From: Andrew Halaney <ahalaney@xxxxxxxxxx> Subject: init: print out unknown kernel parameters It is easy to foobar setting a kernel parameter on the command line without realizing it, there's not much output that you can use to assess what the kernel did with that parameter by default. Make it a little more explicit which parameters on the command line _looked_ like a valid parameter for the kernel, but did not match anything and ultimately got tossed to init. This is very similar to the unknown parameter message received when loading a module. This assumes the parameters are processed in a normal fashion, some parameters (dyndbg= for example) don't register their parameter with the rest of the kernel's parameters, and therefore always show up in this list (and are also given to init - like the rest of this list). Another example is BOOT_IMAGE= is highlighted as an offender, which it technically is, but is passed by LILO and GRUB so most systems will see that complaint. An example output where "foobared" and "unrecognized" are intentionally invalid parameters: Kernel command line: BOOT_IMAGE=/boot/vmlinuz-5.12-dirty debug log_buf_len=4M foobared unrecognized=foo Unknown command line parameters: foobared BOOT_IMAGE=/boot/vmlinuz-5.12-dirty unrecognized=foo Link: https://lkml.kernel.org/r/20210511211009.42259-1-ahalaney@xxxxxxxxxx Signed-off-by: Andrew Halaney <ahalaney@xxxxxxxxxx> Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Suggested-by: Borislav Petkov <bp@xxxxxxx> Acked-by: Borislav Petkov <bp@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- init/main.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) --- a/init/main.c~init-print-out-unknown-kernel-parameters +++ a/init/main.c @@ -872,6 +872,47 @@ void __init __weak arch_call_rest_init(v rest_init(); } +static void __init print_unknown_bootoptions(void) +{ + char *unknown_options; + char *end; + const char *const *p; + size_t len; + + if (panic_later || (!argv_init[1] && !envp_init[2])) + return; + + /* + * Determine how many options we have to print out, plus a space + * before each + */ + len = 1; /* null terminator */ + for (p = &argv_init[1]; *p; p++) { + len++; + len += strlen(*p); + } + for (p = &envp_init[2]; *p; p++) { + len++; + len += strlen(*p); + } + + unknown_options = memblock_alloc(len, SMP_CACHE_BYTES); + if (!unknown_options) { + pr_err("%s: Failed to allocate %zu bytes\n", + __func__, len); + return; + } + end = unknown_options; + + for (p = &argv_init[1]; *p; p++) + end += sprintf(end, " %s", *p); + for (p = &envp_init[2]; *p; p++) + end += sprintf(end, " %s", *p); + + pr_notice("Unknown command line parameters:%s\n", unknown_options); + memblock_free(__pa(unknown_options), len); +} + asmlinkage __visible void __init __no_sanitize_address start_kernel(void) { char *command_line; @@ -913,6 +954,7 @@ asmlinkage __visible void __init __no_sa static_command_line, __start___param, __stop___param - __start___param, -1, -1, NULL, &unknown_bootoption); + print_unknown_bootoptions(); if (!IS_ERR_OR_NULL(after_dashes)) parse_args("Setting init args", after_dashes, NULL, 0, -1, -1, NULL, set_init_arg); _
