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A start.o compiled from start.S with -DPIC and no -DSHARED is used by
both crt1.o and rcrt1.o. So the LoongArch static PIE patch
unintentionally introduced PC-relative addressing for main and
__libc_start_main into crt1.o.
While the latest Binutils (trunk, which will be released as 2.40)
supports the PC-relative relocs against an external function by creating
a PLT entry, the 2.39 release branch doesn't (and won't) support this.
An error is raised:
"PLT stub does not represent and symbol not defined."
So, we need the following changes:
1. Check if ld supports the PC-relative relocs against an external
function. If it's not supported, we deem static PIE unsupported.
2. Change start.S. If static PIE is supported, use PC-relative
addressing for main and __libc_start_main and rely on the linker to
create PLT entries. Otherwise, restore the old behavior (using GOT
to address these functions).
An alternative would be adding a new "static-pie-start.S", and some
custom logic into Makefile to build rcrt1.o with it. And, restore
start.S to the state before static PIE change so crt1.o won't contain
PC-relative relocs against external symbols. But I can't see any
benefit of this alternative, so I'd just keep it simple.
Tested by building glibc with the following configurations:
1. Binutils trunk + GCC trunk. Static PIE enabled. All tests
passed.
2. Binutils 2.39 branch + GCC trunk. Static PIE disabled. Tests
related to ifunc failed (it's a known issue). All other tests
passed.
3. Binutils 2.39 branch + GCC 12 branch, cross compilation with
build-many-glibcs.py from x86_64-linux-gnu. Static PIE disabled.
Build succeeded.
93 lines
3.2 KiB
ArmAsm
93 lines
3.2 KiB
ArmAsm
/* Startup code compliant to the ELF LoongArch ABI.
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Copyright (C) 2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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In addition to the permissions in the GNU Lesser General Public
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License, the Free Software Foundation gives you unlimited
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permission to link the compiled version of this file with other
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programs, and to distribute those programs without any restriction
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coming from the use of this file. (The GNU Lesser General Public
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License restrictions do apply in other respects; for example, they
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cover modification of the file, and distribution when not linked
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into another program.)
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Note that people who make modified versions of this file are not
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obligated to grant this special exception for their modified
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versions; it is their choice whether to do so. The GNU Lesser
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General Public License gives permission to release a modified
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version without this exception; this exception also makes it
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possible to release a modified version which carries forward this
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exception.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define __ASSEMBLY__ 1
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#include <entry.h>
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#include <sys/asm.h>
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/* The entry point's job is to call __libc_start_main. Per the ABI,
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a0 contains the address of a function to be passed to atexit.
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__libc_start_main wants this in a5. */
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/*
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int
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__libc_start_main (int (*main) (int, char **, char **),
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int argc,
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char **argv,
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__typeof (main) init,
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void (*fini) (void),
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void (*rtld_fini) (void),
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void *stack_end);
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*/
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ENTRY (ENTRY_POINT)
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/* Terminate call stack by noting ra is undefined. Use a dummy
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.cfi_label to force starting the FDE. */
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.cfi_label .Ldummy
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cfi_undefined (1)
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or a5, a0, zero /* rtld_fini */
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#if ENABLE_STATIC_PIE
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/* For static PIE, the GOT cannot be used in _start because the GOT entries are
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offsets instead of real addresses before __libc_start_main.
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__libc_start_main and/or main may be not local, so we rely on the linker to
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produce PLT entries for them. GNU ld >= 2.40 supports this. */
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# define LA la.pcrel
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#else
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/* Old GNU ld (< 2.40) cannot handle PC relative address against a non-local
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function correctly. We deem these old linkers failing to support static PIE
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and load the addresses from GOT. */
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# define LA la.got
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#endif
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LA a0, t0, main
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REG_L a1, sp, 0
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ADDI a2, sp, SZREG
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/* Adjust $sp for 16-aligned */
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BSTRINS sp, zero, 3, 0
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move a3, zero /* used to be init */
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move a4, zero /* used to be fini */
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or a6, sp, zero /* stack_end */
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LA ra, t0, __libc_start_main
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jirl ra, ra, 0
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LA ra, t0, abort
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jirl ra, ra, 0
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END (ENTRY_POINT)
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