linux-kernel - [PATCH 6/7] riscv: drop the use of XIP_OFFSET in create_kernel_page

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Message-Id: <8748eab99d76e466a44a0bb81d836ff1c9ad9879.1715286093.git.namcao@linutronix.de>
Date: Fri, 10 May 2024 08:28:44 +0200
From: Nam Cao <namcao@...utronix.de>
To: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Nam Cao <namcao@...utronix.de>
Subject: [PATCH 6/7] riscv: drop the use of XIP_OFFSET in create_kernel_page_table()

XIP_OFFSET is the hard-coded offset of writable data section within the
kernel.

By hard-coding this value, the read-only section of the kernel (which is
placed before the writable data section) is restricted in size.

As a preparation to remove this hard-coded value entirely, stop using
XIP_OFFSET in create_kernel_page_table(). Instead use _sdata and _start to
do the same thing.

Signed-off-by: Nam Cao <namcao@...utronix.de>
---
 arch/riscv/mm/init.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 9846c6924509..62ff4aa2be96 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -907,7 +907,7 @@ static void __init relocate_kernel(void)
 static void __init create_kernel_page_table(pgd_t *pgdir,
 					    __always_unused bool early)
 {
-	uintptr_t va, end_va;
+	uintptr_t va, start_va, end_va;
 
 	/* Map the flash resident part */
 	end_va = kernel_map.virt_addr + kernel_map.xiprom_sz;
@@ -917,10 +917,11 @@ static void __init create_kernel_page_table(pgd_t *pgdir,
 				   PMD_SIZE, PAGE_KERNEL_EXEC);
 
 	/* Map the data in RAM */
+	start_va = kernel_map.virt_addr + (uintptr_t)&_sdata - (uintptr_t)&_start;
 	end_va = kernel_map.virt_addr + kernel_map.size;
-	for (va = kernel_map.virt_addr + XIP_OFFSET; va < end_va; va += PMD_SIZE)
+	for (va = start_va; va < end_va; va += PMD_SIZE)
 		create_pgd_mapping(pgdir, va,
-				   kernel_map.phys_addr + (va - (kernel_map.virt_addr + XIP_OFFSET)),
+				   kernel_map.phys_addr + (va - start_va),
 				   PMD_SIZE, PAGE_KERNEL);
 }
 #else
-- 
2.39.2