1 files changed, 182 insertions, 0 deletions
diff --git a/arch/s390/boot/mem_detect.c b/arch/s390/boot/mem_detect.c
new file mode 100644
index 000000000000..4cb771ba13fa
--- /dev/null
+++ b/arch/s390/boot/mem_detect.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/errno.h>
+#include <linux/init.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"
+
+unsigned long __bootdata(max_physmem_end);
+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(BLK_DEV_INITRD) && INITRD_START && INITRD_SIZE &&
+	    INITRD_START < offset + ENTRIES_EXTENDED_MAX)
+		offset = ALIGN(INITRD_START + INITRD_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 unsigned long get_mem_detect_end(void)
+{
+	if (mem_detect.count)
+		return __get_mem_detect_block_ptr(mem_detect.count - 1)->end;
+	return 0;
+}
+
+static int __diag260(unsigned long rx1, unsigned long rx2)
+{
+	register unsigned long _rx1 asm("2") = rx1;
+	register unsigned long _rx2 asm("3") = rx2;
+	register unsigned long _ry asm("4") = 0x10; /* storage configuration */
+	int rc = -1;				    /* fail */
+	unsigned long reg1, reg2;
+	psw_t old = S390_lowcore.program_new_psw;
+
+	asm volatile(
+		"	epsw	%0,%1\n"
+		"	st	%0,%[psw_pgm]\n"
+		"	st	%1,%[psw_pgm]+4\n"
+		"	larl	%0,1f\n"
+		"	stg	%0,%[psw_pgm]+8\n"
+		"	diag	%[rx],%[ry],0x260\n"
+		"	ipm	%[rc]\n"
+		"	srl	%[rc],28\n"
+		"1:\n"
+		: "=&d" (reg1), "=&a" (reg2),
+		  [psw_pgm] "=Q" (S390_lowcore.program_new_psw),
+		  [rc] "+&d" (rc), [ry] "+d" (_ry)
+		: [rx] "d" (_rx1), "d" (_rx2)
+		: "cc", "memory");
+	S390_lowcore.program_new_psw = old;
+	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 pgm_addr;
+	int rc = -EFAULT;
+	psw_t old = S390_lowcore.program_new_psw;
+
+	S390_lowcore.program_new_psw.mask = __extract_psw();
+	asm volatile(
+		"	larl	%[pgm_addr],1f\n"
+		"	stg	%[pgm_addr],%[psw_pgm_addr]\n"
+		"	tprot	0(%[addr]),0\n"
+		"	ipm	%[rc]\n"
+		"	srl	%[rc],28\n"
+		"1:\n"
+		: [pgm_addr] "=&d"(pgm_addr),
+		  [psw_pgm_addr] "=Q"(S390_lowcore.program_new_psw.addr),
+		  [rc] "+&d"(rc)
+		: [addr] "a"(addr)
+		: "cc", "memory");
+	S390_lowcore.program_new_psw = old;
+	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);
+}
+
+void detect_memory(void)
+{
+	sclp_early_get_memsize(&max_physmem_end);
+
+	if (!sclp_early_read_storage_info()) {
+		mem_detect.info_source = MEM_DETECT_SCLP_STOR_INFO;
+		return;
+	}
+
+	if (!diag260()) {
+		mem_detect.info_source = MEM_DETECT_DIAG260;
+		return;
+	}
+
+	if (max_physmem_end) {
+		add_mem_detect_block(0, max_physmem_end);
+		mem_detect.info_source = MEM_DETECT_SCLP_READ_INFO;
+		return;
+	}
+
+	search_mem_end();
+	mem_detect.info_source = MEM_DETECT_BIN_SEARCH;
+	max_physmem_end = get_mem_detect_end();
+}