Re: [PATCH] powerpc/32: Remove PAGE_KERNEL_TEXT to fix startup failure
From: Erhard Furtner <hidden>
Date: 2025-09-05 14:30:09
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On 9/4/25 18:33, Christophe Leroy wrote:
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.
I can confirm your patch fixes the startup failure for my G4 .config. Thanks! Regards, Erhard
quoted hunk ↗ jump to hunk
Reported-by: Erhard Furtner <redacted> Closes: https://lore.kernel.org/all/342b4120-911c-4723-82ec-d8c9b03a8aef@mailbox.org/ (local) Signed-off-by: Christophe Leroy <redacted> --- 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_Xdiff --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; }