On Fri, Sep 26, 2014 at 12:30 PM, Rob Landley <[email protected]> wrote: > On Fri, Sep 26, 2014 at 2:23 PM, Chuck Ebbert <[email protected]> wrote: >> On Fri, 26 Sep 2014 12:13:57 -0700 >> Andy Lutomirski <[email protected]> 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 <[email protected]> >>> --- >>> Documentation/kernel-parameters.txt | 8 ++++++++ >>> init/main.c | 16 ++++++++++++++-- >>> 2 files changed, 22 insertions(+), 2 deletions(-) >>> >>> diff --git a/Documentation/kernel-parameters.txt >>> b/Documentation/kernel-parameters.txt >>> index 10d51c2f10d7..1576273edce6 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 option makes no sense 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..2ae0f2776155 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 >>> @@ -960,8 +968,12 @@ static int __ref kernel_init(void *unused) >>> ret = run_init_process(execute_command); >>> if (!ret) >>> return 0; >>> - pr_err("Failed to execute %s (error %d). Attempting >>> defaults...\n", >>> - execute_command, ret); >>> + if (strictinit) >>> + panic("Requested init %s failed (error %d) and >>> strictinit was set.", >>> + execute_command, ret); >>> + else >>> + pr_err("Failed to execute %s (error %d). Attempting >>> defaults...\n", >>> + execute_command, ret); >>> } >>> if (!try_to_run_init_process("/sbin/init") || >>> !try_to_run_init_process("/etc/init") || >> >> Can't you just make it use "init=foo,strict" instead? > > Can't we just change the default behavior and add a > CONFIG_INIT_FALLBACK that defaults to "n" which you can switch on to > get the old behavior? (And then immediately deprecate it?) > > If you're specifying an init, you probably want that init...
Hmm, that's a reasonable point. Thoughts, anyone? I'd be okay with doing that. --Andy > > Rob -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
