[PATCH] x86: Disable kexec if system has unaccepted memory

[Kirill A. Shutemov]

On kexec, the target kernel has to know what memory has been accepted.
Information in EFI map is out of date and cannot be used.

boot_params.unaccepted_memory can be used to pass the bitmap between two
kernels on kexec, but the use-case is not yet implemented.

Disable kexec on machines with unaccepted memory for now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/x86/mm/unaccepted_memory.c | 16 ++++++++++++++++
 include/linux/kexec.h           |  2 ++
 kernel/kexec.c                  |  4 ++++
 kernel/kexec_core.c             |  5 +++++
 kernel/kexec_file.c             |  4 ++++
 5 files changed, 31 insertions(+)

diff --git a/arch/x86/mm/unaccepted_memory.c b/arch/x86/mm/unaccepted_memory.c
index 566c3a72aee8..529c3fd1dab3 100644
--- a/arch/x86/mm/unaccepted_memory.c
+++ b/arch/x86/mm/unaccepted_memory.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kexec.h>
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
@@ -98,3 +99,18 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
 
 	return ret;
 }
+
+#ifdef CONFIG_KEXEC_CORE
+int arch_kexec_load(void)
+{
+	if (!boot_params.unaccepted_memory)
+		return 0;
+
+	/*
+	 * TODO: Information on memory acceptance status has to be communicated
+	 * between kernel.
+	 */
+	pr_warn_once("Disable kexec: not yet supported on systems with unaccepted memory\n");
+	return -EOPNOTSUPP;
+}
+#endif
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index ce6536f1d269..dfd9493d0b4b 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -396,6 +396,8 @@ void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);
 void arch_kexec_protect_crashkres(void);
 void arch_kexec_unprotect_crashkres(void);
 
+int arch_kexec_load(void);
+
 #ifndef page_to_boot_pfn
 static inline unsigned long page_to_boot_pfn(struct page *page)
 {
diff --git a/kernel/kexec.c b/kernel/kexec.c
index b5e40f069768..352b3742f07a 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -195,6 +195,10 @@ static inline int kexec_load_check(unsigned long nr_segments,
 {
 	int result;
 
+	result = arch_kexec_load();
+	if (result)
+		return result;
+
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 4d34c78334ce..4d51b9271f6b 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1238,3 +1238,8 @@ void __weak arch_kexec_protect_crashkres(void)
 
 void __weak arch_kexec_unprotect_crashkres(void)
 {}
+
+int __weak arch_kexec_load(void)
+{
+	return 0;
+}
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 145321a5e798..d531df94ffbb 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -324,6 +324,10 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 	int ret = 0, i;
 	struct kimage **dest_image, *image;
 
+	ret = arch_kexec_load();
+	if (ret)
+		return ret;
+
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
-- 
 Kirill A. Shutemov