Messages in this thread | | | Subject | Re: [PATCH bpf-next] bpf, riscv: Fix stack layout of JITed code on RV32 | From | Daniel Borkmann <> | Date | Thu, 30 Apr 2020 16:23:41 +0200 |
| |
On 4/30/20 4:14 AM, Xi Wang wrote: > On Wed, Apr 29, 2020 at 5:51 PM Luke Nelson <lukenels@cs.washington.edu> wrote: >> >> This patch fixes issues with stackframe unwinding and alignment in the >> current stack layout for BPF programs on RV32. >> >> In the current layout, RV32 fp points to the JIT scratch registers, rather >> than to the callee-saved registers. This breaks stackframe unwinding, >> which expects fp to point just above the saved ra and fp registers. >> >> This patch fixes the issue by moving the callee-saved registers to be >> stored on the top of the stack, pointed to by fp. This satisfies the >> assumptions of stackframe unwinding. >> >> This patch also fixes an issue with the old layout that the stack was >> not aligned to 16 bytes. >> >> Stacktrace from JITed code using the old stack layout: >> >> [ 12.196249 ] [<c0402200>] walk_stackframe+0x0/0x96 >> >> Stacktrace using the new stack layout: >> >> [ 13.062888 ] [<c0402200>] walk_stackframe+0x0/0x96 >> [ 13.063028 ] [<c04023c6>] show_stack+0x28/0x32 >> [ 13.063253 ] [<a403e778>] bpf_prog_82b916b2dfa00464+0x80/0x908 >> [ 13.063417 ] [<c09270b2>] bpf_test_run+0x124/0x39a >> [ 13.063553 ] [<c09276c0>] bpf_prog_test_run_skb+0x234/0x448 >> [ 13.063704 ] [<c048510e>] __do_sys_bpf+0x766/0x13b4 >> [ 13.063840 ] [<c0485d82>] sys_bpf+0xc/0x14 >> [ 13.063961 ] [<c04010f0>] ret_from_syscall+0x0/0x2 >> >> The new code is also simpler to understand and includes an ASCII diagram >> of the stack layout. >> >> Tested on riscv32 QEMU virt machine. >> >> Signed-off-by: Luke Nelson <luke.r.nels@gmail.com> > > Thanks for the fix! > > Acked-by: Xi Wang <xi.wang@gmail.com>
Applied, thanks everyone!
| |