diff options
| author | Jie Meng <jmeng@fb.com> | 2021-10-01 20:56:26 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2021-10-06 15:24:36 +0200 |
| commit | 57a610f1c58fa493315e1c24eef6d992cdf4c4a9 (patch) | |
| tree | b19776aea72a4c4a6bf2d48e8cebccd281375f6d /tools | |
| parent | 0640c77c46cb84328d5e08aa85a781a60be8b02b (diff) | |
| download | linux-57a610f1c58fa493315e1c24eef6d992cdf4c4a9.tar.bz2 | |
bpf, x64: Save bytes for DIV by reducing reg copies
Instead of unconditionally performing push/pop on %rax/%rdx in case of
division/modulo, we can save a few bytes in case of destination register
being either BPF r0 (%rax) or r3 (%rdx) since the result is written in
there anyway.
Also, we do not need to copy the source to %r11 unless the source is either
%rax, %rdx or an immediate.
For example, before the patch:
22: push %rax
23: push %rdx
24: mov %rsi,%r11
27: xor %edx,%edx
29: div %r11
2c: mov %rax,%r11
2f: pop %rdx
30: pop %rax
31: mov %r11,%rax
After:
22: push %rdx
23: xor %edx,%edx
25: div %rsi
28: pop %rdx
Signed-off-by: Jie Meng <jmeng@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211002035626.2041910-1-jmeng@fb.com
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/bpf/verifier/jit.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/verifier/jit.c b/tools/testing/selftests/bpf/verifier/jit.c index eedcb752bf70..79021c30e51e 100644 --- a/tools/testing/selftests/bpf/verifier/jit.c +++ b/tools/testing/selftests/bpf/verifier/jit.c @@ -103,6 +103,53 @@ .retval = 2, }, { + "jit: various div tests", + .insns = { + BPF_LD_IMM64(BPF_REG_2, 0xefeffeULL), + BPF_LD_IMM64(BPF_REG_0, 0xeeff0d413122ULL), + BPF_LD_IMM64(BPF_REG_1, 0xfefeeeULL), + BPF_ALU64_REG(BPF_DIV, BPF_REG_0, BPF_REG_1), + BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_2, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LD_IMM64(BPF_REG_3, 0xeeff0d413122ULL), + BPF_ALU64_IMM(BPF_DIV, BPF_REG_3, 0xfefeeeULL), + BPF_JMP_REG(BPF_JEQ, BPF_REG_3, BPF_REG_2, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LD_IMM64(BPF_REG_2, 0xaa93ULL), + BPF_ALU64_IMM(BPF_MOD, BPF_REG_1, 0xbeefULL), + BPF_JMP_REG(BPF_JEQ, BPF_REG_1, BPF_REG_2, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LD_IMM64(BPF_REG_1, 0xfefeeeULL), + BPF_LD_IMM64(BPF_REG_3, 0xbeefULL), + BPF_ALU64_REG(BPF_MOD, BPF_REG_1, BPF_REG_3), + BPF_JMP_REG(BPF_JEQ, BPF_REG_1, BPF_REG_2, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_LD_IMM64(BPF_REG_2, 0x5ee1dULL), + BPF_LD_IMM64(BPF_REG_1, 0xfefeeeULL), + BPF_LD_IMM64(BPF_REG_3, 0x2bULL), + BPF_ALU32_REG(BPF_DIV, BPF_REG_1, BPF_REG_3), + BPF_JMP_REG(BPF_JEQ, BPF_REG_1, BPF_REG_2, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_ALU32_REG(BPF_DIV, BPF_REG_1, BPF_REG_1), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 1, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_ALU64_REG(BPF_MOD, BPF_REG_2, BPF_REG_2), + BPF_JMP_IMM(BPF_JEQ, BPF_REG_2, 0, 2), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_MOV64_IMM(BPF_REG_0, 2), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .retval = 2, +}, +{ "jit: jsgt, jslt", .insns = { BPF_LD_IMM64(BPF_REG_1, 0x80000000ULL), |