[tip:x86/boot] x86/boot: Add "acpi_rsdp=" early parsing

[tip-bot for Chao Fan]

Commit-ID:  3c98e71b42a7d0c14639ccb565ea315f3c887f92
Gitweb:     https://git.kernel.org/tip/3c98e71b42a7d0c14639ccb565ea315f3c887f92
Author:     Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
AuthorDate: Wed, 23 Jan 2019 19:08:45 +0800
Committer:  Borislav Petkov <bp@xxxxxxx>
CommitDate: Fri, 1 Feb 2019 11:52:54 +0100

x86/boot: Add "acpi_rsdp=" early parsing

KASLR may randomly choose offsets which are located in movable memory
regions resulting in the movable memory becoming immovable.

The ACPI SRAT (System/Static Resource Affinity Table) describes memory
ranges including ranges of memory provided by hot-added memory devices.
In order to access SRAT, one needs the Root System Description Pointer
(RSDP) with which to find the Root/Extended System Description Table
(R/XSDT) which then contains the system description tables of which SRAT
is one of.

In case the RSDP address has been passed on the command line (kexec-ing
a second kernel) parse it from there.

 [ bp: Rewrite the commit message and cleanup the code. ]

Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: bhe@xxxxxxxxxx
Cc: caoj.fnst@xxxxxxxxxxxxxx
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: indou.takao@xxxxxxxxxxxxxx
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: kasong@xxxxxxxxxx
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: msys.mizuma@xxxxxxxxx
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20190123110850.12433-3-fanc.fnst@xxxxxxxxxxxxxx
---
 arch/x86/boot/compressed/acpi.c | 32 ++++++++++++++++++++++++++++++++
 arch/x86/boot/compressed/misc.h |  3 +++
 2 files changed, 35 insertions(+)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
new file mode 100644
index 000000000000..bacfc4ea35ac
--- /dev/null
+++ b/arch/x86/boot/compressed/acpi.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#define BOOT_CTYPE_H
+#include "misc.h"
+#include "error.h"
+#include "../string.h"
+
+#ifdef CONFIG_ACPI
+
+/*
+ * Max length of 64-bit hex address string is 19, prefix "0x" + 16 hex
+ * digits, and '\0' for termination.
+ */
+#define MAX_ADDR_LEN 19
+
+static acpi_physical_address get_acpi_rsdp(void)
+{
+	acpi_physical_address addr = 0;
+
+#ifdef CONFIG_KEXEC
+	char val[MAX_ADDR_LEN] = { };
+	int ret;
+
+	ret = cmdline_find_option("acpi_rsdp", val, MAX_ADDR_LEN);
+	if (ret < 0)
+		return 0;
+
+	if (kstrtoull(val, 16, &addr))
+		return 0;
+#endif
+	return addr;
+}
+#endif /* CONFIG_ACPI */
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index a1d5918765f3..764ad50c0119 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -25,6 +25,9 @@
 #include <asm/bootparam.h>
 #include <asm/bootparam_utils.h>
 
+#define BOOT_CTYPE_H
+#include <linux/acpi.h>
+
 #define BOOT_BOOT_H
 #include "../ctype.h"