[PATCH v5] ARM: xip: Use correct symbol for end of ROM marker

[Chris Brandt]

For an XIP build, _etext does not represent the end of the
binary image that needs to stay mapped into the MODULES_VADDR area.
Years ago, data came before text in the memory map. However,
now that the order is text/init/data, an XIP_KERNEL needs to map
up to the data location in order to keep from cutting off
parts of the kernel that are needed.
We only map up to the beginning of data because data has already been
copied, so there's no reason to keep it around anymore.

This fixes the bug where you might lose the end of your kernel area
after page table setup is complete.

Signed-off-by: Chris Brandt <chris.brandt at renesas.com>
---
v5:
* Switched from using __data_loc to _exiprom (new symbol)
v4:
* Switched from using _edata_loc __data_loc.
* Made commit text more accurate.
v3:
* Removed sections.h from Kbuild
v2:
* Added change for MODULES_VADDR
* Moved extern to new file asm/sections.h
---
 arch/arm/include/asm/Kbuild     | 1 -
 arch/arm/include/asm/sections.h | 8 ++++++++
 arch/arm/kernel/module.c        | 2 +-
 arch/arm/kernel/vmlinux.lds.S   | 2 ++
 arch/arm/mm/mmu.c               | 8 ++++++--
 5 files changed, 17 insertions(+), 4 deletions(-)
 create mode 100644 arch/arm/include/asm/sections.h

diff --git a/arch/arm/include/asm/Kbuild b/arch/arm/include/asm/Kbuild
index 16da638..3f6616b 100644
--- a/arch/arm/include/asm/Kbuild
+++ b/arch/arm/include/asm/Kbuild
@@ -23,7 +23,6 @@ generic-y += preempt.h
 generic-y += resource.h
 generic-y += rwsem.h
 generic-y += seccomp.h
-generic-y += sections.h
 generic-y += segment.h
 generic-y += sembuf.h
 generic-y += serial.h
diff --git a/arch/arm/include/asm/sections.h b/arch/arm/include/asm/sections.h
new file mode 100644
index 0000000..803bbf2
--- /dev/null
+++ b/arch/arm/include/asm/sections.h
@@ -0,0 +1,8 @@
+#ifndef _ASM_ARM_SECTIONS_H
+#define _ASM_ARM_SECTIONS_H
+
+#include <asm-generic/sections.h>
+
+extern char _exiprom[];
+
+#endif	/* _ASM_ARM_SECTIONS_H */
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index efdddcb..4f14b5c 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -34,7 +34,7 @@
  * recompiling the whole kernel when CONFIG_XIP_KERNEL is turned on/off.
  */
 #undef MODULES_VADDR
-#define MODULES_VADDR	(((unsigned long)_etext + ~PMD_MASK) & PMD_MASK)
+#define MODULES_VADDR	(((unsigned long)_exiprom + ~PMD_MASK) & PMD_MASK)
 #endif
 
 #ifdef CONFIG_MMU
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 8b60fde..d18e4e5 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -86,6 +86,7 @@ SECTIONS
 
 #ifdef CONFIG_XIP_KERNEL
 	. = XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR);
+	_xiprom = .;			/* XIP ROM area to be mapped */
 #else
 	. = PAGE_OFFSET + TEXT_OFFSET;
 #endif
@@ -228,6 +229,7 @@ SECTIONS
 #endif
 
 #ifdef CONFIG_XIP_KERNEL
+	_exiprom = .;			/* End of XIP ROM area */
 	__data_loc = ALIGN(4);		/* location in binary */
 	. = PAGE_OFFSET + TEXT_OFFSET;
 #else
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 434d76f..e4b681a 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1253,7 +1253,7 @@ static inline void prepare_page_table(void)
 
 #ifdef CONFIG_XIP_KERNEL
 	/* The XIP kernel is mapped in the module area -- skip over it */
-	addr = ((unsigned long)_etext + PMD_SIZE - 1) & PMD_MASK;
+	addr = ((unsigned long)_exiprom + PMD_SIZE - 1) & PMD_MASK;
 #endif
 	for ( ; addr < PAGE_OFFSET; addr += PMD_SIZE)
 		pmd_clear(pmd_off_k(addr));
@@ -1335,7 +1335,7 @@ static void __init devicemaps_init(const struct machine_desc *mdesc)
 #ifdef CONFIG_XIP_KERNEL
 	map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK);
 	map.virtual = MODULES_VADDR;
-	map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;
+	map.length = ((unsigned long)_exiprom - map.virtual + ~SECTION_MASK) & SECTION_MASK;
 	map.type = MT_ROM;
 	create_mapping(&map);
 #endif
@@ -1426,7 +1426,11 @@ static void __init kmap_init(void)
 static void __init map_lowmem(void)
 {
 	struct memblock_region *reg;
+#ifdef CONFIG_XIP_KERNEL
+	phys_addr_t kernel_x_start = round_down(__pa(_sdata), SECTION_SIZE);
+#else
 	phys_addr_t kernel_x_start = round_down(__pa(_stext), SECTION_SIZE);
+#endif
 	phys_addr_t kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE);
 
 	/* Map all the lowmem memory banks. */
-- 
1.9.1