[PATCH 14/19] ARM: linker script: create separate PT_LOAD segments for text, rodata, and data

[Sascha Hauer <s.hauer@pengutronix.de>]

Fix the linker scripts to generate three distinct PT_LOAD segments with
correct permissions instead of combining .rodata with .data.

Before this fix, the linker auto-generated only two PT_LOAD segments:
1. Text segment (PF_R|PF_X)
2. Data segment (PF_R|PF_W) - containing .rodata, .data, .bss, etc.

This caused .rodata to be mapped with write permissions when
pbl_mmu_setup_from_elf() set up MMU permissions based on ELF segments,
defeating the W^X protection that commit d9ccb0cf14 intended to provide.

With explicit PHDRS directives, we now generate three segments:
1. text segment (PF_R|PF_X): .text and related code sections
2. rodata segment (PF_R): .rodata and unwind tables
3. data segment (PF_R|PF_W): .data, .bss, and related sections

This ensures pbl_mmu_setup_from_elf() correctly maps .rodata as
read-only (MAP_CACHED_RO) instead of read-write (MAP_CACHED).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 arch/arm/include/asm/barebox.lds.h | 14 +++++++-------
 arch/arm/lib/pbl.lds.S             |  2 +-
 arch/arm/lib32/barebox.lds.S       | 35 +++++++++++++++++++++++------------
 arch/arm/lib64/barebox.lds.S       | 31 +++++++++++++++++++++----------
 4 files changed, 52 insertions(+), 30 deletions(-)

diff --git a/arch/arm/include/asm/barebox.lds.h b/arch/arm/include/asm/barebox.lds.h
index 72aabe155b5c9e8b9159c7da6c6f0fa1f7b93375..a3ccea91196ccce71c54483c5e1ad5caeb3c1d32 100644
--- a/arch/arm/include/asm/barebox.lds.h
+++ b/arch/arm/include/asm/barebox.lds.h
@@ -14,13 +14,13 @@
 #define BAREBOX_RELOCATION_TYPE	rela
 #endif
 
-#define BAREBOX_RELOCATION_TABLE					\
-	.rel_dyn_start : { *(.__rel_dyn_start) }			\
-	.BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) }	\
-	.rel_dyn_end : { *(.__rel_dyn_end) }				\
-	.__dynsym_start :  { *(.__dynsym_start) }			\
-	.dynsym : { *(.dynsym) }					\
-	.__dynsym_end : { *(.__dynsym_end) }
+#define BAREBOX_RELOCATION_TABLE(PHDR)					\
+	.rel_dyn_start : { *(.__rel_dyn_start) } PHDR			\
+	.BAREBOX_RELOCATION_TYPE.dyn : { *(.BAREBOX_RELOCATION_TYPE*) }	PHDR \
+	.rel_dyn_end : { *(.__rel_dyn_end) } PHDR			\
+	.__dynsym_start :  { *(.__dynsym_start) } PHDR			\
+	.dynsym : { *(.dynsym) } PHDR					\
+	.__dynsym_end : { *(.__dynsym_end) } PHDR
 
 
 #include <asm-generic/barebox.lds.h>
diff --git a/arch/arm/lib/pbl.lds.S b/arch/arm/lib/pbl.lds.S
index 53b21084cff2e3d916cd37485281f2f78166c37d..98e25a543525e2bc16b8d10ec24c2ba6b8cbec90 100644
--- a/arch/arm/lib/pbl.lds.S
+++ b/arch/arm/lib/pbl.lds.S
@@ -95,7 +95,7 @@ SECTIONS
 	}
 	__shasum_end = .;
 
-	BAREBOX_RELOCATION_TABLE
+	BAREBOX_RELOCATION_TABLE()
 
 	pbl_code_size =  .;
 
diff --git a/arch/arm/lib32/barebox.lds.S b/arch/arm/lib32/barebox.lds.S
index 9b2b65e2f17d62d5134fc367621cce733dcea06a..c91c101d6aa5c2a0fcbf79a151a4234d924b3881 100644
--- a/arch/arm/lib32/barebox.lds.S
+++ b/arch/arm/lib32/barebox.lds.S
@@ -7,14 +7,23 @@
 OUTPUT_FORMAT(BAREBOX_OUTPUT_FORMAT)
 OUTPUT_ARCH(BAREBOX_OUTPUT_ARCH)
 ENTRY(start)
+
+PHDRS
+{
+	text PT_LOAD FLAGS(5);     /* PF_R | PF_X */
+	rodata PT_LOAD FLAGS(4);   /* PF_R */
+	data PT_LOAD FLAGS(6);     /* PF_R | PF_W */
+	dynamic PT_DYNAMIC FLAGS(6); /* PF_R | PF_W */
+}
+
 SECTIONS
 {
 	. = 0x0;
-	.image_start : { *(.__image_start) }
+	.image_start : { *(.__image_start) } :text
 
 	. = ALIGN(4);
 
-	._text : { *(._text) }
+	._text : { *(._text) } :text
 	.text      :
 	{
 		_stext = .;
@@ -31,7 +40,7 @@ SECTIONS
 		KEEP(*(.text_inplace_exceptions*))
 		__inplace_exceptions_stop = .;
 		*(.text*)
-	}
+	} :text
 	BAREBOX_BARE_INIT_SIZE
 
 	. = ALIGN(4096);
@@ -39,7 +48,7 @@ SECTIONS
 	.rodata : {
 		*(.rodata*)
 		RO_DATA_SECTION
-	}
+	} :rodata
 
 #ifdef CONFIG_ARM_UNWIND
 	/*
@@ -50,12 +59,12 @@ SECTIONS
 		__start_unwind_idx = .;
 		*(.ARM.exidx*)
 		__stop_unwind_idx = .;
-	}
+	} :rodata
 	.ARM.unwind_tab : {
 		__start_unwind_tab = .;
 		*(.ARM.extab*)
 		__stop_unwind_tab = .;
-	}
+	} :rodata
 #endif
 	. = ALIGN(4096);
 	__end_rodata = .;
@@ -65,19 +74,21 @@ SECTIONS
 	. = ALIGN(4);
 	.data : { *(.data*)
 		CONSTRUCTORS
-	}
+	} :data
+
+	.dynamic : { *(.dynamic) } :data :dynamic
 
 	. = .;
 
-	BAREBOX_RELOCATION_TABLE
+	BAREBOX_RELOCATION_TABLE(:data)
 
 	_edata = .;
-	.image_end : { *(.__image_end) }
+	.image_end : { *(.__image_end) } :data
 
 	. = ALIGN(4);
-	.__bss_start :  { *(.__bss_start) }
-	.bss : { *(.bss*) }
-	.__bss_stop :  { *(.__bss_stop) }
+	.__bss_start :  { *(.__bss_start) } :data
+	.bss : { *(.bss*) } :data
+	.__bss_stop :  { *(.__bss_stop) } :data
 
 #ifdef CONFIG_ARM_SECURE_MONITOR
 	. = ALIGN(16);
diff --git a/arch/arm/lib64/barebox.lds.S b/arch/arm/lib64/barebox.lds.S
index e2f1164c47f7e5d300028d112a6e90e2fa368c65..603e0ab77490d3221fbfd3341250e6dcae840d91 100644
--- a/arch/arm/lib64/barebox.lds.S
+++ b/arch/arm/lib64/barebox.lds.S
@@ -6,14 +6,23 @@
 OUTPUT_FORMAT(BAREBOX_OUTPUT_FORMAT)
 OUTPUT_ARCH(BAREBOX_OUTPUT_ARCH)
 ENTRY(start)
+
+PHDRS
+{
+	text PT_LOAD FLAGS(5);     /* PF_R | PF_X */
+	rodata PT_LOAD FLAGS(4);   /* PF_R */
+	data PT_LOAD FLAGS(6);     /* PF_R | PF_W */
+	dynamic PT_DYNAMIC FLAGS(6); /* PF_R | PF_W */
+}
+
 SECTIONS
 {
 	. = 0x0;
 
-	.image_start : { *(.__image_start) }
+	.image_start : { *(.__image_start) } :text
 
 	. = ALIGN(4);
-	._text : { *(._text) }
+	._text : { *(._text) } :text
 	.text      :
 	{
 		_stext = .;
@@ -22,7 +31,7 @@ SECTIONS
 		*(.text_bare_init*)
 		__bare_init_end = .;
 		*(.text*)
-	}
+	} :text
 	BAREBOX_BARE_INIT_SIZE
 
 	. = ALIGN(4096);
@@ -30,7 +39,7 @@ SECTIONS
 	.rodata : {
 		*(.rodata*)
 		RO_DATA_SECTION
-	}
+	} :rodata
 
 	. = ALIGN(4096);
 
@@ -38,18 +47,20 @@ SECTIONS
 	_etext = .;
 	_sdata = .;
 
-	.data : { *(.data*) }
+	.data : { *(.data*) } :data
+
+	.dynamic : { *(.dynamic) } :data :dynamic
 
-	BAREBOX_RELOCATION_TABLE
+	BAREBOX_RELOCATION_TABLE(:data)
 
 	_edata = .;
 
-	.image_end : { *(.__image_end) }
+	.image_end : { *(.__image_end) } :data
 
 	. = ALIGN(4);
-	.__bss_start :  { *(.__bss_start) }
-	.bss : { *(.bss*) }
-	.__bss_stop :  { *(.__bss_stop) }
+	.__bss_start :  { *(.__bss_start) } :data
+	.bss : { *(.bss*) } :data
+	.__bss_stop :  { *(.__bss_stop) } :data
 	_end = .;
 	_barebox_image_size = __bss_start;
 }

-- 
2.47.3