linux-kernel - Re: [PATCH v1 1/3] Recieve boot

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Message-ID: <2D63735B-FA76-428E-8F68-8EBCAEA0985E@zytor.com>
Date: Mon, 23 Jun 2025 08:24:16 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Khalid Ali <khaliidcaliy@...il.com>, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, ubizjak@...il.com
CC: x86@...nel.org, linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/3] Recieve boot_param from RDI Instead of RSI

On June 23, 2025 1:15:23 AM PDT, Khalid Ali <khaliidcaliy@...il.com> wrote:
>From: Khalid Ali <khaliidcaliy@...il.com>
>
>Adjust the kernel entry point to recieve arguments from RDI instead of
>RSI.
>
>Signed-off-by: Khalid Ali <khaliidcaliy@...il.com>
>---
> arch/x86/kernel/head_64.S | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
>index dfb5390e5c9a..d24fea15b6a6 100644
>--- a/arch/x86/kernel/head_64.S
>+++ b/arch/x86/kernel/head_64.S
>@@ -43,7 +43,7 @@ SYM_CODE_START_NOALIGN(startup_64)
> 	 * for us.  These identity mapped page tables map all of the
> 	 * kernel pages and possibly all of memory.
> 	 *
>-	 * %RSI holds the physical address of the boot_params structure
>+	 * %RDI holds the physical address of the boot_params structure
> 	 * provided by the bootloader. Preserve it in %R15 so C function calls
> 	 * will not clobber it.
> 	 *
>@@ -56,7 +56,7 @@ SYM_CODE_START_NOALIGN(startup_64)
> 	 * compiled to run at we first fixup the physical addresses in our page
> 	 * tables and then reload them.
> 	 */
>-	mov	%rsi, %r15
>+	mov	%rdi, %r15
> 
> 	/* Set up the stack for verify_cpu() */
> 	leaq	__top_init_kernel_stack(%rip), %rsp

This is an ABI.

Nacked-by: H. Peter Anvin <hpa@...or.com>