100644
--- a/extra/Configs/Config.in
+++ b/extra/Configs/Config.in
@@ -34,6 +34,21 @@ config BUILD_UCLIBC_LDSO
 	  be built for your target architecture.  If this option is available,
 	  to you, then you almost certainly want to answer Y.
 
+config FORCE_SHAREABLE_TEXT_SEGMENTS
+	bool "Only load shared libraries which can share their text segment"
+	depends on BUILD_UCLIBC_LDSO && UCLIBC_COMPLETELY_PIC
+	default n
+	help
+	  If you answer Y here, the uClibc native shared library loader will
+	  only load shared libraries, which do not need to modify any non-writable
+	  segments. These libraries haven't set the DT_TEXTREL tag in the dynamic
+	  section (==> objdump). So all your libraries must be compiled with
+	  -fPIC or -fpic, and all assembler function must be written as position
+	  independend code (PIC). 
+	  Enabling this option will makes uClibc's shared library loader a
+	  little bit smaller and guarantee that no memory will be wasted by badly
+	  coded shared libraries.
+
 config LDSO_LDD_SUPPORT
 	bool "Native shared library loader 'ldd' support"
 	depends on BUILD_UCLIBC_LDSO
diff --git a/extra/Configs/Config.sh b/extra/Configs/Config.sh
index 4bc77625b..45aed28f5 100644
--- a/extra/Configs/Config.sh
+++ b/extra/Configs/Config.sh
@@ -24,6 +24,10 @@ config HAVE_DOT_HIDDEN
         bool
 	default y
 
+config UCLIBC_COMPLETELY_PIC
+        bool
+	default y
+
 choice
 	prompt "Target Processor Type"
 	default CONFIG_SH4
diff --git a/ldso/ldso/Makefile b/ldso/ldso/Makefile
index 53c3c6385..13063616f 100644
--- a/ldso/ldso/Makefile
+++ b/ldso/ldso/Makefile
@@ -55,6 +55,9 @@ ifeq ($(strip $(SUPPORT_LD_DEBUG_EARLY)),y)
 XXFLAGS+=-D__SUPPORT_LD_DEBUG_EARLY__
 endif
 
+ifeq ($(strip $(FORCE_SHAREABLE_TEXT_SEGMENTS)),y)
+XXFLAGS+=-DFORCE_SHAREABLE_TEXT_SEGMENTS
+endif
 
 all: lib
 
diff --git a/ldso/ldso/dl-elf.c b/ldso/ldso/dl-elf.c
index b259da401..7a0e3fcef 100644
--- a/ldso/ldso/dl-elf.c
+++ b/ldso/ldso/dl-elf.c
@@ -573,7 +573,7 @@ struct elf_resolve *_dl_load_elf_shared_library(int secure,
 	   back again later. */
 
 	if (dynamic_info[DT_TEXTREL]) {
-#ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#ifndef FORCE_SHAREABLE_TEXT_SEGMENTS
 		ppnt = (elf_phdr *)(intptr_t) & header[epnt->e_phoff];
 		for (i = 0; i < epnt->e_phnum; i++, ppnt++) {
 			if (ppnt->p_type == PT_LOAD && !(ppnt->p_flags & PF_W))
diff --git a/ldso/ldso/ldso.c b/ldso/ldso/ldso.c
index c83c5cbb2..01ec298c2 100644
--- a/ldso/ldso/ldso.c
+++ b/ldso/ldso/ldso.c
@@ -30,10 +30,6 @@
  * SUCH DAMAGE.
  */
 
-/* Enable mprotect protection munging.  ARM and MIPS Linux needs this
- * it seems, so leave this enabled by default */
-#define FORCE_SHAREABLE_TEXT_SEGMENTS
-
 // Support a list of library preloads in /etc/ld.so.preload
 //#define SUPPORT_LDSO_PRELOAD_FILE
 
@@ -434,7 +430,7 @@ LD_BOOT(unsigned long args)
 					}
 					app_tpnt->dynamic_info[dpnt->d_tag] = dpnt->d_un.d_val;
 					if (dpnt->d_tag == DT_DEBUG)
-#ifndef FORCE_SHAREABLE_TEXT_SEGMENTS
+#ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
 						dpnt->d_un.d_val = (unsigned long) debug_addr;
 #else
 						dpnt_debug = dpnt;
@@ -455,7 +451,7 @@ LD_BOOT(unsigned long args)
 	tpnt->elf_buckets = hash_addr;
 	hash_addr += tpnt->nbucket;
 
-#ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#ifndef FORCE_SHAREABLE_TEXT_SEGMENTS
 	/* Ugly, ugly.  We need to call mprotect to change the protection of
 	   the text pages so that we can do the dynamic linking.  We can set the
 	   protection back again once we are done */
@@ -1186,7 +1182,7 @@ static void _dl_get_ready_to_run(struct elf_resolve *tpnt, struct elf_resolve *a
 		*_dl_envp = (unsigned long) envp;
 	}
 
-#ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#ifndef FORCE_SHAREABLE_TEXT_SEGMENTS
 	{
 		unsigned int j;
 		elf_phdr *myppnt;
diff --git a/ldso/ldso/linuxelf.h b/ldso/ldso/linuxelf.h
index 5a6e8b85f..26d3937c4 100644
--- a/ldso/ldso/linuxelf.h
+++ b/ldso/ldso/linuxelf.h
@@ -31,7 +31,15 @@ extern int _dl_linux_resolve(void);
 
 
 #ifndef SVR4_BUGCOMPAT
-#define SVR4_BUGCOMPAT 1
+# ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#  define SVR4_BUGCOMPAT 0
+# else
+#  define SVR4_BUGCOMPAT 1
+# endif
+#else
+# ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#  error option SVR4_BUGCOMPAT combined with option FORCE_SHAREABLE_TEXT_SEGMENTS makes no sense
+# endif
 #endif
 
 #if ELF_CLASS == ELFCLASS32
diff --git a/ldso/ldso/readelflib1.c b/ldso/ldso/readelflib1.c
index b259da401..7a0e3fcef 100644
--- a/ldso/ldso/readelflib1.c
+++ b/ldso/ldso/readelflib1.c
@@ -573,7 +573,7 @@ struct elf_resolve *_dl_load_elf_shared_library(int secure,
 	   back again later. */
 
 	if (dynamic_info[DT_TEXTREL]) {
-#ifdef FORCE_SHAREABLE_TEXT_SEGMENTS
+#ifndef FORCE_SHAREABLE_TEXT_SEGMENTS
 		ppnt = (elf_phdr *)(intptr_t) & header[epnt->e_phoff];
 		for (i = 0; i < epnt->e_phnum; i++, ppnt++) {
 			if (ppnt->p_type == PT_LOAD && !(ppnt->p_flags & PF_W))