this repo has no description
Add support code needed for gdb-darling
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platform-include/mach-o/dyld_images.h
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platform-include/mach-o/dyld_images.h
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#include <stdbool.h>
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#include <unistd.h>
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#ifndef MLDR_BUILD
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#include <mach/mach.h>
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#else
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#include <stdint.h>
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#endif
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#ifdef __cplusplus
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extern "C" {
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/* then file has been modified since dyld loaded it */
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};
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#ifndef MLDR_BUILD
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struct dyld_uuid_info {
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const struct mach_header* imageLoadAddress; /* base address image is mapped into */
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uuid_t imageUUID; /* UUID of image */
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};
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#endif
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typedef void (*dyld_image_notifier)(enum dyld_image_mode mode, uint32_t infoCount, const struct dyld_image_info info[]);
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src/dyld/CMakeLists.txt
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src/dyld/CMakeLists.txt
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enable_language(C ASM)
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c11")
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add_definitions(-DINSTALL_PREFIX="${CMAKE_INSTALL_PREFIX}" -D_GNU_SOURCE)
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c11 -ggdb")
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add_definitions(-DINSTALL_PREFIX="${CMAKE_INSTALL_PREFIX}" -D_GNU_SOURCE -DMLDR_BUILD)
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add_executable(darling darling.c)
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···
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set(mldr_sources
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mldr.c
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threads.c
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gdb.c
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)
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add_executable(mldr ${mldr_sources})
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target_link_libraries(mldr -lpthread -ldl)
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src/dyld/gdb.c
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src/dyld/gdb.c
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#include "gdb.h"
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#include <string.h>
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#include <stdio.h>
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__attribute__ ((noinline))
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static void gdb_notifier(enum dyld_image_mode mode, uint32_t infoCount, const struct dyld_image_info info[]);
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static void dyld_notification_wrapper(enum dyld_image_mode mode, uint32_t infoCount, const struct dyld_image_info info[]);
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static struct dyld_all_image_infos* orig_dyld_all_image_infos;
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// This is the symbol GDB looks for
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struct dyld_all_image_infos _dyld_all_image_infos = {
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.version = 15,
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.infoArrayCount = 0,
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.infoArray = NULL,
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.notification = &gdb_notifier,
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};
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void gdb_notifier(enum dyld_image_mode mode, uint32_t infoCount, const struct dyld_image_info info[])
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{
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// GDB sets a breakpoint in this function
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}
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struct jump
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{
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uint16_t mov;
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void* addr;
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uint16_t jump;
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} __attribute__ ((packed));
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void setup_gdb_notifications(uint64_t slide, uint64_t addr)
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{
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orig_dyld_all_image_infos = (struct dyld_all_image_infos*)(addr + slide);
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// dyld will later rebase the address in notification,
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// but at this point we must add slide manually.
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struct jump* jump = (struct jump*)(((uint64_t)orig_dyld_all_image_infos->notification) + slide);
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// Rewrite instructions in the notification function to redirect the call to us.
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#ifdef __x86_64__
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jump->mov = 0xb948; // movabs imm,%rcx
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jump->addr = (void*) &dyld_notification_wrapper; // immediate for preceding movabs
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jump->jump = 0xe1ff; // jmpq *%ecx
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#else
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# error TODO: Unsupported platform
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#endif
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}
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void dyld_notification_wrapper(enum dyld_image_mode mode, uint32_t infoCount, const struct dyld_image_info info[])
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{
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// Copy over all data from dyld's copy of the structure to the one GDB can find (ours)
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memcpy(&_dyld_all_image_infos, orig_dyld_all_image_infos, sizeof(_dyld_all_image_infos));
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_dyld_all_image_infos.notification = &gdb_notifier;
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printf("Got notification from dyld\n");
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gdb_notifier(mode, infoCount, info);
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}
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+9
src/dyld/gdb.h
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src/dyld/gdb.h
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src/dyld/mldr.c
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src/dyld/mldr.c
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#include <dlfcn.h>
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#include "elfcalls.h"
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#include "threads.h"
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#include "gdb.h"
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#ifndef PAGE_SIZE
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# define PAGE_SIZE 4096
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if (seg->fileoff == 0)
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mappedHeader = (struct mach_header_64*) (seg->vmaddr + slide);
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}
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if (strcmp(SEG_DATA, seg->segname) == 0)
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{
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// Look for section named __all_image_info for GDB integration
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struct section_64* sect = (struct section_64*) (seg+1);
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struct section_64* end = (struct section_64*) (&cmds[p + lc->cmdsize]);
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while (sect < end)
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{
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if (strncmp(sect->sectname, "__all_image_info", 16) == 0)
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{
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setup_gdb_notifications(slide, sect->addr);
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break;
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}
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sect++;
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}
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}
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break;
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}