On Wed, Mar 9, 2022 at 5:01 PM Hou Tao <houtao1@xxxxxxxxxx> wrote:
>
> Hi,
>
> On 3/10/2022 7:22 AM, Alexei Starovoitov wrote:
> > On Wed, Mar 09, 2022 at 08:33:20PM +0800, Hou Tao wrote:
> >> It is the bpf_jit_harden counterpart to commit 60b58afc96c9 ("bpf: fix
> >> net.core.bpf_jit_enable race"). bpf_jit_harden will be tested twice
> >> for each subprog if there are subprogs in bpf program and constant
> >> blinding may increase the length of program, so when running
> >> "./test_progs -t subprogs" and toggling bpf_jit_harden between 0 and 2,
> >> jit_subprogs may fail because constant blinding increases the length
> >> of subprog instructions during extra passs.
> >>
> >> So cache the value of bpf_jit_blinding_enabled() during program
> >> allocation, and use the cached value during constant blinding, subprog
> >> JITing and args tracking of tail call.
> > Looks like this patch alone is enough.
> > With race fixed. Patches 1 and 2 are no longer necessary, right?
> Yes and no. With patch 3 applied, the problems described in patch 1 and patch 2
> are gone, but it may recur due to other issue in JIT. So I post these two patch
> together and hope these fixes can also be merged.
What kind of 'issues in JIT'?
I'd rather fix them than do defensive programming.
patch 2 is a hack that should not happen in a correct JIT.
