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Subject[RFC PATCH v4 02/22] bootconfig: Load boot config from the tail of initrd
Date
Load the extended boot config data from the tail of initrd
image. If there is an SKC data there, it has
[(u32)size][(u32)checksum] header (in really, this is a
footer) at the end of initrd. If the checksum (simple sum
of bytes) is match, this starts parsing it from there.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
Changes in v4:
- Rename skc to bootconfig.
---
init/Kconfig | 1 +
init/main.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 55 insertions(+)

diff --git a/init/Kconfig b/init/Kconfig
index 13bb3eac804c..0e85a5f56817 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1237,6 +1237,7 @@ endif

config BOOT_CONFIG
bool "Boot config support"
+ depends on BLK_DEV_INITRD
select LIBXBC
default y
help
diff --git a/init/main.c b/init/main.c
index 91f6ebb30ef0..27f70fa37b18 100644
--- a/init/main.c
+++ b/init/main.c
@@ -28,6 +28,7 @@
#include <linux/initrd.h>
#include <linux/memblock.h>
#include <linux/acpi.h>
+#include <linux/bootconfig.h>
#include <linux/console.h>
#include <linux/nmi.h>
#include <linux/percpu.h>
@@ -245,6 +246,58 @@ static int __init loglevel(char *str)

early_param("loglevel", loglevel);

+#ifdef CONFIG_BOOT_CONFIG
+u32 boot_config_checksum(unsigned char *p, u32 size)
+{
+ u32 ret = 0;
+
+ while (size--)
+ ret += *p++;
+
+ return ret;
+}
+
+static void __init setup_boot_config(void)
+{
+ u32 size, csum;
+ char *data, *copy;
+ u32 *hdr;
+
+ if (!initrd_end)
+ return;
+
+ hdr = (u32 *)(initrd_end - 8);
+ size = hdr[0];
+ csum = hdr[1];
+
+ if (size >= XBC_DATA_MAX)
+ return;
+
+ data = ((void *)hdr) - size;
+ if ((unsigned long)data < initrd_start)
+ return;
+
+ if (boot_config_checksum((unsigned char *)data, size) != csum)
+ return;
+
+ copy = memblock_alloc(size + 1, SMP_CACHE_BYTES);
+ if (!copy) {
+ pr_err("Failed to allocate memory for boot config\n");
+ return;
+ }
+
+ memcpy(copy, data, size);
+ copy[size] = '\0';
+
+ if (xbc_init(copy) < 0)
+ pr_err("Failed to parse boot config\n");
+ else
+ pr_info("Load boot config: %d bytes\n", size);
+}
+#else
+#define setup_boot_config() do { } while (0)
+#endif
+
/* Change NUL term back to "=", to make "param" the whole string. */
static int __init repair_env_string(char *param, char *val,
const char *unused, void *arg)
@@ -595,6 +648,7 @@ asmlinkage __visible void __init start_kernel(void)
pr_notice("%s", linux_banner);
early_security_init();
setup_arch(&command_line);
+ setup_boot_config();
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();
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