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Commit a9be2ee0 authored Aug 31, 2016 by Ard Biesheuvel Committed by Will Deacon Sep 02, 2016

arm64: head.S: document the use of callee saved registers



Now that the only remaining occurrences of the use of callee saved
registers are on the primary boot path, add a comment to the code
which register is used for what.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 60699ba1

arch/arm64/kernel/head.S

+10 −0

Original line number	Diff line number	Diff line
		@@ -208,6 +208,16 @@ efi_header_end:

		__INIT

		/*
		* The following callee saved general purpose registers are used on the
		* primary lowlevel boot path:
		*
		* Register Scope Purpose
		* x21 stext() .. start_kernel() FDT pointer passed at boot in x0
		* x23 stext() .. start_kernel() physical misalignment/KASLR offset
		* x28 __create_page_tables() callee preserved temp register
		* x19/x20 __primary_switch() callee preserved temp registers
		*/
		ENTRY(stext)
		bl preserve_boot_args
		bl el2_setup // Drop to EL1, w0=cpu_boot_mode