diff mbox series

[v6,bpf-next,14/17] bpf: generalize is_branch_taken to handle all conditional jumps in one place

Message ID 20231102033759.2541186-15-andrii@kernel.org (mailing list archive)
State Accepted
Commit 171de12646d23b240fc73113acf1f62d85dd9d02
Delegated to: BPF
Headers show
Series BPF register bounds logic and testing improvements | expand

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bpf/vmtest-bpf-next-PR success PR summary
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netdev/series_format fail Series longer than 15 patches (and no cover letter)
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 1356 this patch: 1356
netdev/cc_maintainers warning 8 maintainers not CCed: jolsa@kernel.org sdf@google.com john.fastabend@gmail.com kpsingh@kernel.org song@kernel.org yonghong.song@linux.dev haoluo@google.com martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 1370 this patch: 1370
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 1381 this patch: 1381
netdev/checkpatch warning WARNING: line length of 82 exceeds 80 columns WARNING: line length of 86 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-4 success Logs for aarch64-gcc / test (test_maps, false, 360) / test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-5 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-6 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-7 success Logs for aarch64-gcc / test (test_verifier, false, 360) / test_verifier on aarch64 with gcc
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bpf/vmtest-bpf-next-VM_Test-21 success Logs for x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-22 success Logs for x86_64-gcc / test (test_verifier, false, 360) / test_verifier on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-23 success Logs for x86_64-gcc / veristat / veristat on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-24 success Logs for x86_64-llvm-16 / build / build for x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-25 success Logs for x86_64-llvm-16 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-28 success Logs for x86_64-llvm-16 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-16
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bpf/vmtest-bpf-next-VM_Test-27 success Logs for x86_64-llvm-16 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-13 success Logs for s390x-gcc / test (test_verifier, false, 360) / test_verifier on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-11 success Logs for s390x-gcc / test (test_progs, false, 360) / test_progs on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-12 success Logs for s390x-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-10 success Logs for s390x-gcc / test (test_maps, false, 360) / test_maps on s390x with gcc

Commit Message

Andrii Nakryiko Nov. 2, 2023, 3:37 a.m. UTC 
Make is_branch_taken() a single entry point for branch pruning decision
making, handling both pointer vs pointer, pointer vs scalar, and scalar
vs scalar cases in one place. This also nicely cleans up check_cond_jmp_op().

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 kernel/bpf/verifier.c | 49 ++++++++++++++++++++++---------------------
 1 file changed, 25 insertions(+), 24 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c5d187d43fa1..d5213cef5389 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14167,6 +14167,19 @@  static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
 	}));
 }
 
+/* check if register is a constant scalar value */
+static bool is_reg_const(struct bpf_reg_state *reg, bool subreg32)
+{
+	return reg->type == SCALAR_VALUE &&
+	       tnum_is_const(subreg32 ? tnum_subreg(reg->var_off) : reg->var_off);
+}
+
+/* assuming is_reg_const() is true, return constant value of a register */
+static u64 reg_const_value(struct bpf_reg_state *reg, bool subreg32)
+{
+	return subreg32 ? tnum_subreg(reg->var_off).value : reg->var_off.value;
+}
+
 /*
  * <reg1> <op> <reg2>, currently assuming reg2 is a constant
  */
@@ -14408,12 +14421,20 @@  static int is_pkt_ptr_branch_taken(struct bpf_reg_state *dst_reg,
 static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_state *reg2,
 			   u8 opcode, bool is_jmp32)
 {
-	struct tnum reg2_tnum = is_jmp32 ? tnum_subreg(reg2->var_off) : reg2->var_off;
 	u64 val;
 
-	if (!tnum_is_const(reg2_tnum))
+	if (reg_is_pkt_pointer_any(reg1) && reg_is_pkt_pointer_any(reg2) && !is_jmp32)
+		return is_pkt_ptr_branch_taken(reg1, reg2, opcode);
+
+	/* try to make sure reg2 is a constant SCALAR_VALUE */
+	if (!is_reg_const(reg2, is_jmp32)) {
+		opcode = flip_opcode(opcode);
+		swap(reg1, reg2);
+	}
+	/* for now we expect reg2 to be a constant to make any useful decisions */
+	if (!is_reg_const(reg2, is_jmp32))
 		return -1;
-	val = reg2_tnum.value;
+	val = reg_const_value(reg2, is_jmp32);
 
 	if (__is_pointer_value(false, reg1)) {
 		if (!reg_not_null(reg1))
@@ -14894,27 +14915,7 @@  static int check_cond_jmp_op(struct bpf_verifier_env *env,
 	}
 
 	is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;
-
-	if (BPF_SRC(insn->code) == BPF_K) {
-		pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
-	} else if (src_reg->type == SCALAR_VALUE &&
-		   is_jmp32 && tnum_is_const(tnum_subreg(src_reg->var_off))) {
-		pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
-	} else if (src_reg->type == SCALAR_VALUE &&
-		   !is_jmp32 && tnum_is_const(src_reg->var_off)) {
-		pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
-	} else if (dst_reg->type == SCALAR_VALUE &&
-		   is_jmp32 && tnum_is_const(tnum_subreg(dst_reg->var_off))) {
-		pred = is_branch_taken(src_reg, dst_reg, flip_opcode(opcode), is_jmp32);
-	} else if (dst_reg->type == SCALAR_VALUE &&
-		   !is_jmp32 && tnum_is_const(dst_reg->var_off)) {
-		pred = is_branch_taken(src_reg, dst_reg, flip_opcode(opcode), is_jmp32);
-	} else if (reg_is_pkt_pointer_any(dst_reg) &&
-		   reg_is_pkt_pointer_any(src_reg) &&
-		   !is_jmp32) {
-		pred = is_pkt_ptr_branch_taken(dst_reg, src_reg, opcode);
-	}
-
+	pred = is_branch_taken(dst_reg, src_reg, opcode, is_jmp32);
 	if (pred >= 0) {
 		/* If we get here with a dst_reg pointer type it is because
 		 * above is_branch_taken() special cased the 0 comparison.