diff options
| author | Alexander Graf | 2023-12-07 23:56:54 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-12-15 17:23:00 +0100 |
| commit | 2678fd2fe9ee2c569e9cb6b17e786bc8f0753538 (patch) | |
| tree | 39376d0d83d700190d27c1f48b3103edf4b96807 /init | |
| parent | 5133bee62f0ea5d4c316d503cc0040cac5637601 (diff) | |
initramfs: Expose retained initrd as sysfs file
When the kernel command line option "retain_initrd" is set, we do not
free the initrd memory. However, we also don't expose it to anyone for
consumption. That leaves us in a weird situation where the only user of
this feature is ppc64 and arm64 specific kexec tooling.
To make it more generally useful, this patch adds a kobject to the
firmware object that contains the initrd context when "retain_initrd"
is set. That way, we can access the initrd any time after boot from
user space and for example hand it into kexec as --initrd parameter
if we want to reboot the same initrd. Or inspect it directly locally.
With this patch applied, there is a new /sys/firmware/initrd file when
the kernel was booted with an initrd and "retain_initrd" command line
option is set.
Signed-off-by: Alexander Graf <graf@amazon.com>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Link: https://lore.kernel.org/r/20231207235654.16622-1-graf@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'init')
| -rw-r--r-- | init/initramfs.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/init/initramfs.c b/init/initramfs.c index 8d0fd946cdd2..76deb48c38cb 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -574,6 +574,16 @@ extern unsigned long __initramfs_size; #include <linux/initrd.h> #include <linux/kexec.h> +static ssize_t raw_read(struct file *file, struct kobject *kobj, + struct bin_attribute *attr, char *buf, + loff_t pos, size_t count) +{ + memcpy(buf, attr->private + pos, count); + return count; +} + +static BIN_ATTR(initrd, 0440, raw_read, NULL, 0); + void __init reserve_initrd_mem(void) { phys_addr_t start; @@ -715,8 +725,14 @@ done: * If the initrd region is overlapped with crashkernel reserved region, * free only memory that is not part of crashkernel region. */ - if (!do_retain_initrd && initrd_start && !kexec_free_initrd()) + if (!do_retain_initrd && initrd_start && !kexec_free_initrd()) { free_initrd_mem(initrd_start, initrd_end); + } else if (do_retain_initrd && initrd_start) { + bin_attr_initrd.size = initrd_end - initrd_start; + bin_attr_initrd.private = (void *)initrd_start; + if (sysfs_create_bin_file(firmware_kobj, &bin_attr_initrd)) + pr_err("Failed to create initrd sysfs file"); + } initrd_start = 0; initrd_end = 0; |