On Fri, Jan 15, 2021 at 07:53PM +0100, Andrey Konovalov wrote: > The initially proposed KASAN command line parameters are redundant. > > This change drops the complex "kasan.mode=off/prod/full" parameter > and adds a simpler kill switch "kasan=off/on" instead. The new parameter > together with the already existing ones provides a cleaner way to > express the same set of features. > > The full set of parameters with this change: > > kasan=off/on - whether KASAN is enabled > kasan.fault=report/panic - whether to only print a report or also panic > kasan.stacktrace=off/on - whether to collect alloc/free stack traces > > Default values: > > kasan=on > kasan.fault=report > kasan.stacktrace=on (if CONFIG_DEBUG_KERNEL=y) > kasan.stacktrace=off (otherwise) > > Link: https://linux-review.googlesource.com/id/Ib3694ed90b1e8ccac6cf77dfd301847af4aba7b8 > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Thanks for the simplification. Reviewed-by: Marco Elver <elver@xxxxxxxxxx> > --- > Documentation/dev-tools/kasan.rst | 27 +++-------- > mm/kasan/hw_tags.c | 77 +++++++++++++------------------ > 2 files changed, 38 insertions(+), 66 deletions(-) > > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst > index 0fc3fb1860c4..1651d961f06a 100644 > --- a/Documentation/dev-tools/kasan.rst > +++ b/Documentation/dev-tools/kasan.rst > @@ -160,29 +160,14 @@ intended for use in production as a security mitigation. Therefore it supports > boot parameters that allow to disable KASAN competely or otherwise control > particular KASAN features. > > -The things that can be controlled are: > +- ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``). > > -1. Whether KASAN is enabled at all. > -2. Whether KASAN collects and saves alloc/free stacks. > -3. Whether KASAN panics on a detected bug or not. > +- ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack > + traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``, otherwise > + ``off``). > > -The ``kasan.mode`` boot parameter allows to choose one of three main modes: > - > -- ``kasan.mode=off`` - KASAN is disabled, no tag checks are performed > -- ``kasan.mode=prod`` - only essential production features are enabled > -- ``kasan.mode=full`` - all KASAN features are enabled > - > -The chosen mode provides default control values for the features mentioned > -above. However it's also possible to override the default values by providing: > - > -- ``kasan.stacktrace=off`` or ``=on`` - enable alloc/free stack collection > - (default: ``on`` for ``mode=full``, > - otherwise ``off``) > -- ``kasan.fault=report`` or ``=panic`` - only print KASAN report or also panic > - (default: ``report``) > - > -If ``kasan.mode`` parameter is not provided, it defaults to ``full`` when > -``CONFIG_DEBUG_KERNEL`` is enabled, and to ``prod`` otherwise. > +- ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN > + report or also panic the kernel (default: ``report``). > > For developers > ~~~~~~~~~~~~~~ > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > index 55bd6f09c70f..e529428e7a11 100644 > --- a/mm/kasan/hw_tags.c > +++ b/mm/kasan/hw_tags.c > @@ -19,11 +19,10 @@ > > #include "kasan.h" > > -enum kasan_arg_mode { > - KASAN_ARG_MODE_DEFAULT, > - KASAN_ARG_MODE_OFF, > - KASAN_ARG_MODE_PROD, > - KASAN_ARG_MODE_FULL, > +enum kasan_arg { > + KASAN_ARG_DEFAULT, > + KASAN_ARG_OFF, > + KASAN_ARG_ON, > }; > > enum kasan_arg_stacktrace { > @@ -38,7 +37,7 @@ enum kasan_arg_fault { > KASAN_ARG_FAULT_PANIC, > }; > > -static enum kasan_arg_mode kasan_arg_mode __ro_after_init; > +static enum kasan_arg kasan_arg __ro_after_init; > static enum kasan_arg_stacktrace kasan_arg_stacktrace __ro_after_init; > static enum kasan_arg_fault kasan_arg_fault __ro_after_init; > > @@ -52,26 +51,24 @@ DEFINE_STATIC_KEY_FALSE(kasan_flag_stacktrace); > /* Whether panic or disable tag checking on fault. */ > bool kasan_flag_panic __ro_after_init; > > -/* kasan.mode=off/prod/full */ > -static int __init early_kasan_mode(char *arg) > +/* kasan=off/on */ > +static int __init early_kasan_flag(char *arg) > { > if (!arg) > return -EINVAL; > > if (!strcmp(arg, "off")) > - kasan_arg_mode = KASAN_ARG_MODE_OFF; > - else if (!strcmp(arg, "prod")) > - kasan_arg_mode = KASAN_ARG_MODE_PROD; > - else if (!strcmp(arg, "full")) > - kasan_arg_mode = KASAN_ARG_MODE_FULL; > + kasan_arg = KASAN_ARG_OFF; > + else if (!strcmp(arg, "on")) > + kasan_arg = KASAN_ARG_ON; > else > return -EINVAL; > > return 0; > } > -early_param("kasan.mode", early_kasan_mode); > +early_param("kasan", early_kasan_flag); > > -/* kasan.stack=off/on */ > +/* kasan.stacktrace=off/on */ > static int __init early_kasan_flag_stacktrace(char *arg) > { > if (!arg) > @@ -113,8 +110,8 @@ void kasan_init_hw_tags_cpu(void) > * as this function is only called for MTE-capable hardware. > */ > > - /* If KASAN is disabled, do nothing. */ > - if (kasan_arg_mode == KASAN_ARG_MODE_OFF) > + /* If KASAN is disabled via command line, don't initialize it. */ > + if (kasan_arg == KASAN_ARG_OFF) > return; > > hw_init_tags(KASAN_TAG_MAX); > @@ -124,43 +121,28 @@ void kasan_init_hw_tags_cpu(void) > /* kasan_init_hw_tags() is called once on boot CPU. */ > void __init kasan_init_hw_tags(void) > { > - /* If hardware doesn't support MTE, do nothing. */ > + /* If hardware doesn't support MTE, don't initialize KASAN. */ > if (!system_supports_mte()) > return; > > - /* Choose KASAN mode if kasan boot parameter is not provided. */ > - if (kasan_arg_mode == KASAN_ARG_MODE_DEFAULT) { > - if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) > - kasan_arg_mode = KASAN_ARG_MODE_FULL; > - else > - kasan_arg_mode = KASAN_ARG_MODE_PROD; > - } > - > - /* Preset parameter values based on the mode. */ > - switch (kasan_arg_mode) { > - case KASAN_ARG_MODE_DEFAULT: > - /* Shouldn't happen as per the check above. */ > - WARN_ON(1); > - return; > - case KASAN_ARG_MODE_OFF: > - /* If KASAN is disabled, do nothing. */ > + /* If KASAN is disabled via command line, don't initialize it. */ > + if (kasan_arg == KASAN_ARG_OFF) > return; > - case KASAN_ARG_MODE_PROD: > - static_branch_enable(&kasan_flag_enabled); > - break; > - case KASAN_ARG_MODE_FULL: > - static_branch_enable(&kasan_flag_enabled); > - static_branch_enable(&kasan_flag_stacktrace); > - break; > - } > > - /* Now, optionally override the presets. */ > + /* Enable KASAN. */ > + static_branch_enable(&kasan_flag_enabled); > > switch (kasan_arg_stacktrace) { > case KASAN_ARG_STACKTRACE_DEFAULT: > + /* > + * Default to enabling stack trace collection for > + * debug kernels. > + */ > + if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) > + static_branch_enable(&kasan_flag_stacktrace); > break; > case KASAN_ARG_STACKTRACE_OFF: > - static_branch_disable(&kasan_flag_stacktrace); > + /* Do nothing, kasan_flag_stacktrace keeps its default value. */ > break; > case KASAN_ARG_STACKTRACE_ON: > static_branch_enable(&kasan_flag_stacktrace); > @@ -169,11 +151,16 @@ void __init kasan_init_hw_tags(void) > > switch (kasan_arg_fault) { > case KASAN_ARG_FAULT_DEFAULT: > + /* > + * Default to no panic on report. > + * Do nothing, kasan_flag_panic keeps its default value. > + */ > break; > case KASAN_ARG_FAULT_REPORT: > - kasan_flag_panic = false; > + /* Do nothing, kasan_flag_panic keeps its default value. */ > break; > case KASAN_ARG_FAULT_PANIC: > + /* Enable panic on report. */ > kasan_flag_panic = true; > break; > } > -- > 2.30.0.284.gd98b1dd5eaa7-goog >
