From: "Marc-André Lureau" <marcandre.lureau@gmail.com>
To: Steve Sistare <steven.sistare@oracle.com>
Cc: "Jason Zeng" <jason.zeng@linux.intel.com>,
"Juan Quintela" <quintela@redhat.com>,
"Eric Blake" <eblake@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
QEMU <qemu-devel@nongnu.org>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Daniel P. Berrange" <berrange@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Markus Armbruster" <armbru@redhat.com>
Subject: Re: [PATCH V5 10/25] util: env var helpers
Date: Thu, 8 Jul 2021 19:10:45 +0400 [thread overview]
Message-ID: <CAJ+F1CKEPHdJLNc7gHzsRm8xz7=qXES2v-mjPrp_6WS+73hp6Q@mail.gmail.com> (raw)
In-Reply-To: <1625678434-240960-11-git-send-email-steven.sistare@oracle.com>
[-- Attachment #1: Type: text/plain, Size: 6008 bytes --]
Hi
On Wed, Jul 7, 2021 at 9:30 PM Steve Sistare <steven.sistare@oracle.com>
wrote:
> Add functions for saving fd's and other values in the environment via
> setenv, and for reading them back via getenv.
>
>
I understand that the rest of the series will rely on environment variables
to associate and recover the child-passed FDs, but I am not really
convinced that it is a good idea.
Environment variables have a number of issues that we may encounter down
the road: namespace, limits, concurrency, observability etc.. I wonder if
the VMState couldn't have a section about the FD to recover. Or maybe just
another shared memory region?
Some comments below. These new utils could also have some unit tests.
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
> MAINTAINERS | 2 ++
> include/qemu/env.h | 23 +++++++++++++
> util/env.c | 95
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> util/meson.build | 1 +
> 4 files changed, 121 insertions(+)
> create mode 100644 include/qemu/env.h
> create mode 100644 util/env.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c48dd37..8647a97 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2865,6 +2865,8 @@ S: Maintained
> F: include/migration/cpr.h
> F: migration/cpr.c
> F: qapi/cpr.json
> +F: include/qemu/env.h
> +F: util/env.c
>
> Record/replay
> M: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
> diff --git a/include/qemu/env.h b/include/qemu/env.h
> new file mode 100644
> index 0000000..3dad503
> --- /dev/null
> +++ b/include/qemu/env.h
> @@ -0,0 +1,23 @@
> +/*
> + * Copyright (c) 2021 Oracle and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef QEMU_ENV_H
> +#define QEMU_ENV_H
> +
> +#define FD_PREFIX "QEMU_FD_"
> +
> +typedef int (*walkenv_cb)(const char *name, const char *val, void
> *handle);
> +
> +int getenv_fd(const char *name);
> +void setenv_fd(const char *name, int fd);
> +void unsetenv_fd(const char *name);
> +void unsetenv_fdv(const char *fmt, ...);
> +int walkenv(const char *prefix, walkenv_cb cb, void *handle);
> +void printenv(void);
>
Please use qemu prefix, that avoids potential confusion with system
libraries.
+
> +#endif
> diff --git a/util/env.c b/util/env.c
> new file mode 100644
> index 0000000..863678d
> --- /dev/null
> +++ b/util/env.c
> @@ -0,0 +1,95 @@
> +/*
> + * Copyright (c) 2021 Oracle and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/cutils.h"
> +#include "qemu/env.h"
> +
> +static uint64_t getenv_ulong(const char *prefix, const char *name, int
> *err)
> +{
> + char var[80], *val;
> + uint64_t res = 0;
> +
> + snprintf(var, sizeof(var), "%s%s", prefix, name);
>
No check for success / truncation...
Please use g_autofree char *var = g_strdup_printf()..
+ val = getenv(var);
>
For consistency, I'd use g_getenv()
+ if (val) {
> + *err = qemu_strtoul(val, NULL, 10, &res);
> + } else {
> + *err = -ENOENT;
> + }
> + return res;
> +}
> +
> +static void setenv_ulong(const char *prefix, const char *name, uint64_t
> val)
> +{
> + char var[80], val_str[80];
> + snprintf(var, sizeof(var), "%s%s", prefix, name);
> + snprintf(val_str, sizeof(val_str), "%"PRIu64, val);
>
g_strdup_printf
+ setenv(var, val_str, 1);
>
g_setenv(), and return error value (or assert() if that makes more sense)
+}
> +
> +static void unsetenv_ulong(const char *prefix, const char *name)
> +{
> + char var[80];
> + snprintf(var, sizeof(var), "%s%s", prefix, name);
>
g_strdup_printf
> + unsetenv(var);
>
g_unsetenv
+}
> +
> +int getenv_fd(const char *name)
> +{
> + int err;
> + int fd = getenv_ulong(FD_PREFIX, name, &err);
>
I'd try to use qemu_parse_fd() instead.
+ return err ? -1 : fd;
> +}
> +
> +void setenv_fd(const char *name, int fd)
> +{
>
Maybe check fd >= 0 ?
+ setenv_ulong(FD_PREFIX, name, fd);
> +}
> +
> +void unsetenv_fd(const char *name)
> +{
> + unsetenv_ulong(FD_PREFIX, name);
> +}
> +
> +void unsetenv_fdv(const char *fmt, ...)
> +{
> + va_list args;
> + char buf[80];
> + va_start(args, fmt);
> + vsnprintf(buf, sizeof(buf), fmt, args);
> + va_end(args);
>
That seems to be a leftover.
+}
> +
> +int walkenv(const char *prefix, walkenv_cb cb, void *handle)
>
+{
> + char *str, name[128];
> + char **envp = environ;
> + size_t prefix_len = strlen(prefix);
> +
> + while (*envp) {
> + str = *envp++;
> + if (!strncmp(str, prefix, prefix_len)) {
>
+ char *val = strchr(str, '=');
> + str += prefix_len;
> + strncpy(name, str, val - str);
>
g_strndup() to avoid potential buffer overflow.
+ name[val - str] = 0;
> + if (cb(name, val + 1, handle)) {
> + return 1;
> + }
> + }
> + }
> + return 0;
> +}
> +
> +void printenv(void)
> +{
> + char **ptr = environ;
> + while (*ptr) {
> + puts(*ptr++);
> + }
> +}
>
Is this really useful? I doubt it.
> diff --git a/util/meson.build b/util/meson.build
> index 0ffd7f4..5e8097a 100644
> --- a/util/meson.build
> +++ b/util/meson.build
> @@ -23,6 +23,7 @@ util_ss.add(files('host-utils.c'))
> util_ss.add(files('bitmap.c', 'bitops.c'))
> util_ss.add(files('fifo8.c'))
> util_ss.add(files('cacheinfo.c', 'cacheflush.c'))
> +util_ss.add(files('env.c'))
> util_ss.add(files('error.c', 'qemu-error.c'))
> util_ss.add(files('qemu-print.c'))
> util_ss.add(files('id.c'))
> --
> 1.8.3.1
>
>
>
--
Marc-André Lureau
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next prev parent reply other threads:[~2021-07-08 15:11 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 17:20 [PATCH V5 00/25] Live Update Steve Sistare
2021-07-07 17:20 ` [PATCH V5 01/25] qemu_ram_volatile Steve Sistare
2021-07-08 12:01 ` Marc-André Lureau
2021-07-12 17:06 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 02/25] cpr: reboot mode Steve Sistare
2021-07-08 12:25 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-08-04 15:48 ` Eric Blake
2021-07-07 17:20 ` [PATCH V5 03/25] cpr: QMP interfaces for reboot Steve Sistare
2021-07-08 13:27 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-08-04 15:48 ` Eric Blake
2021-08-04 20:27 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 04/25] cpr: HMP " Steve Sistare
2021-07-28 4:55 ` Zheng Chuan
2021-07-07 17:20 ` [PATCH V5 05/25] as_flat_walk Steve Sistare
2021-07-08 13:49 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 06/25] oslib: qemu_clr_cloexec Steve Sistare
2021-07-08 13:58 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 07/25] machine: memfd-alloc option Steve Sistare
2021-07-08 14:20 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-07-12 17:45 ` Marc-André Lureau
2021-07-07 17:20 ` [PATCH V5 08/25] vl: add helper to request re-exec Steve Sistare
2021-07-08 14:31 ` Marc-André Lureau
2021-07-12 17:07 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 09/25] string to strList Steve Sistare
2021-07-08 14:37 ` Marc-André Lureau
2021-07-07 17:20 ` [PATCH V5 10/25] util: env var helpers Steve Sistare
2021-07-08 15:10 ` Marc-André Lureau [this message]
2021-07-12 19:19 ` Steven Sistare
2021-07-12 19:36 ` Marc-André Lureau
2021-07-13 16:15 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 11/25] cpr: restart mode Steve Sistare
2021-07-08 15:43 ` Marc-André Lureau
2021-07-08 15:54 ` Marc-André Lureau
2021-07-12 19:19 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 12/25] cpr: QMP interfaces for restart Steve Sistare
2021-07-08 15:49 ` Marc-André Lureau
2021-07-12 19:19 ` Steven Sistare
2021-08-04 16:00 ` Eric Blake
2021-08-04 20:22 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 13/25] cpr: HMP " Steve Sistare
2021-07-28 4:56 ` Zheng Chuan
2021-07-07 17:20 ` [PATCH V5 14/25] pci: export functions for cpr Steve Sistare
2021-07-07 17:20 ` [PATCH V5 15/25] vfio-pci: refactor " Steve Sistare
2021-07-07 17:20 ` [PATCH V5 16/25] vfio-pci: cpr part 1 Steve Sistare
2021-07-16 17:45 ` Alex Williamson
2021-07-19 17:43 ` Steven Sistare
2021-07-28 4:56 ` Zheng Chuan
2021-07-30 12:50 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 17/25] vfio-pci: cpr part 2 Steve Sistare
2021-07-16 20:51 ` Alex Williamson
2021-07-19 17:44 ` Steven Sistare
2021-07-19 18:10 ` Alex Williamson
2021-07-19 18:38 ` Steven Sistare
2021-07-28 4:56 ` Zheng Chuan
2021-07-30 12:52 ` Steven Sistare
2021-07-31 6:07 ` Zheng Chuan
2021-07-07 17:20 ` [PATCH V5 18/25] vhost: reset vhost devices upon cprsave Steve Sistare
2021-07-07 17:20 ` [PATCH V5 19/25] hostmem-memfd: cpr support Steve Sistare
2021-07-07 17:20 ` [PATCH V5 20/25] chardev: cpr framework Steve Sistare
2021-07-08 16:03 ` Marc-André Lureau
2021-07-12 19:20 ` Steven Sistare
2021-07-12 19:49 ` Marc-André Lureau
2021-07-13 14:34 ` Steven Sistare
2021-07-07 17:20 ` [PATCH V5 21/25] chardev: cpr for simple devices Steve Sistare
2021-07-07 17:20 ` [PATCH V5 22/25] chardev: cpr for pty Steve Sistare
2021-07-07 17:20 ` [PATCH V5 23/25] chardev: cpr for sockets Steve Sistare
2021-07-29 4:04 ` Zheng Chuan
2021-07-07 17:20 ` [PATCH V5 24/25] cpr: only-cpr-capable option Steve Sistare
2021-07-07 17:20 ` [PATCH V5 25/25] simplify savevm Steve Sistare
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