[PATCH v14 1/5] x86/boot: Introduce get_acpi_rsdp() to parse RSDP in cmdline from KEXEC

[Chao Fan]

Memory information in SRAT is necessary to fix the conflict between
KASLR and memory-hotremove.

ACPI SRAT (System/Static Resource Affinity Table) shows the details
about memory ranges, including ranges of memory provided by hot-added
memory devices. SRAT is introduced by Root System Description
Pointer(RSDP), so RSDP should be found firstly.

When booting form KEXEC/EFI/BIOS, the methods to find RSDP
are different. When booting from KEXEC, 'acpi_rsdp' may have been
added to cmdline, so parse cmdline to find RSDP.

Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/boot/compressed/acpi.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 arch/x86/boot/compressed/acpi.c

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
new file mode 100644
index 000000000000..44f19546c169
--- /dev/null
+++ b/arch/x86/boot/compressed/acpi.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+#define BOOT_CTYPE_H
+#include "misc.h"
+#include "error.h"
+
+#include <linux/efi.h>
+#include <linux/numa.h>
+#include <linux/acpi.h>
+#include <asm/efi.h>
+
+/* Max length of 64-bit hex address string is 18, prefix "0x" + 16 hex digits */
+#define MAX_ADDRESS_LENGTH 18
+
+static acpi_physical_address get_acpi_rsdp(void)
+{
+#ifdef CONFIG_KEXEC
+	char val[MAX_ADDRESS_LENGTH+1];
+	unsigned long long res;
+	int len;
+
+	len = cmdline_find_option("acpi_rsdp", val, MAX_ADDRESS_LENGTH+1);
+	if (len > 0) {
+		char *e;
+
+		val[len] = '\0';
+		return (acpi_physical_address)simple_strtoull(val, &e, 16);
+	}
+#endif
+	return 0;
+}
-- 
2.19.2