glibc/sysdeps/powerpc/dl-machine.h
Ulrich Drepper 5929563ff2 Update.
1997-04-01 00:37  Ulrich Drepper  <drepper@cygnus.com>

	* math/Makefile: Prevent inlining for test-{float,double,longdouble}.
	* math/libm-test.c (initialize): Make strings unique and force
	values to memory.

	* posix/regex.c: Debug debugging code.

	* sysdeps/i386/asm-syntax.h: Define `L' macro to emit correct
	syntax for local label.
	* sysdeps/i386/add_n.S: Use correct local label syntax for the
	binary format.
	* sysdeps/i386/addmul_1.S: Likewise.
	* sysdeps/i386/lshift.S: Likewise.
	* sysdeps/i386/memchr.S: Likewise.
	* sysdeps/i386/memset.S: Likewise.
	* sysdeps/i386/mul_1.S: Likewise.
	* sysdeps/i386/rshift.S: Likewise.
	* sysdeps/i386/stpcpy.S: Likewise.
	* sysdeps/i386/stpncpy.S: Likewise.
	* sysdeps/i386/strchr.S: Likewise.
	* sysdeps/i386/strcspn.S: Likewise.
	* sysdeps/i386/strlen.S: Likewise.
	* sysdeps/i386/strpbrk.S: Likewise.
	* sysdeps/i386/strrchr.S: Likewise.
	* sysdeps/i386/strspn.S: Likewise.
	* sysdeps/i386/strtok.S: Likewise.
	* sysdeps/i386/sub_n.S: Likewise.
	* sysdeps/i386/submul_1.S: Likewise.
	* sysdeps/i386/i486/strcat.S: Likewise.
	* sysdeps/i386/i486/strlen.S: Likewise.
	* sysdeps/i386/i586/add_n.S: Likewise.
	* sysdeps/i386/i586/addmul_1.S: Likewise.
	* sysdeps/i386/i586/lshift.S: Likewise.
	* sysdeps/i386/i586/memset.S: Likewise.
	* sysdeps/i386/i586/mul_1.S: Likewise.
	* sysdeps/i386/i586/rshift.S: Likewise.
	* sysdeps/i386/i586/strchr.S: Likewise.
	* sysdeps/i386/i586/strlen.S: Likewise.
	* sysdeps/i386/i586/sub_n.S: Likewise.
	* sysdeps/i386/i586/submul_1.S: Likewise.

	* sysdeps/stub/s_log2l.c: Correct function name.

	* time/africa: Updated from ADO tzdata1997e.
	* time/aantarctica: Likewise.
	* time/asia: Likewise.
	* time/australia: Likewise.
	* time/europe: Likewise.
	* time/northamerica: Likewise.
	* time/southamerica: Likewise.
	* time/private.h: Updated from ADO tzcode1997d.
	* time/scheck.c: Likewise.

1997-03-31 12:42  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/unix/sysv/linux/powerpc/Dist: Add kernel_*.h files.

1997-03-23 01:41  Geoff Keating  <geoffk@ozemail.com.au>

	* sysdeps/powerpc/strlen.s: Rewrote for more speed.
	* string/tst-strlen.c: Also test various string alignments.

1997-03-19 06:11  Geoff Keating  <geoffk@ozemail.com.au>

	* sysdeps/unix/sysv/linux/powerpc/statbuf.h: Removed.
	* sysdeps/unix/sysv/linux/powerpc/kernel_stat.h: Added.

	* sysdeps/powerpc/dl-machine.h (ELF_PREFERRED_ADDRESS): Assume
	program base address is 0x01800000 if we can't otherwise tell what
	it is.
	(elf_machine_rela): Replace `assertion failed' with real error
	messages.

	* sysdeps/powerpc/dl-machine.h: More comments, more GNU indenting.
	Put in extra parentheses to make explicit the relative precedence
	of + and >>.

	* sysdeps/powerpc/bsd-setjmp.S: Add `__setjmp' symbol so the tests
	pass.
	* sysdeps/powerpc/clone.S: Rewrite.  Probably still doesn't work.

	* sysdeps/unix/sysv/linux/powerpc/sys/sysdep.h: Use .section "text"
	instead of .text.

1997-03-31 02:28  Ulrich Drepper  <drepper@cygnus.com>

	* misc/tst-tsearch.c: Don't write to stderr, write to stdout
	instead.

	* inet/inet_ntoa.c (inet_ntoa): Complete rewrite.  Now uses
	thread-specific memory in multi-threaded programs.

	* sysdeps/stub/s_exp2.c: New file.  Stub version for exp2 function.
	* sysdeps/stub/s_exp2f.c: New file.
	* sysdeps/stub/s_exp2l.c: New file.
	Reported by a sun <asun@zoology.washington.edu>.

	* sysdeps/unix/sysv/linux/netatalk/atalk.h: Rename to...
	* sysdeps/unix/sysv/linux/netatalk/at.h: ...this.
	Suggested by a sun <asun@zoology.washington.edu>.

1997-03-30 14:53  Ulrich Drepper  <drepper@cygnus.com>

	* sysdeps/unix/sysv/linux/netinet/ip_icmp.h: Add former contents
	of <netinet/icmp.h>.
	Patch by a sun <asun@zoology.washington.edu>.

	* sysdeps/powerpc/strlen.S: Added.
1997-03-31 22:56:24 +00:00

635 lines
20 KiB
C

/* Machine-dependent ELF dynamic relocation inline functions. PowerPC version.
Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#define ELF_MACHINE_NAME "powerpc"
#include <assert.h>
#include <string.h>
#include <link.h>
/* stuff for the PLT */
#define PLT_INITIAL_ENTRY_WORDS 18
#define PLT_LONGBRANCH_ENTRY_WORDS 10
#define PLT_DOUBLE_SIZE (1<<13)
#define PLT_ENTRY_START_WORDS(entry_number) \
(PLT_INITIAL_ENTRY_WORDS + (entry_number)*2 + \
((entry_number) > PLT_DOUBLE_SIZE ? \
((entry_number) - PLT_DOUBLE_SIZE)*2 : \
0))
#define PLT_DATA_START_WORDS(num_entries) PLT_ENTRY_START_WORDS(num_entries)
#define OPCODE_ADDI(rd,ra,simm) \
(0x38000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADDIS(rd,ra,simm) \
(0x3c000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADD(rd,ra,rb) \
(0x7c000214 | (rd) << 21 | (ra) << 16 | (rb) << 11)
#define OPCODE_B(target) (0x48000000 | (target) & 0x03fffffc)
#define OPCODE_BA(target) (0x48000002 | (target) & 0x03fffffc)
#define OPCODE_BCTR() 0x4e800420
#define OPCODE_LWZ(rd,d,ra) \
(0x80000000 | (rd) << 21 | (ra) << 16 | (d) & 0xffff)
#define OPCODE_MTCTR(rd) (0x7C0903A6 | (rd) << 21)
#define OPCODE_RLWINM(ra,rs,sh,mb,me) \
(0x54000000 | (rs) << 21 | (ra) << 16 | (sh) << 11 | (mb) << 6 | (me) << 1)
#define OPCODE_LI(rd,simm) OPCODE_ADDI(rd,0,simm)
#define OPCODE_SLWI(ra,rs,sh) OPCODE_RLWINM(ra,rs,sh,0,31-sh)
#define PPC_DCBST(where) asm __volatile__ ("dcbst 0,%0" : : "r"(where))
#define PPC_SYNC asm __volatile__ ("sync")
#define PPC_ISYNC asm __volatile__ ("sync; isync")
#define PPC_ICBI(where) asm __volatile__ ("icbi 0,%0" : : "r"(where))
/* Use this when you've modified some code, but it won't be in the
instruction fetch queue (or when it doesn't matter if it is). */
#define MODIFIED_CODE_NOQUEUE(where) \
do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); } while (0)
/* Use this when it might be in the instruction queue. */
#define MODIFIED_CODE(where) \
do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); PPC_ISYNC; } while (0)
/* Return nonzero iff E_MACHINE is compatible with the running host. */
static inline int
elf_machine_matches_host (Elf32_Half e_machine)
{
return e_machine == EM_PPC;
}
/* Return the link-time address of _DYNAMIC, stored as
the first value in the GOT. */
static inline Elf32_Addr
elf_machine_dynamic (void)
{
Elf32_Addr *got;
asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
: "=l"(got));
return *got;
}
/* Return the run-time load address of the shared object. */
static inline Elf32_Addr
elf_machine_load_address (void)
{
unsigned *got;
unsigned *branchaddr;
/* This is much harder than you'd expect. Possibly I'm missing something.
The 'obvious' way:
Apparently, "bcl 20,31,$+4" is what should be used to load LR
with the address of the next instruction.
I think this is so that machines that do bl/blr pairing don't
get confused.
asm ("bcl 20,31,0f ;"
"0: mflr 0 ;"
"lis %0,0b@ha;"
"addi %0,%0,0b@l;"
"subf %0,%0,0"
: "=b" (addr) : : "r0", "lr");
doesn't work, because the linker doesn't have to (and in fact doesn't)
update the @ha and @l references; the loader (which runs after this
code) will do that.
Instead, we use the following trick:
The linker puts the _link-time_ address of _DYNAMIC at the first
word in the GOT. We could branch to that address, if we wanted,
by using an @local reloc; the linker works this out, so it's safe
to use now. We can't, of course, actually branch there, because
we'd cause an illegal instruction exception; so we need to compute
the address ourselves. That gives us the following code: */
/* Get address of the 'b _DYNAMIC@local'... */
asm ("bl 0f ;"
"b _DYNAMIC@local;"
"0:"
: "=l"(branchaddr));
/* ... and the address of the GOT. */
asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
: "=l"(got));
/* So now work out the difference between where the branch actually points,
and the offset of that location in memory from the start of the file. */
return (Elf32_Addr)branchaddr - *got +
(*branchaddr & 0x3fffffc |
(int)(*branchaddr << 6 & 0x80000000) >> 6);
}
#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */
/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
LOADADDR is the load address of the object; INFO is an array indexed
by DT_* of the .dynamic section info. */
#ifdef RESOLVE
static inline void
elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
const Elf32_Sym *sym, const struct r_found_version *version)
{
Elf32_Addr *const reloc_addr = (Elf32_Addr *)(map->l_addr + reloc->r_offset);
Elf32_Word loadbase, finaladdr;
const int rinfo = ELF32_R_TYPE (reloc->r_info);
if (rinfo == R_PPC_NONE)
return;
assert (sym != NULL);
if (ELF32_ST_TYPE (sym->st_info) == STT_SECTION ||
rinfo == R_PPC_RELATIVE)
{
/* Has already been relocated. */
loadbase = map->l_addr;
finaladdr = loadbase + reloc->r_addend;
}
else
{
int flags;
/* We never want to use a PLT entry as the destination of a
reloc, when what is being relocated is a branch. This is
partly for efficiency, but mostly so we avoid loops. */
if (rinfo == R_PPC_REL24 ||
rinfo == R_PPC_ADDR24 ||
rinfo == R_PPC_JMP_SLOT)
flags = DL_LOOKUP_NOPLT;
else if (rinfo == R_PPC_COPY)
flags = DL_LOOKUP_NOEXEC;
else
flags = 0;
loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version, flags));
if (sym == NULL)
{
/* Weak symbol that wasn't actually defined anywhere. */
assert(loadbase == 0);
finaladdr = reloc->r_addend;
}
else
finaladdr = (loadbase + (Elf32_Word) (char *) sym->st_value
+ reloc->r_addend);
}
/* This is an if/else if chain because GCC 2.7.2.[012] turns case
statements into non-PIC table lookups. When a later version
comes out that fixes this, this should be changed. */
if (rinfo == R_PPC_UADDR32 ||
rinfo == R_PPC_GLOB_DAT ||
rinfo == R_PPC_ADDR32 ||
rinfo == R_PPC_RELATIVE)
{
*reloc_addr = finaladdr;
}
else if (rinfo == R_PPC_ADDR16_LO)
{
*(Elf32_Half*) reloc_addr = finaladdr;
}
else if (rinfo == R_PPC_ADDR16_HI)
{
*(Elf32_Half*) reloc_addr = finaladdr >> 16;
}
else if (rinfo == R_PPC_ADDR16_HA)
{
*(Elf32_Half*) reloc_addr = (finaladdr + 0x8000) >> 16;
}
#ifndef RTLD_BOOTSTRAP
else if (rinfo == R_PPC_REL24)
{
Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
if (delta << 6 >> 6 != delta)
_dl_signal_error (0, map->l_name,
"R_PPC_REL24 relocation out of range");
*reloc_addr = *reloc_addr & 0xfc000003 | delta & 0x3fffffc;
}
else if (rinfo == R_PPC_ADDR24)
{
if (finaladdr << 6 >> 6 != finaladdr)
_dl_signal_error (0, map->l_name,
"R_PPC_ADDR24 relocation out of range");
*reloc_addr = *reloc_addr & 0xfc000003 | finaladdr & 0x3fffffc;
}
else if (rinfo == R_PPC_COPY)
{
memcpy (reloc_addr, (char *) finaladdr, sym->st_size);
}
#endif
else if (rinfo == R_PPC_REL32)
{
*reloc_addr = finaladdr - (Elf32_Word) (char *) reloc_addr;
}
else if (rinfo == R_PPC_JMP_SLOT)
{
Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
if (delta << 6 >> 6 == delta)
*reloc_addr = OPCODE_B (delta);
else if (finaladdr <= 0x01fffffc || finaladdr >= 0xfe000000)
*reloc_addr = OPCODE_BA (finaladdr);
else
{
Elf32_Word *plt;
Elf32_Word index;
plt = (Elf32_Word *)((char *)map->l_addr
+ map->l_info[DT_PLTGOT]->d_un.d_val);
index = (reloc_addr - plt - PLT_INITIAL_ENTRY_WORDS)/2;
if (index >= PLT_DOUBLE_SIZE)
{
/* Slots greater than or equal to 2^13 have 4 words available
instead of two. */
reloc_addr[0] = OPCODE_LI (11, finaladdr);
reloc_addr[1] = OPCODE_ADDIS (11, 11, finaladdr + 0x8000 >> 16);
reloc_addr[2] = OPCODE_MTCTR (11);
reloc_addr[3] = OPCODE_BCTR ();
}
else
{
Elf32_Word num_plt_entries;
num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
/ sizeof(Elf32_Rela));
reloc_addr[0] = OPCODE_LI (11, index*4);
reloc_addr[1] =
OPCODE_B (-(4*(index*2
+ 1
- PLT_LONGBRANCH_ENTRY_WORDS
+ PLT_INITIAL_ENTRY_WORDS)));
plt[index+PLT_DATA_START_WORDS (num_plt_entries)] = finaladdr;
}
}
MODIFIED_CODE (reloc_addr);
}
else
assert (! "unexpected dynamic reloc type");
if (rinfo == R_PPC_ADDR16_LO ||
rinfo == R_PPC_ADDR16_HI ||
rinfo == R_PPC_ADDR16_HA ||
rinfo == R_PPC_REL24 ||
rinfo == R_PPC_ADDR24)
MODIFIED_CODE_NOQUEUE (reloc_addr);
}
#define ELF_MACHINE_NO_REL 1
#endif
/* Nonzero iff TYPE describes relocation of a PLT entry, so
PLT entries should not be allowed to define the value. */
#define elf_machine_pltrel_p(type) ((type) == R_PPC_JMP_SLOT)
/* Set up the loaded object described by L so its unrelocated PLT
entries will jump to the on-demand fixup code in dl-runtime.c.
Also install a small trampoline to be used by entries that have
been relocated to an address too far away for a single branch. */
/* A PLT entry does one of three things:
(i) Jumps to the actual routine. Such entries are set up above, in
elf_machine_rela.
(ii) Jumps to the actual routine via glue at the start of the PLT.
We do this by putting the address of the routine in space
allocated at the end of the PLT, and when the PLT entry is
called we load the offset of that word (from the start of the
space) into r11, then call the glue, which loads the word and
branches to that address. These entries are set up in
elf_machine_rela, but the glue is set up here.
(iii) Loads the index of this PLT entry (we count the double-size
entries as one entry for this purpose) into r11, then
branches to code at the start of the PLT. This code then
calls `fixup', in dl-runtime.c, via the glue in the macro
ELF_MACHINE_RUNTIME_TRAMPOLINE, which resets the PLT entry to
be one of the above two types. These entries are set up here. */
static inline void
elf_machine_runtime_setup (struct link_map *map, int lazy)
{
if (map->l_info[DT_JMPREL])
{
int i;
/* Fill in the PLT. Its initial contents are directed to a
function earlier in the PLT which arranges for the dynamic
linker to be called back. */
Elf32_Word *plt = (Elf32_Word *) ((char *) map->l_addr
+ map->l_info[DT_PLTGOT]->d_un.d_val);
Elf32_Word num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
/ sizeof (Elf32_Rela));
Elf32_Word rel_offset_words = PLT_DATA_START_WORDS (num_plt_entries);
extern void _dl_runtime_resolve (void);
Elf32_Word size_modified;
if (lazy)
for (i = 0; i < num_plt_entries; i++)
{
Elf32_Word offset = PLT_ENTRY_START_WORDS (i);
if (i >= PLT_DOUBLE_SIZE)
{
plt[offset ] = OPCODE_LI (11, i * 4);
plt[offset+1] = OPCODE_ADDIS (11, 11, (i * 4 + 0x8000) >> 16);
plt[offset+2] = OPCODE_B (-(4 * (offset + 2)));
}
else
{
plt[offset ] = OPCODE_LI (11, i * 4);
plt[offset+1] = OPCODE_B (-(4 * (offset + 1)));
}
}
/* Multiply index of entry by 3 (in r11). */
plt[0] = OPCODE_SLWI (12, 11, 1);
plt[1] = OPCODE_ADD (11, 12, 11);
if ((Elf32_Word) (char *) _dl_runtime_resolve <= 0x01fffffc ||
(Elf32_Word) (char *) _dl_runtime_resolve >= 0xfe000000)
{
/* Load address of link map in r12. */
plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) map);
plt[3] = OPCODE_ADDIS (12, 12, (((Elf32_Word) (char *) map
+ 0x8000) >> 16));
/* Call _dl_runtime_resolve. */
plt[4] = OPCODE_BA ((Elf32_Word) (char *) _dl_runtime_resolve);
}
else
{
/* Get address of _dl_runtime_resolve in CTR. */
plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) _dl_runtime_resolve);
plt[3] = OPCODE_ADDIS (12, 12, ((((Elf32_Word) (char *)
_dl_runtime_resolve)
+ 0x8000) >> 16));
plt[4] = OPCODE_MTCTR (12);
/* Load address of link map in r12. */
plt[5] = OPCODE_LI (12, (Elf32_Word) (char *) map);
plt[6] = OPCODE_ADDIS (12, 12, (((Elf32_Word) (char *) map
+ 0x8000) >> 16));
/* Call _dl_runtime_resolve. */
plt[7] = OPCODE_BCTR ();
}
/* Convert the index in r11 into an actual address, and get the
word at that address. */
plt[PLT_LONGBRANCH_ENTRY_WORDS] =
OPCODE_ADDIS (11, 11, (((Elf32_Word) (char*) (plt + rel_offset_words)
+ 0x8000) >> 16));
plt[PLT_LONGBRANCH_ENTRY_WORDS+1] =
OPCODE_LWZ (11, (Elf32_Word) (char*) (plt+rel_offset_words), 11);
/* Call the procedure at that address. */
plt[PLT_LONGBRANCH_ENTRY_WORDS+2] = OPCODE_MTCTR (11);
plt[PLT_LONGBRANCH_ENTRY_WORDS+3] = OPCODE_BCTR ();
/* Now, we've modified code (quite a lot of code, possibly). We
need to write the changes from the data cache to a
second-level unified cache, then make sure that stale data in
the instruction cache is removed. (In a multiprocessor
system, the effect is more complex.)
Assumes the cache line size is at least 32 bytes, or at least
that dcbst and icbi apply to 32-byte lines. At present, all
PowerPC processors have line sizes of exactly 32 bytes. */
size_modified = lazy ? rel_offset_words : PLT_INITIAL_ENTRY_WORDS;
for (i = 0; i < size_modified; i+=8)
PPC_DCBST (plt + i);
PPC_SYNC;
for (i = 0; i < size_modified; i+=8)
PPC_ICBI (plt + i);
PPC_ISYNC;
}
}
static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
{
assert (ELF32_R_TYPE (reloc->r_info) == R_PPC_JMP_SLOT);
/* elf_machine_runtime_setup handles this. */
}
/* The PLT uses Elf32_Rela relocs. */
#define elf_machine_relplt elf_machine_rela
/* This code is used in dl-runtime.c to call the `fixup' function
and then redirect to the address it returns. It is called
from code built in the PLT by elf_machine_runtime_setup. */
#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
.section \".text\"
.align 2
.globl _dl_runtime_resolve
.type _dl_runtime_resolve,@function
_dl_runtime_resolve:
# We need to save the registers used to pass parameters.
# We build a stack frame to put them in.
stwu 1,-48(1)
mflr 0
stw 3,16(1)
stw 4,20(1)
stw 0,52(1)
stw 5,24(1)
# We also need to save some of the condition register fields.
mfcr 0
stw 6,28(1)
stw 7,32(1)
stw 8,36(1)
stw 9,40(1)
stw 10,44(1)
stw 0,12(1)
# The code that calls this has put parameters for `fixup' in r12 and r11.
mr 3,12
mr 4,11
bl fixup@local
# 'fixup' returns the address we want to branch to.
mtctr 3
# Put the registers back...
lwz 0,52(1)
lwz 10,44(1)
lwz 9,40(1)
mtlr 0
lwz 0,12(1)
lwz 8,36(1)
lwz 7,32(1)
lwz 6,28(1)
mtcrf 0xFF,0
lwz 5,24(1)
lwz 4,20(1)
lwz 3,16(1)
# ...unwind the stack frame, and jump to the PLT entry we updated.
addi 1,1,48
bctr
0:
.size _dl_runtime_resolve,0b-_dl_runtime_resolve
# undo '.section text'.
.previous
");
/* Initial entry point code for the dynamic linker.
The C function `_dl_start' is the real entry point;
its return value is the user program's entry point. */
#define RTLD_START \
static ElfW(Addr) _dl_start (void *arg) __attribute__((unused)); \
asm ("\
.section \".text\"
.align 2
.globl _start
.type _start,@function
_start:
# We start with the following on the stack, from top:
# argc (4 bytes)
# arguments for program (terminated by NULL)
# environment variables (terminated by NULL)
# arguments for the program loader
# FIXME: perhaps this should do the same trick as elf/start.c?
# Call _dl_start with one parameter pointing at argc
mr 3,1
# (we have to frob the stack pointer a bit to allow room for
# _dl_start to save the link register)
li 4,0
addi 1,1,-16
stw 4,0(1)
bl _dl_start@local
# Now, we do our main work of calling initialisation procedures.
# The ELF ABI doesn't say anything about parameters for these,
# so we just pass argc, argv, and the environment.
# Changing these is strongly discouraged (not least because argc is
# passed by value!).
# put our GOT pointer in r31
bl _GLOBAL_OFFSET_TABLE_-4@local
mflr 31
# the address of _start in r30
mr 30,3
# &_dl_argc in 29, &_dl_argv in 27, and _dl_default_scope in 28
lwz 28,_dl_default_scope@got(31)
lwz 29,_dl_argc@got(31)
lwz 27,_dl_argv@got(31)
0:
# call initfunc = _dl_init_next(_dl_default_scope[2])
lwz 3,8(28)
bl _dl_init_next@plt
# if initfunc is NULL, we exit the loop
mr. 0,3
beq 1f
# call initfunc(_dl_argc, _dl_argv, _dl_argv+_dl_argc+1)
mtlr 0
lwz 3,0(29)
lwz 4,0(27)
slwi 5,3,2
add 5,4,5
addi 5,5,4
blrl
# and loop.
b 0b
1:
# Now, to conform to the ELF ABI, we have to:
# pass argv (actually _dl_argv) in r4
lwz 4,0(27)
# pass argc (actually _dl_argc) in r3
lwz 3,0(29)
# pass envp (actually _dl_argv+_dl_argc+1) in r5
slwi 5,3,2
add 5,4,5
addi 5,5,4
# pass the auxilary vector in r6. This is passed just after _envp.
addi 6,5,-4
2: lwzu 0,4(6)
cmpwi 1,0,0
bne 2b
addi 6,6,4
# pass a termination function pointer (in this case _dl_fini) in r7
lwz 7,_dl_fini@got(31)
# now, call the start function in r30...
mtctr 30
# pass the stack pointer in r1 (so far so good), pointing to a NULL value
# (this lets our startup code distinguish between a program linked statically,
# which linux will call with argc on top of the stack which will hopefully
# never be zero, and a dynamically linked program which will always have
# a NULL on the top of the stack).
# Take the opportunity to clear LR, so anyone who accidentally returns
# from _start gets SEGV.
li 0,0
stw 0,0(1)
mtlr 0
# and also clear _dl_starting_up
lwz 26,_dl_starting_up@got(31)
stw 0,0(26)
# go do it!
bctr
0:
.size _start,0b-_start
# undo '.section text'.
.previous
");
/* The idea here is that to conform to the ABI, we are supposed to try
to load dynamic objects between 0x10000 (we actually use 0x40000 as
the lower bound, to increase the chance of a memory reference from
a null pointer giving a segfault) and the program's load address.
Regrettably, in this code we can't find the program's load address,
so we punt and choose 0x01800000, which is below the ABI's
recommended default, and what GNU ld currently chooses. We only use
the address as a preference for mmap, so if we get it wrong the
worst that happens is that it gets mapped somewhere else.
FIXME: Unfortunately, 'somewhere else' is probably right after the
program's break, which causes malloc to fail. We really need more
information here about the way memory is mapped. */
#define ELF_PREFERRED_ADDRESS_DATA \
static ElfW(Addr) _dl_preferred_address = 1;
#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
( { \
ElfW(Addr) prefd; \
if (mapstartpref != 0 && _dl_preferred_address == 1) \
_dl_preferred_address = mapstartpref; \
if (mapstartpref != 0) \
prefd = mapstartpref; \
else if (_dl_preferred_address == 1) \
prefd = _dl_preferred_address = \
(0x01800000 - maplength - 0x10000) & \
~(_dl_pagesize - 1); \
else if (_dl_preferred_address < maplength + 0x50000) \
prefd = 0; \
else \
prefd = _dl_preferred_address = \
((_dl_preferred_address - maplength - 0x10000) \
& ~(_dl_pagesize - 1)); \
prefd; \
} )
#define ELF_FIXED_ADDRESS(loader, mapstart) \
( { \
if (mapstart != 0 && _dl_preferred_address == 1) \
_dl_preferred_address = mapstart; \
} )
#define ELF_FIXUP_RETURNS_ADDRESS 1