// SPDX-License-Identifier: GPL-2.0
#include <linux/errno.h>
#include <linux/init.h>
#include <asm/setup.h>
#include <asm/processor.h>
#include <asm/sclp.h>
#include <asm/sections.h>
#include <asm/mem_detect.h>
#include <asm/sparsemem.h>
#include "compressed/decompressor.h"
#include "boot.h"

struct mem_detect_info __bootdata(mem_detect);

/* up to 256 storage elements, 1020 subincrements each */
#define ENTRIES_EXTENDED_MAX                                                   \
        (256 * (1020 / 2) * sizeof(struct mem_detect_block))

/*
 * To avoid corrupting old kernel memory during dump, find lowest memory
 * chunk possible either right after the kernel end (decompressed kernel) or
 * after initrd (if it is present and there is no hole between the kernel end
 * and initrd)
 */
static void *mem_detect_alloc_extended(void)
{
        unsigned long offset = ALIGN(mem_safe_offset(), sizeof(u64));

        if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_data.start && initrd_data.size &&
            initrd_data.start < offset + ENTRIES_EXTENDED_MAX)
                offset = ALIGN(initrd_data.start + initrd_data.size, sizeof(u64));

        return (void *)offset;
}

static struct mem_detect_block *__get_mem_detect_block_ptr(u32 n)
{
        if (n < MEM_INLINED_ENTRIES)
                return &mem_detect.entries[n];
        if (unlikely(!mem_detect.entries_extended))
                mem_detect.entries_extended = mem_detect_alloc_extended();
        return &mem_detect.entries_extended[n - MEM_INLINED_ENTRIES];
}

/*
 * sequential calls to add_mem_detect_block with adjacent memory areas
 * are merged together into single memory block.
 */
void add_mem_detect_block(u64 start, u64 end)
{
        struct mem_detect_block *block;

        if (mem_detect.count) {
                block = __get_mem_detect_block_ptr(mem_detect.count - 1);
                if (block->end == start) {
                        block->end = end;
                        return;
                }
        }

        block = __get_mem_detect_block_ptr(mem_detect.count);
        block->start = start;
        block->end = end;
        mem_detect.count++;
}

static int __diag260(unsigned long rx1, unsigned long rx2)
{
        unsigned long reg1, reg2, ry;
        union register_pair rx;
        psw_t old;
        int rc;

        rx.even = rx1;
        rx.odd  = rx2;
        ry = 0x10; /* storage configuration */
        rc = -1;   /* fail */
        asm volatile(
                "       mvc     0(16,%[psw_old]),0(%[psw_pgm])\n"
                "       epsw    %[reg1],%[reg2]\n"
                "       st      %[reg1],0(%[psw_pgm])\n"
                "       st      %[reg2],4(%[psw_pgm])\n"
                "       larl    %[reg1],1f\n"
                "       stg     %[reg1],8(%[psw_pgm])\n"
                "       diag    %[rx],%[ry],0x260\n"
                "       ipm     %[rc]\n"
                "       srl     %[rc],28\n"
                "1:     mvc     0(16,%[psw_pgm]),0(%[psw_old])\n"
                : [reg1] "=&d" (reg1),
                  [reg2] "=&a" (reg2),
                  [rc] "+&d" (rc),
                  [ry] "+&d" (ry),
                  "+Q" (S390_lowcore.program_new_psw),
                  "=Q" (old)
                : [rx] "d" (rx.pair),
                  [psw_old] "a" (&old),
                  [psw_pgm] "a" (&S390_lowcore.program_new_psw)
                : "cc", "memory");
        return rc == 0 ? ry : -1;
}

static int diag260(void)
{
        int rc, i;

        struct {
                unsigned long start;
                unsigned long end;
        } storage_extents[8] __aligned(16); /* VM supports up to 8 extends */

        memset(storage_extents, 0, sizeof(storage_extents));
        rc = __diag260((unsigned long)storage_extents, sizeof(storage_extents));
        if (rc == -1)
                return -1;

        for (i = 0; i < min_t(int, rc, ARRAY_SIZE(storage_extents)); i++)
                add_mem_detect_block(storage_extents[i].start, storage_extents[i].end + 1);
        return 0;
}

static int tprot(unsigned long addr)
{
        unsigned long reg1, reg2;
        int rc = -EFAULT;
        psw_t old;

        asm volatile(
                "       mvc     0(16,%[psw_old]),0(%[psw_pgm])\n"
                "       epsw    %[reg1],%[reg2]\n"
                "       st      %[reg1],0(%[psw_pgm])\n"
                "       st      %[reg2],4(%[psw_pgm])\n"
                "       larl    %[reg1],1f\n"
                "       stg     %[reg1],8(%[psw_pgm])\n"
                "       tprot   0(%[addr]),0\n"
                "       ipm     %[rc]\n"
                "       srl     %[rc],28\n"
                "1:     mvc     0(16,%[psw_pgm]),0(%[psw_old])\n"
                : [reg1] "=&d" (reg1),
                  [reg2] "=&a" (reg2),
                  [rc] "+&d" (rc),
                  "=Q" (S390_lowcore.program_new_psw.addr),
                  "=Q" (old)
                : [psw_old] "a" (&old),
                  [psw_pgm] "a" (&S390_lowcore.program_new_psw),
                  [addr] "a" (addr)
                : "cc", "memory");
        return rc;
}

static void search_mem_end(void)
{
        unsigned long range = 1 << (MAX_PHYSMEM_BITS - 20); /* in 1MB blocks */
        unsigned long offset = 0;
        unsigned long pivot;

        while (range > 1) {
                range >>= 1;
                pivot = offset + range;
                if (!tprot(pivot << 20))
                        offset = pivot;
        }

        add_mem_detect_block(0, (offset + 1) << 20);
}

unsigned long detect_memory(void)
{
        unsigned long max_physmem_end;

        sclp_early_get_memsize(&max_physmem_end);

        if (!sclp_early_read_storage_info()) {
                mem_detect.info_source = MEM_DETECT_SCLP_STOR_INFO;
                return max_physmem_end;
        }

        if (!diag260()) {
                mem_detect.info_source = MEM_DETECT_DIAG260;
                return max_physmem_end;
        }

        if (max_physmem_end) {
                add_mem_detect_block(0, max_physmem_end);
                mem_detect.info_source = MEM_DETECT_SCLP_READ_INFO;
                return max_physmem_end;
        }

        search_mem_end();
        mem_detect.info_source = MEM_DETECT_BIN_SEARCH;
        return get_mem_detect_end();
}