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 <erhar...@mailbox.org> Closes: https://lore.kernel.org/all/342b4120-911c-4723-82ec-d8c9b03a8...@mailbox.org/ Signed-off-by: Christophe Leroy <christophe.le...@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
