linux-kernel - [PATCH 1/3] arm64: mm: Cast start/end markers to char *, not u64

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Message-ID: <20250822041538.467514-2-CFSworks@gmail.com>
Date: Thu, 21 Aug 2025 21:15:36 -0700
From: Sam Edwards <cfsworks@...il.com>
To: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Marc Zyngier <maz@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Baruch Siach <baruch@...s.co.il>,
	Kevin Brodsky <kevin.brodsky@....com>,
	Joey Gouly <joey.gouly@....com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Sam Edwards <CFSworks@...il.com>
Subject: [PATCH 1/3] arm64: mm: Cast start/end markers to char *, not u64

There are a few memset() calls in map_kernel.c that cast marker-symbol
addresses to u64 in order to perform pointer subtraction (range size
computation).

Cast them with (char *) instead, aligning with idiomatic C pointer
arithmetic.

This patch provably has no effect at runtime: I have verified that
.text of vmlinux is identical after this change.

Signed-off-by: Sam Edwards <CFSworks@...il.com>
---
 arch/arm64/kernel/pi/map_kernel.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/pi/map_kernel.c b/arch/arm64/kernel/pi/map_kernel.c
index 0f4bd7771859..2b3047860230 100644
--- a/arch/arm64/kernel/pi/map_kernel.c
+++ b/arch/arm64/kernel/pi/map_kernel.c
@@ -179,7 +179,7 @@ static void __init remap_idmap_for_lpa2(void)
 	 * Don't bother with the FDT, we no longer need it after this.
 	 */
 	memset(init_idmap_pg_dir, 0,
-	       (u64)init_idmap_pg_end - (u64)init_idmap_pg_dir);
+	       (char *)init_idmap_pg_end - (char *)init_idmap_pg_dir);
 
 	create_init_idmap(init_idmap_pg_dir, mask);
 	dsb(ishst);
@@ -188,7 +188,7 @@ static void __init remap_idmap_for_lpa2(void)
 	set_ttbr0_for_lpa2((u64)init_idmap_pg_dir);
 
 	/* wipe the temporary ID map from memory */
-	memset(init_pg_dir, 0, (u64)init_pg_end - (u64)init_pg_dir);
+	memset(init_pg_dir, 0, (char *)init_pg_end - (char *)init_pg_dir);
 }
 
 static void __init map_fdt(u64 fdt)
@@ -242,7 +242,7 @@ asmlinkage void __init early_map_kernel(u64 boot_status, void *fdt)
 	map_fdt((u64)fdt);
 
 	/* Clear BSS and the initial page tables */
-	memset(__bss_start, 0, (u64)init_pg_end - (u64)__bss_start);
+	memset(__bss_start, 0, (char *)init_pg_end - (char *)__bss_start);
 
 	/* Parse the command line for CPU feature overrides */
 	chosen = fdt_path_offset(fdt, chosen_str);
-- 
2.49.1