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Subject[RFC PATCH v4 05/22] proc: bootconfig: Add /proc/bootconfig to show boot config list
Date
Add /proc/bootconfig which shows the list of key-value pairs
in boot config. Since after boot, all boot configs and tree
are removed, this interface just keep a copy of key-value
pairs in text.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v4:
- Remove ; in the end of lines.
- Rename /proc/supp_cmdline to /proc/bootconfig
- Simplify code.
---
MAINTAINERS | 1 +
fs/proc/Makefile | 1 +
fs/proc/bootconfig.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 91 insertions(+)
create mode 100644 fs/proc/bootconfig.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 9ea52e87730f..08185de1652b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15693,6 +15693,7 @@ EXTRA BOOT CONFIG
M: Masami Hiramatsu <mhiramat@kernel.org>
S: Maintained
F: lib/bootconfig.c
+F: fs/proc/bootconfig.c
F: include/linux/bootconfig.h
F: tools/bootconfig/*

diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index ead487e80510..bd08616ed8ba 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -33,3 +33,4 @@ proc-$(CONFIG_PROC_KCORE) += kcore.o
proc-$(CONFIG_PROC_VMCORE) += vmcore.o
proc-$(CONFIG_PRINTK) += kmsg.o
proc-$(CONFIG_PROC_PAGE_MONITOR) += page.o
+proc-$(CONFIG_BOOT_CONFIG) += bootconfig.o
diff --git a/fs/proc/bootconfig.c b/fs/proc/bootconfig.c
new file mode 100644
index 000000000000..9955d75c0585
--- /dev/null
+++ b/fs/proc/bootconfig.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * /proc/bootconfig - Extra boot configuration
+ */
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/printk.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/bootconfig.h>
+#include <linux/slab.h>
+
+static char *saved_boot_config;
+
+static int boot_config_proc_show(struct seq_file *m, void *v)
+{
+ if (saved_boot_config)
+ seq_puts(m, saved_boot_config);
+ return 0;
+}
+
+/* Rest size of buffer */
+#define rest(dst, end) ((end) > (dst) ? (end) - (dst) : 0)
+
+/* Return the needed total length if @size is 0 */
+static int __init copy_xbc_key_value_list(char *dst, size_t size)
+{
+ struct xbc_node *leaf, *vnode;
+ const char *val;
+ char *key, *end = dst + size;
+ int ret = 0;
+
+ key = kzalloc(XBC_KEYLEN_MAX, GFP_KERNEL);
+
+ xbc_for_each_key_value(leaf, val) {
+ ret = xbc_node_compose_key(leaf, key, XBC_KEYLEN_MAX);
+ if (ret < 0)
+ break;
+ ret = snprintf(dst, rest(dst, end), "%s = ", key);
+ if (ret < 0)
+ break;
+ dst += ret;
+ vnode = xbc_node_get_child(leaf);
+ if (vnode && xbc_node_is_array(vnode)) {
+ xbc_array_for_each_value(vnode, val) {
+ ret = snprintf(dst, rest(dst, end), "\"%s\"%s",
+ val, vnode->next ? ", " : "\n");
+ if (ret < 0)
+ goto out;
+ dst += ret;
+ }
+ } else {
+ ret = snprintf(dst, rest(dst, end), "\"%s\"\n", val);
+ if (ret < 0)
+ break;
+ dst += ret;
+ }
+ }
+out:
+ kfree(key);
+
+ return ret < 0 ? ret : dst - (end - size);
+}
+
+static int __init proc_boot_config_init(void)
+{
+ int len;
+
+ len = copy_xbc_key_value_list(NULL, 0);
+ if (len < 0)
+ return len;
+
+ if (len > 0) {
+ saved_boot_config = kzalloc(len + 1, GFP_KERNEL);
+ if (!saved_boot_config)
+ return -ENOMEM;
+
+ len = copy_xbc_key_value_list(saved_boot_config, len + 1);
+ if (len < 0) {
+ kfree(saved_boot_config);
+ return len;
+ }
+ }
+
+ proc_create_single("bootconfig", 0, NULL, boot_config_proc_show);
+
+ return 0;
+}
+fs_initcall(proc_boot_config_init);
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