Commit-ID: eabf2a604e0555b8f86a2c6c05c3a27496facf6d
Gitweb: https://git.kernel.org/tip/eabf2a604e0555b8f86a2c6c05c3a27496facf6d
Author: Kirill A. Shutemov <[email protected]>
AuthorDate: Mon, 4 Dec 2017 15:40:56 +0300
Committer: Thomas Gleixner <[email protected]>
CommitDate: Mon, 4 Dec 2017 21:14:34 +0100
x86/boot/compressed/64: Print error if 5-level paging is not supported
If the machine does not support the paging mode for which the kernel was
compiled, the boot process cannot continue.
It's not possible to let the kernel detect the mismatch as it does not even
reach the point where cpu features can be evaluted due to a triple fault in
the KASLR setup.
Instead of instantaneous silent reboot, emit an error message which gives
the user the information why the boot fails.
Fixes: 77ef56e4f0fb ("x86: Enable 5-level paging support via
CONFIG_X86_5LEVEL=y")
Reported-by: Borislav Petkov <[email protected]>
Signed-off-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Borislav Petkov <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: [email protected]
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Cc: Cyrill Gorcunov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link:
https://lkml.kernel.org/r/[email protected]
---
arch/x86/boot/compressed/misc.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index b50c424..98761a1 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -169,6 +169,16 @@ void __puthex(unsigned long value)
}
}
+static bool l5_supported(void)
+{
+ /* Check if leaf 7 is supported. */
+ if (native_cpuid_eax(0) < 7)
+ return 0;
+
+ /* Check if la57 is supported. */
+ return native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31));
+}
+
#if CONFIG_X86_NEED_RELOCS
static void handle_relocations(void *output, unsigned long output_len,
unsigned long virt_addr)
@@ -362,6 +372,12 @@ asmlinkage __visible void *extract_kernel(void *rmode,
memptr heap,
console_init();
debug_putstr("early console in extract_kernel\n");
+ if (IS_ENABLED(CONFIG_X86_5LEVEL) && !l5_supported()) {
+ error("This linux kernel as configured requires 5-level
paging\n"
+ "This CPU does not support the required 'cr4.la57'
feature\n"
+ "Unable to boot - please use a kernel appropriate for
your CPU\n");
+ }
+
free_mem_ptr = heap; /* Heap */
free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
