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06947aaaf9
linux/arch/mips/kernel
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Maciej W. Rozycki 06947aaaf9 MIPS: Implement random_get_entropy with CP0 Random 
Update to commit 9c9b415c50 [MIPS:
Reimplement get_cycles().]

On systems were for whatever reasons we can't use the cycle counter, fall
back to the c0_random register as an entropy source.  It has however a
very small range that makes it suitable for random_get_entropy only and
not get_cycles.

This optimised version compiles to 8 instructions in the fast path even in
the worst case of all the conditions to check being variable (including a
MFC0 move delay slot that is only required for very old processors):

     828:	8cf90000 	lw	t9,0(a3)
			828: R_MIPS_LO16	jiffies
     82c:	40057800 	mfc0	a1,c0_prid
     830:	3c0200ff 	lui	v0,0xff
     834:	00a21024 	and	v0,a1,v0
     838:	1040007d 	beqz	v0,a30 <add_interrupt_randomness+0x22c>
     83c:	3c030000 	lui	v1,0x0
			83c: R_MIPS_HI16	cpu_data
     840:	40024800 	mfc0	v0,c0_count
     844:	00000000 	nop
     848:	00409021 	move	s2,v0
     84c:	8ce20000 	lw	v0,0(a3)
			84c: R_MIPS_LO16	jiffies

On most targets the sequence will be shorter and on some it will reduce to
a single `MFC0 <reg>,c0_count', as all MIPS architecture (i.e. non-legacy
MIPS) processors require the CP0 Count register to be present.

The only known exception that reports MIPS architecture compliance, but
contrary to that lacks CP0 Count is the Ingenic JZ4740 thingy.  For broken
platforms like that this code requires cpu_has_counter to be hardcoded to
0 (i.e. no variable setting is permitted) so as not to penalise all the
other good platforms out there.

The asm barrier is required so that the compiler does not pull any
potentially costly (cold cache!) `cpu_data' variable access into the fast
path.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: John Crispin <blogic@openwrt.org>
Cc: Andrew McGregor <andrewmcgr@gmail.com>
Cc: Dave Taht <dave.taht@bufferbloat.net>
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Simon Kelley <simon@thekelleys.org.uk>
Cc: Jim Gettys <jg@freedesktop.org>
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6702/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2014-05-30 18:21:30 +02:00
..
.gitignore
8250-platform.c mips: remove needless include of module.h from core kernel files. 2011-10-31 19:30:57 -04:00
asm-offsets.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
binfmt_elfn32.c MIPS: Compat: Fix cputime_to_timeval() arguments in compat binfmt_elf. 2013-06-06 16:11:26 +02:00
binfmt_elfo32.c MIPS: Support for 64-bit FP with O32 binaries 2014-01-13 23:40:56 +01:00
bmips_vec.S MIPS: Fix gigaton of warning building with microMIPS. 2014-03-31 18:17:12 +02:00
branch.c MIPS: Sort out mm_isBranchInstr. 2014-05-23 15:12:37 +02:00
cevt-bcm1480.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cevt-ds1287.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cevt-gic.c MIPS: allow GIC clockevent device config from other CPUs 2014-05-02 16:39:11 +01:00
cevt-gt641xx.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cevt-r4k.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
cevt-sb1250.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cevt-txx9.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
cps-vec.S MIPS: smp-cps: duplicate core0 CCA on secondary cores 2014-05-28 16:20:33 +01:00
cpu-bugs64.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00
cpu-probe.c MIPS: Implement random_get_entropy with CP0 Random 2014-05-30 18:21:30 +02:00
crash_dump.c mips: remove savemaxmem parameter setup 2013-07-03 16:08:03 -07:00
crash.c mips: delete non-required instances of include <linux/init.h> 2014-01-24 22:39:56 +01:00
csrc-bcm1480.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
csrc-gic.c MIPS: Refactor GIC clocksource code. 2013-05-09 17:55:20 +02:00
csrc-ioasic.c MIPS: DECstation HRT initialization rearrangement 2013-09-13 11:56:13 +02:00
csrc-r4k.c
csrc-sb1250.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
early_printk_8250.c MIPS: Add 8250/16550 serial early printk driver 2013-10-29 21:24:36 +01:00
early_printk.c early_printk: consolidate random copies of identical code 2013-04-29 18:28:13 -07:00
entry.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
ftrace.c Most of the changes were largely clean ups, and some documentation. 2014-04-03 10:26:31 -07:00
genex.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
gpio_txx9.c
head.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
i8253.c MIPS: irq: Remove IRQF_DISABLED 2011-12-07 22:03:45 +00:00
i8259.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
idle.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
irq_cpu.c MIPS: Panic messages should not end in \n. 2013-10-29 21:24:19 +01:00
irq_txx9.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq-gic.c MIPS: allow GIC clockevent device config from other CPUs 2014-05-02 16:39:11 +01:00
irq-gt641xx.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq-msc01.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
irq-rm7000.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
irq.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
jump_label.c
kgdb.c MIPS: kernel: {ftrace,kgdb}: Set correct address limit for cache flushes 2014-03-26 23:09:18 +01:00
kprobes.c kprobes/mips: Fix to check double free of insn slot 2013-05-22 12:48:30 +02:00
linux32.c unify compat fanotify_mark(2), switch to COMPAT_SYSCALL_DEFINE 2013-05-09 13:46:38 -04:00
machine_kexec.c MIPS: kdump: Add support 2012-12-13 16:46:47 +01:00
Makefile Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
mcount.S MIPS: Ftrace: Fix function tracing return address to match 2013-09-03 14:46:27 +02:00
mips_ksyms.c MIPS: checksum: Split the 'copy_user' symbol 2014-03-26 23:09:17 +01:00
mips_machine.c MIPS: move mips_{set,get}_machine_name() to a more generic place 2013-05-08 01:19:07 +02:00
mips-cm.c MIPS: Add generic CM probe & access code 2014-03-06 21:25:22 +01:00
mips-cpc.c MIPS: smp-cps: rework core/VPE initialisation 2014-05-28 16:20:28 +01:00
mips-mt-fpaff.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
mips-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
module-rela.c MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
module.c MIPS: Use NUMA_NO_NODE instead of -1 for node ID. 2013-10-29 21:24:14 +01:00
octeon_switch.S MIPS: stack protector: Fix per-task canary switch 2013-10-07 15:31:04 +02:00
perf_event_mipsxx.c MIPS: perf: Add interAptiv support 2014-03-31 18:17:12 +02:00
perf_event.c MIPS: perf: Reorganize contents of perf support files. 2011-10-24 23:34:26 +01:00
pm-cps.c MIPS: pm-cps: add PM state entry code for CPS systems 2014-05-28 16:20:31 +01:00
pm.c MIPS: PM: Implement PM helper macros 2014-05-02 16:39:10 +01:00
proc.c Revert "MIPS: MT: proc: Add support for printing VPE and TC ids" 2014-05-13 00:29:33 +02:00
process.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
prom.c mips: use common of_flat_dt_get_machine_name 2013-10-09 20:03:57 -05:00
ptrace32.c MIPS: Simplify PTRACE_PEEKUSR for FPC_EIR 2014-03-31 18:17:12 +02:00
ptrace.c Merge git://git.infradead.org/users/eparis/audit 2014-04-12 12:38:53 -07:00
r4k_fpu.S Merge branch '3.14-fixes' into mips-for-linux-next 2014-03-31 18:17:33 +02:00
r4k_switch.S MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
r2300_fpu.S MIPS: Whitespace cleanup. 2013-02-01 10:00:22 +01:00
r2300_switch.S MIPS: stack protector: Fix per-task canary switch 2013-10-07 15:31:04 +02:00
r6000_fpu.S
relocate_kernel.S MIPS: kdump: Skip walking indirection page for crashkernels 2013-09-05 20:53:37 +02:00
reset.c mips: migrate core kernel file from module.h --> export.h 2011-10-31 19:30:56 -04:00
rtlx-cmp.c MIPS: APRP: Unregister rtlx interrupt hook at module exit 2014-03-06 20:55:07 +01:00
rtlx-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
rtlx.c MIPS: APRP: Code formatting clean-ups. 2014-01-22 20:19:02 +01:00
scall32-o32.S MIPS: Wire up renameat2 syscall. 2014-05-13 17:57:33 +02:00
scall64-64.S MIPS: Wire up renameat2 syscall. 2014-05-13 17:57:33 +02:00
scall64-n32.S MIPS: Wire up renameat2 syscall. 2014-05-13 17:57:33 +02:00
scall64-o32.S MIPS: Wire up renameat2 syscall. 2014-05-13 17:57:33 +02:00
segment.c MIPS: Add debugfs file to print the segmentation control registers 2014-01-22 20:19:00 +01:00
setup.c MIPS: Fix start of free memory when using initrd 2013-10-29 21:24:23 +01:00
signal32.c MIPS: Save/restore MSA context around signals 2014-03-26 23:09:11 +01:00
signal_n32.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2013-03-02 07:44:16 -08:00
signal-common.h most of set_current_blocked() callers want SIGKILL/SIGSTOP removed from set 2012-06-01 12:58:51 -04:00
signal.c MIPS: kernel: signal: Prevent save/restore FPU context in user memory 2014-03-26 23:09:17 +01:00
smp-bmips.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp-cmp.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp-cps.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
smp-gic.c cpuidle: cpuidle-cps: add MIPS CPS cpuidle driver 2014-05-28 16:20:36 +01:00
smp-mt.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp-up.c MIPS: SMP: Remove plat_smp_ops cpus_done method. 2014-05-27 11:06:42 +02:00
smp.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
spinlock_test.c mips: migrate core kernel file from module.h --> export.h 2011-10-31 19:30:56 -04:00
spram.c MIPS: Use current_cpu_type() instead of c->cputype 2014-03-31 18:17:12 +02:00
stacktrace.c mips: migrate core kernel file from module.h --> export.h 2011-10-31 19:30:56 -04:00
sync-r4k.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
syscall.c MIPS: Fix gigaton of warning building with microMIPS. 2014-03-31 18:17:12 +02:00
time.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
topology.c
traps.c Merge branch 'wip-mips-pm' of https://github.com/paulburton/linux into mips-for-linux-next 2014-05-29 15:08:23 +02:00
unaligned.c MIPS: kernel: unaligned: Handle unaligned accesses for EVA 2014-03-26 23:09:16 +01:00
vdso.c coredump: remove VM_ALWAYSDUMP flag 2012-03-23 16:58:42 -07:00
vmlinux.lds.S MIPS: Discard .eh_frame sections in linker script. 2013-08-26 15:33:41 +02:00
vpe-cmp.c MIPS: APRP: Add VPE loader support for CMP platforms. 2014-01-22 20:19:02 +01:00
vpe-mt.c MIPS: MT: Remove SMTC support 2014-05-24 00:07:01 +02:00
vpe.c Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus 2014-01-30 17:20:32 -08:00
watch.c MIPS: Delete __cpuinit/__CPUINIT usage from MIPS code 2013-07-14 19:36:51 -04:00