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+/* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
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+/* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */
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+
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+/* Copyright (C) 2014 OSCAR lab, Stony Brook University
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+ This file is part of Graphene Library OS.
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+
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+ Graphene Library OS is free software: you can redistribute it and/or
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+ modify it under the terms of the GNU General Public License
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+ as published by the Free Software Foundation, either version 3 of the
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+ License, or (at your option) any later version.
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+
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+ Graphene Library OS 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
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
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+
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+/*
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+ * dl-machine-x86_64.h
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+ *
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+ * This files contain architecture-specific implementation of ELF dynamic
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+ * relocation function.
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+ * The source code is imported and modified from the GNU C Library.
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+ */
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+
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+#define ELF_MACHINE_NAME "x86_64"
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+
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+#include <sys/param.h>
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+#include <sysdep.h>
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+#include <sysdeps/generic/ldsodefs.h>
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+#include "pal_internal.h"
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+
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+/* Return the link-time address of _DYNAMIC. Conveniently, this is the
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+ first element of the GOT. This must be inlined in a function which
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+ uses global data. */
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+static inline Elf64_Addr __attribute__ ((unused))
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+elf_machine_dynamic (void)
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+{
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+ Elf64_Addr addr;
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+
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+ /* This works because we have our GOT address available in the small PIC
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+ model. */
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+ addr = (Elf64_Addr) &_DYNAMIC;
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+
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+ return addr;
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+}
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+
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+/* Return the run-time load address of the shared object. */
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+static inline Elf64_Addr __attribute__ ((unused))
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+elf_machine_load_address (void)
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+{
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+ Elf64_Addr addr;
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+
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+ /* The easy way is just the same as on x86:
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+ leaq _dl_start, %0
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+ leaq _dl_start(%%rip), %1
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+ subq %0, %1
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+ but this does not work with binutils since we then have
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+ a R_X86_64_32S relocation in a shared lib.
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+
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+ Instead we store the address of _dl_start in the data section
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+ and compare it with the current value that we can get via
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+ an RIP relative addressing mode. Note that this is the address
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+ of _dl_start before any relocation performed at runtime. In case
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+ the binary is prelinked the resulting "address" is actually a
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+ load offset which is zero if the binary was loaded at the address
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+ it is prelinked for. */
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+
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+ asm ("leaq " XSTRINGIFY(_ENTRY) "(%%rip), %0\n\t"
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+ "subq 1f(%%rip), %0\n\t"
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+ ".section\t.data.rel.ro\n"
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+ "1:\t.quad " XSTRINGIFY(_ENTRY) "\n\t"
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+ ".previous\n\t"
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+ : "=r" (addr) : : "cc");
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+
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+ return addr;
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+}
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Chia-Che Tsai