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amd64.S
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/*-
* Copyright (c) 2018 The University of Oslo
* Copyright (c) 2018 Dag-Erling Smørgrav
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* void clflush(const void *addr);
*
* Flush an address from the cache.
*/
.global clflush
.type clflush, @function
clflush:
clflush (%rdi)
ret
/*
* uint64_t rdtsc64(void);
*
* entry:
* -
* exit:
* %rax TSC value
*
* Read the 64-bit timestamp counter.
*/
.global rdtsc64
.type rdtsc64, @function
rdtsc64:
rdtsc
shlq $32, %rdx
orq %rdx, %rax
ret
/*
* uint32_t rdtsc32(void);
*
* entry:
* -
* exit:
* %eax lower 32 bits of TSC value
*
* Read the 64-bit timestamp counter, but discard the upper half.
*/
.global rdtsc32
.type rdtsc32, @function
rdtsc32:
rdtsc
ret
/*
* uint64_t timed_read(const void *addr);
*
* entry:
* %rdi addr
* exit:
* %rax TSC delta
*
* Read a word from the specified address and return the time it took
* in delta-TSC. Will occasionally return a wildly inaccurate number
* due to counter wraparound.
*/
.global timed_read
.type timed_read, @function
timed_read:
mfence
lfence
/* read TSC, combine halves and stash */
rdtsc
shlq $32, %rdx
orq %rdx, %rax
movq %rax, %rcx
/* access our target */
movl (%rdi), %eax
lfence
/* read TSC, combine halves and diff */
rdtsc
shlq $32, %rdx
orq %rdx, %rax
subq %rcx, %rax
ret
/*
* void spec_read(const uint8_t *addr, const uint8_t *probe, unsigned int shift);
*
* entry:
* %rdi addr
* %rsi probe
* %rdx shift
* exit:
* -
*
* Read *addr repeatedly until it is non-zero, then read probe[*addr << shift].
*/
.global spec_read
.type spec_read, @function
spec_read:
movq %rdx, %rcx
xor %rax, %rax
/* attempt to read the target */
prefetcht0 (%rdi)
1: movb (%rdi), %al
shlq %cl, %rax
jz 1b
/* access the appropriate probe */
movb (%rsi, %rax, 1), %cl
ret