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libredirect: fix on darwin #144653

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merged 2 commits into from
Nov 6, 2021
Merged

libredirect: fix on darwin #144653

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d1a3b5c
libredirect: use __interpose on darwin
stephank Nov 4, 2021
7acc0e0
libredirect: workaround dyld env not inherited
stephank Nov 4, 2021
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2 changes: 1 addition & 1 deletion pkgs/build-support/libredirect/default.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -38,11 +38,11 @@ stdenv.mkDerivation rec {

install -vD "$libName" "$out/lib/$libName"

# Provide a setup hook that injects our library into every process.
mkdir -p "$hook/nix-support"
cat <<SETUP_HOOK > "$hook/nix-support/setup-hook"
${if stdenv.isDarwin then ''
export DYLD_INSERT_LIBRARIES="$out/lib/$libName"
export DYLD_FORCE_FLAT_NAMESPACE=1
'' else ''
export LD_PRELOAD="$out/lib/$libName"
''}
Expand Down
143 changes: 101 additions & 42 deletions pkgs/build-support/libredirect/libredirect.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <unistd.h>
#include <dlfcn.h>
#include <sys/types.h>
#include <sys/stat.h>
Expand All @@ -13,6 +14,22 @@

#define MAX_REDIRECTS 128

#ifdef __APPLE__
struct dyld_interpose {
const void * replacement;
const void * replacee;
};
#define WRAPPER(ret, name) static ret _libredirect_wrapper_##name
#define LOOKUP_REAL(name) &name
#define WRAPPER_DEF(name) \
__attribute__((used)) static struct dyld_interpose _libredirect_interpose_##name \
__attribute__((section("__DATA,__interpose"))) = { &_libredirect_wrapper_##name, &name };
#else
#define WRAPPER(ret, name) ret name
#define LOOKUP_REAL(name) dlsym(RTLD_NEXT, #name)
#define WRAPPER_DEF(name)
#endif

static int nrRedirects = 0;
static char * from[MAX_REDIRECTS];
static char * to[MAX_REDIRECTS];
Expand Down Expand Up @@ -80,9 +97,9 @@ static int open_needs_mode(int flags)
it contains only what we needed for programs in Nixpkgs. Just add
more functions as needed. */

int open(const char * path, int flags, ...)
WRAPPER(int, open)(const char * path, int flags, ...)
{
int (*open_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open");
int (*open_real) (const char *, int, mode_t) = LOOKUP_REAL(open);
mode_t mode = 0;
if (open_needs_mode(flags)) {
va_list ap;
Expand All @@ -93,10 +110,12 @@ int open(const char * path, int flags, ...)
char buf[PATH_MAX];
return open_real(rewrite(path, buf), flags, mode);
}
WRAPPER_DEF(open)

int open64(const char * path, int flags, ...)
#ifndef __APPLE__
WRAPPER(int, open64)(const char * path, int flags, ...)
{
int (*open64_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open64");
int (*open64_real) (const char *, int, mode_t) = LOOKUP_REAL(open64);
mode_t mode = 0;
if (open_needs_mode(flags)) {
va_list ap;
Expand All @@ -107,10 +126,12 @@ int open64(const char * path, int flags, ...)
char buf[PATH_MAX];
return open64_real(rewrite(path, buf), flags, mode);
}
WRAPPER_DEF(open64)
#endif

int openat(int dirfd, const char * path, int flags, ...)
WRAPPER(int, openat)(int dirfd, const char * path, int flags, ...)
{
int (*openat_real) (int, const char *, int, mode_t) = dlsym(RTLD_NEXT, "openat");
int (*openat_real) (int, const char *, int, mode_t) = LOOKUP_REAL(openat);
mode_t mode = 0;
if (open_needs_mode(flags)) {
va_list ap;
Expand All @@ -121,114 +142,136 @@ int openat(int dirfd, const char * path, int flags, ...)
char buf[PATH_MAX];
return openat_real(dirfd, rewrite(path, buf), flags, mode);
}
WRAPPER_DEF(openat)

FILE * fopen(const char * path, const char * mode)
WRAPPER(FILE *, fopen)(const char * path, const char * mode)
{
FILE * (*fopen_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen");
FILE * (*fopen_real) (const char *, const char *) = LOOKUP_REAL(fopen);
char buf[PATH_MAX];
return fopen_real(rewrite(path, buf), mode);
}
WRAPPER_DEF(fopen)

FILE * __nss_files_fopen(const char * path)
#ifndef __APPLE__
WRAPPER(FILE *, __nss_files_fopen)(const char * path)
{
FILE * (*__nss_files_fopen_real) (const char *) = dlsym(RTLD_NEXT, "__nss_files_fopen");
FILE * (*__nss_files_fopen_real) (const char *) = LOOKUP_REAL(__nss_files_fopen);
char buf[PATH_MAX];
return __nss_files_fopen_real(rewrite(path, buf));
}
WRAPPER_DEF(__nss_files_fopen)
#endif

FILE * fopen64(const char * path, const char * mode)
#ifndef __APPLE__
WRAPPER(FILE *, fopen64)(const char * path, const char * mode)
{
FILE * (*fopen64_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen64");
FILE * (*fopen64_real) (const char *, const char *) = LOOKUP_REAL(fopen64);
char buf[PATH_MAX];
return fopen64_real(rewrite(path, buf), mode);
}
WRAPPER_DEF(fopen64)
#endif

int __xstat(int ver, const char * path, struct stat * st)
#ifndef __APPLE__
WRAPPER(int, __xstat)(int ver, const char * path, struct stat * st)
{
int (*__xstat_real) (int ver, const char *, struct stat *) = dlsym(RTLD_NEXT, "__xstat");
int (*__xstat_real) (int ver, const char *, struct stat *) = LOOKUP_REAL(__xstat);
char buf[PATH_MAX];
return __xstat_real(ver, rewrite(path, buf), st);
}
WRAPPER_DEF(__xstat)
#endif

int __xstat64(int ver, const char * path, struct stat64 * st)
#ifndef __APPLE__
WRAPPER(int, __xstat64)(int ver, const char * path, struct stat64 * st)
{
int (*__xstat64_real) (int ver, const char *, struct stat64 *) = dlsym(RTLD_NEXT, "__xstat64");
int (*__xstat64_real) (int ver, const char *, struct stat64 *) = LOOKUP_REAL(__xstat64);
char buf[PATH_MAX];
return __xstat64_real(ver, rewrite(path, buf), st);
}
WRAPPER_DEF(__xstat64)
#endif

int stat(const char * path, struct stat * st)
WRAPPER(int, stat)(const char * path, struct stat * st)
{
int (*__stat_real) (const char *, struct stat *) = dlsym(RTLD_NEXT, "stat");
int (*__stat_real) (const char *, struct stat *) = LOOKUP_REAL(stat);
char buf[PATH_MAX];
return __stat_real(rewrite(path, buf), st);
}
WRAPPER_DEF(stat)

int access(const char * path, int mode)
WRAPPER(int, access)(const char * path, int mode)
{
int (*access_real) (const char *, int mode) = dlsym(RTLD_NEXT, "access");
int (*access_real) (const char *, int mode) = LOOKUP_REAL(access);
char buf[PATH_MAX];
return access_real(rewrite(path, buf), mode);
}
WRAPPER_DEF(access)

int posix_spawn(pid_t * pid, const char * path,
WRAPPER(int, posix_spawn)(pid_t * pid, const char * path,
const posix_spawn_file_actions_t * file_actions,
const posix_spawnattr_t * attrp,
char * const argv[], char * const envp[])
{
int (*posix_spawn_real) (pid_t *, const char *,
const posix_spawn_file_actions_t *,
const posix_spawnattr_t *,
char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawn");
char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawn);
char buf[PATH_MAX];
return posix_spawn_real(pid, rewrite(path, buf), file_actions, attrp, argv, envp);
}
WRAPPER_DEF(posix_spawn)

int posix_spawnp(pid_t * pid, const char * file,
WRAPPER(int, posix_spawnp)(pid_t * pid, const char * file,
const posix_spawn_file_actions_t * file_actions,
const posix_spawnattr_t * attrp,
char * const argv[], char * const envp[])
{
int (*posix_spawnp_real) (pid_t *, const char *,
const posix_spawn_file_actions_t *,
const posix_spawnattr_t *,
char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawnp");
char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawnp);
char buf[PATH_MAX];
return posix_spawnp_real(pid, rewrite(file, buf), file_actions, attrp, argv, envp);
}
WRAPPER_DEF(posix_spawnp)

int execv(const char * path, char * const argv[])
WRAPPER(int, execv)(const char * path, char * const argv[])
{
int (*execv_real) (const char * path, char * const argv[]) = dlsym(RTLD_NEXT, "execv");
int (*execv_real) (const char * path, char * const argv[]) = LOOKUP_REAL(execv);
char buf[PATH_MAX];
return execv_real(rewrite(path, buf), argv);
}
WRAPPER_DEF(execv)

int execvp(const char * path, char * const argv[])
WRAPPER(int, execvp)(const char * path, char * const argv[])
{
int (*_execvp) (const char *, char * const argv[]) = dlsym(RTLD_NEXT, "execvp");
int (*_execvp) (const char *, char * const argv[]) = LOOKUP_REAL(execvp);
char buf[PATH_MAX];
return _execvp(rewrite(path, buf), argv);
}
WRAPPER_DEF(execvp)

int execve(const char * path, char * const argv[], char * const envp[])
WRAPPER(int, execve)(const char * path, char * const argv[], char * const envp[])
{
int (*_execve) (const char *, char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "execve");
int (*_execve) (const char *, char * const argv[], char * const envp[]) = LOOKUP_REAL(execve);
char buf[PATH_MAX];
return _execve(rewrite(path, buf), argv, envp);
}
WRAPPER_DEF(execve)

DIR * opendir(const char * path)
WRAPPER(DIR *, opendir)(const char * path)
{
char buf[PATH_MAX];
DIR * (*_opendir) (const char*) = dlsym(RTLD_NEXT, "opendir");
DIR * (*_opendir) (const char*) = LOOKUP_REAL(opendir);

return _opendir(rewrite(path, buf));
}
WRAPPER_DEF(opendir)

#define SYSTEM_CMD_MAX 512

char *replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
static char * replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
char head[SYSTEM_CMD_MAX] = {0};
strncpy(head, source, start_ptr - source);

Expand All @@ -241,7 +284,7 @@ char *replace_substring(char * source, char * buf, char * replace_string, char *
return buf;
}

char *replace_string(char * buf, char * from, char * to) {
static char * replace_string(char * buf, char * from, char * to) {
int num_matches = 0;
char * matches[SYSTEM_CMD_MAX];
int from_len = strlen(from);
Expand All @@ -264,32 +307,48 @@ char *replace_string(char * buf, char * from, char * to) {
return buf;
}

void rewriteSystemCall(const char * command, char * buf) {
strcpy(buf, command);
static void rewriteSystemCall(const char * command, char * buf) {
char * p = buf;

#ifdef __APPLE__
// The dyld environment variable is not inherited by the subprocess spawned
// by system(), so this hack redefines it.
Dl_info info;
dladdr(&rewriteSystemCall, &info);
p = stpcpy(p, "export DYLD_INSERT_LIBRARIES=");
p = stpcpy(p, info.dli_fname);
p = stpcpy(p, ";");
#endif

stpcpy(p, command);

for (int n = 0; n < nrRedirects; ++n) {
replace_string(buf, from[n], to[n]);
}
}

int system(const char *command)
WRAPPER(int, system)(const char *command)
{
int (*_system) (const char*) = dlsym(RTLD_NEXT, "system");
int (*_system) (const char*) = LOOKUP_REAL(system);

char newCommand[SYSTEM_CMD_MAX];
rewriteSystemCall(command, newCommand);
return _system(newCommand);
}
WRAPPER_DEF(system)

int mkdir(const char *path, mode_t mode)
WRAPPER(int, mkdir)(const char *path, mode_t mode)
{
int (*mkdir_real) (const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdir");
int (*mkdir_real) (const char *path, mode_t mode) = LOOKUP_REAL(mkdir);
char buf[PATH_MAX];
return mkdir_real(rewrite(path, buf), mode);
}
WRAPPER_DEF(mkdir)

int mkdirat(int dirfd, const char *path, mode_t mode)
WRAPPER(int, mkdirat)(int dirfd, const char *path, mode_t mode)
{
int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdirat");
int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = LOOKUP_REAL(mkdirat);
char buf[PATH_MAX];
return mkdirat_real(dirfd, rewrite(path, buf), mode);
}
WRAPPER_DEF(mkdirat)