linux-kernel - [PATCH 1/7] riscv: cleanup XIP

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Date: Fri, 10 May 2024 08:28:39 +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 1/7] riscv: cleanup XIP_FIXUP macro

The XIP_FIXUP macro is used to fix addresses early during boot before MMU:
generated code "thinks" the data section is in ROM while it is actually in
RAM. So this macro correct the addresses in the data section.

This macro determines if the address needs to be fixed by checking if it is
within the range startting of ROM address up to the size of 2 * XIP_OFFSET

This means addresses within the .text section would incorrectly get fixed.
Also if the kernel size if bigger than (2 * XIP_OFFSET), some addresses
would not be fixed up.

XIP kernel can still work if the above 2 cases do not happen. But this
macro is obviously incorrect.

Rewrite this macro to only fix up addresses within the data section.

Signed-off-by: Nam Cao <namcao@...utronix.de>
---
 arch/riscv/include/asm/pgtable.h | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 58fd7b70b903..fbf342f4afee 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -139,11 +139,14 @@
 
 #ifdef CONFIG_XIP_KERNEL
 #define XIP_FIXUP(addr) ({							\
+	extern char _sdata[], _start[], _end[];					\
+	uintptr_t __rom_start_data = CONFIG_XIP_PHYS_ADDR			\
+				+ (uintptr_t)&_sdata - (uintptr_t)&_start;	\
+	uintptr_t __rom_end_data = CONFIG_XIP_PHYS_ADDR				\
+				+ (uintptr_t)&_end - (uintptr_t)&_start;	\
 	uintptr_t __a = (uintptr_t)(addr);					\
-	(__a >= CONFIG_XIP_PHYS_ADDR && \
-	 __a < CONFIG_XIP_PHYS_ADDR + XIP_OFFSET * 2) ?	\
-		__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET :\
-		__a;								\
+	(__a >= __rom_start_data && __a < __rom_end_data) ?			\
+		__a - __rom_start_data + CONFIG_PHYS_RAM_BASE :	__a;		\
 	})
 #else
 #define XIP_FIXUP(addr)		(addr)
-- 
2.39.2