Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH v5] init: Allow CONFIG_INIT_FALLBACK=n to disable defaults if init= fails | Date | Wed, 1 Oct 2014 15:56:41 -0700 |
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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 is unexpected but probably harmless. 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 config option CONFIG_INIT_FALLBACK. If unset, then a failure to run the specified init= process be fatal.
The intent is to switch the default to N after a while and to possibly even remove the option entirely
Signed-off-by: Andy Lutomirski <luto@amacapital.net> ---
Changes from v4: - Switch the default to y
Changes from v3: - Get rid of the strictinit option. Now the new behavior is the default unless CONFIG_INIT_FALLBACK=y (Rob Landley)
Changes from v2: - Improve docs further, to leave the door open to giving strictinit some sensible semantics if init= is not set. - Improve error output in the failure case (Shuah Khan).
Changes from v1: - Add missing "if" to the docs (Randy Dunlap)
init/Kconfig | 16 ++++++++++++++++ init/main.c | 7 ++++++- 2 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/init/Kconfig b/init/Kconfig index e84c6423a2e5..ebbd5846478e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1299,6 +1299,22 @@ source "usr/Kconfig" endif +config INIT_FALLBACK + bool "Fall back to defaults if init= parameter is bad" + default y + help + If enabled, the kernel will try the default init binaries if an + explicit request from the init= parameter fails. + + This can have unexpected effects. For example, booting + with init=/sbin/kiosk_app will run /sbin/init or even /bin/sh + if /sbin/kiosk_app cannot be executed. + + The default value of Y is consistent with historical behavior. + Selecting N is likely to be more appropriate for most uses, + especially on kiosks and on kernels that are indended to be + run under the control of a script. + config CC_OPTIMIZE_FOR_SIZE bool "Optimize for size" help diff --git a/init/main.c b/init/main.c index bb1aed928f21..2bd6105e5dc5 100644 --- a/init/main.c +++ b/init/main.c @@ -960,8 +960,13 @@ static int __ref kernel_init(void *unused) ret = run_init_process(execute_command); if (!ret) return 0; +#ifndef CONFIG_INIT_FALLBACK + panic("Requested init %s failed (error %d).", + execute_command, ret); +#else pr_err("Failed to execute %s (error %d). Attempting defaults...\n", - execute_command, ret); + execute_command, ret); +#endif } if (!try_to_run_init_process("/sbin/init") || !try_to_run_init_process("/etc/init") || -- 1.9.3
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