From: Daniel Borkmann Date: Tue, 31 Mar 2026 22:20:20 +0000 (+0200) Subject: selftests/bpf: Add more precision tracking tests for atomics X-Git-Tag: v7.0-rc7~24^2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e1b5687a862a43429f1d9f69065b3bbc7780a97a;p=thirdparty%2Fkernel%2Flinux.git selftests/bpf: Add more precision tracking tests for atomics Add verifier precision tracking tests for BPF atomic fetch operations. Validate that backtrack_insn correctly propagates precision from the fetch dst_reg to the stack slot for {fetch_add,xchg,cmpxchg} atomics. For the first two src_reg gets the old memory value, and for the last one r0. The fetched register is used for pointer arithmetic to trigger backtracking. Also add coverage for fetch_{or,and,xor} flavors which exercises the bitwise atomic fetch variants going through the same insn->imm & BPF_FETCH check but with different imm values. Add dual-precision regression tests for fetch_add and cmpxchg where both the fetched value and a reread of the same stack slot are tracked for precision. After the atomic operation, the stack slot is STACK_MISC, so the ldx does not set INSN_F_STACK_ACCESS. These tests verify that stack precision propagates solely through the atomic fetch's load side. Add map-based tests for fetch_add and cmpxchg which validate that non- stack atomic fetch completes precision tracking without falling back to mark_all_scalars_precise. Lastly, add 32-bit variants for {fetch_add, cmpxchg} on map values to cover the second valid atomic operand size. # LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t verifier_precision [...] + /etc/rcS.d/S50-startup ./test_progs -t verifier_precision [ 1.697105] bpf_testmod: loading out-of-tree module taints kernel. [ 1.700220] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel [ 1.777043] tsc: Refined TSC clocksource calibration: 3407.986 MHz [ 1.777619] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x311fc6d7268, max_idle_ns: 440795260133 ns [ 1.778658] clocksource: Switched to clocksource tsc #633/1 verifier_precision/bpf_neg:OK #633/2 verifier_precision/bpf_end_to_le:OK #633/3 verifier_precision/bpf_end_to_be:OK #633/4 verifier_precision/bpf_end_bswap:OK #633/5 verifier_precision/bpf_load_acquire:OK #633/6 verifier_precision/bpf_store_release:OK #633/7 verifier_precision/state_loop_first_last_equal:OK #633/8 verifier_precision/bpf_cond_op_r10:OK #633/9 verifier_precision/bpf_cond_op_not_r10:OK #633/10 verifier_precision/bpf_atomic_fetch_add_precision:OK #633/11 verifier_precision/bpf_atomic_xchg_precision:OK #633/12 verifier_precision/bpf_atomic_fetch_or_precision:OK #633/13 verifier_precision/bpf_atomic_fetch_and_precision:OK #633/14 verifier_precision/bpf_atomic_fetch_xor_precision:OK #633/15 verifier_precision/bpf_atomic_cmpxchg_precision:OK #633/16 verifier_precision/bpf_atomic_fetch_add_dual_precision:OK #633/17 verifier_precision/bpf_atomic_cmpxchg_dual_precision:OK #633/18 verifier_precision/bpf_atomic_fetch_add_map_precision:OK #633/19 verifier_precision/bpf_atomic_cmpxchg_map_precision:OK #633/20 verifier_precision/bpf_atomic_fetch_add_32bit_precision:OK #633/21 verifier_precision/bpf_atomic_cmpxchg_32bit_precision:OK #633/22 verifier_precision/bpf_neg_2:OK #633/23 verifier_precision/bpf_neg_3:OK #633/24 verifier_precision/bpf_neg_4:OK #633/25 verifier_precision/bpf_neg_5:OK #633 verifier_precision:OK Summary: 1/25 PASSED, 0 SKIPPED, 0 FAILED Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/r/20260331222020.401848-2-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov --- diff --git a/tools/testing/selftests/bpf/progs/verifier_precision.c b/tools/testing/selftests/bpf/progs/verifier_precision.c index 1fe090cd6744..4794903aec8e 100644 --- a/tools/testing/selftests/bpf/progs/verifier_precision.c +++ b/tools/testing/selftests/bpf/progs/verifier_precision.c @@ -5,6 +5,13 @@ #include "../../../include/linux/filter.h" #include "bpf_misc.h" +struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, 1); + __type(key, __u32); + __type(value, __u64); +} precision_map SEC(".maps"); + SEC("?raw_tp") __success __log_level(2) __msg("mark_precise: frame0: regs=r2 stack= before 3: (bf) r1 = r10") @@ -301,4 +308,338 @@ __naked int bpf_neg_5(void) ::: __clobber_all); } +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_fetch_add_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[fetch_add_insn];" /* r2 = atomic_fetch_add(*(u64 *)(r10 - 8), r2) */ + "r3 = r10;" + "r3 += r2;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(fetch_add_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_ADD | BPF_FETCH, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_xchg((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_xchg_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[xchg_insn];" /* r2 = atomic_xchg(*(u64 *)(r10 - 8), r2) */ + "r3 = r10;" + "r3 += r2;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(xchg_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_XCHG, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_or((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_fetch_or_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[fetch_or_insn];" /* r2 = atomic_fetch_or(*(u64 *)(r10 - 8), r2) */ + "r3 = r10;" + "r3 += r2;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(fetch_or_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_OR | BPF_FETCH, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_and((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_fetch_and_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[fetch_and_insn];" /* r2 = atomic_fetch_and(*(u64 *)(r10 - 8), r2) */ + "r3 = r10;" + "r3 += r2;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(fetch_and_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_AND | BPF_FETCH, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_xor((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_fetch_xor_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[fetch_xor_insn];" /* r2 = atomic_fetch_xor(*(u64 *)(r10 - 8), r2) */ + "r3 = r10;" + "r3 += r2;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(fetch_xor_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_XOR | BPF_FETCH, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r0 stack= before 5: (bf) r3 = r10") +__msg("mark_precise: frame0: regs=r0 stack= before 4: (db) r0 = atomic64_cmpxchg((u64 *)(r10 -8), r0, r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 3: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r0 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_cmpxchg_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r0 = 0;" + "r2 = 0;" + ".8byte %[cmpxchg_insn];" /* r0 = atomic_cmpxchg(*(u64 *)(r10 - 8), r0, r2) */ + "r3 = r10;" + "r3 += r0;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(cmpxchg_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_CMPXCHG, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +/* Regression test for dual precision: Both the fetched value (r2) and + * a reread of the same stack slot (r3) are tracked for precision. After + * the atomic operation, the stack slot is STACK_MISC. Thus, the ldx at + * insn 4 does NOT set INSN_F_STACK_ACCESS. Precision for the stack slot + * propagates solely through the atomic fetch's load side (insn 3). + */ +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r2,r3 stack= before 4: (79) r3 = *(u64 *)(r10 -8)") +__msg("mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_fetch_add_dual_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = 0;" + ".8byte %[fetch_add_insn];" /* r2 = atomic_fetch_add(*(u64 *)(r10 - 8), r2) */ + "r3 = *(u64 *)(r10 - 8);" + "r4 = r2;" + "r4 += r3;" + "r4 &= 7;" + "r5 = r10;" + "r5 += r4;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(fetch_add_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_ADD | BPF_FETCH, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r0,r3 stack= before 5: (79) r3 = *(u64 *)(r10 -8)") +__msg("mark_precise: frame0: regs=r0 stack= before 4: (db) r0 = atomic64_cmpxchg((u64 *)(r10 -8), r0, r2)") +__msg("mark_precise: frame0: regs= stack=-8 before 3: (b7) r2 = 0") +__msg("mark_precise: frame0: regs= stack=-8 before 2: (b7) r0 = 8") +__msg("mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1") +__msg("mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8") +__naked int bpf_atomic_cmpxchg_dual_precision(void) +{ + asm volatile ( + "r1 = 8;" + "*(u64 *)(r10 - 8) = r1;" + "r0 = 8;" + "r2 = 0;" + ".8byte %[cmpxchg_insn];" /* r0 = atomic_cmpxchg(*(u64 *)(r10 - 8), r0, r2) */ + "r3 = *(u64 *)(r10 - 8);" + "r4 = r0;" + "r4 += r3;" + "r4 &= 7;" + "r5 = r10;" + "r5 += r4;" /* mark_precise */ + "r0 = 0;" + "exit;" + : + : __imm_insn(cmpxchg_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_CMPXCHG, BPF_REG_10, BPF_REG_2, -8)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r1 stack= before 10: (57) r1 &= 7") +__msg("mark_precise: frame0: regs=r1 stack= before 9: (db) r1 = atomic64_fetch_add((u64 *)(r0 +0), r1)") +__not_msg("falling back to forcing all scalars precise") +__naked int bpf_atomic_fetch_add_map_precision(void) +{ + asm volatile ( + "r1 = 0;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = r10;" + "r2 += -8;" + "r1 = %[precision_map] ll;" + "call %[bpf_map_lookup_elem];" + "if r0 == 0 goto 1f;" + "r1 = 0;" + ".8byte %[fetch_add_insn];" /* r1 = atomic_fetch_add(*(u64 *)(r0 + 0), r1) */ + "r1 &= 7;" + "r2 = r10;" + "r2 += r1;" /* mark_precise */ + "1: r0 = 0;" + "exit;" + : + : __imm_addr(precision_map), + __imm(bpf_map_lookup_elem), + __imm_insn(fetch_add_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_ADD | BPF_FETCH, BPF_REG_0, BPF_REG_1, 0)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r0 stack= before 12: (57) r0 &= 7") +__msg("mark_precise: frame0: regs=r0 stack= before 11: (db) r0 = atomic64_cmpxchg((u64 *)(r6 +0), r0, r1)") +__not_msg("falling back to forcing all scalars precise") +__naked int bpf_atomic_cmpxchg_map_precision(void) +{ + asm volatile ( + "r1 = 0;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = r10;" + "r2 += -8;" + "r1 = %[precision_map] ll;" + "call %[bpf_map_lookup_elem];" + "if r0 == 0 goto 1f;" + "r6 = r0;" + "r0 = 0;" + "r1 = 0;" + ".8byte %[cmpxchg_insn];" /* r0 = atomic_cmpxchg(*(u64 *)(r6 + 0), r0, r1) */ + "r0 &= 7;" + "r2 = r10;" + "r2 += r0;" /* mark_precise */ + "1: r0 = 0;" + "exit;" + : + : __imm_addr(precision_map), + __imm(bpf_map_lookup_elem), + __imm_insn(cmpxchg_insn, + BPF_ATOMIC_OP(BPF_DW, BPF_CMPXCHG, BPF_REG_6, BPF_REG_1, 0)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r1 stack= before 10: (57) r1 &= 7") +__msg("mark_precise: frame0: regs=r1 stack= before 9: (c3) r1 = atomic_fetch_add((u32 *)(r0 +0), r1)") +__not_msg("falling back to forcing all scalars precise") +__naked int bpf_atomic_fetch_add_32bit_precision(void) +{ + asm volatile ( + "r1 = 0;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = r10;" + "r2 += -8;" + "r1 = %[precision_map] ll;" + "call %[bpf_map_lookup_elem];" + "if r0 == 0 goto 1f;" + "r1 = 0;" + ".8byte %[fetch_add_insn];" /* r1 = atomic_fetch_add(*(u32 *)(r0 + 0), r1) */ + "r1 &= 7;" + "r2 = r10;" + "r2 += r1;" /* mark_precise */ + "1: r0 = 0;" + "exit;" + : + : __imm_addr(precision_map), + __imm(bpf_map_lookup_elem), + __imm_insn(fetch_add_insn, + BPF_ATOMIC_OP(BPF_W, BPF_ADD | BPF_FETCH, BPF_REG_0, BPF_REG_1, 0)) + : __clobber_all); +} + +SEC("?raw_tp") +__success __log_level(2) +__msg("mark_precise: frame0: regs=r0 stack= before 12: (57) r0 &= 7") +__msg("mark_precise: frame0: regs=r0 stack= before 11: (c3) r0 = atomic_cmpxchg((u32 *)(r6 +0), r0, r1)") +__not_msg("falling back to forcing all scalars precise") +__naked int bpf_atomic_cmpxchg_32bit_precision(void) +{ + asm volatile ( + "r1 = 0;" + "*(u64 *)(r10 - 8) = r1;" + "r2 = r10;" + "r2 += -8;" + "r1 = %[precision_map] ll;" + "call %[bpf_map_lookup_elem];" + "if r0 == 0 goto 1f;" + "r6 = r0;" + "r0 = 0;" + "r1 = 0;" + ".8byte %[cmpxchg_insn];" /* r0 = atomic_cmpxchg(*(u32 *)(r6 + 0), r0, r1) */ + "r0 &= 7;" + "r2 = r10;" + "r2 += r0;" /* mark_precise */ + "1: r0 = 0;" + "exit;" + : + : __imm_addr(precision_map), + __imm(bpf_map_lookup_elem), + __imm_insn(cmpxchg_insn, + BPF_ATOMIC_OP(BPF_W, BPF_CMPXCHG, BPF_REG_6, BPF_REG_1, 0)) + : __clobber_all); +} + char _license[] SEC("license") = "GPL";