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.

1 files changed, 17 insertions, 11 deletions

diff --git a/arch/or1k/crt_arch.h b/arch/or1k/crt_arch.h
index 0f381d2d..84415561 100644
--- a/arch/or1k/crt_arch.h
+++ b/arch/or1k/crt_arch.h
@@ -1,11 +1,17 @@
-__asm__("\
-.global _start \n\
-.align  4 \n\
-_start: \n\
-	l.ori r3, r1, 0 \n\
-	l.addi r2, r0, -8 \n\
-	l.and r1, r1, r2 \n\
-	l.addi r1, r1, -8 \n\
-	l.jal __cstart \n\
-	 l.ori r2, r0, 0 \n\
-");
+__asm__(
+".global " START " \n"
+".align  4 \n"
+START ": \n"
+"	l.jal 1f \n"
+"	 l.ori r3, r1, 0 \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	.word _DYNAMIC-. \n"
+"1:	l.lwz r4, 0(r9) \n"
+"	l.add r4, r4, r9 \n"
+"	l.addi r2, r0, -8 \n"
+"	l.and r1, r1, r2 \n"
+"	l.addi r1, r1, -16 \n"
+"	l.jal " START "_c \n"
+"	 l.ori r2, r0, 0 \n"
+);