[PULL,09/15] bsd-user: Simplify the implementation of execve

Commit Message

Warner Losh July 24, 2024, 10:04 p.m. UTC

From: Doug Rabson <[e-mail]>

This removes the logic which prepends the emulator to each call to
execve and fexecve. This is not necessary with the existing
imgact_binmisc support and it avoids the need to install the emulator
binary into jail environments when using 'binmiscctl --pre-open'.

Signed-off-by: Doug Rabson <[e-mail]>
Reviewed-by: Warner Losh <[e-mail]>
Signed-off-by: Warner Losh <[e-mail]>
Acked-by: Richard Henderson <[e-mail]>
---
 bsd-user/freebsd/os-proc.c | 118 +------------------------------------
 bsd-user/main.c            |  18 ------
 2 files changed, 3 insertions(+), 133 deletions(-)

Patch

diff --git a/bsd-user/freebsd/os-proc.c b/bsd-user/freebsd/os-proc.c
index e0203e259b0..bf993f1b662 100644
--- a/bsd-user/freebsd/os-proc.c
+++ b/bsd-user/freebsd/os-proc.c
@@ -26,65 +26,13 @@  struct kinfo_proc;
 
 #include "qemu.h"
 
-/*
- * Get the filename for the given file descriptor.
- * Note that this may return NULL (fail) if no longer cached in the kernel.
- */
-static char *
-get_filename_from_fd(pid_t pid, int fd, char *filename, size_t len)
-{
-    char *ret = NULL;
-    unsigned int cnt;
-    struct procstat *procstat = NULL;
-    struct kinfo_proc *kp = NULL;
-    struct filestat_list *head = NULL;
-    struct filestat *fst;
-
-    procstat = procstat_open_sysctl();
-    if (procstat == NULL) {
-        goto out;
-    }
-
-    kp = procstat_getprocs(procstat, KERN_PROC_PID, pid, &cnt);
-    if (kp == NULL) {
-        goto out;
-    }
-
-    head = procstat_getfiles(procstat, kp, 0);
-    if (head == NULL) {
-        goto out;
-    }
-
-    STAILQ_FOREACH(fst, head, next) {
-        if (fd == fst->fs_fd) {
-            if (fst->fs_path != NULL) {
-                (void)strlcpy(filename, fst->fs_path, len);
-                ret = filename;
-            }
-            break;
-        }
-    }
-
-out:
-    if (head != NULL) {
-        procstat_freefiles(procstat, head);
-    }
-    if (kp != NULL) {
-        procstat_freeprocs(procstat, kp);
-    }
-    if (procstat != NULL) {
-        procstat_close(procstat);
-    }
-    return ret;
-}
-
 /*
  * execve/fexecve
  */
 abi_long freebsd_exec_common(abi_ulong path_or_fd, abi_ulong guest_argp,
         abi_ulong guest_envp, int do_fexec)
 {
-    char **argp, **envp, **qargp, **qarg1, **qarg0, **qargend;
+    char **argp, **envp, **qarg0;
     int argc, envc;
     abi_ulong gp;
     abi_ulong addr;
@@ -117,9 +65,7 @@  abi_long freebsd_exec_common(abi_ulong path_or_fd, abi_ulong guest_argp,
     qarg0 = argp = g_new0(char *, argc + 9);
     /* save the first argument for the emulator */
     *argp++ = (char *)getprogname();
-    qargp = argp;
     *argp++ = (char *)getprogname();
-    qarg1 = argp;
     envp = g_new0(char *, envc + 1);
     for (gp = guest_argp, q = argp; gp; gp += sizeof(abi_ulong), q++) {
         if (get_user_ual(addr, gp)) {
@@ -137,7 +83,6 @@  abi_long freebsd_exec_common(abi_ulong path_or_fd, abi_ulong guest_argp,
         total_size += strlen(*q) + 1;
     }
     *q++ = NULL;
-    qargend = q;
 
     for (gp = guest_envp, q = envp; gp; gp += sizeof(abi_ulong), q++) {
         if (get_user_ual(addr, gp)) {
@@ -166,71 +111,14 @@  abi_long freebsd_exec_common(abi_ulong path_or_fd, abi_ulong guest_argp,
     }
 
     if (do_fexec) {
-        if (((int)path_or_fd > 0 &&
-            is_target_elf_binary((int)path_or_fd)) == 1) {
-            char execpath[PATH_MAX];
-
-            /*
-             * The executable is an elf binary for the target
-             * arch.  execve() it using the emulator if we can
-             * determine the filename path from the fd.
-             */
-            if (get_filename_from_fd(getpid(), (int)path_or_fd, execpath,
-                        sizeof(execpath)) != NULL) {
-                memmove(qarg1 + 2, qarg1, (qargend - qarg1) * sizeof(*qarg1));
-                qarg1[1] = qarg1[0];
-                qarg1[0] = (char *)"-0";
-                qarg1 += 2;
-                qargend += 2;
-                *qarg1 = execpath;
-#ifndef DONT_INHERIT_INTERP_PREFIX
-                memmove(qarg1 + 2, qarg1, (qargend - qarg1) * sizeof(*qarg1));
-                *qarg1++ = (char *)"-L";
-                *qarg1++ = (char *)interp_prefix;
-#endif
-                ret = get_errno(execve(qemu_proc_pathname, qargp, envp));
-            } else {
-                /* Getting the filename path failed. */
-                ret = -TARGET_EBADF;
-                goto execve_end;
-            }
-        } else {
-            ret = get_errno(fexecve((int)path_or_fd, argp, envp));
-        }
+        ret = get_errno(fexecve((int)path_or_fd, argp, envp));
     } else {
-        int fd;
-
         p = lock_user_string(path_or_fd);
         if (p == NULL) {
             ret = -TARGET_EFAULT;
             goto execve_end;
         }
-
-        /*
-         * Check the header and see if it a target elf binary.  If so
-         * then execute using qemu user mode emulator.
-         */
-        fd = open(p, O_RDONLY | O_CLOEXEC);
-        if (fd > 0 && is_target_elf_binary(fd) == 1) {
-            close(fd);
-            /* execve() as a target binary using emulator. */
-            memmove(qarg1 + 2, qarg1, (qargend - qarg1) * sizeof(*qarg1));
-            qarg1[1] = qarg1[0];
-            qarg1[0] = (char *)"-0";
-            qarg1 += 2;
-            qargend += 2;
-            *qarg1 = (char *)p;
-#ifndef DONT_INHERIT_INTERP_PREFIX
-            memmove(qarg1 + 2, qarg1, (qargend - qarg1) * sizeof(*qarg1));
-            *qarg1++ = (char *)"-L";
-            *qarg1++ = (char *)interp_prefix;
-#endif
-            ret = get_errno(execve(qemu_proc_pathname, qargp, envp));
-        } else {
-            close(fd);
-            /* Execve() as a host native binary. */
-            ret = get_errno(execve(p, argp, envp));
-        }
+        ret = get_errno(execve(p, argp, envp));
         unlock_user(p, path_or_fd, 0);
     }
 
diff --git a/bsd-user/main.c b/bsd-user/main.c
index dcad266c2c9..82e94a03160 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -90,7 +90,6 @@  unsigned long reserved_va;
 
 const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX;
 const char *qemu_uname_release;
-char qemu_proc_pathname[PATH_MAX];  /* full path to exeutable */
 
 unsigned long target_maxtsiz = TARGET_MAXTSIZ;   /* max text size */
 unsigned long target_dfldsiz = TARGET_DFLDSIZ;   /* initial data size limit */
@@ -247,22 +246,6 @@  adjust_ssize(void)
     setrlimit(RLIMIT_STACK, &rl);
 }
 
-static void save_proc_pathname(char *argv0)
-{
-    int mib[4];
-    size_t len;
-
-    mib[0] = CTL_KERN;
-    mib[1] = KERN_PROC;
-    mib[2] = KERN_PROC_PATHNAME;
-    mib[3] = -1;
-
-    len = sizeof(qemu_proc_pathname);
-    if (sysctl(mib, 4, qemu_proc_pathname, &len, NULL, 0)) {
-        perror("sysctl");
-    }
-}
-
 int main(int argc, char **argv)
 {
     const char *filename;
@@ -292,7 +275,6 @@  int main(int argc, char **argv)
         usage();
     }
 
-    save_proc_pathname(argv[0]);
 
     error_init(argv[0]);
     module_call_init(MODULE_INIT_TRACE);