Re: [PATCH v12 06/10] arm64: Treat all entry code as non-kprobe-able

[David Long]

On 05/12/2016 10:49 AM, James Morse wrote:
> Hi David, Pratyush
>
> On 27/04/16 19:53, David Long wrote:
> > From: Pratyush Anand <panand@xxxxxxxxxx>
> >
> > Entry symbols are not kprobe safe. So blacklist them for kprobing.
> >
> > Signed-off-by: Pratyush Anand <panand@xxxxxxxxxx>
>
> > diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
> > index dfa1b1f..6a1292b 100644
> > --- a/arch/arm64/kernel/kprobes.c
> > +++ b/arch/arm64/kernel/kprobes.c
> > @@ -29,6 +29,7 @@
> >   #include <asm/system_misc.h>
> >   #include <asm/insn.h>
> >   #include <asm/uaccess.h>
> > +#include <asm-generic/sections.h>
> >
> >   #include "kprobes-arm64.h"
> >
> > @@ -514,6 +515,15 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
> >   	return 1;
> >   }
> >
> > +bool arch_within_kprobe_blacklist(unsigned long addr)
> > +{
> > +	return  (addr >= (unsigned long)__kprobes_text_start &&
> > +		 addr < (unsigned long)__kprobes_text_end) ||
> > +		(addr >= (unsigned long)__entry_text_start &&
> > +		 addr < (unsigned long)__entry_text_end) ||
> > +		 !!search_exception_tables(addr);
> > +}
> > +
>
> Looking at __kvm_hyp_vector, we don't have support for handling breakpoints at
> EL2, so we should forbid kprobing these address ranges too:
> __hyp_text_start -> __hyp_text_end
> __hyp_idmap_text_start -> __hyp_idmap_text_end
>
> These can probably be guarded with is_kernel_in_hyp_mode(), if this is true then
> we are running with VHE where this code runs at the same exception level as the
> rest of the kernel, so we can probe them. (In this case you may want to add
> 'eret' to aarch64_insn_is_branch() in patch 2)
>
>
> Probing things in the kernel idmap sounds dangerous! Lets blacklist that too:
> __idmap_text_start -> __idmap_text_end

I've made these changes.  I noticed there's no include file definitions 
for these symbols so I've added local extern declarations in 
arch_within_kprobe_blacklist().

Thanks,
-dl