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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2019-02-06 18:29:08 +0300
committerBorislav Petkov <bp@suse.de>2019-02-06 21:08:34 +0300
commit82434d23f36de42f70925f70d645ed3b1394361b (patch)
tree1741f0bf54cc16ffe5145d547da217957e482f8d /arch/x86/boot/compressed/head_64.S
parent8ad382dd11ebed9f87edfeda6e738c472a911203 (diff)
downloadlinux-82434d23f36de42f70925f70d645ed3b1394361b.tar.xz
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@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: dave.hansen@linux.intel.com Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Kyle D Pelton <kyle.d.pelton@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wei Huang <wei@redhat.com> Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190206154756.matwldebbxkmlnae@black.fi.intel.com
Diffstat (limited to 'arch/x86/boot/compressed/head_64.S')
-rw-r--r--arch/x86/boot/compressed/head_64.S9
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 */