linux-kernel - [PATCH] powerpc/32: Remove PAGE_KERNEL

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Message-ID: <4b5e6eb281d7b1ea77619bee17095f905a125168.1757003584.git.christophe.leroy@csgroup.eu>
Date: Thu,  4 Sep 2025 18:33:19 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Andrew Donnellan <ajd@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	Erhard Furtner <erhard_f@...lbox.org>
Subject: [PATCH] powerpc/32: Remove PAGE_KERNEL_TEXT to fix startup failure

PAGE_KERNEL_TEXT is an old macro that is used to tell kernel whether
kernel text has to be mapped read-only or read-write based on build
time options.

But nowadays, with functionnalities like jump_labels, static links,
etc ... more only less all kernels need to be read-write at some
point, and some combinations of configs failed to work due to
innacurate setting of PAGE_KERNEL_TEXT. On the other hand, today
we have CONFIG_STRICT_KERNEL_RWX which implements a more controlled
access to kernel modifications.

Instead of trying to keep PAGE_KERNEL_TEXT accurate with all
possible options that may imply kernel text modification, always
set kernel text read-write at startup and rely on
CONFIG_STRICT_KERNEL_RWX to provide accurate protection.

Reported-by: Erhard Furtner <erhard_f@...lbox.org>
Closes: https://lore.kernel.org/all/342b4120-911c-4723-82ec-d8c9b03a8aef@mailbox.org/
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/pgtable.h | 12 ------------
 arch/powerpc/mm/book3s32/mmu.c     |  4 ++--
 arch/powerpc/mm/pgtable_32.c       |  2 +-
 3 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 93d77ad5a92f..d8f944a5a037 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -20,18 +20,6 @@ struct mm_struct;
 #include <asm/nohash/pgtable.h>
 #endif /* !CONFIG_PPC_BOOK3S */
 
-/*
- * Protection used for kernel text. We want the debuggers to be able to
- * set breakpoints anywhere, so don't write protect the kernel text
- * on platforms where such control is possible.
- */
-#if defined(CONFIG_KGDB) || defined(CONFIG_XMON) || defined(CONFIG_BDI_SWITCH) || \
-	defined(CONFIG_KPROBES) || defined(CONFIG_DYNAMIC_FTRACE)
-#define PAGE_KERNEL_TEXT	PAGE_KERNEL_X
-#else
-#define PAGE_KERNEL_TEXT	PAGE_KERNEL_ROX
-#endif
-
 /* Make modules code happy. We don't set RO yet */
 #define PAGE_KERNEL_EXEC	PAGE_KERNEL_X
 
diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index be9c4106e22f..c42ecdf94e48 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -204,7 +204,7 @@ int mmu_mark_initmem_nx(void)
 
 	for (i = 0; i < nb - 1 && base < top;) {
 		size = bat_block_size(base, top);
-		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
+		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_X);
 		base += size;
 	}
 	if (base < top) {
@@ -215,7 +215,7 @@ int mmu_mark_initmem_nx(void)
 				pr_warn("Some RW data is getting mapped X. "
 					"Adjust CONFIG_DATA_SHIFT to avoid that.\n");
 		}
-		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
+		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_X);
 		base += size;
 	}
 	for (; i < nb; i++)
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 15276068f657..0c9ef705803e 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -104,7 +104,7 @@ static void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
 	p = memstart_addr + s;
 	for (; s < top; s += PAGE_SIZE) {
 		ktext = core_kernel_text(v);
-		map_kernel_page(v, p, ktext ? PAGE_KERNEL_TEXT : PAGE_KERNEL);
+		map_kernel_page(v, p, ktext ? PAGE_KERNEL_X : PAGE_KERNEL);
 		v += PAGE_SIZE;
 		p += PAGE_SIZE;
 	}
-- 
2.49.0