// This file is a part of Julia. License is MIT: https://julialang.org/license

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#ifdef __GLIBC__
#include <link.h>
#endif

#include "platform.h"
#include "julia.h"
#include "julia_internal.h"
#ifdef _OS_WINDOWS_
#include <direct.h>
#else
#include <unistd.h>
#include <dlfcn.h>
#endif
#include "julia_assert.h"

#ifdef __cplusplus
extern "C" {
#endif

#if defined(__APPLE__)
static char const *const extensions[] = { "", ".dylib" };
#elif defined(_OS_WINDOWS_)
static char const *const extensions[] = { "", ".dll" };
extern volatile int needsSymRefreshModuleList;
#else
static char const *const extensions[] = { "", ".so" };
#endif
#define N_EXTENSIONS (sizeof(extensions) / sizeof(char*))

static int endswith_extension(const char *path) JL_NOTSAFEPOINT
{
    if (!path)
        return 0;
    size_t len = strlen(path);
    // Skip the first one since it is empty
    for (size_t i = 1; i < N_EXTENSIONS; i++) {
        const char *ext = extensions[i];
        size_t extlen = strlen(ext);
        if (len < extlen)
            return 0;
        // Skip version extensions if present
        size_t j = len - 1;
        while (j > 0) {
            if (path[j] == '.' || (path[j] >= '0' && path[j] <= '9'))
                j--;
            else
                break;
        }
        if ((j == len-1 || path[j+1] == '.') && memcmp(ext, path + j - extlen + 1, extlen) == 0) {
            return 1;
        }
    }
    return 0;
}

#ifdef _OS_WINDOWS_
#define CRTDLL_BASENAME "msvcrt"

JL_DLLEXPORT const char *jl_crtdll_basename = CRTDLL_BASENAME;
const char *jl_crtdll_name = CRTDLL_BASENAME ".dll";

#undef CRTDLL_BASENAME
#endif

#ifdef _OS_WINDOWS_
void win32_formatmessage(DWORD code, char *reason, int len) JL_NOTSAFEPOINT
{
    DWORD res;
    LPWSTR errmsg;
    res = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                         FORMAT_MESSAGE_FROM_SYSTEM |
                         FORMAT_MESSAGE_IGNORE_INSERTS |
                         FORMAT_MESSAGE_MAX_WIDTH_MASK,
                         NULL, code,
                         MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US),
                         (LPWSTR)&errmsg, 0, NULL);
    if (!res && (GetLastError() == ERROR_MUI_FILE_NOT_FOUND ||
                 GetLastError() == ERROR_RESOURCE_TYPE_NOT_FOUND)) {
      res = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                           FORMAT_MESSAGE_FROM_SYSTEM |
                           FORMAT_MESSAGE_IGNORE_INSERTS |
                           FORMAT_MESSAGE_MAX_WIDTH_MASK,
                           NULL, code,
                           0, (LPWSTR)&errmsg, 0, NULL);
    }
    char *buf = reason;
    size_t buflen = len - 1;
    int err = uv_utf16_to_wtf8((uint16_t*)errmsg, -1, &buf, &buflen);
    assert(err == 0 || err == UV_ENOBUFS); (void)err;
    LocalFree(errmsg);
}
#endif

typedef void* (*dlopen_prototype)(const char* filename, int flags) JL_NOTSAFEPOINT;

#if defined(_COMPILER_MSAN_ENABLED_) || defined(_COMPILER_ASAN_ENABLED_) || defined(_COMPILER_TSAN_ENABLED_)
struct link_map;

/* This function is copied from the memory sanitizer runtime.
   Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   See https://llvm.org/LICENSE.txt for license information.
   SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
*/
static inline uintptr_t RoundUpTo(uintptr_t size, uintptr_t boundary) {
  return (size + boundary - 1) & ~(boundary - 1);
}
static inline uintptr_t RoundDownTo(uintptr_t x, uintptr_t boundary) {
  return x & ~(boundary - 1);
}
void ForEachMappedRegion(struct link_map *map, void (*cb)(const volatile void *, uintptr_t)) {
#if !defined(_OS_FREEBSD_)
  typedef ElfW(Phdr) Elf_Phdr;
  typedef ElfW(Ehdr) Elf_Ehdr;
#endif
  char *base = (char *)map->l_addr;
  Elf_Ehdr *ehdr = (Elf_Ehdr *)base;
  char *phdrs = base + ehdr->e_phoff;
  char *phdrs_end = phdrs + ehdr->e_phnum * ehdr->e_phentsize;

  // Find the segment with the minimum base so we can "relocate" the p_vaddr
  // fields.  Typically ET_DYN objects (DSOs) have base of zero and ET_EXEC
  // objects have a non-zero base.
  uintptr_t preferred_base = (uintptr_t)-1;
  for (char *iter = phdrs; iter != phdrs_end; iter += ehdr->e_phentsize) {
    Elf_Phdr *phdr = (Elf_Phdr *)iter;
    if (phdr->p_type == PT_LOAD && preferred_base > (uintptr_t)phdr->p_vaddr)
      preferred_base = (uintptr_t)phdr->p_vaddr;
  }

  // Compute the delta from the real base to get a relocation delta.
  intptr_t delta = (uintptr_t)base - preferred_base;
  // Now we can figure out what the loader really mapped.
  for (char *iter = phdrs; iter != phdrs_end; iter += ehdr->e_phentsize) {
    Elf_Phdr *phdr = (Elf_Phdr *)iter;
    if (phdr->p_type == PT_LOAD) {
      uintptr_t seg_start = phdr->p_vaddr + delta;
      uintptr_t seg_end = seg_start + phdr->p_memsz;
      // None of these values are aligned.  We consider the ragged edges of the
      // load command as defined, since they are mapped from the file.
      seg_start = RoundDownTo(seg_start, jl_page_size);
      seg_end = RoundUpTo(seg_end, jl_page_size);
      cb((void *)seg_start, seg_end - seg_start);
    }
  }
}
#endif

#if defined(_OS_WINDOWS_)
JL_DLLEXPORT void *jl_dlopen(const char *filename, unsigned flags) JL_NOTSAFEPOINT
{
    ssize_t len = uv_wtf8_length_as_utf16(filename);
    if (len < 0) return NULL;
    WCHAR *wfilename = (WCHAR*)alloca(len * sizeof(WCHAR));
    uv_wtf8_to_utf16(filename, (uint16_t*)wfilename, len);
    HANDLE lib;
    if (flags & JL_RTLD_NOLOAD) {
        lib = GetModuleHandleW(wfilename);
    }
    else {
        lib = LoadLibraryExW(wfilename, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
    }
    return lib;
}
#else

#define JL_RTLD(flags, FLAG) (flags & JL_RTLD_ ## FLAG ? RTLD_ ## FLAG : 0)

int jl_running_under_sanitizer(int recheck) JL_NOTSAFEPOINT
{
#if defined(_COMPILER_ASAN_ENABLED_) || defined(_COMPILER_TSAN_ENABLED_) || defined(_COMPILER_MSAN_ENABLED_)
    return 1;
#else
    static _Atomic(int) detected_ = -1;
    int detected = jl_atomic_load_relaxed(&detected_);
    if (detected < 0 || recheck) {
        const char *env = getenv("JULIA_ASAN_COMPAT");
        if (env != NULL && env[0] != '\0')
            detected = strcmp(env, "0") != 0 ? 1 : 0;
        else if (dlsym(RTLD_DEFAULT, "__asan_init") != NULL)
            detected = 1;
        else
            detected = 0;
        jl_atomic_store_relaxed(&detected_, detected);
    }
    return detected == 1;
#endif
}

#ifdef RTLD_DEEPBIND
// RTLD_DEEPBIND is incompatible with the sanitizers' libc interposition
// (c.f. https://github.com/google/sanitizers/issues/611)
static int jl_use_rtld_deepbind(int recheck) JL_NOTSAFEPOINT
{
    static _Atomic(int) enabled_ = -1;
    int enabled = jl_atomic_load_relaxed(&enabled_);
    if (enabled < 0 || recheck) {
        const char *env = getenv("JULIA_USE_RTLD_DEEPBIND");
        if (env != NULL && env[0] != '\0')
            enabled = strcmp(env, "0") != 0;
        else
            enabled = !jl_running_under_sanitizer(recheck);
        jl_atomic_store_relaxed(&enabled_, enabled);
    }
    return enabled == 1;
}
#endif

/* The sanitizers break RUNPATH use in dlopen for annoying reasons that are
   are hard to fix. Specifically, libc will use the return address of the
   caller to determine certain paths and flags that affect .so location lookup.
   To work around this, we need to avoid using the sanitizer's dlopen interposition,
   instead using the real dlopen directly from the current shared library.
   Of course, this does mean that we need to manually perform the work that
   the sanitizers would otherwise do. */
static JL_NO_SANITIZE dlopen_prototype resolve_dlopen(void) JL_NOTSAFEPOINT
{
#if defined(__GLIBC__)
    // When a sanitizer is active, bypass its dlopen interposition by resolving and
    // caching the real libdl dlopen; otherwise use dlopen directly.
    if (jl_running_under_sanitizer(/*recheck*/0)) {
        static dlopen_prototype real_dlopen = NULL;
        if (!real_dlopen) {
            real_dlopen = (dlopen_prototype)dlsym(RTLD_NEXT, "dlopen");
            if (!real_dlopen)
                return NULL;
            void *libdl_handle = real_dlopen("libdl.so.2", RTLD_NOW | RTLD_NOLOAD);
            assert(libdl_handle);
            real_dlopen = (dlopen_prototype)dlsym(libdl_handle, "dlopen");
            dlclose(libdl_handle);
            assert(real_dlopen);
        }
        // The real interceptors check the validity of the string here, but let's
        // just skip that for the time being.
        return real_dlopen;
    }
#endif
    return &dlopen;
}

JL_DLLEXPORT JL_NO_SANITIZE void *jl_dlopen(const char *filename, unsigned flags) JL_NOTSAFEPOINT
{
    dlopen_prototype dlopen_fptr = resolve_dlopen();
    if (dlopen_fptr == NULL)
        return NULL;
    int real_flags = (flags & JL_RTLD_NOW ? RTLD_NOW : RTLD_LAZY)
                  | JL_RTLD(flags, LOCAL)
                  | JL_RTLD(flags, GLOBAL)
#ifdef RTLD_NODELETE
                  | JL_RTLD(flags, NODELETE)
#endif
#ifdef RTLD_NOLOAD
                  | JL_RTLD(flags, NOLOAD)
#endif
#ifdef RTLD_FIRST
                  | JL_RTLD(flags, FIRST)
#endif
                  ;
#ifdef RTLD_DEEPBIND
    if (jl_use_rtld_deepbind(/*recheck*/0))
        real_flags = real_flags | JL_RTLD(flags, DEEPBIND);
#endif
    void *hnd = dlopen_fptr(filename, real_flags);
#if defined(_COMPILER_MSAN_ENABLED_) && defined(__GLIBC__)
    struct link_map *map = (struct link_map*)hnd;
    if (filename && map)
      ForEachMappedRegion(map, __msan_unpoison);
#endif
    return hnd;
}
#endif


JL_DLLEXPORT int jl_dlclose(void *handle) JL_NOTSAFEPOINT
{
#ifdef _OS_WINDOWS_
    if (!handle) {
        return -1;
    }
    return !FreeLibrary((HMODULE) handle);
#else
    if (!handle) {
        dlerror(); /* Reset error status. */
        return -1;
    }
    return dlclose(handle);
#endif
}

void *jl_find_dynamic_library_by_addr(void *symbol, int throw_err, int close) JL_NOTSAFEPOINT
{
    void *handle;
#ifdef _OS_WINDOWS_
    if (!GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
                            (LPCWSTR)symbol,
                            (HMODULE*)&handle)) {
        if (throw_err)
            jl_error("could not load base module");
        return NULL;
    }
#else
    const char *path = jl_pathname_for_symbol(symbol);
    if (path == NULL) {
        if (throw_err)
            jl_error("could not load base module");
        return NULL;
    }
    if (path[0] == '\0') { // symbol is in the main executable
        handle = dlopen(NULL, RTLD_NOW | RTLD_NOLOAD | RTLD_LOCAL);
    } else {
        handle = dlopen(path, RTLD_NOW | RTLD_NOLOAD | RTLD_LOCAL);
    }
    if (handle != NULL && close)
        dlclose(handle); // Undo ref count increment from `dlopen`
#endif
    return handle;
}

JL_DLLEXPORT void *jl_load_dynamic_library(const char *modname, unsigned flags, int throw_err)
{
    ios_t path, relocated;
    int i;
#ifdef _OS_WINDOWS_
    int err;
#endif
    uv_stat_t stbuf;
    void *handle;
    int abspath;
    int is_atpath;
    // number of extensions to try — if modname already ends with the
    // standard extension, then we don't try adding additional extensions
    int n_extensions = endswith_extension(modname) ? 1 : N_EXTENSIONS;

    // modname == NULL is a sentinel value requesting the handle of libjulia-internal
    if (modname == NULL)
        return jl_libjulia_internal_handle;

    abspath = jl_isabspath(modname);
    is_atpath = 0;

    JL_TIMING(DL_OPEN, DL_OPEN);
    if (!(flags & JL_RTLD_NOLOAD))
        jl_timing_puts(JL_TIMING_DEFAULT_BLOCK, modname);

    // Detect if our `modname` is something like `@rpath/libfoo.dylib`
#ifdef _OS_DARWIN_
    size_t nameLen = strlen(modname);
    const char *const atPaths[] = {"@executable_path/", "@loader_path/", "@rpath/"};
    for (i = 0; i < sizeof(atPaths)/sizeof(char*); ++i) {
        size_t atLen = strlen(atPaths[i]);
        if (nameLen >= atLen && 0 == strncmp(modname, atPaths[i], atLen)) {
            is_atpath = 1;
        }
    }
#endif

    ios_mem(&path, IOS_INLSIZE);
    ios_mem(&relocated, IOS_INLSIZE);

    /*
      this branch permutes all base paths in DL_LOAD_PATH with all extensions
      note: skip when !jl_base_module to avoid UndefVarError(:DL_LOAD_PATH),
            and also skip for absolute paths
            and also skip for `@`-paths on macOS
      We also do simple string replacement here for elements starting with `@executable_path/`.
      While these exist as OS concepts on Darwin, we want to use them on other platforms
      such as Windows, so we emulate them here.
    */
    if (!abspath && !is_atpath && jl_base_module != NULL && jl_typeinf_world != 1) {
        jl_binding_t *b = jl_get_module_binding(jl_base_module, jl_symbol("DL_LOAD_PATH"), 0);
        jl_array_t *DL_LOAD_PATH = (jl_array_t*)(b ? jl_get_binding_value_in_world(b, jl_typeinf_world) : NULL);
        if (DL_LOAD_PATH != NULL) {
            size_t j;
            for (j = 0; j < jl_array_nrows(DL_LOAD_PATH); j++) {
                char *dl_path = jl_string_data(jl_array_ptr_data(DL_LOAD_PATH)[j]);
                if (*dl_path == 0)
                    continue;

                ios_trunc(&relocated, 0);

                // Is this entry supposed to be relative to the bindir?
                if (strncmp(dl_path, "@executable_path", 16) == 0) {
                    ios_printf(&relocated, "%s%s", jl_options.julia_bindir, dl_path + 16);
                } else {
                    ios_puts(dl_path, &relocated);
                }
                ios_putc(0, &relocated);
                for (i = 0; i < n_extensions; i++) {
                    ios_trunc(&path, 0);
                    const char *ext = extensions[i];
                    if (relocated.buf[relocated.bpos - 2] == PATHSEPSTRING[0])
                        ios_printf(&path, "%s%s%s", relocated.buf, modname, ext);
                    else
                        ios_printf(&path, "%s" PATHSEPSTRING "%s%s", relocated.buf, modname, ext);
                    ios_putc(0, &path);

#ifdef _OS_WINDOWS_
                    if (i == 0) { // LoadLibrary already tested the extensions, we just need to check the `stat` result
#endif
                        handle = jl_dlopen(path.buf, flags);
                        if (handle && !(flags & JL_RTLD_NOLOAD))
                            jl_timing_puts(JL_TIMING_DEFAULT_BLOCK, jl_pathname_for_handle(handle));
                        if (handle)
                            goto success;
#ifdef _OS_WINDOWS_
                        err = GetLastError();
                    }
#endif
                    // bail out and show the error if file actually exists
                    if (jl_stat(path.buf, (char *)&stbuf) == 0) {
                        if (!S_ISDIR(stbuf.st_mode)) {
                            goto notfound;
                        }
                    }
                }
            }
        }
    }

    // now fall back and look in default library paths, for all extensions
    for (i = 0; i < n_extensions; i++) {
        ios_trunc(&path, 0);
        const char *ext = extensions[i];
        ios_printf(&path, "%s%s", modname, ext);
        ios_putc(0, &path);
        handle = jl_dlopen(path.buf, flags);
        if (handle && !(flags & JL_RTLD_NOLOAD))
            jl_timing_puts(JL_TIMING_DEFAULT_BLOCK, jl_pathname_for_handle(handle));
        if (handle)
            goto success;
#ifdef _OS_WINDOWS_
        err = GetLastError();
        break; // LoadLibrary already tested the rest
#else
        // bail out and show the error if file actually exists
        if (jl_stat(path.buf, (char *)&stbuf) == 0) {
            if (!S_ISDIR(stbuf.st_mode)) {
                break;
            }
        }
#endif
    }

notfound:
    if (throw_err) {
#ifdef _OS_WINDOWS_
        char reason[256];
        win32_formatmessage(err, reason, sizeof(reason));
#else
        const char *reason = dlerror();
#endif
        ios_close(&relocated);
        ios_close(&path);
        jl_errorf("could not load library \"%s\"\n%s", modname, reason);
    }
    handle = NULL;

success:
    ios_close(&relocated);
    ios_close(&path);
    return handle;
}

/*
 * When search_deps is 1, act like dlsym and search both the library for the
 * handle and all its dependencies.  Use this option only when compatibility
 * with dlsym(3) is required, though this behaviour is not possible on Windows.
 *
 * At time of writing, only Base.dlsym() uses search_deps = 1.
 */
JL_DLLEXPORT int jl_dlsym(void *handle, const char *symbol, void ** value, int throw_err, int search_deps) JL_NOTSAFEPOINT
{
    int symbol_found = 0;

    /* First, get the symbol value */
#if defined(_OS_WINDOWS_)
    *value = GetProcAddress((HMODULE) handle, symbol);
#elif defined(_OS_DARWIN_)
    /* When !search_deps and the handle isn't special, force RTLD_FIRST. */
    if (!search_deps && handle != RTLD_NEXT && handle != RTLD_DEFAULT &&
        handle != RTLD_SELF && handle != RTLD_MAIN_ONLY)
        handle = (void *)((uintptr_t)handle | 1);
    *value = dlsym(handle, symbol);
#else
    *value = dlsym(handle, symbol);
#endif

    /* Next, check for errors. On Windows, a NULL pointer means the symbol was
     * not found. On everything else, we can have NULL symbols, so we check for
     * non-NULL returns from dlerror(). Since POSIX doesn't require `dlerror`
     * to be implemented safely, FreeBSD doesn't (unlike everyone else, who
     * realized decades ago that threads are here to stay), so we avoid calling
     * `dlerror` unless we need to get the error message.
     * https://github.com/freebsd/freebsd-src/blob/12db51d20823a5e3b9e5f8a2ea73156fe1cbfc28/libexec/rtld-elf/rtld.c#L198
     */
    symbol_found = *value != NULL;
#ifndef _OS_WINDOWS_
    const char *err = "";
    if (!symbol_found) {
        dlerror(); /* Reset error status. */
        *value = dlsym(handle, symbol);
        err = dlerror();
        symbol_found = *value != NULL || err == NULL;
    }
#endif

#if !defined(_OS_DARWIN_) && !defined(_OS_WINDOWS_)
    /*
     * Unlike GetProcAddress, dlsym will search the dependencies of the given
     * library, so we must check where the symbol came from.
     */
    if (symbol_found && !search_deps && handle != jl_RTLD_DEFAULT_handle) {
        void *symbol_handle = jl_find_dynamic_library_by_addr(*value, 0, 1);
        symbol_found = handle == symbol_handle;
    }
#endif

    if (!symbol_found) {
        if (throw_err) {
#ifdef _OS_WINDOWS_
            char err[256];
            win32_formatmessage(GetLastError(), err, sizeof(err));
#endif
            jl_errorf("could not load symbol \"%s\":\n%s", symbol, err);
        }
        return 0;
    }

    return 1;
}

// Look for symbols in internal libraries
JL_DLLEXPORT const char *jl_dlfind(const char *f_name)
{
#ifdef _OS_FREEBSD_
    // This is a workaround for FreeBSD <= 13.2 which do not have
    // https://cgit.freebsd.org/src/commit/?id=21a52f99440c9bec7679f3b0c5c9d888901c3694
    // (See https://github.com/JuliaLang/julia/issues/50846)
    if (strcmp(f_name, "dl_iterate_phdr") == 0)
        return NULL;
#endif
    void * dummy;
    if (jl_dlsym(jl_libjulia_internal_handle, f_name, &dummy, 0, 0))
        return JL_LIBJULIA_INTERNAL_DL_LIBNAME;
    if (jl_dlsym(jl_libjulia_handle, f_name, &dummy, 0, 0))
        return JL_LIBJULIA_DL_LIBNAME;
    if (jl_dlsym(jl_exe_handle, f_name, &dummy, 0, 0))
        return JL_EXE_LIBNAME;
#ifdef _OS_WINDOWS_
    if (jl_dlsym(jl_kernel32_handle, f_name, &dummy, 0, 0))
        return "kernel32";
    if (jl_dlsym(jl_crtdll_handle, f_name, &dummy, 0, 0)) // Prefer crtdll over ntdll
        return jl_crtdll_basename;
    if (jl_dlsym(jl_ntdll_handle, f_name, &dummy, 0, 0))
        return "ntdll";
    if (jl_dlsym(jl_winsock_handle, f_name, &dummy, 0, 0))
        return "ws2_32";
#endif
    // additional common libraries (libc?) could be added here, but in general,
    // it is better to specify the library explicitly in the code. This exists
    // mainly to ease compatibility with linux, and for libraries that don't
    // have a name (julia.exe and libjulia.dll)
    // We could also loop over all libraries that have been used so far, but, again,
    // explicit is preferred over implicit
    return NULL;
    // oops, we didn't find it. NULL defaults to searching jl_RTLD_DEFAULT_handle,
    // which defaults to jl_libjulia_internal_handle, where we won't find it, and
    // will throw the appropriate error.
}

#ifdef __cplusplus
}
#endif
