On 9/21/22 4:21 AM, Jie Meng wrote:
Instead of shr/sar/shl that implicitly use %cl, emit their more flexible
alternatives provided in BMI2
Signed-off-by: Jie Meng <jmeng@xxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 53 ++++++++++++++++++++++
tools/testing/selftests/bpf/verifier/jit.c | 7 +--
2 files changed, 57 insertions(+), 3 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ae89f4143eb4..81a3b34327ae 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -889,6 +889,35 @@ static void emit_nops(u8 **pprog, int len)
*pprog = prog;
}
+static void emit_3vex(u8 **pprog, bool r, bool x, bool b, u8 m,
+ bool w, u8 src_reg2, bool l, u8 p)
+{
+ u8 *prog = *pprog;
+ u8 b0 = 0xc4, b1, b2;
+ u8 src2 = reg2hex[src_reg2];
+
+ if (is_ereg(src_reg2))
+ src2 |= 1 << 3;
+
+ /*
+ * 7 0
+ * +---+---+---+---+---+---+---+---+
+ * |~R |~X |~B | m |
+ * +---+---+---+---+---+---+---+---+
+ */
+ b1 = (!r << 7) | (!x << 6) | (!b << 5) | (m & 0x1f);
+ /*
+ * 7 0
+ * +---+---+---+---+---+---+---+---+
+ * | W | ~vvvv | L | pp |
+ * +---+---+---+---+---+---+---+---+
+ */
+ b2 = (w << 7) | ((~src2 & 0xf) << 3) | (l << 2) | (p & 3);
+
+ EMIT3(b0, b1, b2);
+ *pprog = prog;
+}
+
#define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image,
@@ -1135,7 +1164,31 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image
case BPF_ALU64 | BPF_LSH | BPF_X:
case BPF_ALU64 | BPF_RSH | BPF_X:
case BPF_ALU64 | BPF_ARSH | BPF_X:
+ if (boot_cpu_has(X86_FEATURE_BMI2)) {
+ /* shrx/sarx/shlx dst_reg, dst_reg, src_reg */
+ bool r = is_ereg(dst_reg);
+ u8 m = 2; /* escape code 0f38 */
+ bool w = (BPF_CLASS(insn->code) == BPF_ALU64);
+ u8 p;
+
+ switch (BPF_OP(insn->code)) {
+ case BPF_LSH:
+ p = 1; /* prefix 0x66 */
+ break;
+ case BPF_RSH:
+ p = 3; /* prefix 0xf2 */
+ break;
+ case BPF_ARSH:
+ p = 2; /* prefix 0xf3 */
+ break;
+ }
+
+ emit_3vex(&prog, r, false, r, m,
+ w, src_reg, false, p);
+ EMIT2(0xf7, add_2reg(0xC0, dst_reg, dst_reg));
+ break;
+ }
/* Check for bad case when dst_reg == rcx */
if (dst_reg == BPF_REG_4) {
/* mov r11, dst_reg */
Nice!
diff --git a/tools/testing/selftests/bpf/verifier/jit.c b/tools/testing/selftests/bpf/verifier/jit.c
index 79021c30e51e..3323b93f0972 100644
--- a/tools/testing/selftests/bpf/verifier/jit.c
+++ b/tools/testing/selftests/bpf/verifier/jit.c
@@ -4,15 +4,16 @@
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_MOV64_IMM(BPF_REG_1, 0xff),
BPF_ALU64_IMM(BPF_LSH, BPF_REG_1, 1),
- BPF_ALU32_IMM(BPF_LSH, BPF_REG_1, 1),
+ BPF_ALU32_REG(BPF_LSH, BPF_REG_1, BPF_REG_0),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0x3fc, 1),
BPF_EXIT_INSN(),
- BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 1),
+ BPF_ALU64_REG(BPF_RSH, BPF_REG_1, BPF_REG_0),
BPF_ALU32_IMM(BPF_RSH, BPF_REG_1, 1),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0xff, 1),
BPF_EXIT_INSN(),
BPF_ALU64_IMM(BPF_ARSH, BPF_REG_1, 1),
- BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0x7f, 1),
+ BPF_ALU32_REG(BPF_ARSH, BPF_REG_1, BPF_REG_0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0x3f, 1),
Could you add this as separate commit with adding tests rather than changing
existing ones?
Would also be great to include lib/test_bpf.ko test results into above commit
message given it has more extensive JIT tests than test_verifier.
BPF_EXIT_INSN(),
BPF_MOV64_IMM(BPF_REG_0, 2),
BPF_EXIT_INSN(),
