// 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;

        VM_WARN_ON_ONCE(size < start_phys_aligned - start_phys);

        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);
}