On Tue, Jun 23, 2020 at 11:05:05AM +0200, Christoph Hellwig wrote: > On Sat, Jun 20, 2020 at 07:16:16PM -0700, Andrew Morton wrote: > > On Thu, 18 Jun 2020 08:43:06 +0200 Christoph Hellwig <[email protected]> wrote: > > > > > Use PAGE_KERNEL_ROX directly instead of allocating RWX and setting the > > > page read-only just after the allocation. > > > > > > --- a/arch/arm64/kernel/probes/kprobes.c > > > +++ b/arch/arm64/kernel/probes/kprobes.c > > > @@ -120,15 +120,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) > > > > > > void *alloc_insn_page(void) > > > { > > > - void *page; > > > - > > > - page = vmalloc_exec(PAGE_SIZE); > > > - if (page) { > > > - set_memory_ro((unsigned long)page, 1); > > > - set_vm_flush_reset_perms(page); > > > - } > > > - > > > - return page; > > > + return __vmalloc_node_range(PAGE_SIZE, 1, VMALLOC_START, VMALLOC_END, > > > + GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS, > > > + NUMA_NO_NODE, __func__); > > > } > > > > > > /* arm kprobe: install breakpoint in text */ > > > > But why. I think this is just a cleanup, doesn't address any runtime issue? > > It doesn't "fix" an issue - it just simplifies and speeds up the code.
Ok, but I don't understand the PLT comment from Peter in [email protected]: | I think this has the exact same range issue as the x86 user. But it | might be less fatal if their PLT magic can cover the full range. Peter, please could you elaborate on your concern? I feel like I'm missing some context. Cheers, Will
