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RowHammer: Move inline asm rowhammer loop to assembly. #2

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RowHammer: Move inline asm rowhammer loop to assembly. #2

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7 changes: 5 additions & 2 deletions src/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ CFLAGS= -Wall -march=i486 -m32 -O0 -fomit-frame-pointer -fno-builtin \

OBJS= head.o reloc.o main.o test.o init.o lib.o patn.o screen_buffer.o \
config.o cpuid.o linuxbios.o pci.o memsize.o spd.o error.o dmi.o controller.o \
smp.o vmem.o random.o
smp.o vmem.o random.o rowhammer.o


all: clean memtest.bin memtest
Expand Down Expand Up @@ -57,7 +57,10 @@ test.o: test.c

random.o: random.c
$(CC) -c -Wall -march=i486 -m32 -O3 -fomit-frame-pointer -fno-builtin -ffreestanding random.c


rowhammer.o: rowhammer.S
$(AS) -32 -o rowhammer.o rowhammer.S

# rule for build number generation
build_number:
sh make_buildnum.sh
Expand Down
27 changes: 27 additions & 0 deletions src/rowhammer.S
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@@ -0,0 +1,27 @@
/* void do_rowhammer(char *addr1, char *addr2, int count); */
/*
* Load from addr1, addr2; clflush addr1 and addr2; mfence; repeat count times.
* See 'Code 1' in ISCA '14 paper for code rationale.
*
* If addr1 and addr2 map to different rows of the same DRAM bank, it may
* be possible to witness other rows in the bank cleared, perhaps by
* coupling from repeated ACT/PRE signals on row activation lines.
*/
.globl do_rowhammer
do_rowhammer:
movl 12(%esp), %ecx /* count */
movl 8(%esp), %edx /* addr2 */
movl 4(%esp), %eax /* addr1 */
pushl %esi
pushl %edi
/* Core loop has no memory accesses beyond ifetch, load, clflush */
1: movl (%eax), %esi /* load addr1 */
movl (%edx), %edi /* load addr2 */
clflush (%eax) /* clflush addr1 */
clflush (%edx) /* clflush addr2 */
mfence
decl %ecx
jnz 1b
popl %edi
popl %esi
ret
9 changes: 2 additions & 7 deletions src/test.c
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Expand Up @@ -25,6 +25,7 @@ extern int test_ticks, nticks;
extern struct tseq tseq[];
extern void update_err_counts(void);
extern void print_err_counts(void);
extern void do_rowhammer(char *addr1, char *addr2, int count);
void rand_seed( unsigned int seed1, unsigned int seed2, int me);
ulong rand(int me);
void poll_errors();
Expand Down Expand Up @@ -1580,13 +1581,7 @@ void rowhammer(int row_max, int *row_cnt, int toggle_max, int me)
break;

// open and close row-pair (addr1 & addr2) repeatedly
for (int toggle = 0; toggle < toggle_max; toggle++) {
asm volatile("movl (%0), %%eax" : : "r" (addr1) : "eax");
asm volatile("movl (%0), %%ebx" : : "r" (addr2) : "ebx");
asm volatile("clflush (%0)" : : "r" (addr1) : "memory");
asm volatile("clflush (%0)" : : "r" (addr2) : "memory");
//asm volatile("mfence");
}
do_rowhammer(addr1, addr2, toggle_max);

(*row_cnt)++;

Expand Down