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bsd-user: Simplify the implementation of execve
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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 <[email protected]>
Reviewed-by: Warner Losh <[email protected]>
Signed-off-by: Warner Losh <[email protected]>
Acked-by: Richard Henderson <[email protected]>
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@dfr @bsdimp
dfr authored and bsdimp committed Jul 23, 2024
1 parent ce6c541 commit e6e102b
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Showing 2 changed files with 3 additions and 133 deletions.
118 changes: 3 additions & 115 deletions bsd-user/freebsd/os-proc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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)) {
Expand All @@ -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)) {
Expand Down Expand Up @@ -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);
}

Expand Down
18 changes: 0 additions & 18 deletions bsd-user/main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down

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