Peter S. Mazinger writes:

Hello Erik!

I have made some cosmetical changes to the files, removed the added
SCRT=-fPIC option from building the crt0.S file (but it is a requirement
to build them with -fPIC), and changed some comments. I have left the
ldso.c patch with PIE_SUPPORT ifdefs, but consider applying it w/o them
(see some earlier comment from PaX Team on this issue, as it is considered
a bug). To have it work correctly, you'll also need removing
COMPLETELY_PIC.
One thing is missing: PIE_SUPPORT should be usable only for i386 (for
now).

Also added the support for propolice protection (that works for me and
catches memcpy/strcpy attacks (but needs a special gcc version).

Thanks, Peter

2 files changed, 33 insertions, 2 deletions

diff --git a/libc/sysdeps/linux/i386/Makefile b/libc/sysdeps/linux/i386/Makefile
index 9ba60f59e..c7f88b681 100644
--- a/libc/sysdeps/linux/i386/Makefile
+++ b/libc/sysdeps/linux/i386/Makefile
@@ -22,6 +22,9 @@ ASFLAGS=$(CFLAGS)
 
 CRT0_SRC = crt0.S
 CRT0_OBJ = crt0.o crt1.o gcrt1.o
+ifeq ($(strip $(UCLIBC_PIE_SUPPORT)),y)
+CRT0_OBJ += Scrt0.o Scrt1.o
+endif
 CRT0_DEPS=gmon-start.S
 CTOR_TARGETS=$(TOPDIR)lib/crti.o $(TOPDIR)lib/crtn.o
 
@@ -44,6 +47,13 @@ $(LIBC): ar-target
 ar-target: $(OBJS) $(CRT0_OBJ) $(CTOR_TARGETS)
 	$(AR) $(ARFLAGS) $(LIBC) $(OBJS)
 	cp $(CRT0_OBJ) $(TOPDIR)lib/
+ifeq ($(strip $(UCLIBC_PIE_SUPPORT)),y)
+ifeq ($(strip $(UCLIBC_CTOR_DTOR)),y)
+	$(RM) $(TOPDIR)lib/Scrt0.o
+else
+	mv $(TOPDIR)lib/Scrt0.o $(TOPDIR)lib/Scrt1.o
+endif
+endif
 
 $(CRT0_OBJ): $(CRT0_SRC)
 	$(CC) $(CFLAGS) -DL_$* $< -c -o $*.o
diff --git a/libc/sysdeps/linux/i386/crt0.S b/libc/sysdeps/linux/i386/crt0.S
index a488d6508..e7df6992b 100644
--- a/libc/sysdeps/linux/i386/crt0.S
+++ b/libc/sysdeps/linux/i386/crt0.S
@@ -18,6 +18,7 @@ Cambridge, MA 02139, USA.  */
 
 
 /*  Based on the code from GNU libc, but hacked up by John Beppu and Erik Andersen */
+/*  adapted by PaX Team for ET_DYN/PIE binaries */
 
 /*
     When we enter this piece of code, the program stack looks like this:
@@ -37,7 +38,7 @@ Cambridge, MA 02139, USA.  */
 
 	.global	_start
 	.type	_start,%function
-#if defined L_crt0 || ! defined __UCLIBC_CTOR_DTOR__
+#if defined L_crt0 || defined L_Scrt0 || ! defined __UCLIBC_CTOR_DTOR__
 	.type	__uClibc_main,%function
 #else
 	.weak	_init
@@ -74,10 +75,22 @@ _start:
 	pushl %ebp      /* callers %ebp (frame pointer) */
 	movl %esp,%ebp  /* mark callers stack frame as invalid */
 
-#if (defined L_crt1 || defined L_gcrt1 ) && defined __UCLIBC_CTOR_DTOR__
+#if defined L_Scrt0 || defined L_Scrt1
+	call .L0
+.L0:
+	pop %edx
+	addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%edx
+#endif
+
+#if (defined L_crt1 || defined L_Scrt1 || defined L_gcrt1 ) && defined __UCLIBC_CTOR_DTOR__
 	/* Push .init and .fini arguments to __uClibc_start_main() on the stack */
+#ifdef L_Scrt1
+	pushl _fini@GOT(%edx)
+	pushl _init@GOT(%edx)
+#else
 	pushl $_fini
 	pushl $_init
+#endif
 
 	/* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */ 
 	pushl %eax	/* Environment pointer */
@@ -85,15 +98,23 @@ _start:
 	pushl %ecx	/* And the argument count */
 
 	/* Ok, now run uClibc's main() -- shouldn't return */
+#ifdef L_Scrt1
+	call *__uClibc_start_main@GOT(%edx)
+#else
 	call __uClibc_start_main
+#endif
 #else
 	/* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */ 
 	pushl %eax	/* Environment pointer */
 	pushl %ebx	/* Argument pointer */
 	pushl %ecx	/* And the argument count */
 
+#ifdef L_Scrt0
+	call *__uClibc_main@GOT(%edx)
+#else
 	call __uClibc_main
 #endif
+#endif
 
 	/* Crash if somehow `exit' returns anyways.  */
 	hlt