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author | Rich Felker <dalias@aerifal.cx> | 2015-04-13 02:56:26 -0400 |
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committer | Rich Felker <dalias@aerifal.cx> | 2015-04-13 03:04:42 -0400 |
commit | f3ddd173806fd5c60b3f034528ca24542aecc5b9 (patch) | |
tree | 63cc7432a3c40f011c4818de32ef6257acbf0e73 /arch/arm | |
parent | 385c01112c083eb383d972da45836d497cc0556d (diff) | |
download | musl-f3ddd173806fd5c60b3f034528ca24542aecc5b9.tar.gz musl-f3ddd173806fd5c60b3f034528ca24542aecc5b9.tar.xz musl-f3ddd173806fd5c60b3f034528ca24542aecc5b9.zip |
dynamic linker bootstrap overhaul
this overhaul further reduces the amount of arch-specific code needed by the dynamic linker and removes a number of assumptions, including: - that symbolic function references inside libc are bound at link time via the linker option -Bsymbolic-functions. - that libc functions used by the dynamic linker do not require access to data symbols. - that static/internal function calls and data accesses can be made without performing any relocations, or that arch-specific startup code handled any such relocations needed. removing these assumptions paves the way for allowing libc.so itself to be built with stack protector (among other things), and is achieved by a three-stage bootstrap process: 1. relative relocations are processed with a flat function. 2. symbolic relocations are processed with no external calls/data. 3. main program and dependency libs are processed with a fully-functional libc/ldso. reduction in arch-specific code is achived through the following: - crt_arch.h, used for generating crt1.o, now provides the entry point for the dynamic linker too. - asm is no longer responsible for skipping the beginning of argv[] when ldso is invoked as a command. - the functionality previously provided by __reloc_self for heavily GOT-dependent RISC archs is now the arch-agnostic stage-1. - arch-specific relocation type codes are mapped directly as macros rather than via an inline translation function/switch statement.
Diffstat (limited to 'arch/arm')
-rw-r--r-- | arch/arm/crt_arch.h | 25 | ||||
-rw-r--r-- | arch/arm/reloc.h | 36 |
2 files changed, 27 insertions, 34 deletions
diff --git a/arch/arm/crt_arch.h b/arch/arm/crt_arch.h index bed99c27..d1f9a662 100644 --- a/arch/arm/crt_arch.h +++ b/arch/arm/crt_arch.h @@ -1,10 +1,15 @@ -__asm__("\ -.global _start \n\ -.type _start,%function \n\ -_start: \n\ - mov fp, #0 \n\ - mov lr, #0 \n\ - mov a1, sp \n\ - and sp, sp, #-16 \n\ - bl __cstart \n\ -"); +__asm__( +".global " START " \n" +".type " START ",%function \n" +START ": \n" +" mov fp, #0 \n" +" mov lr, #0 \n" +" mov a1, sp \n" +" ldr a2, 1f \n" +"2: add a2, pc, a2 \n" +" and sp, sp, #-16 \n" +" bl " START "_c \n" +".weak _DYNAMIC \n" +".hidden _DYNAMIC \n" +"1: .word _DYNAMIC-2b-8 \n" +); diff --git a/arch/arm/reloc.h b/arch/arm/reloc.h index ee39b7fd..dec0031e 100644 --- a/arch/arm/reloc.h +++ b/arch/arm/reloc.h @@ -1,5 +1,3 @@ -#include <string.h> -#include <elf.h> #include <endian.h> #if __BYTE_ORDER == __BIG_ENDIAN @@ -20,25 +18,15 @@ #define TPOFF_K 8 -static int remap_rel(int type) -{ - switch(type) { - case R_ARM_ABS32: - return REL_SYMBOLIC; - case R_ARM_GLOB_DAT: - return REL_GOT; - case R_ARM_JUMP_SLOT: - return REL_PLT; - case R_ARM_RELATIVE: - return REL_RELATIVE; - case R_ARM_COPY: - return REL_COPY; - case R_ARM_TLS_DTPMOD32: - return REL_DTPMOD; - case R_ARM_TLS_DTPOFF32: - return REL_DTPOFF; - case R_ARM_TLS_TPOFF32: - return REL_TPOFF; - } - return 0; -} +#define REL_SYMBOLIC R_ARM_ABS32 +#define REL_GOT R_ARM_GLOB_DAT +#define REL_PLT R_ARM_JUMP_SLOT +#define REL_RELATIVE R_ARM_RELATIVE +#define REL_COPY R_ARM_COPY +#define REL_DTPMOD R_ARM_TLS_DTPMOD32 +#define REL_DTPOFF R_ARM_TLS_DTPOFF32 +#define REL_TPOFF R_ARM_TLS_TPOFF32 +//#define REL_TLSDESC R_ARM_TLS_DESC + +#define CRTJMP(pc,sp) __asm__ __volatile__( \ + "mov sp,%1 ; tst %0,#1 ; moveq pc,%0 ; bx %0" : : "r"(pc), "r"(sp) : "memory" ) |