Re: [PATCH 1/2] objtool/LoongArch: Restrict stack operation instruction

[Tiezhu Yang]

On 7/30/24 18:57, Jinyang He wrote:
> On 2024-07-30 17:49, Tiezhu Yang wrote:
> > On 07/30/2024 05:28 PM, Jinyang He wrote:
> > > On 2024-07-30 14:19, Tiezhu Yang wrote:
> > >
> > > > After commit a0f7085f6a63 ("LoongArch: Add RANDOMIZE_KSTACK_OFFSET
> > > > support"), the code flow of do_syscall() was changed when compiled
> > > > with GCC due to the secondary stack of add_random_kstack_offset(),
> > > > something like this:
> > > >
> > > >    addi.d          $sp, $sp, -32
> > > >    st.d            $fp, $sp, 16
> > > >    st.d            $ra, $sp, 24
> > > >    addi.d          $fp, $sp, 32
> > > >    ...
> > > >    sub.d           $sp, $sp, $t1
> > > Have you checked the ORC info whether is right or tried backtrace which
> > > passed do_syscall? The "sub.d $sp, $sp, $t1" has modified the $sp so the
> > > $sp cannot express CFA here. This patch just clear the warning but 
> > > ignore
> > > the validity of ORC info. The wrong ORC info may cause illegally access
> > > memory when backtrace.
> >
> > I did testing many times before submitting, the call trace is
> > expected when testing "echo l > /proc/sysrq-trigger".
> Make sure the RANDOMIZE_KSTACK_OFFSET is enable. I tested it by
> CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=y on qemu and it did
> not show the frame about handle_syscall.

I tested with the defconfig, CONFIG_RANDOMIZE_KSTACK_OFFSET is set but
CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT is not set, the call trace has
handle_syscall() which is the previous frame of do_syscall(), and the
orc dump info is correct.

Let me modify the config file and test again with the following configs:
CONFIG_RANDOMIZE_KSTACK_OFFSET=y CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT=y

If there exists problem, I will fix it.

Thanks,
Tiezhu