[PATCH v9 5/8] x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdlien from kexec

[Chao Fan]

If KEXEC write the RSDP pointer to cmdline, parse the cmdline
and use it.
Imitate from early_param of "acpi_rsdp".

Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/boot/compressed/acpitb.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
index 50fa65cf824d..37b1f4407be8 100644
--- a/arch/x86/boot/compressed/acpitb.c
+++ b/arch/x86/boot/compressed/acpitb.c
@@ -8,6 +8,9 @@
 #include <linux/numa.h>
 #include <linux/acpi.h>
 
+#define STATIC
+#include <linux/decompress/mm.h>
+
 /* Search EFI table for RSDP table. */
 static void efi_get_rsdp_addr(acpi_physical_address *rsdp_addr)
 {
@@ -200,3 +203,23 @@ static void bios_get_rsdp_addr(acpi_physical_address *rsdp_addr)
 		*rsdp_addr = (acpi_physical_address)address;
 	}
 }
+
+static void get_acpi_rsdp(acpi_physical_address *rsdp_addr)
+{
+#ifdef CONFIG_KEXEC
+	unsigned long long res;
+	int len = 0;
+	char *val;
+
+	val = malloc(20);
+	len = cmdline_find_option("acpi_rsdp", val, 20);
+
+	if (len == -1)
+		return;
+
+	if (len > 0) {
+		val[len] = 0;
+		*rsdp_addr = (acpi_physical_address)kstrtoull(val, 0, &res);
+	}
+#endif
+}
-- 
2.17.2