On 09/10/2021 05:19 PM, Daniel Borkmann wrote:
The tailcall_3 test program uses bpf_tail_call_static() where the JIT
would patch a direct jump. Add a new tailcall_6 test program replicating
exactly the same test just ensuring that bpf_tail_call() uses a map
index where the verifier cannot make assumptions this time.
In other words, this will now cover both on x86-64 JIT, meaning, JIT
images with emit_bpf_tail_call_direct() emission as well as JIT images
with emit_bpf_tail_call_indirect() emission.
# echo 1 > /proc/sys/net/core/bpf_jit_enable
# ./test_progs -t tailcalls
#136/1 tailcalls/tailcall_1:OK
#136/2 tailcalls/tailcall_2:OK
#136/3 tailcalls/tailcall_3:OK
#136/4 tailcalls/tailcall_4:OK
#136/5 tailcalls/tailcall_5:OK
#136/6 tailcalls/tailcall_6:OK
#136/7 tailcalls/tailcall_bpf2bpf_1:OK
#136/8 tailcalls/tailcall_bpf2bpf_2:OK
#136/9 tailcalls/tailcall_bpf2bpf_3:OK
#136/10 tailcalls/tailcall_bpf2bpf_4:OK
#136/11 tailcalls/tailcall_bpf2bpf_5:OK
#136 tailcalls:OK
Summary: 1/11 PASSED, 0 SKIPPED, 0 FAILED
# echo 0 > /proc/sys/net/core/bpf_jit_enable
# ./test_progs -t tailcalls
#136/1 tailcalls/tailcall_1:OK
#136/2 tailcalls/tailcall_2:OK
#136/3 tailcalls/tailcall_3:OK
#136/4 tailcalls/tailcall_4:OK
#136/5 tailcalls/tailcall_5:OK
#136/6 tailcalls/tailcall_6:OK
[...]
For interpreter, the tailcall_1-6 tests are passing as well. The later
tailcall_bpf2bpf_* are failing due lack of bpf2bpf + tailcall support
in interpreter, so this is expected.
Also, manual inspection shows that both loaded programs from tailcall_3
and tailcall_6 test case emit the expected opcodes:
* tailcall_3 disasm, emit_bpf_tail_call_direct():
[...]
b: push %rax
c: push %rbx
d: push %r13
f: mov %rdi,%rbx
12: movabs $0xffff8d3f5afb0200,%r13
1c: mov %rbx,%rdi
1f: mov %r13,%rsi
22: xor %edx,%edx _
24: mov -0x4(%rbp),%eax | limit check
2a: cmp $0x20,%eax |
2d: ja 0x0000000000000046 |
2f: add $0x1,%eax |
32: mov %eax,-0x4(%rbp) |_
38: nopl 0x0(%rax,%rax,1)
3d: pop %r13
3f: pop %rbx
40: pop %rax
41: jmpq 0xffffffffffffe377
[...]
* tailcall_6 disasm, emit_bpf_tail_call_indirect():
[...]
47: movabs $0xffff8d3f59143a00,%rsi
51: mov %edx,%edx
53: cmp %edx,0x24(%rsi)
56: jbe 0x0000000000000093 _
58: mov -0x4(%rbp),%eax | limit check
5e: cmp $0x20,%eax |
61: ja 0x0000000000000093 |
63: add $0x1,%eax |
66: mov %eax,-0x4(%rbp) |_
6c: mov 0x110(%rsi,%rdx,8),%rcx
74: test %rcx,%rcx
77: je 0x0000000000000093
79: pop %rax
7a: mov 0x30(%rcx),%rcx
7e: add $0xb,%rcx
82: callq 0x000000000000008e
87: pause
89: lfence
8c: jmp 0x0000000000000087
8e: mov %rcx,(%rsp)
92: retq
[...]
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Johan Almbladh <johan.almbladh@xxxxxxxxxxxxxxxxx>
Cc: Paul Chaignon <paul@xxxxxxxxx>
Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
Link: https://lore.kernel.org/bpf/CAM1=_QRyRVCODcXo_Y6qOm1iT163HoiSj8U2pZ8Rj3hzMTT=HQ@xxxxxxxxxxxxxx
Tested-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
