Add APE fexecve() support (#733)

libc/calls/execve-sysv.c

@@ -19,6 +19,7 @@
 #include "libc/calls/blockcancel.internal.h"
 #include "libc/calls/blocksigs.internal.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/execve-sysv.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
@@ -37,6 +38,11 @@ static bool CanExecute(const char *path) {
   return !sys_faccessat(AT_FDCWD, path, X_OK, 0);
 }
 
+bool IsAPEMagic(char buf[8]) {
+  return READ64LE(buf) == READ64LE("MZqFpD='") ||
+         READ64LE(buf) == READ64LE("JTqFpD='");
+}
+
 static bool IsApeBinary(const char *path) {
   int fd;
   char buf[8];
@@ -44,11 +50,7 @@ static bool IsApeBinary(const char *path) {
   // TODO(jart): Should we block signals too?
   BLOCK_CANCELLATIONS;
   if ((fd = sys_open(path, O_RDONLY, 0)) != -1) {
-    if (sys_read(fd, buf, 8) == 8 &&  //
+    res = sys_read(fd, buf, 8) == 8 && IsAPEMagic(buf);
-        (READ64LE(buf) == READ64LE("MZqFpD='") ||
-         READ64LE(buf) == READ64LE("JTqFpD='"))) {
-      res = true;
-    }
     sys_close(fd);
   }
   ALLOW_CANCELLATIONS;

libc/calls/execve-sysv.internal.h

@@ -0,0 +1,10 @@
+#ifndef COSMOPOLITAN_LIBC_CALLS_EXECVE_SYSV_H_
+#define COSMOPOLITAN_LIBC_CALLS_EXECVE_SYSV_H_
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+bool IsAPEMagic(char[8]) _Hide;
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_CALLS_EXECVE_SYSV_H_ */

libc/calls/fexecve.c

@@ -16,21 +16,147 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
+#include "libc/calls/blockcancel.internal.h"
+#include "libc/calls/blocksigs.internal.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/cp.internal.h"
+#include "libc/calls/execve-sysv.internal.h"
+#include "libc/calls/struct/stat.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
+#include "libc/errno.h"
 #include "libc/fmt/itoa.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/str/str.h"
+#include "libc/sysv/consts/map.h"
+#include "libc/sysv/consts/mfd.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/prot.h"
+#include "libc/sysv/consts/shm.h"
 #include "libc/sysv/errfuns.h"
 
+static bool IsAPEFd(const int fd) {
+  char buf[8];
+  bool res;
+  return (sys_pread(fd, buf, 8, 0, 0) == 8) && IsAPEMagic(buf);
+}
+
+static int fexecve_impl(const int fd, char *const argv[], char *const envp[]) {
+  int rc;
+  if (IsLinux()) {
+    char path[14 + 12];
+    FormatInt32(stpcpy(path, "/proc/self/fd/"), fd);
+    rc = __sys_execve(path, argv, envp);
+  } else if (IsFreebsd()) {
+    rc = sys_fexecve(fd, argv, envp);
+  } else {
+    rc = enosys();
+  }
+  return rc;
+}
+
+typedef enum {
+  PTF_NUM = 1 << 0,
+  PTF_NUM2 = 1 << 1,
+  PTF_NUM3 = 1 << 2,
+  PTF_ANY = 1 << 3
+} PTF_PARSE;
+
+static bool ape_to_elf(void *ape, const size_t apesize) {
+  static const char printftok[] = "printf '";
+  static const size_t printftoklen = sizeof(printftok) - 1;
+  const char *tok = memmem(ape, apesize, printftok, printftoklen);
+  if (tok) {
+    tok += printftoklen;
+    uint8_t *dest = ape;
+    PTF_PARSE state = PTF_ANY;
+    uint8_t value = 0;
+    for (; tok < (const char *)(dest + apesize); tok++) {
+      if ((state & (PTF_NUM | PTF_NUM2 | PTF_NUM3)) &&
+          (*tok >= '0' && *tok <= '7')) {
+        value = (value << 3) | (*tok - '0');
+        state <<= 1;
+        if (state & PTF_ANY) {
+          *dest++ = value;
+        }
+      } else if (state & PTF_NUM) {
+        break;
+      } else {
+        if (state & (PTF_NUM2 | PTF_NUM3)) {
+          *dest++ = value;
+        }
+        if (*tok == '\\') {
+          state = PTF_NUM;
+          value = 0;
+        } else if (*tok == '\'') {
+          return true;
+        } else {
+          *dest++ = *tok;
+          state = PTF_ANY;
+        }
+      }
+    }
+  }
+  errno = ENOEXEC;
+  return false;
+}
+
+static int ape_fd_to_mem_elf_fd(const int infd, char *path) {
+  if (!IsLinux() && !IsFreebsd() || !_weaken(mmap) || !_weaken(munmap)) {
+    return enosys();
+  }
+
+  struct stat st;
+  if (sys_fstat(infd, &st) == -1) {
+    return -1;
+  }
+  int fd;
+  if (IsLinux()) {
+    fd = sys_memfd_create(__func__, MFD_CLOEXEC);
+    if ((fd != -1) && path) {
+      FormatInt32(stpcpy(path, "/proc/self/fd/"), fd);
+    }
+  } else if (IsFreebsd()) {
+    fd = sys_shm_open(SHM_ANON, O_CREAT | O_RDWR, 0);
+  } else {
+    return enosys();
+  }
+  if (fd == -1) {
+    return -1;
+  }
+  void *space;
+  if ((sys_ftruncate(fd, st.st_size, st.st_size) != -1) &&
+      ((space = _weaken(mmap)(0, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+                              fd, 0)) != MAP_FAILED)) {
+    ssize_t readRc;
+    readRc = sys_pread(infd, space, st.st_size, 0, 0);
+    bool success = readRc != -1;
+    if (success && (st.st_size > 8) && IsAPEMagic(space)) {
+      success = ape_to_elf(space, st.st_size);
+    }
+    const int e = errno;
+    if ((_weaken(munmap)(space, st.st_size) != -1) && success) {
+      _unassert(readRc == st.st_size);
+      return fd;
+    } else if (!success) {
+      errno = e;
+    }
+  }
+  const int e = errno;
+  close(fd);
+  errno = e;
+  return -1;
+}
+
 /**
  * Executes binary executable at file descriptor.
  *
- * This is only supported on Linux and FreeBSD. APE binaries currently
+ * This is only supported on Linux and FreeBSD. APE binaries are
- * aren't supported.
+ * supported.
  *
  * @param fd is opened executable and current file position is ignored
  * @return doesn't return on success, otherwise -1 w/ errno
@@ -39,7 +165,6 @@
  */
 int fexecve(int fd, char *const argv[], char *const envp[]) {
   int rc;
-  size_t i;
   if (!argv || !envp ||
       (IsAsan() &&
        (!__asan_is_valid_strlist(argv) || !__asan_is_valid_strlist(envp)))) {
@@ -47,14 +172,21 @@ int fexecve(int fd, char *const argv[], char *const envp[]) {
   } else {
     STRACE("fexecve(%d, %s, %s) → ...", fd, DescribeStringList(argv),
            DescribeStringList(envp));
-    if (IsLinux()) {
+    rc = fexecve_impl(fd, argv, envp);
-      char path[14 + 12];
+    if ((errno == ENOEXEC) && (IsLinux() || IsFreebsd())) {
-      FormatInt32(stpcpy(path, "/proc/self/fd/"), fd);
+      int newfd = -1;
-      rc = __sys_execve(path, argv, envp);
+      BEGIN_CANCELLATION_POINT;
-    } else if (IsFreebsd()) {
+      BLOCK_SIGNALS;
-      rc = sys_fexecve(fd, argv, envp);
+      strace_enabled(-1);
-    } else {
+      if (IsAPEFd(fd)) {
-      rc = enosys();
+        newfd = ape_fd_to_mem_elf_fd(fd, NULL);
+      }
+      strace_enabled(+1);
+      ALLOW_SIGNALS;
+      END_CANCELLATION_POINT;
+      if (newfd != -1) {
+        rc = fexecve_impl(newfd, argv, envp);
+      }
     }
   }
   STRACE("fexecve(%d) failed %d% m", fd, rc);

libc/calls/syscall-sysv.internal.h

@@ -105,6 +105,7 @@ i32 sys_setresuid(u32, u32, u32) _Hide;
 i32 sys_setreuid(u32, u32) _Hide;
 i32 sys_setsid(void) _Hide;
 i32 sys_setuid(i32) _Hide;
+i32 sys_shm_open(const char *, i32, u32) _Hide;
 i32 sys_sigaction(i32, const void *, void *, i64, i64) _Hide;
 i32 sys_sigaltstack(const void *, void *) _Hide;
 i32 sys_symlinkat(const char *, i32, const char *) _Hide;

libc/sysv/consts.sh

@@ -1620,6 +1620,7 @@ syscon	shm	SHM_HUGETLB				0x0800			0			0			0			0			0
 syscon	shm	SHM_LOCKED				0x0400			0			0			0			0			0
 syscon	shm	SHM_NORESERVE				0x1000			0			0			0			0			0
 syscon	shm	SHM_REMAP				0x4000			0			0			0			0			0
+syscon	shm	SHM_ANON				0			0			1			0			0			0
 
 syscon	lock	LOCK_UNLOCK_CACHE			54			0			0			0			0			0			# wut
 

libc/sysv/consts/SHM_ANON.s

@@ -0,0 +1,2 @@
+.include "o/libc/sysv/consts/syscon.internal.inc"
+.syscon shm,SHM_ANON,0,0,1,0,0,0

libc/sysv/consts/shm.h

@@ -2,24 +2,26 @@
 #define COSMOPOLITAN_LIBC_SYSV_CONSTS_SHM_H_
 #include "libc/runtime/symbolic.h"
 
-#define SHM_DEST SYMBOLIC(SHM_DEST)
+#define SHM_ANON      SYMBOLIC(SHM_ANON)
-#define SHM_EXEC SYMBOLIC(SHM_EXEC)
+#define SHM_DEST      SYMBOLIC(SHM_DEST)
-#define SHM_HUGETLB SYMBOLIC(SHM_HUGETLB)
+#define SHM_EXEC      SYMBOLIC(SHM_EXEC)
-#define SHM_INFO SYMBOLIC(SHM_INFO)
+#define SHM_HUGETLB   SYMBOLIC(SHM_HUGETLB)
-#define SHM_LOCK SYMBOLIC(SHM_LOCK)
+#define SHM_INFO      SYMBOLIC(SHM_INFO)
-#define SHM_LOCKED SYMBOLIC(SHM_LOCKED)
+#define SHM_LOCK      SYMBOLIC(SHM_LOCK)
+#define SHM_LOCKED    SYMBOLIC(SHM_LOCKED)
 #define SHM_NORESERVE SYMBOLIC(SHM_NORESERVE)
-#define SHM_R SYMBOLIC(SHM_R)
+#define SHM_R         SYMBOLIC(SHM_R)
-#define SHM_RDONLY SYMBOLIC(SHM_RDONLY)
+#define SHM_RDONLY    SYMBOLIC(SHM_RDONLY)
-#define SHM_REMAP SYMBOLIC(SHM_REMAP)
+#define SHM_REMAP     SYMBOLIC(SHM_REMAP)
-#define SHM_RND SYMBOLIC(SHM_RND)
+#define SHM_RND       SYMBOLIC(SHM_RND)
-#define SHM_STAT SYMBOLIC(SHM_STAT)
+#define SHM_STAT      SYMBOLIC(SHM_STAT)
-#define SHM_UNLOCK SYMBOLIC(SHM_UNLOCK)
+#define SHM_UNLOCK    SYMBOLIC(SHM_UNLOCK)
-#define SHM_W SYMBOLIC(SHM_W)
+#define SHM_W         SYMBOLIC(SHM_W)
 
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
+extern const char *SHM_ANON;
 extern const int SHM_DEST;
 extern const int SHM_EXEC;
 extern const int SHM_HUGETLB;

test/libc/calls/fexecve_test.c

@@ -86,3 +86,14 @@ TEST(fexecve, memfd_create) {
   fexecve(fd, (char *const[]){0}, (char *const[]){0});
   EXITS(42);
 }
+
+TEST(fexecve, APE) {
+  if (!IsLinux() && !IsFreebsd()) return;
+  testlib_extract("/zip/life-nomod.com", "life-nomod.com", 0555);
+  SPAWN(fork);
+  int fd = open("life-nomod.com", O_RDONLY);
+  ASSERT_NE(-1, fd);
+  if (fd == -1 && errno == ENOSYS) _Exit(42);
+  fexecve(fd, (char *const[]){0}, (char *const[]){0});
+  EXITS(42);
+}

test/libc/calls/test.mk

@@ -93,6 +93,7 @@ o/$(MODE)/test/libc/calls/fexecve_test.com.dbg:				\
 		o/$(MODE)/test/libc/calls/fexecve_test.o		\
 		o/$(MODE)/test/libc/calls/calls.pkg			\
 		o/$(MODE)/tool/build/echo.zip.o				\
+		o/$(MODE)/test/libc/calls/life-nomod.com.zip.o		\
 		$(LIBC_TESTMAIN)					\
 		$(CRT)							\
 		$(APE_NO_MODIFY_SELF)