Messages in this thread Patch in this message | | | Date | Wed, 26 Oct 2022 09:15:31 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 0/5] x86/ftrace: Cure boot time W+X mapping |
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On Tue, Oct 25, 2022 at 04:07:25PM -0700, Linus Torvalds wrote:
> It does strike me that it's stupid to make those be two calls that do > exactly the same thing, and we should have a combined "set it > read-only and executable" function, but that's a separate issue.
Right, and we have it all over the place. Something like the below perhaps? I'll feed it to the robots, see if something breaks.
> The slowness is probably not the trampilines, but just the regular > "text_poke of kernel text" that we probably want to keep special just > because otherwise it's _so_ slow to do for every alternative etc.
I tried with and without the patches, it's dead slow either way and I couldn't spot a noticable difference between the two -- so I'm assuming it's simply the trace overhead, not the trace-enable time.
--- --- a/arch/arm/mach-omap1/sram-init.c +++ b/arch/arm/mach-omap1/sram-init.c @@ -74,8 +74,7 @@ void *omap_sram_push(void *funcp, unsign dst = fncpy(sram, funcp, size); - set_memory_ro(base, pages); - set_memory_x(base, pages); + set_memory_rox(base, pages); return dst; } @@ -126,8 +125,7 @@ static void __init omap_detect_and_map_s base = (unsigned long)omap_sram_base; pages = PAGE_ALIGN(omap_sram_size) / PAGE_SIZE; - set_memory_ro(base, pages); - set_memory_x(base, pages); + set_memory_rox(base, pages); } static void (*_omap_sram_reprogram_clock)(u32 dpllctl, u32 ckctl); --- a/arch/arm/mach-omap2/sram.c +++ b/arch/arm/mach-omap2/sram.c @@ -96,8 +96,7 @@ void *omap_sram_push(void *funcp, unsign dst = fncpy(sram, funcp, size); - set_memory_ro(base, pages); - set_memory_x(base, pages); + set_memory_rox(base, pages); return dst; } @@ -217,8 +216,7 @@ static void __init omap2_map_sram(void) base = (unsigned long)omap_sram_base; pages = PAGE_ALIGN(omap_sram_size) / PAGE_SIZE; - set_memory_ro(base, pages); - set_memory_x(base, pages); + set_memory_rox(base, pages); } static void (*_omap2_sram_ddr_init)(u32 *slow_dll_ctrl, u32 fast_dll_ctrl, --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -134,10 +134,9 @@ void *alloc_insn_page(void) if (!page) return NULL; - if (strict_module_rwx_enabled()) { - set_memory_ro((unsigned long)page, 1); - set_memory_x((unsigned long)page, 1); - } + if (strict_module_rwx_enabled()) + set_memory_rox((unsigned long)page, 1); + return page; } --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -415,8 +415,7 @@ create_trampoline(struct ftrace_ops *ops set_vm_flush_reset_perms(trampoline); - set_memory_ro((unsigned long)trampoline, npages); - set_memory_x((unsigned long)trampoline, npages); + set_memory_rox((unsigned long)trampoline, npages); return (unsigned long)trampoline; fail: tramp_free(trampoline); --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -415,17 +415,12 @@ void *alloc_insn_page(void) return NULL; set_vm_flush_reset_perms(page); - /* - * First make the page read-only, and only then make it executable to - * prevent it from being W+X in between. - */ - set_memory_ro((unsigned long)page, 1); /* * TODO: Once additional kernel code protection mechanisms are set, ensure * that the page was not maliciously altered and it is still zeroed. */ - set_memory_x((unsigned long)page, 1); + set_memory_rox((unsigned long)page, 1); return page; } --- a/drivers/misc/sram-exec.c +++ b/drivers/misc/sram-exec.c @@ -106,10 +106,7 @@ void *sram_exec_copy(struct gen_pool *po dst_cpy = fncpy(dst, src, size); - ret = set_memory_ro((unsigned long)base, pages); - if (ret) - goto error_out; - ret = set_memory_x((unsigned long)base, pages); + ret = set_memory_rox((unsigned long)base, pages); if (ret) goto error_out; --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -860,8 +860,7 @@ static inline void bpf_prog_lock_ro(stru static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr) { set_vm_flush_reset_perms(hdr); - set_memory_ro((unsigned long)hdr, hdr->size >> PAGE_SHIFT); - set_memory_x((unsigned long)hdr, hdr->size >> PAGE_SHIFT); + set_memory_rox((unsigned long)hdr, hdr->size >> PAGE_SHIFT); } int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap); --- a/include/linux/set_memory.h +++ b/include/linux/set_memory.h @@ -14,6 +14,14 @@ static inline int set_memory_x(unsigned static inline int set_memory_nx(unsigned long addr, int numpages) { return 0; } #endif +static inline int set_memory_rox(unsigned long addr, int numpages) +{ + int ret = set_memory_ro(addr, numpages); + if (ret) + return ret; + return set_memory_x(addr, numpages); +} + #ifndef CONFIG_ARCH_HAS_SET_DIRECT_MAP static inline int set_direct_map_invalid_noflush(struct page *page) { --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -494,8 +494,7 @@ static int bpf_struct_ops_map_update_ele refcount_set(&kvalue->refcnt, 1); bpf_map_inc(map); - set_memory_ro((long)st_map->image, 1); - set_memory_x((long)st_map->image, 1); + set_memory_rox((long)st_map->image, 1); err = st_ops->reg(kdata); if (likely(!err)) { /* Pair with smp_load_acquire() during lookup_elem(). --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -864,8 +864,7 @@ static struct bpf_prog_pack *alloc_new_p list_add_tail(&pack->list, &pack_list); set_vm_flush_reset_perms(pack->ptr); - set_memory_ro((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE); - set_memory_x((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE); + set_memory_rox((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE); return pack; } @@ -883,8 +882,7 @@ void *bpf_prog_pack_alloc(u32 size, bpf_ if (ptr) { bpf_fill_ill_insns(ptr, size); set_vm_flush_reset_perms(ptr); - set_memory_ro((unsigned long)ptr, size / PAGE_SIZE); - set_memory_x((unsigned long)ptr, size / PAGE_SIZE); + set_memory_rox((unsigned long)ptr, size / PAGE_SIZE); } goto out; } --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -468,8 +468,7 @@ static int bpf_trampoline_update(struct if (err < 0) goto out; - set_memory_ro((long)im->image, 1); - set_memory_x((long)im->image, 1); + set_memory_rox((long)im->image, 1); WARN_ON(tr->cur_image && tr->selector == 0); WARN_ON(!tr->cur_image && tr->selector); --- a/net/bpf/bpf_dummy_struct_ops.c +++ b/net/bpf/bpf_dummy_struct_ops.c @@ -124,8 +124,7 @@ int bpf_struct_ops_test_run(struct bpf_p if (err < 0) goto out; - set_memory_ro((long)image, 1); - set_memory_x((long)image, 1); + set_memory_rox((long)image, 1); prog_ret = dummy_ops_call_op(image, args); err = dummy_ops_copy_args(args);
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