Messages in this thread Patch in this message | | | Date | Thu, 9 May 2019 15:02:57 +0800 | From | Baoquan He <> | Subject | [PATCH v5 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel |
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If the running kernel has 5-level paging activated, the 5-level paging mode is preserved across kexec. If the kexec'ed kernel does not contain support for handling active 5-level paging mode in the decompressor, the decompressor will crash with #GP.
Prevent this situation at load time. If 5-level paging is active, check the xloadflags whether the kexec kernel can handle 5-level paging at least in the decompressor. If not, reject the load attempt and print out error message.
Signed-off-by: Baoquan He <bhe@redhat.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- v4->v5: Update the output error message per tglx's comment.
arch/x86/kernel/kexec-bzimage64.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c index 22f60dd26460..7f439739ea3d 100644 --- a/arch/x86/kernel/kexec-bzimage64.c +++ b/arch/x86/kernel/kexec-bzimage64.c @@ -321,6 +321,11 @@ static int bzImage64_probe(const char *buf, unsigned long len) return ret; } + if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) { + pr_err("bzImage cannot handle 5-level paging mode.\n"); + return ret; + } + /* I've got a bzImage */ pr_debug("It's a relocatable bzImage64\n"); ret = 0; -- 2.17.2
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