linux/mm/memtest.c
Qiang Zhang 82634d7e24 memtest: use {READ,WRITE}_ONCE in memory scanning
memtest failed to find bad memory when compiled with clang.  So use
{WRITE,READ}_ONCE to access memory to avoid compiler over optimization.

Link: https://lkml.kernel.org/r/20240312080422.691222-1-qiang4.zhang@intel.com
Signed-off-by: Qiang Zhang <qiang4.zhang@intel.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-03-13 12:12:21 -07:00

138 lines
3.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/memblock.h>
#include <linux/seq_file.h>
static bool early_memtest_done;
static phys_addr_t early_memtest_bad_size;
static u64 patterns[] __initdata = {
/* The first entry has to be 0 to leave memtest with zeroed memory */
0,
0xffffffffffffffffULL,
0x5555555555555555ULL,
0xaaaaaaaaaaaaaaaaULL,
0x1111111111111111ULL,
0x2222222222222222ULL,
0x4444444444444444ULL,
0x8888888888888888ULL,
0x3333333333333333ULL,
0x6666666666666666ULL,
0x9999999999999999ULL,
0xccccccccccccccccULL,
0x7777777777777777ULL,
0xbbbbbbbbbbbbbbbbULL,
0xddddddddddddddddULL,
0xeeeeeeeeeeeeeeeeULL,
0x7a6c7258554e494cULL, /* yeah ;-) */
};
static void __init reserve_bad_mem(u64 pattern, phys_addr_t start_bad, phys_addr_t end_bad)
{
pr_info(" %016llx bad mem addr %pa - %pa reserved\n",
cpu_to_be64(pattern), &start_bad, &end_bad);
memblock_reserve(start_bad, end_bad - start_bad);
early_memtest_bad_size += (end_bad - start_bad);
}
static void __init memtest(u64 pattern, phys_addr_t start_phys, phys_addr_t size)
{
u64 *p, *start, *end;
phys_addr_t start_bad, last_bad;
phys_addr_t start_phys_aligned;
const size_t incr = sizeof(pattern);
start_phys_aligned = ALIGN(start_phys, incr);
start = __va(start_phys_aligned);
end = start + (size - (start_phys_aligned - start_phys)) / incr;
start_bad = 0;
last_bad = 0;
for (p = start; p < end; p++)
WRITE_ONCE(*p, pattern);
for (p = start; p < end; p++, start_phys_aligned += incr) {
if (READ_ONCE(*p) == pattern)
continue;
if (start_phys_aligned == last_bad + incr) {
last_bad += incr;
continue;
}
if (start_bad)
reserve_bad_mem(pattern, start_bad, last_bad + incr);
start_bad = last_bad = start_phys_aligned;
}
if (start_bad)
reserve_bad_mem(pattern, start_bad, last_bad + incr);
early_memtest_done = true;
}
static void __init do_one_pass(u64 pattern, phys_addr_t start, phys_addr_t end)
{
u64 i;
phys_addr_t this_start, this_end;
for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE, &this_start,
&this_end, NULL) {
this_start = clamp(this_start, start, end);
this_end = clamp(this_end, start, end);
if (this_start < this_end) {
pr_info(" %pa - %pa pattern %016llx\n",
&this_start, &this_end, cpu_to_be64(pattern));
memtest(pattern, this_start, this_end - this_start);
}
}
}
/* default is disabled */
static unsigned int memtest_pattern __initdata;
static int __init parse_memtest(char *arg)
{
int ret = 0;
if (arg)
ret = kstrtouint(arg, 0, &memtest_pattern);
else
memtest_pattern = ARRAY_SIZE(patterns);
return ret;
}
early_param("memtest", parse_memtest);
void __init early_memtest(phys_addr_t start, phys_addr_t end)
{
unsigned int i;
unsigned int idx = 0;
if (!memtest_pattern)
return;
pr_info("early_memtest: # of tests: %u\n", memtest_pattern);
for (i = memtest_pattern-1; i < UINT_MAX; --i) {
idx = i % ARRAY_SIZE(patterns);
do_one_pass(patterns[idx], start, end);
}
}
void memtest_report_meminfo(struct seq_file *m)
{
unsigned long early_memtest_bad_size_kb;
if (!IS_ENABLED(CONFIG_PROC_FS))
return;
if (!early_memtest_done)
return;
early_memtest_bad_size_kb = early_memtest_bad_size >> 10;
if (early_memtest_bad_size && !early_memtest_bad_size_kb)
early_memtest_bad_size_kb = 1;
/* When 0 is reported, it means there actually was a successful test */
seq_printf(m, "EarlyMemtestBad: %5lu kB\n", early_memtest_bad_size_kb);
}