linux-kernel - [PATCH] x86/boot: Use current_stack_pointer to avoid asm() in init

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Message-ID: <20240520083011.135342-1-ubizjak@gmail.com>
Date: Mon, 20 May 2024 10:29:55 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: linux-kernel@...r.kernel.org,
	x86@...nel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH] x86/boot: Use current_stack_pointer to avoid asm() in init_heap()

Use current_stack_pointer to avoid asm() in the calculation of
stack_end in init_heap(). The new code is more readable and
results in exactly the same object file.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---
 arch/x86/boot/main.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index 9049f390d834..ac78f8c01908 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -119,9 +119,8 @@ static void init_heap(void)
 	char *stack_end;
 
 	if (boot_params.hdr.loadflags & CAN_USE_HEAP) {
-		asm("leal %n1(%%esp),%0"
-		    : "=r" (stack_end) : "i" (STACK_SIZE));
-
+		stack_end = (char *)
+			(current_stack_pointer - STACK_SIZE);
 		heap_end = (char *)
 			((size_t)boot_params.hdr.heap_end_ptr + 0x200);
 		if (heap_end > stack_end)
-- 
2.45.1