lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <20191210093605.GA31145@Nover> Date: Tue, 10 Dec 2019 10:36:06 +0100 From: Paul Chaignon <paul.chaignon@...nge.com> To: Björn Töpel <bjorn.topel@...il.com> Cc: Paul Burton <paulburton@...nel.org>, Mahshid Khezri <khezri.mahshid@...il.com>, paul.chaignon@...il.com, bpf <bpf@...r.kernel.org>, Netdev <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, linux-riscv@...ts.infradead.org Subject: Re: [PATCH bpf 1/2] bpf, riscv: limit to 33 tail calls On Mon, Dec 09, 2019 at 08:57:27PM +0100, Björn Töpel wrote: > On Mon, 9 Dec 2019 at 19:52, Paul Chaignon <paul.chaignon@...nge.com> wrote: > > > > All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls > > limit at runtime. In addition, a test was recently added, in tailcalls2, > > to check this limit. > > > > This patch updates the tail call limit in RISC-V's JIT compiler to allow > > 33 tail calls. I tested it using the above selftest on an emulated > > RISCV64. > > > > 33! ICK! ;-) Thanks for finding this! Actually, Mahshid found it during her internship because she wanted to check that the number of tail calls was limited. And now I feel so naive for trusting the doc... > > Acked-by: Björn Töpel <bjorn.topel@...il.com> > > > Fixes: 2353ecc6f91f ("bpf, riscv: add BPF JIT for RV64G") > > Reported-by: Mahshid Khezri <khezri.mahshid@...il.com> > > Signed-off-by: Paul Chaignon <paul.chaignon@...nge.com> > > --- > > arch/riscv/net/bpf_jit_comp.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/riscv/net/bpf_jit_comp.c b/arch/riscv/net/bpf_jit_comp.c > > index 5451ef3845f2..7fbf56aab661 100644 > > --- a/arch/riscv/net/bpf_jit_comp.c > > +++ b/arch/riscv/net/bpf_jit_comp.c > > @@ -631,14 +631,14 @@ static int emit_bpf_tail_call(int insn, struct rv_jit_context *ctx) > > return -1; > > emit(rv_bgeu(RV_REG_A2, RV_REG_T1, off >> 1), ctx); > > > > - /* if (--TCC < 0) > > + /* if (TCC-- < 0) > > * goto out; > > */ > > emit(rv_addi(RV_REG_T1, tcc, -1), ctx); > > off = (tc_ninsn - (ctx->ninsns - start_insn)) << 2; > > if (is_13b_check(off, insn)) > > return -1; > > - emit(rv_blt(RV_REG_T1, RV_REG_ZERO, off >> 1), ctx); > > + emit(rv_blt(tcc, RV_REG_ZERO, off >> 1), ctx); > > > > /* prog = array->ptrs[index]; > > * if (!prog) > > -- > > 2.17.1 > >
Powered by blists - more mailing lists