From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Erhard Furtner <erhard_f@mailbox.org>
Subject: [PATCH v2] powerpc/32: Remove PAGE_KERNEL_TEXT to fix startup failure
Date: Tue, 9 Sep 2025 12:03:49 +0200 [thread overview]
Message-ID: <8e2d793abf87ae3efb8f6dce10f974ac0eda61b8.1757412205.git.christophe.leroy@csgroup.eu> (raw)
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.
Do this by passing PAGE_KERNEL_X to map_kernel_page() in
__maping_ram_chunk() instead of passing PAGE_KERNEL_TEXT. Once
this is done, the only remaining user of PAGE_KERNEL_TEXT is
mmu_mark_initmem_nx() which uses it in a call to setibat().
As setibat() ignores the RW/RO, we can seamlessly replace
PAGE_KERNEL_TEXT by PAGE_KERNEL_X here as well and get rid of
PAGE_KERNEL_TEXT completely.
Reported-by: Erhard Furtner <erhard_f@mailbox.org>
Closes: https://lore.kernel.org/all/342b4120-911c-4723-82ec-d8c9b03a8aef@mailbox.org/
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v2: Revised commit message
---
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
next reply other threads:[~2025-09-09 10:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-09 10:03 Christophe Leroy [this message]
2025-09-22 5:43 ` [PATCH v2] powerpc/32: Remove PAGE_KERNEL_TEXT to fix startup failure Madhavan Srinivasan
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