From affc66bb08fcb62aa1dd06b5524d360eaddcbeff Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 4 Feb 2020 07:33:53 -0500 Subject: [PATCH] bootconfig: Only load bootconfig if "bootconfig" is on the kernel cmdline As the bootconfig is appended to the initrd it is not as easy to modify as the kernel command line. If there's some issue with the kernel, and the developer wants to boot a pristine kernel, it should not be needed to modify the initrd to remove the bootconfig for a single boot. As bootconfig is silently added (if the admin does not know where to look they may not know it's being loaded). It should be explicitly added to the kernel cmdline. The loading of the bootconfig is only done if "bootconfig" is on the kernel command line. This will let admins know that the kernel command line is extended. Note, after adding printk()s for when the size is too great or the checksum is wrong, exposed that the current method always looked for the boot config, and if this size and checksum matched, it would parse it (as if either is wrong a printk has been added to show this). It's better to only check this if the boot config is asked to be looked for. Link: https://lore.kernel.org/r/CAHk-=wjfjO+h6bQzrTf=YCZA53Y3EDyAs3Z4gEsT7icA3u_Psw@mail.gmail.com Acked-by: Masami Hiramatsu Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (VMware) --- Documentation/admin-guide/bootconfig.rst | 2 ++ .../admin-guide/kernel-parameters.txt | 6 ++++ init/main.c | 28 ++++++++++++++----- 3 files changed, 29 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index 4d617693c0c8c..b342a67963927 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -123,6 +123,8 @@ To remove the config from the image, you can use -d option as below:: # tools/bootconfig/bootconfig -d /boot/initrd.img-X.Y.Z +Then add "bootconfig" on the normal kernel command line to tell the +kernel to look for the bootconfig at the end of the initrd file. Config File Limitation ====================== diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ade4e6ec23e03..b48c70ba98416 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -437,6 +437,12 @@ no delay (0). Format: integer + bootconfig [KNL] + Extended command line options can be added to an initrd + and this will cause the kernel to look for it. + + See Documentation/admin-guide/bootconfig.rst + bert_disable [ACPI] Disable BERT OS support on buggy BIOSes. diff --git a/init/main.c b/init/main.c index dd7da62d99a5f..f174a59d39035 100644 --- a/init/main.c +++ b/init/main.c @@ -336,28 +336,39 @@ u32 boot_config_checksum(unsigned char *p, u32 size) return ret; } -static void __init setup_boot_config(void) +static void __init setup_boot_config(const char *cmdline) { u32 size, csum; char *data, *copy; + const char *p; u32 *hdr; - if (!initrd_end) + p = strstr(cmdline, "bootconfig"); + if (!p || (p != cmdline && !isspace(*(p-1))) || + (p[10] && !isspace(p[10]))) return; + if (!initrd_end) + goto not_found; + hdr = (u32 *)(initrd_end - 8); size = hdr[0]; csum = hdr[1]; - if (size >= XBC_DATA_MAX) + if (size >= XBC_DATA_MAX) { + pr_err("bootconfig size %d greater than max size %d\n", + size, XBC_DATA_MAX); return; + } data = ((void *)hdr) - size; if ((unsigned long)data < initrd_start) - return; + goto not_found; - if (boot_config_checksum((unsigned char *)data, size) != csum) + if (boot_config_checksum((unsigned char *)data, size) != csum) { + pr_err("bootconfig checksum failed\n"); return; + } copy = memblock_alloc(size + 1, SMP_CACHE_BYTES); if (!copy) { @@ -377,9 +388,12 @@ static void __init setup_boot_config(void) /* Also, "init." keys are init arguments */ extra_init_args = xbc_make_cmdline("init"); } + return; +not_found: + pr_err("'bootconfig' found on command line, but no bootconfig found\n"); } #else -#define setup_boot_config() do { } while (0) +#define setup_boot_config(cmdline) do { } while (0) #endif /* Change NUL term back to "=", to make "param" the whole string. */ @@ -760,7 +774,7 @@ asmlinkage __visible void __init start_kernel(void) pr_notice("%s", linux_banner); early_security_init(); setup_arch(&command_line); - setup_boot_config(); + setup_boot_config(command_line); setup_command_line(command_line); setup_nr_cpu_ids(); setup_per_cpu_areas(); -- 2.39.5