On Tue, Aug 12, 2025 at 9:56 AM Andrew Morton akpm@linux-foundation.org wrote:
On Mon, 21 Jul 2025 18:13:43 +0800 Huacai Chen chenhuacai@loongson.cn wrote:
BootLoader (Grub, LILO, etc) may pass an identifier such as "BOOT_IMAGE= /boot/vmlinuz-x.y.z" to kernel parameters. But these identifiers are not recognized by the kernel itself so will be passed to user space. However user space init program also doesn't recognized it.
KEXEC/KDUMP (kexec-tools) may also pass an identifier such as "kexec" on some architectures.
We cannot change BootLoader's behavior, because this behavior exists for many years, and there are already user space programs search BOOT_IMAGE= in /proc/cmdline to obtain the kernel image locations:
https://github.com/linuxdeepin/deepin-ab-recovery/blob/master/util.go (search getBootOptions) https://github.com/linuxdeepin/deepin-ab-recovery/blob/master/main.go (search getKernelReleaseWithBootOption)
So the the best way is handle (ignore) it by the kernel itself, which can avoid such boot warnings (if we use something like init=/bin/bash, bootloader identifier can even cause a crash):
Kernel command line: BOOT_IMAGE=(hd0,1)/vmlinuz-6.x root=/dev/sda3 ro console=tty Unknown kernel command line parameters "BOOT_IMAGE=(hd0,1)/vmlinuz-6.x", will be passed to user space.
Cc: stable@vger.kernel.org
I think I'll keep this in -next until 6.18-rc1 - I suspect any issues here will take a while to discover.
--- a/init/main.c +++ b/init/main.c @@ -545,6 +545,12 @@ static int __init unknown_bootoption(char *param, char *val, const char *unused, void *arg) { size_t len = strlen(param);
/** Well-known bootloader identifiers:* 1. LILO/Grub pass "BOOT_IMAGE=...";* 2. kexec/kdump (kexec-tools) pass "kexec".*/const char *bootloader[] = { "BOOT_IMAGE=", "kexec", NULL }; /* Handle params aliased to sysctls */ if (sysctl_is_alias(param))@@ -552,6 +558,12 @@ static int __init unknown_bootoption(char *param, char *val,
repair_env_string(param, val);
/* Handle bootloader identifier */for (int i = 0; bootloader[i]; i++) {if (!strncmp(param, bootloader[i], strlen(bootloader[i])))return 0;}We have str_has_prefix().
And strstarts()! Both of which are awfully similar and both of which lamely do two passes across a string.
OK, I will send V4 with strstarts().
Huacai