find_pdb_path.c

#define UNICODE
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define WIN32_LEAN_AND_MEAN
#include <windows.h>

static void free_pdb_path(wchar_t* path) {
    free(path);
}

// freed with free_pdb_path
static wchar_t* find_pdb(char* image_base) {
    if (image_base == NULL) {
        return NULL;
    }

    // we expect a DOS header
    char* ptr = image_base;
    if (memcmp(ptr, "MZ", 2) == 0) {
        // we'll find the pointer to the PE header at the end of the DOS header
        ptr = image_base + *((uint32_t*) (ptr + 60));
    }

    if (memcmp(ptr, "PE\0\0", 4) != 0) {
        fprintf(stderr, "error: no PE header! got %.*s\n", 4, ptr);
        return NULL;
    }

    IMAGE_NT_HEADERS64* nt = (IMAGE_NT_HEADERS64*) ptr;

    // debug directory is [6]
    IMAGE_DEBUG_DIRECTORY* debug_dir = (IMAGE_DEBUG_DIRECTORY*) (image_base + nt->OptionalHeader.DataDirectory[6].VirtualAddress);
    if (debug_dir->Type != IMAGE_DEBUG_TYPE_CODEVIEW) {
        return NULL;
    }

    size_t debug_section_size = debug_dir->SizeOfData;
    char* debug_section = image_base + debug_dir->AddressOfRawData;

    if (debug_section_size <= 24) {
        fprintf(stderr, "error: Executable image doesn't have a PDB file!");
        return NULL;
    }

    char* path = debug_section + 24;

    wchar_t* output = malloc(FILENAME_MAX * sizeof(wchar_t));
    MultiByteToWideChar(CP_UTF8, 0, path, -1, output, FILENAME_MAX);
    return output;
}

int wmain(int argc, wchar_t** argv) {
    char* image_base = NULL;
    if (argc >= 2) {
        image_base = (char*) GetModuleHandle(argv[1]);

        if (image_base == NULL) {
            // if it wasn't loaded already, load it now
            printf("Loading %S...\n", argv[1]);
            image_base = (char*) LoadLibrary(argv[1]);

            if (image_base == NULL) {
                printf("Could not load %S\n", argv[1]);
                return 1;
            }
        }
    } else {
        image_base = (char*) GetModuleHandle(NULL);
    }

    wchar_t* pdb_path = find_pdb(image_base);
    if (pdb_path == NULL) {
        printf("PDB path could not be found!");
        return 1;
    }

    printf("PDB path is at: %S\n", pdb_path);
    free_pdb_path(pdb_path);
    return 0;
}