* [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
@ 2017-12-05 4:48 Richard Henderson
2017-12-05 4:53 ` no-reply
2017-12-07 13:05 ` Peter Maydell
0 siblings, 2 replies; 7+ messages in thread
From: Richard Henderson @ 2017-12-05 4:48 UTC (permalink / raw)
To: qemu-devel; +Cc: peter.maydell, Richard Henderson
From: Richard Henderson <rth@twiddle.net>
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 <rth@twiddle.net>
---
Changes since v1 (Nov 2016):
* Require interp_dirfd set before trying the *at path.
r~
---
linux-user/qemu.h | 1 +
linux-user/elfload.c | 12 ++-
linux-user/main.c | 3 +-
linux-user/syscall.c | 236 ++++++++++++++++++++++++++++++++++++++++++---------
4 files changed, 208 insertions(+), 44 deletions(-)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 4edd7d0c08..d04924fd2e 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -437,6 +437,7 @@ 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/elfload.c b/linux-user/elfload.c
index 20f3d8c2c3..5d3f7aa11d 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -2203,7 +2203,17 @@ static void load_elf_interp(const char *filename, struct image_info *info,
{
int fd, retval;
- fd = open(path(filename), O_RDONLY);
+ switch (interp_dirfd > 0 && filename[0] == '/') {
+ case true:
+ 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 6286661bd3..06edc2c6bc 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -99,6 +99,7 @@ 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
@@ -4297,7 +4298,7 @@ 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/syscall.c b/linux-user/syscall.c
index 11c9116c4a..dc4387e3e6 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7228,7 +7228,18 @@ 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 (interp_dirfd > 0 && name[0] == '/') {
+ case true:
+ 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):
@@ -7604,6 +7615,7 @@ 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);
@@ -7643,7 +7655,18 @@ 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 (interp_dirfd > 0 && pathname[0] == '/') {
+ case true:
+ 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
@@ -7729,6 +7752,7 @@ 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
@@ -8260,10 +8284,21 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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
@@ -8277,18 +8312,42 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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 */
@@ -8415,7 +8474,7 @@ 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;
@@ -9181,14 +9240,14 @@ 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. */
@@ -9202,10 +9261,21 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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
@@ -9213,20 +9283,31 @@ 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 (interp_dirfd && fn[0] == '/') {
+ case true:
+ 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
@@ -9395,7 +9476,7 @@ 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)) {
@@ -9425,7 +9506,7 @@ 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)) {
@@ -9654,18 +9735,42 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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:
@@ -10745,20 +10850,44 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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;
@@ -10777,9 +10906,21 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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;
@@ -11776,12 +11917,23 @@ 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 (interp_dirfd > 0 && fn[0] == '/') {
+ case true:
+ 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;
@@ -11811,7 +11963,7 @@ 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
--
2.13.6
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-05 4:48 [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents Richard Henderson
@ 2017-12-05 4:53 ` no-reply
2017-12-07 13:05 ` Peter Maydell
1 sibling, 0 replies; 7+ messages in thread
From: no-reply @ 2017-12-05 4:53 UTC (permalink / raw)
To: richard.henderson; +Cc: famz, qemu-devel, peter.maydell, rth
Hi,
This series seems to have some coding style problems. See output below for
more information:
Subject: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
Type: series
Message-id: 20171205044844.3597-1-richard.henderson@linaro.org
=== TEST SCRIPT BEGIN ===
#!/bin/bash
BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0
git config --local diff.renamelimit 0
git config --local diff.renames True
commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
failed=1
echo
fi
n=$((n+1))
done
exit $failed
=== TEST SCRIPT END ===
Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
t [tag update] patchew/1510087611-1851-1-git-send-email-cota@braap.org -> patchew/1510087611-1851-1-git-send-email-cota@braap.org
t [tag update] patchew/1512154296-5652-1-git-send-email-peter.maydell@linaro.org -> patchew/1512154296-5652-1-git-send-email-peter.maydell@linaro.org
* [new tag] patchew/20171205044844.3597-1-richard.henderson@linaro.org -> patchew/20171205044844.3597-1-richard.henderson@linaro.org
Switched to a new branch 'test'
88b8681d57 linux-user: Use *at functions instead of caching interp_prefix contents
=== OUTPUT BEGIN ===
Checking PATCH 1/1: linux-user: Use *at functions instead of caching interp_prefix contents...
ERROR: do not use assignment in if condition
#135: FILE: linux-user/syscall.c:8287:
+ if (!(fn = lock_user_string(arg2)))
ERROR: braces {} are necessary for all arms of this statement
#135: FILE: linux-user/syscall.c:8287:
+ if (!(fn = lock_user_string(arg2)))
[...]
ERROR: do not use assignment in if condition
#160: FILE: linux-user/syscall.c:8315:
+ if (!(fn = lock_user_string(arg1))) {
ERROR: do not use assignment in if condition
#183: FILE: linux-user/syscall.c:8335:
+ if (!(fn = lock_user_string(arg2))) {
ERROR: do not use assignment in if condition
#315: FILE: linux-user/syscall.c:9738:
+ if (!(fn = lock_user_string(arg1))) {
ERROR: do not use assignment in if condition
#338: FILE: linux-user/syscall.c:9758:
+ if (!(fn = lock_user_string(arg1))) {
ERROR: do not use assignment in if condition
#364: FILE: linux-user/syscall.c:10853:
+ if (!(fn = lock_user_string(arg1))) {
ERROR: do not use assignment in if condition
#389: FILE: linux-user/syscall.c:10875:
+ if (!(fn = lock_user_string(arg1))) {
ERROR: do not use assignment in if condition
#415: FILE: linux-user/syscall.c:10909:
+ if (!(fn = lock_user_string(arg2)))
ERROR: braces {} are necessary for all arms of this statement
#415: FILE: linux-user/syscall.c:10909:
+ if (!(fn = lock_user_string(arg2)))
[...]
ERROR: do not use assignment in if condition
#439: FILE: linux-user/syscall.c:11920:
+ if (!(fn = lock_user_string(arg2))) {
total: 11 errors, 0 warnings, 419 lines checked
Your patch has style problems, please review. If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
=== OUTPUT END ===
Test command exited with code: 1
---
Email generated automatically by Patchew [http://patchew.org/].
Please send your feedback to patchew-devel@freelists.org
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-05 4:48 [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents Richard Henderson
2017-12-05 4:53 ` no-reply
@ 2017-12-07 13:05 ` Peter Maydell
2017-12-07 14:43 ` Richard Henderson
1 sibling, 1 reply; 7+ messages in thread
From: Peter Maydell @ 2017-12-07 13:05 UTC (permalink / raw)
To: Richard Henderson; +Cc: QEMU Developers, Richard Henderson
On 5 December 2017 at 04:48, Richard Henderson
<richard.henderson@linaro.org> wrote:
> From: Richard Henderson <rth@twiddle.net>
>
> 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 <rth@twiddle.net>
> ---
>
> Changes since v1 (Nov 2016):
> * Require interp_dirfd set before trying the *at path.
>
>
> r~
> ---
> linux-user/qemu.h | 1 +
> linux-user/elfload.c | 12 ++-
> linux-user/main.c | 3 +-
> linux-user/syscall.c | 236 ++++++++++++++++++++++++++++++++++++++++++---------
> 4 files changed, 208 insertions(+), 44 deletions(-)
>
> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
> index 4edd7d0c08..d04924fd2e 100644
> --- a/linux-user/qemu.h
> +++ b/linux-user/qemu.h
> @@ -437,6 +437,7 @@ 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/elfload.c b/linux-user/elfload.c
> index 20f3d8c2c3..5d3f7aa11d 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2203,7 +2203,17 @@ static void load_elf_interp(const char *filename, struct image_info *info,
> {
> int fd, retval;
>
> - fd = open(path(filename), O_RDONLY);
> + switch (interp_dirfd > 0 && filename[0] == '/') {
> + case true:
gcc doesn't like this pattern:
/home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c: In
function ‘do_name_to_handle_at’:
/home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c:7231:13:
error: switch condition has boolean value [-Werror=switch-bool]
switch (interp_dirfd > 0 && name[0] == '/') {
^
It seems like an odd way to write an if().
thanks
-- PMM
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-07 13:05 ` Peter Maydell
@ 2017-12-07 14:43 ` Richard Henderson
2017-12-07 14:57 ` Peter Maydell
2017-12-07 17:06 ` Eric Blake
0 siblings, 2 replies; 7+ messages in thread
From: Richard Henderson @ 2017-12-07 14:43 UTC (permalink / raw)
To: Peter Maydell, Richard Henderson; +Cc: QEMU Developers
On 12/07/2017 05:05 AM, Peter Maydell wrote:
> On 5 December 2017 at 04:48, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>> From: Richard Henderson <rth@twiddle.net>
>>
>> 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 <rth@twiddle.net>
>> ---
>>
>> Changes since v1 (Nov 2016):
>> * Require interp_dirfd set before trying the *at path.
>>
>>
>> r~
>> ---
>> linux-user/qemu.h | 1 +
>> linux-user/elfload.c | 12 ++-
>> linux-user/main.c | 3 +-
>> linux-user/syscall.c | 236 ++++++++++++++++++++++++++++++++++++++++++---------
>> 4 files changed, 208 insertions(+), 44 deletions(-)
>>
>> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
>> index 4edd7d0c08..d04924fd2e 100644
>> --- a/linux-user/qemu.h
>> +++ b/linux-user/qemu.h
>> @@ -437,6 +437,7 @@ 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/elfload.c b/linux-user/elfload.c
>> index 20f3d8c2c3..5d3f7aa11d 100644
>> --- a/linux-user/elfload.c
>> +++ b/linux-user/elfload.c
>> @@ -2203,7 +2203,17 @@ static void load_elf_interp(const char *filename, struct image_info *info,
>> {
>> int fd, retval;
>>
>> - fd = open(path(filename), O_RDONLY);
>> + switch (interp_dirfd > 0 && filename[0] == '/') {
>> + case true:
>
> gcc doesn't like this pattern:
>
> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c: In
> function ‘do_name_to_handle_at’:
> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c:7231:13:
> error: switch condition has boolean value [-Werror=switch-bool]
> switch (interp_dirfd > 0 && name[0] == '/') {
> ^
>
> It seems like an odd way to write an if().
Huh. My gcc likes it just fine. What version are you using?
It's an IF with a /* fallthru */, so there are very few
less ugly ways to write it...
r~
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-07 14:43 ` Richard Henderson
@ 2017-12-07 14:57 ` Peter Maydell
2017-12-07 17:06 ` Eric Blake
1 sibling, 0 replies; 7+ messages in thread
From: Peter Maydell @ 2017-12-07 14:57 UTC (permalink / raw)
To: Richard Henderson; +Cc: Richard Henderson, QEMU Developers
On 7 December 2017 at 14:43, Richard Henderson <rth@twiddle.net> wrote:
> On 12/07/2017 05:05 AM, Peter Maydell wrote:
>> gcc doesn't like this pattern:
>>
>> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c: In
>> function ‘do_name_to_handle_at’:
>> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c:7231:13:
>> error: switch condition has boolean value [-Werror=switch-bool]
>> switch (interp_dirfd > 0 && name[0] == '/') {
>> ^
>>
>> It seems like an odd way to write an if().
>
> Huh. My gcc likes it just fine. What version are you using?
>
> It's an IF with a /* fallthru */, so there are very few
> less ugly ways to write it...
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.5) 5.4.0 20160609
(for x86-64).
thanks
-- PMM
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-07 14:43 ` Richard Henderson
2017-12-07 14:57 ` Peter Maydell
@ 2017-12-07 17:06 ` Eric Blake
2017-12-07 19:31 ` Richard Henderson
1 sibling, 1 reply; 7+ messages in thread
From: Eric Blake @ 2017-12-07 17:06 UTC (permalink / raw)
To: Richard Henderson, Peter Maydell, Richard Henderson; +Cc: QEMU Developers
[-- Attachment #1: Type: text/plain, Size: 1173 bytes --]
On 12/07/2017 08:43 AM, Richard Henderson wrote:
>>> - fd = open(path(filename), O_RDONLY);
>>> + switch (interp_dirfd > 0 && filename[0] == '/') {
>>> + case true:
>>
>> gcc doesn't like this pattern:
>>
>> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c: In
>> function ‘do_name_to_handle_at’:
>> /home/petmay01/linaro/qemu-from-laptop/qemu/linux-user/syscall.c:7231:13:
>> error: switch condition has boolean value [-Werror=switch-bool]
>> switch (interp_dirfd > 0 && name[0] == '/') {
>> ^
>>
>> It seems like an odd way to write an if().
>
> Huh. My gcc likes it just fine. What version are you using?
>
> It's an IF with a /* fallthru */, so there are very few
> less ugly ways to write it...
Maybe:
while (1) {
if (interp_dirfd > 0 && filename[0] == '/') {
fd = openat(interp_dirfd, filename + 1, O_RDONLY);
if (fd >= 0 || errno != ENOENT) {
break;
}
}
fd = open(filename, O_RDONLY);
break;
}
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 619 bytes --]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Qemu-devel] [PATCH v2] linux-user: Use *at functions instead of caching interp_prefix contents
2017-12-07 17:06 ` Eric Blake
@ 2017-12-07 19:31 ` Richard Henderson
0 siblings, 0 replies; 7+ messages in thread
From: Richard Henderson @ 2017-12-07 19:31 UTC (permalink / raw)
To: Eric Blake, Peter Maydell, Richard Henderson; +Cc: QEMU Developers
On 12/07/2017 09:06 AM, Eric Blake wrote:
>> It's an IF with a /* fallthru */, so there are very few
>> less ugly ways to write it...
>
> Maybe:
>
> while (1) {
> if (interp_dirfd > 0 && filename[0] == '/') {
> fd = openat(interp_dirfd, filename + 1, O_RDONLY);
> if (fd >= 0 || errno != ENOENT) {
> break;
> }
> }
> fd = open(filename, O_RDONLY);
> break;
> }
Nice. I'd been pondering
if (interp_dirfd < 0
|| filename[0] != '/'
|| (fd = openat(interp_dirfd, filename + 1, O_RDONLY),
fd < 0 && errno == ENOENT)) {
fd = open(filename, O_RDONLY);
}
r~
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2017-12-07 19:31 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2017-12-05 4:53 ` no-reply
2017-12-07 13:05 ` Peter Maydell
2017-12-07 14:43 ` Richard Henderson
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