Commit-ID: 82434d23f36de42f70925f70d645ed3b1394361b Gitweb: https://git.kernel.org/tip/82434d23f36de42f70925f70d645ed3b1394361b Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> AuthorDate: Wed, 6 Feb 2019 18:29:08 +0300 Committer: Borislav Petkov <bp@xxxxxxx> CommitDate: Wed, 6 Feb 2019 19:08:34 +0100 x86/boot/compressed/64: Explain paging_prepare()'s return value paging_prepare() returns a two-quadword structure which lands into RDX:RAX: - Address of the trampoline is returned in RAX. - Non zero RDX means trampoline needs to enable 5-level paging. Document that explicitly. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: dave.hansen@xxxxxxxxxxxxxxx Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Kyle D Pelton <kyle.d.pelton@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Wei Huang <wei@xxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20190206154756.matwldebbxkmlnae@xxxxxxxxxxxxxxxxxx --- arch/x86/boot/compressed/head_64.S | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index b27b338d2f6d..73b9d7e91a9c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -358,8 +358,11 @@ ENTRY(startup_64) * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. * - * Address of the trampoline is returned in RAX. - * Non zero RDX on return means we need to enable 5-level paging. + * paging_prepare() returns a two-quadword structure which lands + * into RDX:RAX: + * - Address of the trampoline is returned in RAX. + * - Non zero RDX means trampoline needs to enable 5-level + * paging. * * RSI holds real mode data and needs to be preserved across * this function call. @@ -565,7 +568,7 @@ adjust_got: * * RDI contains the return address (might be above 4G). * ECX contains the base address of the trampoline memory. - * Non zero RDX on return means we need to enable 5-level paging. + * Non zero RDX means trampoline needs to enable 5-level paging. */ ENTRY(trampoline_32bit_src) /* Set up data and stack segments */
|