On 09/26/2014 12:04 PM, Andy Lutomirski wrote:
> If a user puts init=/whatever on the command line and /whatever
> can't be run, then the kernel will try a few default options before
> giving up. If init=/whatever came from a bootloader prompt, then
> this probably makes sense. On the other hand, if it comes from a
> script (e.g. a tool like virtme or perhaps a future kselftest
> script), then the fallbacks are likely to exist, but they'll do the
> wrong thing. For example, they might unexpectedly invoke systemd.
>
> This adds a new option called strictinit. If init= and strictinit
> are both set, and the init= binary is not executable, then the
> kernel will panic immediately. If strictinit is set but init= is
> not set, then strictinit will have no effect, because the only real
> alternative would be to panic regardless of the contents of the root
> fs.
>
> Signed-off-by: Andy Lutomirski <l...@amacapital.net>
> ---
>
> Now cc-ing Rusty (who probably cares more about startup options than
> anyone else) and Shuah (who might want to use this at some point).
>
> Changes from v1:
> - Add missing "if" to the docs (Randy Dunlap)
>
> Documentation/kernel-parameters.txt | 8 ++++++++
> init/main.c | 10 ++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 10d51c2f10d7..3dc921714002 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3236,6 +3236,14 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted.
> stifb= [HW]
> Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
>
> + strictinit [KNL,BOOT]
> + Normally, if the kernel can't find the init binary
> + specified by rdinit= and/or init=, then it will
> + try several fallbacks. If strictinit is set
> + and the value specified by init= does not work,
> + then the kernel will panic instead.
> + This has no effect if init= is not specified.
> +
> sunrpc.min_resvport=
> sunrpc.max_resvport=
> [NFS,SUNRPC]
> diff --git a/init/main.c b/init/main.c
> index bb1aed928f21..4fd80dcef9d0 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -131,6 +131,7 @@ static char *initcall_command_line;
>
> static char *execute_command;
> static char *ramdisk_execute_command;
> +static bool strictinit;
>
> /*
> * Used to generate warnings if static_key manipulation functions are used
> @@ -347,6 +348,13 @@ static int __init rdinit_setup(char *str)
> }
> __setup("rdinit=", rdinit_setup);
>
> +static int __init strictinit_setup(char *str)
> +{
> + strictinit = true;
> + return 1;
> +}
> +__setup("strictinit", strictinit_setup);
> +
> #ifndef CONFIG_SMP
> static const unsigned int setup_max_cpus = NR_CPUS;
> #ifdef CONFIG_X86_LOCAL_APIC
> @@ -962,6 +970,8 @@ static int __ref kernel_init(void *unused)
> return 0;
> pr_err("Failed to execute %s (error %d). Attempting
> defaults...\n",
> execute_command, ret);
> + if (strictinit)
> + panic("Requested init failed and strictinit was set.");
It would make sense to not print Attempting defaults for strictinit
case. I would recommend making it an else case and changing the
strictinit message to or something along the lines:
panic("Failed to execute %s (error %d). Not attempting defaults in
strictinit mode...\n", execute_command, ret);
-- Shuah
--
Shuah Khan
Sr. Linux Kernel Developer
Samsung Research America (Silicon Valley)
shua...@osg.samsung.com | (970) 217-8978
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