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https://github.com/Fishwaldo/linux-bl808.git
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38addce8b6
This adds a new gcc plugin named "latent_entropy". It is designed to extract as much possible uncertainty from a running system at boot time as possible, hoping to capitalize on any possible variation in CPU operation (due to runtime data differences, hardware differences, SMP ordering, thermal timing variation, cache behavior, etc). At the very least, this plugin is a much more comprehensive example for how to manipulate kernel code using the gcc plugin internals. The need for very-early boot entropy tends to be very architecture or system design specific, so this plugin is more suited for those sorts of special cases. The existing kernel RNG already attempts to extract entropy from reliable runtime variation, but this plugin takes the idea to a logical extreme by permuting a global variable based on any variation in code execution (e.g. a different value (and permutation function) is used to permute the global based on loop count, case statement, if/then/else branching, etc). To do this, the plugin starts by inserting a local variable in every marked function. The plugin then adds logic so that the value of this variable is modified by randomly chosen operations (add, xor and rol) and random values (gcc generates separate static values for each location at compile time and also injects the stack pointer at runtime). The resulting value depends on the control flow path (e.g., loops and branches taken). Before the function returns, the plugin mixes this local variable into the latent_entropy global variable. The value of this global variable is added to the kernel entropy pool in do_one_initcall() and _do_fork(), though it does not credit any bytes of entropy to the pool; the contents of the global are just used to mix the pool. Additionally, the plugin can pre-initialize arrays with build-time random contents, so that two different kernel builds running on identical hardware will not have the same starting values. Signed-off-by: Emese Revfy <re.emese@gmail.com> [kees: expanded commit message and code comments] Signed-off-by: Kees Cook <keescook@chromium.org>
141 lines
3.6 KiB
C
141 lines
3.6 KiB
C
/*
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* include/linux/random.h
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*
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* Include file for the random number generator.
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*/
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#ifndef _LINUX_RANDOM_H
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#define _LINUX_RANDOM_H
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#include <linux/list.h>
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#include <linux/once.h>
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#include <uapi/linux/random.h>
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struct random_ready_callback {
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struct list_head list;
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void (*func)(struct random_ready_callback *rdy);
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struct module *owner;
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};
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extern void add_device_randomness(const void *, unsigned int);
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#if defined(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) && !defined(__CHECKER__)
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static inline void add_latent_entropy(void)
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{
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add_device_randomness((const void *)&latent_entropy,
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sizeof(latent_entropy));
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}
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#else
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static inline void add_latent_entropy(void) {}
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#endif
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extern void add_input_randomness(unsigned int type, unsigned int code,
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unsigned int value);
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extern void add_interrupt_randomness(int irq, int irq_flags);
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extern void get_random_bytes(void *buf, int nbytes);
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extern int add_random_ready_callback(struct random_ready_callback *rdy);
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extern void del_random_ready_callback(struct random_ready_callback *rdy);
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extern void get_random_bytes_arch(void *buf, int nbytes);
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extern int random_int_secret_init(void);
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#ifndef MODULE
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extern const struct file_operations random_fops, urandom_fops;
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#endif
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unsigned int get_random_int(void);
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unsigned long get_random_long(void);
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unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len);
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u32 prandom_u32(void);
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void prandom_bytes(void *buf, size_t nbytes);
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void prandom_seed(u32 seed);
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void prandom_reseed_late(void);
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struct rnd_state {
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__u32 s1, s2, s3, s4;
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};
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u32 prandom_u32_state(struct rnd_state *state);
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void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes);
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void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
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#define prandom_init_once(pcpu_state) \
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DO_ONCE(prandom_seed_full_state, (pcpu_state))
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/**
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* prandom_u32_max - returns a pseudo-random number in interval [0, ep_ro)
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* @ep_ro: right open interval endpoint
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*
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* Returns a pseudo-random number that is in interval [0, ep_ro). Note
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* that the result depends on PRNG being well distributed in [0, ~0U]
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* u32 space. Here we use maximally equidistributed combined Tausworthe
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* generator, that is, prandom_u32(). This is useful when requesting a
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* random index of an array containing ep_ro elements, for example.
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*
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* Returns: pseudo-random number in interval [0, ep_ro)
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*/
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static inline u32 prandom_u32_max(u32 ep_ro)
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{
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return (u32)(((u64) prandom_u32() * ep_ro) >> 32);
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}
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/*
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* Handle minimum values for seeds
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*/
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static inline u32 __seed(u32 x, u32 m)
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{
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return (x < m) ? x + m : x;
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}
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/**
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* prandom_seed_state - set seed for prandom_u32_state().
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* @state: pointer to state structure to receive the seed.
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* @seed: arbitrary 64-bit value to use as a seed.
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*/
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static inline void prandom_seed_state(struct rnd_state *state, u64 seed)
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{
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u32 i = (seed >> 32) ^ (seed << 10) ^ seed;
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state->s1 = __seed(i, 2U);
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state->s2 = __seed(i, 8U);
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state->s3 = __seed(i, 16U);
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state->s4 = __seed(i, 128U);
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}
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#ifdef CONFIG_ARCH_RANDOM
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# include <asm/archrandom.h>
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#else
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static inline bool arch_get_random_long(unsigned long *v)
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{
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return 0;
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}
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static inline bool arch_get_random_int(unsigned int *v)
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{
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return 0;
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}
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static inline bool arch_has_random(void)
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{
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return 0;
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}
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static inline bool arch_get_random_seed_long(unsigned long *v)
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{
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return 0;
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}
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static inline bool arch_get_random_seed_int(unsigned int *v)
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{
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return 0;
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}
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static inline bool arch_has_random_seed(void)
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{
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return 0;
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}
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#endif
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/* Pseudo random number generator from numerical recipes. */
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static inline u32 next_pseudo_random32(u32 seed)
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{
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return seed * 1664525 + 1013904223;
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}
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#endif /* _LINUX_RANDOM_H */
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