From 2f738540d708321613a90a4fdc5e4d1c0f866f94 Mon Sep 17 00:00:00 2001 From: Kurt Miller Date: Wed, 14 Jan 2009 19:45:21 +0000 Subject: Re-enable pie support on macppc (still off by default but usable again). Due to the way executable sections are loaded by the kernel, a one page .got section with the blrl instruction may be in the data cache and not flushed causing random crashes upon process startup. Flush the data cache before ___start() jumps there. Also mprotect the .got section to be read/exec instead of read/write/exec. ld.so knows how to cope and static binaries don't write to .got. written by and okay drahn@ --- lib/csu/powerpc/Makefile | 14 ++++----- lib/csu/powerpc/crt0.c | 74 ++++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 76 insertions(+), 12 deletions(-) (limited to 'lib/csu') diff --git a/lib/csu/powerpc/Makefile b/lib/csu/powerpc/Makefile index d1ff5d85084..acdea1b84d6 100644 --- a/lib/csu/powerpc/Makefile +++ b/lib/csu/powerpc/Makefile @@ -1,4 +1,4 @@ -# $OpenBSD: Makefile,v 1.18 2008/11/21 19:19:13 otto Exp $ +# $OpenBSD: Makefile,v 1.19 2009/01/14 19:45:20 kurt Exp $ # from: @(#)Makefile 8.1 (Berkeley) 6/1/93 CFLAGS+= -DLIBC_SCCS @@ -14,8 +14,8 @@ CFLAGS+= -I${ELFDIR} -I${.CURDIR} all: ${OBJS} crt0.o: crt0.c - @echo ${COMPILE.c} -DCRT0 ${.CURDIR}/crt0.c -o ${.TARGET} - @${COMPILE.c} -DCRT0 ${.CURDIR}/crt0.c -o ${.TARGET}.o + @echo ${COMPILE.c} -fpie -DCRT0 ${.CURDIR}/crt0.c -o ${.TARGET} + @${COMPILE.c} -fpie -DCRT0 ${.CURDIR}/crt0.c -o ${.TARGET}.o @${LD} -x -r -o ${.TARGET} ${.TARGET}.o @rm -f ${.TARGET}.o @@ -26,8 +26,8 @@ gcrt0.o: crt0.c @rm -f ${.TARGET}.o crtbegin.o: crtbegin.c - @echo ${COMPILE.c} ${ELFDIR}/crtbegin.c -o ${.TARGET} - @${COMPILE.c} ${ELFDIR}/crtbegin.c -o ${.TARGET}.o + @echo ${COMPILE.c} -fpie ${ELFDIR}/crtbegin.c -o ${.TARGET} + @${COMPILE.c} -fpie ${ELFDIR}/crtbegin.c -o ${.TARGET}.o @${LD} -x -r -o ${.TARGET} ${.TARGET}.o @rm -f ${.TARGET}.o @@ -38,8 +38,8 @@ crtbeginS.o: crtbeginS.c @rm -f ${.TARGET}.o crtend.o: crtend.c - @echo ${COMPILE.c} ${ELFDIR}/crtend.c -o ${.TARGET} - @${COMPILE.c} ${ELFDIR}/crtend.c -o ${.TARGET}.o + @echo ${COMPILE.c} -fpie ${ELFDIR}/crtend.c -o ${.TARGET} + @${COMPILE.c} -fpie ${ELFDIR}/crtend.c -o ${.TARGET}.o @${LD} -x -r -o ${.TARGET} ${.TARGET}.o @rm -f ${.TARGET}.o diff --git a/lib/csu/powerpc/crt0.c b/lib/csu/powerpc/crt0.c index 901ba23dbc0..2d2f9104114 100644 --- a/lib/csu/powerpc/crt0.c +++ b/lib/csu/powerpc/crt0.c @@ -1,4 +1,4 @@ -/* $OpenBSD: crt0.c,v 1.3 2003/08/25 17:59:42 drahn Exp $ */ +/* $OpenBSD: crt0.c,v 1.4 2009/01/14 19:45:20 kurt Exp $ */ /* $NetBSD: crt0.c,v 1.1 1996/09/12 16:59:02 cgd Exp $ */ /* * Copyright (c) 1995 Christopher G. Demetriou @@ -32,6 +32,7 @@ */ #include #include +#include char **environ; char * __progname = ""; @@ -46,11 +47,74 @@ extern unsigned char _etext, _eprol; static inline char * _strrchr(const char *p, char ch); -__asm(".globl __start"); -__asm(".type __start@function"); -__asm("__start = _start"); +#define STR(x) __STRING(x) +__asm( +" .text \n" +" .section \".text\" \n" +" .align 2 \n" +" .globl _start \n" +" .type _start, @function \n" +" .globl __start \n" +" .type __start, @function \n" +"_start: \n" +"__start: \n" +" # move argument registers to saved registers for startup flush \n" +" mr %r26, %r3 \n" +" mr %r25, %r4 \n" +" mr %r24, %r5 \n" +" mr %r23, %r6 \n" +" mr %r22, %r7 \n" +" mflr %r27 /* save off old link register */ \n" +" bl 1f \n" +" # this instruction never gets executed but can be used \n" +" # to find the virtual address where the page is loaded. \n" +" bl _GLOBAL_OFFSET_TABLE_@local-4 \n" +"1: \n" +" mflr %r5 # this stores where we are (+4) \n" +" lwz %r18, 0(%r5) # load the instruction at offset_sym \n" +" # it contains an offset to the location \n" +" # of the GOT. \n" +" \n" +" rlwinm %r18,%r18,0,8,30 # mask off the offset portion of the instr. \n" +" \n" +" /* \n" +" * these adds effectively calculate the value the \n" +" * bl _GLOBAL_OFFSET_TABLE_@local-4 \n" +" * operation that would be below would calulate. \n" +" */ \n" +" add %r28, %r18, %r5 \n" +" mr %r6, %r5 # save offset for later use \n" +" \n" +" /* mprotect GOT-4 for correct execution of blrl instruction */ \n" +" li %r0, " STR(SYS_mprotect) " \n" +" mr %r3, %r28 \n" +" li %r4, 4 \n" +" li %r5, 5 /* (PROT_READ|PROT_EXEC) */ \n" +" sc \n" +" \n" +" mr %r5, %r6 \n" +" \n" +" li %r0, 0 \n" +" # flush the blrl instruction out of the data cache \n" +" dcbf %r5, %r18 \n" +" sync \n" +" isync \n" +" # make certain that the got table addr is not in the icache \n" +" icbi %r5, %r18 \n" +" sync \n" +" isync \n" +" mtlr %r27 \n" +" # move argument registers back from saved registers \n" +" mr %r3, %r26 \n" +" mr %r4, %r25 \n" +" mr %r5, %r24 \n" +" mr %r6, %r23 \n" +" mr %r7, %r22 \n" +" b ___start \n" +); + void -_start(int argc, char **argv, char **envp, void *aux, void (*cleanup)(void)) +___start(int argc, char **argv, char **envp, void *aux, void (*cleanup)(void)) { char *s; -- cgit v1.2.3