From: Jason A. Donenfeld Date: Tue, 1 Mar 2022 14:14:04 +0000 (+0100) Subject: random: do not export add_vmfork_randomness() unless needed X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a4107d34f960df99ca07fa8eb022425a804f59f3;p=linux.git random: do not export add_vmfork_randomness() unless needed Since add_vmfork_randomness() is only called from vmgenid.o, we can guard it in CONFIG_VMGENID, similarly to how we do with add_disk_randomness() and CONFIG_BLOCK. If we ever have multiple things calling into add_vmfork_randomness(), we can add another shared Kconfig symbol for that, but for now, this is good enough. Even though add_vmfork_randomess() is a pretty small function, removing it means that there are only calls to crng_reseed(false) and none to crng_reseed(true), which means the compiler can constant propagate the false, removing branches from crng_reseed() and its descendants. Additionally, we don't even need the symbol to be exported if CONFIG_VMGENID is not a module, so conditionalize that too. Cc: Dominik Brodowski Cc: Theodore Ts'o Signed-off-by: Jason A. Donenfeld --- diff --git a/drivers/char/random.c b/drivers/char/random.c index 2b323f6bd96c3..bc2a4f7e36554 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -1168,6 +1168,7 @@ void add_bootloader_randomness(const void *buf, size_t size) } EXPORT_SYMBOL_GPL(add_bootloader_randomness); +#if IS_ENABLED(CONFIG_VMGENID) /* * Handle a new unique VM ID, which is unique, not secret, so we * don't credit it, but we do immediately force a reseed after so @@ -1181,7 +1182,10 @@ void add_vmfork_randomness(const void *unique_vm_id, size_t size) pr_notice("crng reseeded due to virtual machine fork\n"); } } +#if IS_MODULE(CONFIG_VMGENID) EXPORT_SYMBOL_GPL(add_vmfork_randomness); +#endif +#endif struct fast_pool { union { diff --git a/include/linux/random.h b/include/linux/random.h index 117468f3a92ee..f209f1a788996 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,7 +34,9 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq) __latent_entropy; extern void add_hwgenerator_randomness(const void *buffer, size_t count, size_t entropy); +#if IS_ENABLED(CONFIG_VMGENID) extern void add_vmfork_randomness(const void *unique_vm_id, size_t size); +#endif extern void get_random_bytes(void *buf, size_t nbytes); extern int wait_for_random_bytes(void);