[PATCH v2 9/9] arm64: head.S: document the use of callee saved registers
From: Ard Biesheuvel <hidden>
Date: 2016-08-24 14:36:06
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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. Signed-off-by: Ard Biesheuvel <redacted> --- arch/arm64/kernel/head.S | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index ad1dc61d67ac..8bc9458f9add 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S@@ -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
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2.7.4