relocate()
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const R_AMD64_RELATIVE = 8;
const R_386_RELATIVE = 8;
const R_ARC_RELATIVE = 56;
const R_ARM_RELATIVE = 23;
const R_AARCH64_RELATIVE = 1027;
const R_CSKY_RELATIVE = 9;
const R_HEXAGON_RELATIVE = 35;
const R_LARCH_RELATIVE = 3;
const R_68K_RELATIVE = 22;
const R_MIPS_RELATIVE = 128;
const R_PPC_RELATIVE = 22;
const R_RISCV_RELATIVE = 3;
const R_390_RELATIVE = 12;
const R_SPARC_RELATIVE = 22;
const R_RELATIVE = switch (builtin.cpu.arch) {
.x86 => R_386_RELATIVE,
.x86_64 => R_AMD64_RELATIVE,
.arc => R_ARC_RELATIVE,
.arm, .armeb, .thumb, .thumbeb => R_ARM_RELATIVE,
.aarch64, .aarch64_be => R_AARCH64_RELATIVE,
.csky => R_CSKY_RELATIVE,
.hexagon => R_HEXAGON_RELATIVE,
.loongarch32, .loongarch64 => R_LARCH_RELATIVE,
.m68k => R_68K_RELATIVE,
.mips, .mipsel, .mips64, .mips64el => R_MIPS_RELATIVE,
.powerpc, .powerpcle, .powerpc64, .powerpc64le => R_PPC_RELATIVE,
.riscv32, .riscv64 => R_RISCV_RELATIVE,
.s390x => R_390_RELATIVE,
.sparc, .sparc64 => R_SPARC_RELATIVE,
else => @compileError("Missing R_RELATIVE definition for this target"),
};
// Obtain a pointer to the _DYNAMIC array.
// We have to compute its address as a PC-relative quantity not to require a
// relocation that, at this point, is not yet applied.
inline fn getDynamicSymbol() [*]elf.Dyn {
return switch (builtin.cpu.arch) {
.x86 => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ call 1f
\\ 1: pop %[ret]
\\ lea _DYNAMIC-1b(%[ret]), %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
),
.x86_64 => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ lea _DYNAMIC(%%rip), %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
),
.arc => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ add %[ret], pcl, _DYNAMIC@pcl
: [ret] "=r" (-> [*]elf.Dyn),
),
// Work around the limited offset range of `ldr`
.arm, .armeb, .thumb, .thumbeb => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ ldr %[ret], 1f
\\ add %[ret], pc
\\ b 2f
\\ 1: .word _DYNAMIC-1b
\\ 2:
: [ret] "=r" (-> [*]elf.Dyn),
),
// A simple `adr` is not enough as it has a limited offset range
.aarch64, .aarch64_be => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ adrp %[ret], _DYNAMIC
\\ add %[ret], %[ret], #:lo12:_DYNAMIC
: [ret] "=r" (-> [*]elf.Dyn),
),
// The CSKY ABI requires the gb register to point to the GOT. Additionally, the first
// entry in the GOT is defined to hold the address of _DYNAMIC.
.csky => asm volatile (
\\ mov %[ret], gb
\\ ldw %[ret], %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
),
.hexagon => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ jump 1f
\\ .word _DYNAMIC - .
\\ 1:
\\ r1 = pc
\\ r1 = add(r1, #-4)
\\ %[ret] = memw(r1)
\\ %[ret] = add(r1, %[ret])
: [ret] "=r" (-> [*]elf.Dyn),
:
: "r1"
),
.loongarch32, .loongarch64 => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ la.local %[ret], _DYNAMIC
: [ret] "=r" (-> [*]elf.Dyn),
),
// Note that the - 8 is needed because pc in the second lea instruction points into the
// middle of that instruction. (The first lea is 6 bytes, the second is 4 bytes.)
.m68k => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ lea _DYNAMIC - . - 8, %[ret]
\\ lea (%[ret], %%pc), %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
),
.mips, .mipsel => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ bal 1f
\\ .gpword _DYNAMIC
\\ 1:
\\ lw %[ret], 0($ra)
\\ addu %[ret], %[ret], $gp
: [ret] "=r" (-> [*]elf.Dyn),
:
: "lr"
),
.mips64, .mips64el => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ .balign 8
\\ bal 1f
\\ .gpdword _DYNAMIC
\\ 1:
\\ ld %[ret], 0($ra)
\\ daddu %[ret], %[ret], $gp
: [ret] "=r" (-> [*]elf.Dyn),
:
: "lr"
),
.powerpc, .powerpcle => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ bl 1f
\\ .long _DYNAMIC - .
\\ 1:
\\ mflr %[ret]
\\ lwz 4, 0(%[ret])
\\ add %[ret], 4, %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
:
: "lr", "r4"
),
.powerpc64, .powerpc64le => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ bl 1f
\\ .quad _DYNAMIC - .
\\ 1:
\\ mflr %[ret]
\\ ld 4, 0(%[ret])
\\ add %[ret], 4, %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
:
: "lr", "r4"
),
.riscv32, .riscv64 => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ lla %[ret], _DYNAMIC
: [ret] "=r" (-> [*]elf.Dyn),
),
.s390x => asm volatile (
\\ .weak _DYNAMIC
\\ .hidden _DYNAMIC
\\ larl %[ret], 1f
\\ ag %[ret], 0(%[ret])
\\ jg 2f
\\ 1: .quad _DYNAMIC - .
\\ 2:
: [ret] "=r" (-> [*]elf.Dyn),
),
// The compiler does not necessarily have any obligation to load the `l7` register (pointing
// to the GOT), so do it ourselves just in case.
.sparc, .sparc64 => asm volatile (
\\ sethi %%hi(_GLOBAL_OFFSET_TABLE_ - 4), %%l7
\\ call 1f
\\ add %%l7, %%lo(_GLOBAL_OFFSET_TABLE_ + 4), %%l7
\\ 1:
\\ add %%l7, %%o7, %[ret]
: [ret] "=r" (-> [*]elf.Dyn),
),
else => {
@compileError("PIE startup is not yet supported for this target!");
},
};
}
pub fn relocate(phdrs: []elf.Phdr) void {
@setRuntimeSafety(false);
@disableInstrumentation();
const dynv = getDynamicSymbol();
// Recover the delta applied by the loader by comparing the effective and
// the theoretical load addresses for the `_DYNAMIC` symbol.
const base_addr = base: {
for (phdrs) |*phdr| {
if (phdr.p_type != elf.PT_DYNAMIC) continue;
break :base @intFromPtr(dynv) - phdr.p_vaddr;
}
// This is not supposed to happen for well-formed binaries.
@trap();
};
var sorted_dynv: [elf.DT_NUM]elf.Addr = undefined;
// Zero-initialized this way to prevent the compiler from turning this into
// `memcpy` or `memset` calls (which can require relocations).
for (&sorted_dynv) |*dyn| {
const pdyn: *volatile elf.Addr = @ptrCast(dyn);
pdyn.* = 0;
}
{
// `dynv` has no defined order. Fix that.
var i: usize = 0;
while (dynv[i].d_tag != elf.DT_NULL) : (i += 1) {
if (dynv[i].d_tag < elf.DT_NUM) sorted_dynv[@bitCast(dynv[i].d_tag)] = dynv[i].d_val;
}
}
// Deal with the GOT relocations that MIPS uses first.
if (builtin.cpu.arch.isMIPS()) {
const count: elf.Addr = blk: {
// This is an architecture-specific tag, so not part of `sorted_dynv`.
var i: usize = 0;
while (dynv[i].d_tag != elf.DT_NULL) : (i += 1) {
if (dynv[i].d_tag == elf.DT_MIPS_LOCAL_GOTNO) break :blk dynv[i].d_val;
}
break :blk 0;
};
const got: [*]usize = @ptrFromInt(base_addr + sorted_dynv[elf.DT_PLTGOT]);
for (0..count) |i| {
got[i] += base_addr;
}
}
// Apply normal relocations.
const rel = sorted_dynv[elf.DT_REL];
if (rel != 0) {
const rels = @call(.always_inline, std.mem.bytesAsSlice, .{
elf.Rel,
@as([*]u8, @ptrFromInt(base_addr + rel))[0..sorted_dynv[elf.DT_RELSZ]],
});
for (rels) |r| {
if (r.r_type() != R_RELATIVE) continue;
@as(*usize, @ptrFromInt(base_addr + r.r_offset)).* += base_addr;
}
}
const rela = sorted_dynv[elf.DT_RELA];
if (rela != 0) {
const relas = @call(.always_inline, std.mem.bytesAsSlice, .{
elf.Rela,
@as([*]u8, @ptrFromInt(base_addr + rela))[0..sorted_dynv[elf.DT_RELASZ]],
});
for (relas) |r| {
if (r.r_type() != R_RELATIVE) continue;
@as(*usize, @ptrFromInt(base_addr + r.r_offset)).* = base_addr + @as(usize, @bitCast(r.r_addend));
}
}
const relr = sorted_dynv[elf.DT_RELR];
if (relr != 0) {
const relrs = @call(.always_inline, std.mem.bytesAsSlice, .{
elf.Relr,
@as([*]u8, @ptrFromInt(base_addr + relr))[0..sorted_dynv[elf.DT_RELRSZ]],
});
var current: [*]usize = undefined;
for (relrs) |r| {
if ((r & 1) == 0) {
current = @ptrFromInt(base_addr + r);
current[0] += base_addr;
current += 1;
} else {
// Skip the first bit; there are 63 locations in the bitmap.
var i: if (@sizeOf(usize) == 8) u6 else u5 = 1;
while (i < @bitSizeOf(elf.Relr)) : (i += 1) {
if (((r >> i) & 1) != 0) current[i] += base_addr;
}
current += @bitSizeOf(elf.Relr) - 1;
}
}
}
}
|
zig/lib/std /
os/linux/pie.zig