powerpc/vmlinux.lds: Add an explicit symbol for the SRWX boundary

[ Upstream commit b150a4d ] Currently __init_begin is used as the boundary for strict RWX between executable/read-only text and data, and non-executable (after boot) code and data. But that's a little subtle, so add an explicit symbol to document that the SRWX boundary lies there, and add a comment making it clear that __init_begin must also begin there. Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/[email protected] Stable-dep-of: 111bcb3 ("powerpc/64s/radix: Fix RWX mapping with relocated kernel") Signed-off-by: Sasha Levin <[email protected]>
ammarfaizi2 · Feb 24, 2023 · de82609 · de82609
1 parent f951b71
commit de82609
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Showing 4 changed files with 11 additions and 5 deletions.
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
@@ -9,6 +9,7 @@
 #include <asm-generic/sections.h>
 
 extern char __head_end[];
+extern char __srwx_boundary[];
 
 #ifdef __powerpc64__
 

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
@@ -208,11 +208,16 @@ SECTIONS
 	}
 #endif
 
+	/*
+	 * Various code relies on __init_begin being at the strict RWX boundary.
+	 */
+	. = ALIGN(STRICT_ALIGN_SIZE);
+	__srwx_boundary = .;
+	__init_begin = .;
+
 /*
  * Init sections discarded at runtime
  */
-	. = ALIGN(STRICT_ALIGN_SIZE);
-	__init_begin = .;
 	.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
 		_sinittext = .;
 		INIT_TEXT

diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
@@ -159,7 +159,7 @@ static unsigned long __init __mmu_mapin_ram(unsigned long base, unsigned long to
 unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 {
 	unsigned long done;
-	unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
+	unsigned long border = (unsigned long)__srwx_boundary - PAGE_OFFSET;
 	unsigned long size;
 
 	size = roundup_pow_of_two((unsigned long)_einittext - PAGE_OFFSET);

diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -260,8 +260,8 @@ print_mapping(unsigned long start, unsigned long end, unsigned long size, bool e
 static unsigned long next_boundary(unsigned long addr, unsigned long end)
 {
 #ifdef CONFIG_STRICT_KERNEL_RWX
-	if (addr < __pa_symbol(__init_begin))
-		return __pa_symbol(__init_begin);
+	if (addr < __pa_symbol(__srwx_boundary))
+		return __pa_symbol(__srwx_boundary);
 #endif
 	return end;
 }