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ld: implement support for exposing ld functions to loaded executables

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This commit is contained in:
max 🍓
2026-05-30 10:17:43 +01:00
parent ce52afe5b4
commit 08abe467ea
12 changed files with 425 additions and 59 deletions
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sys/ld/CMakeLists.txt
+4
View File
@@ -12,8 +12,12 @@ target_link_libraries(ld
interface::fs)
target_compile_options(ld PRIVATE
-fvisibility=hidden
-fPIC -fno-stack-protector -nostdlib -ffreestanding)
target_link_options(ld PRIVATE
-fvisibility=hidden -Wl,--exclude-libs,ALL
# -Wl,--entry="_ld_start"
-T ${CMAKE_CURRENT_SOURCE_DIR}/arch/${CMAKE_SYSTEM_PROCESSOR}/layout.ld
-fPIC -nostdlib -ffreestanding -Wl,-shared)
sysroot_add_program(
sys/ld/arch/x86_64/layout.ld
+249 -23
View File
@@ -1,30 +1,256 @@
ENTRY(_start)
SECTIONS {
.text ALIGN(4K) : {
*(.text)
*(.rodata)
/* Copyright (C) 2014-2025 Free Software Foundation, Inc.
Copying and distribution of this script, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. */
OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
OUTPUT_ARCH(i386:x86-64)
ENTRY(_ld_start)
SECTIONS
{
/* Read-only sections, merged into text segment: */
PROVIDE(_ld_image_base = . + 1024);
. = SEGMENT_START("text-segment", 0) + SIZEOF_HEADERS;
/* Place the build-id as close to the ELF headers as possible. This
maximises the chance the build-id will be present in core files,
which GDB can then use to locate the associated debuginfo file. */
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*(.rela.init)
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/* Start of the executable code region. */
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KEEP (*(SORT_NONE(.init)))
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*(.tdata .tdata.* .gnu.linkonce.td.*)
}
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.preinit_array :
{
KEEP (*(.preinit_array))
}
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{
KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
}
.fini_array :
{
KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
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/* gcc uses crtbegin.o to find the start of
the constructors, so we make sure it is
first. Because this is a wildcard, it
doesn't matter if the user does not
actually link against crtbegin.o; the
linker won't look for a file to match a
wildcard. The wildcard also means that it
doesn't matter which directory crtbegin.o
is in. */
KEEP (*crtbegin.o(.ctors))
KEEP (*crtbegin?.o(.ctors))
/* We don't want to include the .ctor section from
the crtend.o file until after the sorted ctors.
The .ctor section from the crtend file contains the
end of ctors marker and it must be last */
KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
KEEP (*(SORT(.ctors.*)))
KEEP (*(.ctors))
}
.dtors :
{
KEEP (*crtbegin.o(.dtors))
KEEP (*crtbegin?.o(.dtors))
KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
KEEP (*(SORT(.dtors.*)))
KEEP (*(.dtors))
}
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. = DATA_SEGMENT_RELRO_END (SIZEOF (.got.plt) >= 24 ? 24 : 0, .);
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{
*(.data .data.* .gnu.linkonce.d.*)
SORT(CONSTRUCTORS)
}
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PROVIDE (_edata = .);
PROVIDE (edata = .);
. = ALIGN(ALIGNOF(NEXT_SECTION));
PROVIDE (__bss_start = .);
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*(COMMON)
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type of .bss section, the section occupies space up to _end.
Align after .bss to ensure correct alignment even if the
.bss section disappears because there are no input sections.
FIXME: Why do we need it? When there is no .bss section, we do not
pad the .data section. */
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}
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*(.dynlbss)
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}
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. = ALIGN(. != 0 ? 64 / 8 : 1);
}
. = ALIGN(64 / 8);
PROVIDE (_end = .);
PROVIDE (end = .);
PROVIDE(_ld_image_limit = .);
. = DATA_SEGMENT_END (.);
/* Start of the Tiny Data region. */
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
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Symbols in the DWARF debugging sections are relative to the beginning
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.gnu.attributes 0 : { KEEP (*(.gnu.attributes)) }
/DISCARD/ : { *(.note.GNU-stack) *(.gnu_debuglink) *(.gnu.lto_*) *(.gnu_object_only) }
}
sys/ld/arch/x86_64/start.S
+6 -3
View File
@@ -1,7 +1,7 @@
.code64
.global _start
.type _start, @function
.global _ld_start
.type _ld_start, @function
.extern main
.type main, @function
@@ -9,7 +9,10 @@
.extern task_exit
.type task_exit, @function
_start:
_ld_start:
nop
mov $0xFFFFFFFF, %rbp
call main
mov %rax, %rdi
call task_exit
sys/ld/elf.c
+28 -9
View File
@@ -6,10 +6,10 @@
#include <errno.h>
#include <fcntl.h>
#include <mango/config.h>
#include <mango/handle.h>
#include <mango/log.h>
#include <mango/vm.h>
#include <magenta/config.h>
#include <magenta/handle.h>
#include <magenta/log.h>
#include <magenta/vm.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
@@ -112,14 +112,17 @@ static int map_image(struct elf_image *image)
int r = read(image->e_fd, &phdr, sizeof phdr);
if (r < 0) {
kern_tracef("PHDR read failed");
return -r;
}
if (r != sizeof phdr) {
kern_tracef("PHDR bad size");
return ENOEXEC;
}
if (phdr.p_type != PT_LOAD) {
kern_tracef("PHDR != PT_LOAD");
continue;
}
@@ -163,7 +166,8 @@ static int map_image(struct elf_image *image)
fd,
offset);
if (p == MAP_FAILED) {
return EIO;
kern_tracef("PHDR map failed (%d)", errno);
return errno;
}
kern_tracef(
@@ -184,6 +188,8 @@ static int map_image(struct elf_image *image)
}
}
close(image->e_fd);
image->e_fd = -1;
kern_tracef("ld: image %s -> %zx", image->e_leaf.l_name, image->e_base);
return SUCCESS;
}
@@ -274,23 +280,27 @@ static void resolve_symbol(unsigned int slot)
static int do_rela(struct elf_image *image, elf_rela_t *rela, bool lazy)
{
#if 0
kern_tracef(
"do_rela(%p, %d, %d, %d)",
image,
rela->r_info,
rela->r_addend,
rela->r_offset);
#endif
int type = ELF64_R_TYPE(rela->r_info);
elf_sym_t *sym = NULL;
switch (type) {
case R_X86_64_JUMP_SLOT:
*(uint64_t *)(image->e_base + rela->r_offset) += image->e_base;
#if 0
kern_tracef(
"JUMP_SLOT: offset=%zx, symbol=%zu, addend=%zx",
rela->r_offset,
ELF64_R_SYM(rela->r_info),
rela->r_addend);
#endif
break;
case R_X86_64_GLOB_DAT:
sym = get_dynsym(image, ELF64_R_SYM(rela->r_info));
@@ -300,11 +310,13 @@ static int do_rela(struct elf_image *image, elf_rela_t *rela, bool lazy)
*(uint64_t *)(image->e_base + rela->r_offset)
= image->e_base + sym->st_value + rela->r_addend;
#if 0
kern_tracef(
"GLOB_DAT: offset=%zx, symbol=%zu, addend=%zx",
rela->r_offset,
ELF64_R_SYM(rela->r_info),
rela->r_addend);
#endif
break;
case R_X86_64_64:
sym = get_dynsym(image, ELF64_R_SYM(rela->r_info));
@@ -314,19 +326,23 @@ static int do_rela(struct elf_image *image, elf_rela_t *rela, bool lazy)
*(uint64_t *)(image->e_base + rela->r_offset)
= image->e_base + sym->st_value + rela->r_addend;
#if 0
kern_tracef(
"64: offset=%zx, symbol=%zu, addend=%zx",
rela->r_offset,
ELF64_R_SYM(rela->r_info),
rela->r_addend);
#endif
break;
case R_X86_64_RELATIVE:
*(uint64_t *)(image->e_base + rela->r_offset)
= image->e_base + rela->r_addend;
#if 0
kern_tracef(
"RELATIVE: offset=%zx, addend=%zx",
rela->r_offset,
rela->r_addend);
#endif
break;
default:
kern_trace("Unknown relocation type");
@@ -409,13 +425,14 @@ static int load_dependency(struct elf_image *image, const char *name)
return ENOEXEC;
}
static int parse_dynamic(struct elf_image *image)
int elf_image_parse_dynamic(struct elf_image *image)
{
if (image->e_dynamic.p_type != PT_DYNAMIC) {
return SUCCESS;
}
image->e_dyn = (elf_dyn_t *)(image->e_base + image->e_dynamic.p_vaddr);
kern_tracef("%s .dynamic = %zx", image->e_leaf.l_name, image->e_dyn);
int status = SUCCESS;
@@ -507,8 +524,9 @@ static int parse_dynamic(struct elf_image *image)
static int reserve_exec_region(struct elf_image *image)
{
static virt_addr_t next_base = 0x10000000;
void *base
= mmap(NULL,
= mmap((void *)next_base,
image->e_length,
PROT_NONE,
MAP_ANONYMOUS | MAP_PRIVATE,
@@ -518,6 +536,7 @@ static int reserve_exec_region(struct elf_image *image)
return ENOMEM;
}
next_base += 0x10000000;
image->e_base = (virt_addr_t)base;
return KERN_OK;
}
@@ -613,7 +632,7 @@ int elf_image_load(struct elf_image *img)
return e;
}
e = parse_dynamic(img);
e = elf_image_parse_dynamic(img);
if (e != SUCCESS) {
return e;
}
@@ -737,7 +756,7 @@ int elf_image_add_dependency(struct elf_image *img, struct elf_image *dep)
void elf_image_close(struct elf_image *image)
{
if (image->e_fd) {
if (image->e_fd != -1) {
close(image->e_fd);
}
sys/ld/elf.h
+2 -1
View File
@@ -3,7 +3,7 @@
#include "image-list.h"
#include <mango/types.h>
#include <magenta/types.h>
#include <stdint.h>
enum elf_image_status {
@@ -360,6 +360,7 @@ extern int elf_image_collect_dependencies(
extern int elf_image_add_dependency(
struct elf_image *img,
struct elf_image *dep);
extern int elf_image_parse_dynamic(struct elf_image *image);
extern int elf_image_link(struct elf_image *img);
extern void elf_image_close(struct elf_image *img);
sys/ld/exec.c
+35
View File
@@ -0,0 +1,35 @@
#include "self.h"
#include <errno.h>
#include <magenta/log.h>
LD_API int ld_execl(const char *path, const char *arg, ...)
{
return -ENOSYS;
}
LD_API int ld_execlp(const char *file, const char *arg, ...)
{
kern_log("ld_execlp()");
return -ENOSYS;
}
LD_API int ld_execle(const char *path, const char *arg, ...)
{
return -ENOSYS;
}
LD_API int ld_execv(const char *path, char *const argv[])
{
return -ENOSYS;
}
LD_API int ld_execvp(const char *file, char *const argv[])
{
return -ENOSYS;
}
LD_API int ld_execvpe(const char *file, char *const argv[], char *const envp[])
{
return -ENOSYS;
}
sys/ld/exec.h
+13
View File
@@ -0,0 +1,13 @@
#ifndef EXEC_H_
#define EXEC_H_
#include <stdarg.h>
extern int ld_execl(const char *path, const char *arg1, va_list arg);
extern int ld_execlp(const char *file, const char *arg1, va_list arg);
extern int ld_execle(const char *path, const char *arg1, va_list arg);
extern int ld_execv(const char *path, char *const argv[]);
extern int ld_execvp(const char *file, char *const argv[]);
extern int ld_execvpe(const char *file, char *const argv[], char *const envp[]);
#endif
sys/ld/image-list.c
+1 -1
View File
@@ -2,7 +2,7 @@
#include "hash.h"
#include <mango/log.h>
#include <magenta/log.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
sys/ld/main.c
+20 -13
View File
@@ -2,15 +2,16 @@
#define MSG_NO_MALLOC
#include "elf.h"
#include "self.h"
#include <errno.h>
#include <fcntl.h>
#include <heap/heap.h>
#include <mango/log.h>
#include <mango/msg.h>
#include <mango/task.h>
#include <mango/types.h>
#include <mango/vm.h>
#include <magenta/log.h>
#include <magenta/msg.h>
#include <magenta/task.h>
#include <magenta/types.h>
#include <magenta/vm.h>
#include <rosetta/bootstrap.h>
#include <rosetta/fs.h>
#include <stdarg.h>
@@ -101,7 +102,7 @@ static int load_images(const char *task_name, struct image_list *list)
report_error(
task_name,
status,
"error while loading %s",
"C error while loading %s",
image->e_leaf.l_name);
return status;
}
@@ -112,7 +113,7 @@ static int load_images(const char *task_name, struct image_list *list)
report_error(
task_name,
status,
"error while loading %s",
"B error while loading %s",
image->e_leaf.l_name);
return status;
}
@@ -123,8 +124,8 @@ static int load_images(const char *task_name, struct image_list *list)
report_error(
task_name,
status,
"error while loading %s",
image->e_leaf.l_name);
"A error while loading %s",
image);
return status;
}
case ELF_IMAGE_LOADED:
@@ -139,7 +140,7 @@ static int load_images(const char *task_name, struct image_list *list)
report_error(
task_name,
-new_dependencies,
"error while loading %s",
"F error while loading %s",
image->e_leaf.l_name);
return -new_dependencies;
}
@@ -174,7 +175,7 @@ static int link_images(const char *task_name, struct image_list *list)
report_error(
task_name,
status,
"error while loading %s",
"E error while loading %s",
image->e_leaf.l_name);
return status;
}
@@ -221,6 +222,9 @@ int main(const struct rosetta_bootstrap *bs)
const char *task_name = bs->bs_argv[2];
const char *image_name = get_image_name(exec_path);
kern_tracef("ld: exec_path=%s", exec_path);
kern_tracef("ld: task_name=%s", task_name);
image_list_init(&images);
struct elf_image *exec = NULL;
@@ -229,7 +233,7 @@ int main(const struct rosetta_bootstrap *bs)
report_error(
task_name,
err,
"error while loading %s",
"D error while loading %s",
exec_path);
return -1;
}
@@ -251,6 +255,9 @@ int main(const struct rosetta_bootstrap *bs)
return -1;
}
struct elf_image *self = get_self();
image_list_put(&images, &self->e_leaf);
struct image_list_iterator it;
image_list_iterator_begin(&it, &images);
@@ -265,7 +272,7 @@ int main(const struct rosetta_bootstrap *bs)
image_list_iterator_move_next(&it);
}
dump_loaded_images(&images);
// dump_loaded_images(&images);
kern_tracef("ld finished");
struct rosetta_bootstrap exec_bsinfo;
memcpy(&exec_bsinfo, bs, sizeof exec_bsinfo);
sys/ld/resolve.c
+7 -3
View File
@@ -1,6 +1,6 @@
#include "elf.h"
#include <mango/log.h>
#include <magenta/log.h>
#include <stdint.h>
#include <stdio.h>
@@ -13,11 +13,13 @@ uintptr_t dl_runtime_resolve(struct elf_image *img, unsigned long sym_id)
= (elf_rela_t *)((virt_addr_t)img->e_base
+ img->e_rel_offset[ELF_RT_PLTREL]);
elf_rela_t *rela_sym = &rela[sym_id];
#if 0
kern_tracef(
"rela %u -> .dynsym %u, .got %u",
sym_id,
ELF64_R_SYM(rela_sym->r_info),
slot_id);
#endif
sym_id = ELF64_R_SYM(rela_sym->r_info);
/* the first three entries in the GOT are not symbols. */
slot_id += 3;
@@ -34,18 +36,20 @@ uintptr_t dl_runtime_resolve(struct elf_image *img, unsigned long sym_id)
= (virt_addr_t *)((virt_addr_t)img->e_base + img->e_got_plt);
const char *sym_name = (const char *)img->e_base + img->e_strtab
+ sym[sym_id].st_name;
#if 0
kern_tracef(
"%s: request for symbol %u: %s",
img->e_leaf.l_name,
sym_id,
sym_name);
#endif
#if 0
virt_addr_t sym_addr = elf_image_find_linked_symbol(img, sym_name);
#else
virt_addr_t sym_addr = find_global_symbol(sym_name);
#endif
kern_tracef("symbol %s = %zx", sym_name, sym_addr);
kern_tracef("slot %s = %zx", sym_name, &got[slot_id]);
// kern_logf("symbol %s = %zx", sym_name, sym_addr);
// kern_tracef("slot %s = %zx", sym_name, &got[slot_id]);
got[slot_id] = sym_addr;
return sym_addr;
}
sys/ld/self.c
+44
View File
@@ -0,0 +1,44 @@
#include "elf.h"
#include <magenta/config.h>
#include <stdio.h>
#include <stdlib.h>
#define LD_NAME "ld64.so"
#define LD_IMAGE_BASE_OFFSET 1024
extern char _DYNAMIC[];
extern char _ld_image_base[];
extern char _ld_image_limit[];
struct elf_image *get_self(void)
{
struct elf_image *self = malloc(sizeof *self);
memset(self, 0x0, sizeof *self);
snprintf(
self->e_leaf.l_name,
sizeof self->e_leaf.l_name,
"%s",
LD_NAME);
kern_config_get(
KERN_CFG_PAGE_SIZE,
&self->e_page_size,
sizeof self->e_page_size);
self->e_base = (virt_addr_t)_ld_image_base - LD_IMAGE_BASE_OFFSET;
self->e_length = (virt_addr_t)_ld_image_limit - self->e_base;
if (self->e_length & (self->e_page_size - 1)) {
self->e_length &= ~(self->e_page_size - 1);
self->e_length += self->e_page_size;
}
self->e_dynamic.p_type = PT_DYNAMIC;
self->e_dynamic.p_align = 8;
self->e_dynamic.p_memsz = self->e_dynamic.p_filesz = (size_t)-1;
self->e_dynamic.p_vaddr = (virt_addr_t)_DYNAMIC - self->e_base;
elf_image_parse_dynamic(self);
return self;
}
sys/ld/self.h
+10
View File
@@ -0,0 +1,10 @@
#ifndef SELF_H_
#define SELF_H_
#define LD_API __attribute__((visibility("default")))
struct elf_image;
extern struct elf_image *get_self(void);
#endif