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    SubjectRe: [PATCH 0/5] x86/ftrace: Cure boot time W+X mapping
    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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