On powerpc, immediate load instructions are sign extended. In case of unsigned types, arguments should be explicitly zero-extended by the caller. For kfunc call, this needs to be handled in the JIT code. In bpf_kfunc_call_test4(), that tests for sign-extension of signed argument types in kfunc calls, add some additional failure checks. And add bpf_kfunc_call_test5() to test zero-extension of unsigned argument types in kfunc calls.
Signed-off-by: Hari Bathini <[email protected]> --- Changes in v2: - Added asm version of the selftest for consistent testing across different BPF ISA versions. - Added comments clearly stating the intent of the test cases. - Updated sign-extension selftest to have additional failure checks. .../selftests/bpf/prog_tests/kfunc_call.c | 2 + .../selftests/bpf/progs/kfunc_call_test.c | 98 +++++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 54 +++++++++- .../bpf/test_kmods/bpf_testmod_kfunc.h | 1 + 4 files changed, 154 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c index f79c8e53cb3e..62f3fb79f5d1 100644 --- a/tools/testing/selftests/bpf/prog_tests/kfunc_call.c +++ b/tools/testing/selftests/bpf/prog_tests/kfunc_call.c @@ -74,6 +74,8 @@ static struct kfunc_test_params kfunc_tests[] = { TC_TEST(kfunc_call_test1, 12), TC_TEST(kfunc_call_test2, 3), TC_TEST(kfunc_call_test4, -1234), + TC_TEST(kfunc_call_test5, 0), + TC_TEST(kfunc_call_test5_asm, 0), TC_TEST(kfunc_call_test_ref_btf_id, 0), TC_TEST(kfunc_call_test_get_mem, 42), SYSCALL_TEST(kfunc_syscall_test, 0), diff --git a/tools/testing/selftests/bpf/progs/kfunc_call_test.c b/tools/testing/selftests/bpf/progs/kfunc_call_test.c index 8b86113a0126..5edc51564f71 100644 --- a/tools/testing/selftests/bpf/progs/kfunc_call_test.c +++ b/tools/testing/selftests/bpf/progs/kfunc_call_test.c @@ -2,8 +2,106 @@ /* Copyright (c) 2021 Facebook */ #include <vmlinux.h> #include <bpf/bpf_helpers.h> +#include "bpf_misc.h" #include "../test_kmods/bpf_testmod_kfunc.h" +SEC("tc") +int kfunc_call_test5(struct __sk_buff *skb) +{ + struct bpf_sock *sk = skb->sk; + int ret; + u32 val32; + u16 val16; + u8 val8; + + if (!sk) + return -1; + + sk = bpf_sk_fullsock(sk); + if (!sk) + return -1; + + /* + * Test with constant values to verify zero-extension. + * ISA-dependent BPF asm: + * With ALU32: w1 = 0xFF; w2 = 0xFFFF; w3 = 0xFFFFffff + * Without ALU32: r1 = 0xFF; r2 = 0xFFFF; r3 = 0xFFFFffff + * Both zero-extend to 64-bit before the kfunc call. + */ + ret = bpf_kfunc_call_test5(0xFF, 0xFFFF, 0xFFFFffffULL); + if (ret) + return ret; + + val32 = bpf_get_prandom_u32(); + val16 = val32 & 0xFFFF; + val8 = val32 & 0xFF; + ret = bpf_kfunc_call_test5(val8, val16, val32); + if (ret) + return ret; + + /* + * Test multiplication with different operand sizes: + * + * val8 * 0xFF: + * - Both operands promote to int (32-bit signed) + * - Result: 32-bit multiplication, truncated to u8, then zero-extended + * + * val16 * 0xFFFF: + * - Both operands promote to int (32-bit signed) + * - Result: 32-bit multiplication, truncated to u16, then zero-extended + * + * val32 * 0xFFFFffffULL: + * - val32 (u32) promotes to unsigned long long (due to ULL suffix) + * - Result: 64-bit unsigned multiplication, truncated to u32, then zero-extended + */ + ret = bpf_kfunc_call_test5(val8 * 0xFF, val16 * 0xFFFF, val32 * 0xFFFFffffULL); + if (ret) + return ret; + + return 0; +} + +/* + * Assembly version testing the multiplication edge case explicitly. + * This ensures consistent testing across different ISA versions. + */ +SEC("tc") +__naked int kfunc_call_test5_asm(void) +{ + asm volatile ( + /* Get a random u32 value */ + "call %[bpf_get_prandom_u32];" + "r6 = r0;" /* Save val32 in r6 */ + + /* Prepare first argument: val8 * 0xFF */ + "r1 = r6;" + "r1 &= 0xFF;" /* val8 = val32 & 0xFF */ + "r7 = 0xFF;" + "r1 *= r7;" /* 64-bit mult: r1 = r1 * r7 */ + + /* Prepare second argument: val16 * 0xFFFF */ + "r2 = r6;" + "r2 &= 0xFFFF;" /* val16 = val32 & 0xFFFF */ + "r7 = 0xFFFF;" + "r2 *= r7;" /* 64-bit mult: r2 = r2 * r7 */ + + /* Prepare third argument: val32 * 0xFFFFffff */ + "r3 = r6;" /* val32 */ + "r7 = 0xFFFFffff;" + "r3 *= r7;" /* 64-bit mult: r3 = r3 * r7 */ + + /* Call kfunc with multiplication results */ + "call bpf_kfunc_call_test5;" + + /* Check return value */ + "if r0 != 0 goto exit_%=;" + "r0 = 0;" + "exit_%=: exit;" + : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + SEC("tc") int kfunc_call_test4(struct __sk_buff *skb) { diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index e62c6b78657f..94edbd2afa67 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -760,12 +760,63 @@ __bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk) __bpf_kfunc long noinline bpf_kfunc_call_test4(signed char a, short b, int c, long d) { - /* Provoke the compiler to assume that the caller has sign-extended a, + /* + * Make val as volatile to avoid compiler optimizations. + * Verify that negative signed values remain negative after + * sign-extension (JIT must sign-extend, not zero-extend). + */ + volatile long val; + + /* val will be positive, if JIT does zero-extension instead of sign-extension */ + val = a; + if (val >= 0) + return 1; + + val = b; + if (val >= 0) + return 2; + + val = c; + if (val >= 0) + return 3; + + /* + * Provoke the compiler to assume that the caller has sign-extended a, * b and c on platforms where this is required (e.g. s390x). */ return (long)a + (long)b + (long)c + d; } +__bpf_kfunc int bpf_kfunc_call_test5(u8 a, u16 b, u32 c) +{ + /* + * Make val as volatile to avoid compiler optimizations on the below checks + * In C, assigning u8/u16/u32 to long performs zero-extension. + */ + volatile long val = a; + + /* Check zero-extension */ + if (val != (unsigned long)a) + return 1; + /* Check no sign-extension */ + if (val < 0) + return 2; + + val = b; + if (val != (unsigned long)b) + return 3; + if (val < 0) + return 4; + + val = c; + if (val != (unsigned long)c) + return 5; + if (val < 0) + return 6; + + return 0; +} + static struct prog_test_ref_kfunc prog_test_struct = { .a = 42, .b = 108, @@ -1228,6 +1279,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test1) BTF_ID_FLAGS(func, bpf_kfunc_call_test2) BTF_ID_FLAGS(func, bpf_kfunc_call_test3) BTF_ID_FLAGS(func, bpf_kfunc_call_test4) +BTF_ID_FLAGS(func, bpf_kfunc_call_test5) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_pass1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail1) BTF_ID_FLAGS(func, bpf_kfunc_call_test_mem_len_fail2) diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h index b393bf771131..aa0b8d41e71b 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod_kfunc.h @@ -110,6 +110,7 @@ __u64 bpf_kfunc_call_test1(struct sock *sk, __u32 a, __u64 b, int bpf_kfunc_call_test2(struct sock *sk, __u32 a, __u32 b) __ksym; struct sock *bpf_kfunc_call_test3(struct sock *sk) __ksym; long bpf_kfunc_call_test4(signed char a, short b, int c, long d) __ksym; +int bpf_kfunc_call_test5(__u8 a, __u16 b, __u32 c) __ksym; void bpf_kfunc_call_test_pass_ctx(struct __sk_buff *skb) __ksym; void bpf_kfunc_call_test_pass1(struct prog_test_pass1 *p) __ksym; -- 2.53.0
