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[Qemu-devel] [PATCH] linux-user: Use *at functions instead of caching in
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From: |
Richard Henderson |
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Subject: |
[Qemu-devel] [PATCH] linux-user: Use *at functions instead of caching interp_prefix contents |
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Date: |
Wed, 11 Jan 2017 20:05:34 -0800 |
If the interp_prefix is a complete chroot, it may have a *lot* of files.
Setting up the cache for this is quite expensive. Instead, use the *at
versions of various syscalls to attempt the operation in the prefix.
Signed-off-by: Richard Henderson <address@hidden>
---
linux-user/elfload.c | 12 ++-
linux-user/main.c | 3 +-
linux-user/qemu.h | 1 +
linux-user/syscall.c | 236 ++++++++++++++++++++++++++++++++++++++++++---------
util/Makefile.objs | 2 +-
util/path.c | 178 --------------------------------------
6 files changed, 209 insertions(+), 223 deletions(-)
delete mode 100644 util/path.c
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 547053c..8b947fd 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2026,7 +2026,17 @@ static void load_elf_interp(const char *filename, struct
image_info *info,
{
int fd, retval;
- fd = open(path(filename), O_RDONLY);
+ switch (filename[0]) {
+ case '/':
+ fd = openat(interp_dirfd, filename + 1, O_RDONLY);
+ if (fd >= 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ fd = open(filename, O_RDONLY);
+ break;
+ }
if (fd < 0) {
goto exit_perror;
}
diff --git a/linux-user/main.c b/linux-user/main.c
index c1d5eb4..dba988b 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -81,6 +81,7 @@ unsigned long reserved_va;
static void usage(int exitcode);
static const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX;
+int interp_dirfd;
const char *qemu_uname_release;
/* XXX: on x86 MAP_GROWSDOWN only works if ESP <= address + 32, so
@@ -4013,7 +4014,7 @@ int main(int argc, char **argv, char **envp)
memset(&bprm, 0, sizeof (bprm));
/* Scan interp_prefix dir for replacement files. */
- init_paths(interp_prefix);
+ interp_dirfd = open(interp_prefix, O_CLOEXEC | O_DIRECTORY | O_PATH);
init_qemu_uname_release();
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index da73a01..f91e2d5 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -434,6 +434,7 @@ void mmap_fork_start(void);
void mmap_fork_end(int child);
/* main.c */
+extern int interp_dirfd;
extern unsigned long guest_stack_size;
/* user access */
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 7b77503..18d40bb 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7055,7 +7055,18 @@ static abi_long do_name_to_handle_at(abi_long dirfd,
abi_long pathname,
fh = g_malloc0(total_size);
fh->handle_bytes = size;
- ret = get_errno(name_to_handle_at(dirfd, path(name), fh, &mid, flags));
+ switch (name[0]) {
+ case '/':
+ ret = name_to_handle_at(interp_dirfd, name + 1, fh, &mid, flags);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = name_to_handle_at(dirfd, name, fh, &mid, flags);
+ break;
+ }
+ ret = get_errno(ret);
unlock_user(name, pathname, 0);
/* man name_to_handle_at(2):
@@ -7464,6 +7475,7 @@ static int do_openat(void *cpu_env, int dirfd, const char
*pathname, int flags,
#endif
{ NULL, NULL, NULL }
};
+ int ret;
if (is_proc_myself(pathname, "exe")) {
int execfd = qemu_getauxval(AT_EXECFD);
@@ -7503,7 +7515,18 @@ static int do_openat(void *cpu_env, int dirfd, const
char *pathname, int flags,
return fd;
}
- return safe_openat(dirfd, path(pathname), flags, mode);
+ switch (pathname[0]) {
+ case '/':
+ ret = safe_openat(interp_dirfd, pathname + 1, flags, mode);
+ if (ret >= 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = safe_openat(dirfd, pathname, flags, mode);
+ break;
+ }
+ return ret;
}
#define TIMER_MAGIC 0x0caf0000
@@ -7540,6 +7563,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
struct stat st;
struct statfs stfs;
void *p;
+ char *fn;
#if defined(DEBUG_ERESTARTSYS)
/* Debug-only code for exercising the syscall-restart code paths
@@ -8058,10 +8082,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
} else {
tvp = NULL;
}
- if (!(p = lock_user_string(arg2)))
+ if (!(fn = lock_user_string(arg2)))
goto efault;
- ret = get_errno(futimesat(arg1, path(p), tvp));
- unlock_user(p, arg2, 0);
+ switch (fn[0]) {
+ case '/':
+ ret = futimesat(interp_dirfd, fn + 1, tvp);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = futimesat(arg1, fn, tvp);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg2, 0);
}
break;
#endif
@@ -8075,18 +8110,42 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
#endif
#ifdef TARGET_NR_access
case TARGET_NR_access:
- if (!(p = lock_user_string(arg1)))
+ if (!(fn = lock_user_string(arg1))) {
goto efault;
- ret = get_errno(access(path(p), arg2));
- unlock_user(p, arg1, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = faccessat(interp_dirfd, fn + 1, arg2, 0);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = access(fn, arg2);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg1, 0);
break;
#endif
#if defined(TARGET_NR_faccessat) && defined(__NR_faccessat)
case TARGET_NR_faccessat:
- if (!(p = lock_user_string(arg2)))
+ if (!(fn = lock_user_string(arg2))) {
goto efault;
- ret = get_errno(faccessat(arg1, p, arg3, 0));
- unlock_user(p, arg2, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = faccessat(interp_dirfd, fn + 1, arg3, 0);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = faccessat(arg1, fn, arg3, 0);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg2, 0);
break;
#endif
#ifdef TARGET_NR_nice /* not on alpha */
@@ -8213,7 +8272,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
} else {
if (!(p = lock_user_string(arg1)))
goto efault;
- ret = get_errno(acct(path(p)));
+ ret = get_errno(acct(p));
unlock_user(p, arg1, 0);
}
break;
@@ -8955,14 +9014,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
case TARGET_NR_readlink:
{
void *p2;
- p = lock_user_string(arg1);
+ fn = lock_user_string(arg1);
p2 = lock_user(VERIFY_WRITE, arg2, arg3, 0);
- if (!p || !p2) {
+ if (!fn || !p2) {
ret = -TARGET_EFAULT;
} else if (!arg3) {
/* Short circuit this for the magic exe check. */
ret = -TARGET_EINVAL;
- } else if (is_proc_myself((const char *)p, "exe")) {
+ } else if (is_proc_myself(fn, "exe")) {
char real[PATH_MAX], *temp;
temp = realpath(exec_path, real);
/* Return value is # of bytes that we wrote to the buffer. */
@@ -8976,10 +9035,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
memcpy(p2, real, ret);
}
} else {
- ret = get_errno(readlink(path(p), p2, arg3));
+ switch (fn[0]) {
+ case '/':
+ ret = readlinkat(interp_dirfd, fn + 1, p2, arg3);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = readlink(fn, p2, arg3);
+ break;
+ }
+ ret = get_errno(ret);
}
unlock_user(p2, arg2, ret);
- unlock_user(p, arg1, 0);
+ unlock_user(fn, arg1, 0);
}
break;
#endif
@@ -8987,20 +9057,31 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
case TARGET_NR_readlinkat:
{
void *p2;
- p = lock_user_string(arg2);
+ fn = lock_user_string(arg2);
p2 = lock_user(VERIFY_WRITE, arg3, arg4, 0);
- if (!p || !p2) {
+ if (!fn || !p2) {
ret = -TARGET_EFAULT;
- } else if (is_proc_myself((const char *)p, "exe")) {
+ } else if (is_proc_myself(fn, "exe")) {
char real[PATH_MAX], *temp;
temp = realpath(exec_path, real);
ret = temp == NULL ? get_errno(-1) : strlen(real) ;
snprintf((char *)p2, arg4, "%s", real);
} else {
- ret = get_errno(readlinkat(arg1, path(p), p2, arg4));
+ switch (fn[0]) {
+ case '/':
+ ret = readlinkat(interp_dirfd, fn + 1, p2, arg4);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = readlinkat(arg1, fn, p2, arg4);
+ break;
+ }
+ ret = get_errno(ret);
}
unlock_user(p2, arg3, ret);
- unlock_user(p, arg2, 0);
+ unlock_user(fn, arg2, 0);
}
break;
#endif
@@ -9169,7 +9250,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
case TARGET_NR_statfs:
if (!(p = lock_user_string(arg1)))
goto efault;
- ret = get_errno(statfs(path(p), &stfs));
+ ret = get_errno(statfs(p, &stfs));
unlock_user(p, arg1, 0);
convert_statfs:
if (!is_error(ret)) {
@@ -9199,7 +9280,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
case TARGET_NR_statfs64:
if (!(p = lock_user_string(arg1)))
goto efault;
- ret = get_errno(statfs(path(p), &stfs));
+ ret = get_errno(statfs(p, &stfs));
unlock_user(p, arg1, 0);
convert_statfs64:
if (!is_error(ret)) {
@@ -9429,18 +9510,42 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
break;
#ifdef TARGET_NR_stat
case TARGET_NR_stat:
- if (!(p = lock_user_string(arg1)))
+ if (!(fn = lock_user_string(arg1))) {
goto efault;
- ret = get_errno(stat(path(p), &st));
- unlock_user(p, arg1, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = fstatat(interp_dirfd, fn + 1, &st, 0);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = stat(fn, &st);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg1, 0);
goto do_stat;
#endif
#ifdef TARGET_NR_lstat
case TARGET_NR_lstat:
- if (!(p = lock_user_string(arg1)))
+ if (!(fn = lock_user_string(arg1))) {
goto efault;
- ret = get_errno(lstat(path(p), &st));
- unlock_user(p, arg1, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = fstatat(interp_dirfd, fn + 1, &st, AT_SYMLINK_NOFOLLOW);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = lstat(fn, &st);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg1, 0);
goto do_stat;
#endif
case TARGET_NR_fstat:
@@ -10513,20 +10618,44 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
#endif
#ifdef TARGET_NR_stat64
case TARGET_NR_stat64:
- if (!(p = lock_user_string(arg1)))
+ if (!(fn = lock_user_string(arg1))) {
goto efault;
- ret = get_errno(stat(path(p), &st));
- unlock_user(p, arg1, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = fstatat(interp_dirfd, fn + 1, &st, 0);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = stat(fn, &st);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg1, 0);
if (!is_error(ret))
ret = host_to_target_stat64(cpu_env, arg2, &st);
break;
#endif
#ifdef TARGET_NR_lstat64
case TARGET_NR_lstat64:
- if (!(p = lock_user_string(arg1)))
+ if (!(fn = lock_user_string(arg1))) {
goto efault;
- ret = get_errno(lstat(path(p), &st));
- unlock_user(p, arg1, 0);
+ }
+ switch (fn[0]) {
+ case '/':
+ ret = fstatat(interp_dirfd, fn + 1, &st, AT_SYMLINK_NOFOLLOW);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = lstat(fn, &st);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg1, 0);
if (!is_error(ret))
ret = host_to_target_stat64(cpu_env, arg2, &st);
break;
@@ -10545,9 +10674,21 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
#ifdef TARGET_NR_newfstatat
case TARGET_NR_newfstatat:
#endif
- if (!(p = lock_user_string(arg2)))
+ if (!(fn = lock_user_string(arg2)))
goto efault;
- ret = get_errno(fstatat(arg1, path(p), &st, arg4));
+ switch (fn[0]) {
+ case '/':
+ ret = fstatat(interp_dirfd, fn + 1, &st, arg4);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = fstatat(arg1, fn, &st, arg4);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg2, 0);
if (!is_error(ret))
ret = host_to_target_stat64(cpu_env, arg3, &st);
break;
@@ -11529,12 +11670,23 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
if (!arg2)
ret = get_errno(sys_utimensat(arg1, NULL, tsp, arg4));
else {
- if (!(p = lock_user_string(arg2))) {
+ if (!(fn = lock_user_string(arg2))) {
ret = -TARGET_EFAULT;
goto fail;
}
- ret = get_errno(sys_utimensat(arg1, path(p), tsp, arg4));
- unlock_user(p, arg2, 0);
+ switch (fn[0]) {
+ case '/':
+ ret = sys_utimensat(interp_dirfd, fn + 1, tsp, arg4);
+ if (ret == 0 || errno != ENOENT) {
+ break;
+ }
+ /* fallthru */
+ default:
+ ret = sys_utimensat(arg1, fn, tsp, arg4);
+ break;
+ }
+ ret = get_errno(ret);
+ unlock_user(fn, arg2, 0);
}
}
break;
@@ -11557,7 +11709,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long
arg1,
#if defined(TARGET_NR_inotify_add_watch) && defined(__NR_inotify_add_watch)
case TARGET_NR_inotify_add_watch:
p = lock_user_string(arg2);
- ret = get_errno(sys_inotify_add_watch(arg1, path(p), arg3));
+ ret = get_errno(sys_inotify_add_watch(arg1, p, arg3));
unlock_user(p, arg2, 0);
break;
#endif
diff --git a/util/Makefile.objs b/util/Makefile.objs
index ad0f9c7..429d1b0 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -10,7 +10,7 @@ util-obj-$(CONFIG_WIN32) += event_notifier-win32.o
util-obj-$(CONFIG_POSIX) += memfd.o
util-obj-$(CONFIG_WIN32) += oslib-win32.o
util-obj-$(CONFIG_WIN32) += qemu-thread-win32.o
-util-obj-y += envlist.o path.o module.o
+util-obj-y += envlist.o module.o
util-obj-$(call lnot,$(CONFIG_INT128)) += host-utils.o
util-obj-y += bitmap.o bitops.o hbitmap.o
util-obj-y += fifo8.o
diff --git a/util/path.c b/util/path.c
deleted file mode 100644
index 5479f76..0000000
--- a/util/path.c
+++ /dev/null
@@ -1,178 +0,0 @@
-/* Code to mangle pathnames into those matching a given prefix.
- eg. open("/lib/foo.so") => open("/usr/gnemul/i386-linux/lib/foo.so");
-
- The assumption is that this area does not change.
-*/
-#include "qemu/osdep.h"
-#include <sys/param.h>
-#include <dirent.h>
-#include "qemu-common.h"
-#include "qemu/cutils.h"
-#include "qemu/path.h"
-
-struct pathelem
-{
- /* Name of this, eg. lib */
- char *name;
- /* Full path name, eg. /usr/gnemul/x86-linux/lib. */
- char *pathname;
- struct pathelem *parent;
- /* Children */
- unsigned int num_entries;
- struct pathelem *entries[0];
-};
-
-static struct pathelem *base;
-
-/* First N chars of S1 match S2, and S2 is N chars long. */
-static int strneq(const char *s1, unsigned int n, const char *s2)
-{
- unsigned int i;
-
- for (i = 0; i < n; i++)
- if (s1[i] != s2[i])
- return 0;
- return s2[i] == 0;
-}
-
-static struct pathelem *add_entry(struct pathelem *root, const char *name,
- unsigned type);
-
-static struct pathelem *new_entry(const char *root,
- struct pathelem *parent,
- const char *name)
-{
- struct pathelem *new = g_malloc(sizeof(*new));
- new->name = g_strdup(name);
- new->pathname = g_strdup_printf("%s/%s", root, name);
- new->num_entries = 0;
- return new;
-}
-
-#define streq(a,b) (strcmp((a), (b)) == 0)
-
-/* Not all systems provide this feature */
-#if defined(DT_DIR) && defined(DT_UNKNOWN) && defined(DT_LNK)
-# define dirent_type(dirent) ((dirent)->d_type)
-# define is_dir_maybe(type) \
- ((type) == DT_DIR || (type) == DT_UNKNOWN || (type) == DT_LNK)
-#else
-# define dirent_type(dirent) (1)
-# define is_dir_maybe(type) (type)
-#endif
-
-static struct pathelem *add_dir_maybe(struct pathelem *path)
-{
- DIR *dir;
-
- if ((dir = opendir(path->pathname)) != NULL) {
- struct dirent *dirent;
-
- while ((dirent = readdir(dir)) != NULL) {
- if (!streq(dirent->d_name,".") && !streq(dirent->d_name,"..")){
- path = add_entry(path, dirent->d_name, dirent_type(dirent));
- }
- }
- closedir(dir);
- }
- return path;
-}
-
-static struct pathelem *add_entry(struct pathelem *root, const char *name,
- unsigned type)
-{
- struct pathelem **e;
-
- root->num_entries++;
-
- root = g_realloc(root, sizeof(*root)
- + sizeof(root->entries[0])*root->num_entries);
- e = &root->entries[root->num_entries-1];
-
- *e = new_entry(root->pathname, root, name);
- if (is_dir_maybe(type)) {
- *e = add_dir_maybe(*e);
- }
-
- return root;
-}
-
-/* This needs to be done after tree is stabilized (ie. no more reallocs!). */
-static void set_parents(struct pathelem *child, struct pathelem *parent)
-{
- unsigned int i;
-
- child->parent = parent;
- for (i = 0; i < child->num_entries; i++)
- set_parents(child->entries[i], child);
-}
-
-/* FIXME: Doesn't handle DIR/.. where DIR is not in emulated dir. */
-static const char *
-follow_path(const struct pathelem *cursor, const char *name)
-{
- unsigned int i, namelen;
-
- name += strspn(name, "/");
- namelen = strcspn(name, "/");
-
- if (namelen == 0)
- return cursor->pathname;
-
- if (strneq(name, namelen, ".."))
- return follow_path(cursor->parent, name + namelen);
-
- if (strneq(name, namelen, "."))
- return follow_path(cursor, name + namelen);
-
- for (i = 0; i < cursor->num_entries; i++)
- if (strneq(name, namelen, cursor->entries[i]->name))
- return follow_path(cursor->entries[i], name + namelen);
-
- /* Not found */
- return NULL;
-}
-
-void init_paths(const char *prefix)
-{
- char pref_buf[PATH_MAX];
-
- if (prefix[0] == '\0' ||
- !strcmp(prefix, "/"))
- return;
-
- if (prefix[0] != '/') {
- char *cwd = getcwd(NULL, 0);
- size_t pref_buf_len = sizeof(pref_buf);
-
- if (!cwd)
- abort();
- pstrcpy(pref_buf, sizeof(pref_buf), cwd);
- pstrcat(pref_buf, pref_buf_len, "/");
- pstrcat(pref_buf, pref_buf_len, prefix);
- free(cwd);
- } else
- pstrcpy(pref_buf, sizeof(pref_buf), prefix + 1);
-
- base = new_entry("", NULL, pref_buf);
- base = add_dir_maybe(base);
- if (base->num_entries == 0) {
- g_free(base->pathname);
- g_free(base->name);
- g_free(base);
- base = NULL;
- } else {
- set_parents(base, base);
- }
-}
-
-/* Look for path in emulation dir, otherwise return name. */
-const char *path(const char *name)
-{
- /* Only do absolute paths: quick and dirty, but should mostly be OK.
- Could do relative by tracking cwd. */
- if (!base || !name || name[0] != '/')
- return name;
-
- return follow_path(base, name) ?: name;
-}
--
2.9.3
- [Qemu-devel] [PATCH] linux-user: Use *at functions instead of caching interp_prefix contents,
Richard Henderson <=