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  1. 14 5月, 2022 19 次提交
    • J
      random: insist on random_get_entropy() existing in order to simplify · 4b758eda
      由 Jason A. Donenfeld 提交于 
      All platforms are now guaranteed to provide some value for
random_get_entropy(). In case some bug leads to this not being so, we
print a warning, because that indicates that something is really very
wrong (and likely other things are impacted too). This should never be
hit, but it's a good and cheap way of finding out if something ever is
problematic.

Since we now have viable fallback code for random_get_entropy() on all
platforms, which is, in the worst case, not worse than jiffies, we can
count on getting the best possible value out of it. That means there's
no longer a use for using jiffies as entropy input. It also means we no
longer have a reason for doing the round-robin register flow in the IRQ
handler, which was always of fairly dubious value.

Instead we can greatly simplify the IRQ handler inputs and also unify
the construction between 64-bits and 32-bits. We now collect the cycle
counter and the return address, since those are the two things that
matter. Because the return address and the irq number are likely
related, to the extent we mix in the irq number, we can just xor it into
the top unchanging bytes of the return address, rather than the bottom
changing bytes of the cycle counter as before. Then, we can do a fixed 2
rounds of SipHash/HSipHash. Finally, we use the same construction of
hashing only half of the [H]SipHash state on 32-bit and 64-bit. We're
not actually discarding any entropy, since that entropy is carried
through until the next time. And more importantly, it lets us do the
same sponge-like construction everywhere.

Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      4b758eda
    • J
      xtensa: use fallback for random_get_entropy() instead of zero · e10e2f58
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      e10e2f58
    • J
      sparc: use fallback for random_get_entropy() instead of zero · ac9756c7
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      ac9756c7
    • J
      um: use fallback for random_get_entropy() instead of zero · 9f13fb0c
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

This is accomplished by just including the asm-generic code like on
other architectures, which means we can get rid of the empty stub
function here.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Acked-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      9f13fb0c
    • J
      x86/tsc: Use fallback for random_get_entropy() instead of zero · 3bd4abc0
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is suboptimal. Instead, fallback
to calling random_get_entropy_fallback(), which isn't extremely high
precision or guaranteed to be entropic, but is certainly better than
returning zero all the time.

If CONFIG_X86_TSC=n, then it's possible for the kernel to run on systems
without RDTSC, such as 486 and certain 586, so the fallback code is only
required for that case.

As well, fix up both the new function and the get_cycles() function from
which it was derived to use cpu_feature_enabled() rather than
boot_cpu_has(), and use !IS_ENABLED() instead of #ifndef.
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
      3bd4abc0
    • J
      nios2: use fallback for random_get_entropy() instead of zero · c04e7270
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NDinh Nguyen <dinguyen@kernel.org>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      c04e7270
    • J
      arm: use fallback for random_get_entropy() instead of zero · ff8a8f59
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: NRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      ff8a8f59
    • J
      mips: use fallback for random_get_entropy() instead of just c0 random · 1c99c6a7
      由 Jason A. Donenfeld 提交于 
      For situations in which we don't have a c0 counter register available,
we've been falling back to reading the c0 "random" register, which is
usually bounded by the amount of TLB entries and changes every other
cycle or so. This means it wraps extremely often. We can do better by
combining this fast-changing counter with a potentially slower-changing
counter from random_get_entropy_fallback() in the more significant bits.
This commit combines the two, taking into account that the changing bits
are in a different bit position depending on the CPU model. In addition,
we previously were falling back to 0 for ancient CPUs that Linux does
not support anyway; remove that dead path entirely.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Tested-by: NMaciej W. Rozycki <macro@orcam.me.uk>
Acked-by: NThomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      1c99c6a7
    • J
      riscv: use fallback for random_get_entropy() instead of zero · 6d012386
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Acked-by: NPalmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: NPalmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      6d012386
    • J
      m68k: use fallback for random_get_entropy() instead of zero · 0f392c95
      由 Jason A. Donenfeld 提交于 
      In the event that random_get_entropy() can't access a cycle counter or
similar, falling back to returning 0 is really not the best we can do.
Instead, at least calling random_get_entropy_fallback() would be
preferable, because that always needs to return _something_, even
falling back to jiffies eventually. It's not as though
random_get_entropy_fallback() is super high precision or guaranteed to
be entropic, but basically anything that's not zero all the time is
better than returning zero all the time.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      0f392c95
    • J
      timekeeping: Add raw clock fallback for random_get_entropy() · 1366992e
      由 Jason A. Donenfeld 提交于 
      The addition of random_get_entropy_fallback() provides access to
whichever time source has the highest frequency, which is useful for
gathering entropy on platforms without available cycle counters. It's
not necessarily as good as being able to quickly access a cycle counter
that the CPU has, but it's still something, even when it falls back to
being jiffies-based.

In the event that a given arch does not define get_cycles(), falling
back to the get_cycles() default implementation that returns 0 is really
not the best we can do. Instead, at least calling
random_get_entropy_fallback() would be preferable, because that always
needs to return _something_, even falling back to jiffies eventually.
It's not as though random_get_entropy_fallback() is super high precision
or guaranteed to be entropic, but basically anything that's not zero all
the time is better than returning zero all the time.

Finally, since random_get_entropy_fallback() is used during extremely
early boot when randomizing freelists in mm_init(), it can be called
before timekeeping has been initialized. In that case there really is
nothing we can do; jiffies hasn't even started ticking yet. So just give
up and return 0.
Suggested-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Theodore Ts'o <tytso@mit.edu>
      1366992e
    • J
      openrisc: start CPU timer early in boot · 516dd4aa
      由 Jason A. Donenfeld 提交于 
      In order to measure the boot process, the timer should be switched on as
early in boot as possible. As well, the commit defines the get_cycles
macro, like the previous patches in this series, so that generic code is
aware that it's implemented by the platform, as is done on other archs.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Acked-by: NStafford Horne <shorne@gmail.com>
Reported-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      516dd4aa
    • J
      powerpc: define get_cycles macro for arch-override · 40883583
      由 Jason A. Donenfeld 提交于 
      PowerPC defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@ozlabs.org>
Cc: Paul Mackerras <paulus@samba.org>
Acked-by: NMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      40883583
    • J
      alpha: define get_cycles macro for arch-override · 1097710b
      由 Jason A. Donenfeld 提交于 
      Alpha defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Acked-by: NMatt Turner <mattst88@gmail.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      1097710b
    • J
      parisc: define get_cycles macro for arch-override · 8865bbe6
      由 Jason A. Donenfeld 提交于 
      PA-RISC defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NHelge Deller <deller@gmx.de>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      8865bbe6
    • J
      s390: define get_cycles macro for arch-override · 2e3df523
      由 Jason A. Donenfeld 提交于 
      S390x defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Acked-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      2e3df523
    • J
      ia64: define get_cycles macro for arch-override · 57c0900b
      由 Jason A. Donenfeld 提交于 
      Itanium defines a get_cycles() function, but it does not do the usual
`#define get_cycles get_cycles` dance, making it impossible for generic
code to see if an arch-specific function was defined. While the
get_cycles() ifdef is not currently used, the following timekeeping
patch in this series will depend on the macro existing (or not existing)
when defining random_get_entropy().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      57c0900b
    • J
      init: call time_init() before rand_initialize() · fe222a6c
      由 Jason A. Donenfeld 提交于 
      Currently time_init() is called after rand_initialize(), but
rand_initialize() makes use of the timer on various platforms, and
sometimes this timer needs to be initialized by time_init() first. In
order for random_get_entropy() to not return zero during early boot when
it's potentially used as an entropy source, reverse the order of these
two calls. The block doing random initialization was right before
time_init() before, so changing the order shouldn't have any complicated
effects.

Cc: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: NStafford Horne <shorne@gmail.com>
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      fe222a6c
    • J
      random: fix sysctl documentation nits · 069c4ea6
      由 Jason A. Donenfeld 提交于 
      A semicolon was missing, and the almost-alphabetical-but-not ordering
was confusing, so regroup these by category instead.
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      069c4ea6
  3. 09 5月, 2022 21 次提交