diff options
| author | Kirill A. Shutemov <[email protected]> | 2019-02-06 18:29:08 +0300 |
|---|---|---|
| committer | Borislav Petkov <[email protected]> | 2019-02-06 19:08:34 +0100 |
| commit | 82434d23f36de42f70925f70d645ed3b1394361b (patch) | |
| tree | 1741f0bf54cc16ffe5145d547da217957e482f8d | |
| parent | 8ad382dd11ebed9f87edfeda6e738c472a911203 (diff) | |
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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Cc: [email protected]
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Kyle D Pelton <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Wei Huang <[email protected]>
Cc: x86-ml <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
| -rw-r--r-- | arch/x86/boot/compressed/head_64.S | 9 |
1 files 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 */ |