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[Qemu-devel] [PATCH v3] fw_cfg: insert string blobs via qemu cmdline
From: |
Gabriel L. Somlo |
Subject: |
[Qemu-devel] [PATCH v3] fw_cfg: insert string blobs via qemu cmdline |
Date: |
Mon, 28 Sep 2015 19:05:19 -0400 |
Allow users to provide custom fw_cfg blobs with ascii string
payloads specified directly on the qemu command line.
Suggested-by: Jordan Justen <address@hidden>
Suggested-by: Laszlo Ersek <address@hidden>
Signed-off-by: Gabriel Somlo <address@hidden>
Reviewd-by: Laszlo Ersek <address@hidden>
---
Changes from v2: documentation now clearly states that QEMU transparently
passes through whatever characters it gets from the shell
re. the fw_cfg blob name and/or the value of the content
string. ASCII is a mere recommendation to avoid surprises
potentially caused by the shell, nothing more.
Thanks,
--Gabriel
docs/specs/fw_cfg.txt | 15 +++++++++++++++
qemu-options.hx | 7 ++++++-
vl.c | 33 +++++++++++++++++++++++++++------
3 files changed, 48 insertions(+), 7 deletions(-)
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index b5f4b5d..fa75e2c 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -236,6 +236,21 @@ the following syntax:
where <item_name> is the fw_cfg item name, and <path> is the location
on the host file system of a file containing the data to be inserted.
+Small enough items may be provided directly as strings on the command
+line, using the syntax:
+
+ -fw_cfg [name=]<item_name>,content=<string>
+
+The terminating NUL character of the content <string> will NOT be
+included as part of the fw_cfg item data, which is consistent with
+the absence of a NUL terminator for items inserted via the file option.
+
+Both <item_name> and, if applicable, the content <string> are passed
+through by QEMU without any interpretation, expansion, or further
+processing. Any such processing (potentially performed e.g., by the shell)
+is outside of QEMU's responsibility; as such, using plain ASCII characters
+is recommended.
+
NOTE: Users *SHOULD* choose item names beginning with the prefix "opt/"
when using the "-fw_cfg" command line option, to avoid conflicting with
item names used internally by QEMU. For instance:
diff --git a/qemu-options.hx b/qemu-options.hx
index 328404c..0b6f5bd 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2724,13 +2724,18 @@ ETEXI
DEF("fw_cfg", HAS_ARG, QEMU_OPTION_fwcfg,
"-fw_cfg [name=]<name>,file=<file>\n"
- " add named fw_cfg entry from file\n",
+ " add named fw_cfg entry from file\n"
+ "-fw_cfg [name=]<name>,content=<str>\n"
+ " add named fw_cfg entry from string\n",
QEMU_ARCH_ALL)
STEXI
@item -fw_cfg address@hidden,address@hidden
@findex -fw_cfg
Add named fw_cfg entry from file. @var{name} determines the name of
the entry in the fw_cfg file directory exposed to the guest.
+
address@hidden -fw_cfg address@hidden,address@hidden
+Add named fw_cfg entry from string.
ETEXI
DEF("serial", HAS_ARG, QEMU_OPTION_serial, \
diff --git a/vl.c b/vl.c
index e211f6a..24ea82d 100644
--- a/vl.c
+++ b/vl.c
@@ -512,6 +512,10 @@ static QemuOptsList qemu_fw_cfg_opts = {
.type = QEMU_OPT_STRING,
.help = "Sets the name of the file from which\n"
"the fw_cfg blob will be loaded",
+ }, {
+ .name = "content",
+ .type = QEMU_OPT_STRING,
+ .help = "Sets the content of the fw_cfg blob to be inserted",
},
{ /* end of list */ }
},
@@ -2232,11 +2236,16 @@ char *qemu_find_file(int type, const char *name)
return NULL;
}
+static inline bool nonempty_str(const char *str)
+{
+ return str && *str;
+}
+
static int parse_fw_cfg(void *opaque, QemuOpts *opts, Error **errp)
{
gchar *buf;
size_t size;
- const char *name, *file;
+ const char *name, *file, *cont;
if (opaque == NULL) {
error_report("fw_cfg device not available");
@@ -2244,8 +2253,15 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts,
Error **errp)
}
name = qemu_opt_get(opts, "name");
file = qemu_opt_get(opts, "file");
- if (name == NULL || *name == '\0' || file == NULL || *file == '\0') {
- error_report("invalid argument value");
+ cont = qemu_opt_get(opts, "content");
+
+ /* we need name and either a file or the content string */
+ if (!(nonempty_str(name) && (nonempty_str(file) || nonempty_str(cont)))) {
+ error_report("invalid argument(s)");
+ return -1;
+ }
+ if (nonempty_str(file) && nonempty_str(cont)) {
+ error_report("file and content are mutually exclusive");
return -1;
}
if (strlen(name) > FW_CFG_MAX_FILE_PATH - 1) {
@@ -2256,9 +2272,14 @@ static int parse_fw_cfg(void *opaque, QemuOpts *opts,
Error **errp)
error_report("WARNING: externally provided fw_cfg item names "
"should be prefixed with \"opt/\"!");
}
- if (!g_file_get_contents(file, &buf, &size, NULL)) {
- error_report("can't load %s", file);
- return -1;
+ if (nonempty_str(cont)) {
+ size = strlen(cont); /* NUL terminator NOT included in fw_cfg blob */
+ buf = g_memdup(cont, size);
+ } else {
+ if (!g_file_get_contents(file, &buf, &size, NULL)) {
+ error_report("can't load %s", file);
+ return -1;
+ }
}
fw_cfg_add_file((FWCfgState *)opaque, name, buf, size);
return 0;
--
2.4.3
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