Messages in this thread | | | Date | Wed, 14 Apr 2021 15:14:45 +0800 | From | Jisheng Zhang <> | Subject | Re: [PATCH] x86/kprobes: Simplify alloc_insn_page() with __vmalloc_node_range |
| |
On Tue, 13 Apr 2021 22:00:30 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote:
> > > Hi,
Hi
> > On Tue, 13 Apr 2021 18:03:24 +0800 > Jisheng Zhang <Jisheng.Zhang@synaptics.com> wrote: > > > Use the __vmalloc_node_range() to simplify x86's alloc_insn_page() > > implementation. > > Have you checked this is equivarent to the original code on > all architecture? IIRC, some arch has a special module_alloc(),
Indeed, this isn't equivarent to the original code. FWICT, the differences on x86 are:
1) module_alloc() allocates a special vmalloc range 2) module_alloc() randomizes the return address via. module_load_offset() 3) module_alloc() also supports kasan instrumentation by kasan_module_alloc()
But I'm not sure whether the above differences are useful for kprobes ss insn slot page or not. Take 1) for example, special range in module_alloc is due to relative jump limitation, modules need to call kernel .text. does kprobes ss ins slot needs this limitation too?
Thanks
> thus I NACKed similar patch previously. > > Thank you, > > > > > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com> > > --- > > arch/x86/kernel/kprobes/core.c | 24 ++++-------------------- > > 1 file changed, 4 insertions(+), 20 deletions(-) > > > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > > index df776cdca327..75081f3dbe44 100644 > > --- a/arch/x86/kernel/kprobes/core.c > > +++ b/arch/x86/kernel/kprobes/core.c > > @@ -383,26 +383,10 @@ static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p, > > /* Make page to RO mode when allocate it */ > > void *alloc_insn_page(void) > > { > > - void *page; > > - > > - page = module_alloc(PAGE_SIZE); > > - if (!page) > > - 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); > > - > > - return page; > > + return __vmalloc_node_range(PAGE_SIZE, PAGE_SIZE, VMALLOC_START, > > + VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX, > > + VM_FLUSH_RESET_PERMS, NUMA_NO_NODE, > > + __builtin_return_address(0)); > > } > > > > /* Recover page to RW mode before releasing it */ > > -- > > 2.31.0 > > > > > -- > Masami Hiramatsu <mhiramat@kernel.org>
| |