path: root/arch/x86_64/reloc.h
diff options
authorRich Felker <>2015-04-13 02:56:26 -0400
committerRich Felker <>2015-04-13 03:04:42 -0400
commitf3ddd173806fd5c60b3f034528ca24542aecc5b9 (patch)
tree63cc7432a3c40f011c4818de32ef6257acbf0e73 /arch/x86_64/reloc.h
parent385c01112c083eb383d972da45836d497cc0556d (diff)
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 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/x86_64/reloc.h')
1 files changed, 13 insertions, 30 deletions
diff --git a/arch/x86_64/reloc.h b/arch/x86_64/reloc.h
index 9bc58496..84c075c3 100644
--- a/arch/x86_64/reloc.h
+++ b/arch/x86_64/reloc.h
@@ -1,32 +1,15 @@
-#include <stdint.h>
-#include <string.h>
-#include <elf.h>
#define LDSO_ARCH "x86_64"
-static int remap_rel(int type)
- switch(type) {
- case R_X86_64_64:
- return REL_SYMBOLIC;
- case R_X86_64_PC32:
- return REL_OFFSET32;
- case R_X86_64_GLOB_DAT:
- return REL_GOT;
- case R_X86_64_JUMP_SLOT:
- return REL_PLT;
- case R_X86_64_RELATIVE:
- return REL_RELATIVE;
- case R_X86_64_COPY:
- return REL_COPY;
- case R_X86_64_DTPMOD64:
- return REL_DTPMOD;
- case R_X86_64_DTPOFF64:
- return REL_DTPOFF;
- case R_X86_64_TPOFF64:
- return REL_TPOFF;
- case R_X86_64_TLSDESC:
- return REL_TLSDESC;
- }
- return 0;
+#define REL_SYMBOLIC R_X86_64_64
+#define REL_OFFSET32 R_X86_64_PC32
+#define REL_GOT R_X86_64_GLOB_DAT
+#define REL_PLT R_X86_64_JUMP_SLOT
+#define REL_COPY R_X86_64_COPY
+#define REL_DTPMOD R_X86_64_DTPMOD64
+#define REL_DTPOFF R_X86_64_DTPOFF64
+#define REL_TPOFF R_X86_64_TPOFF64
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+ "mov %1,%%rsp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )