From 29eef85be2f60b1027214b4bfc4b1a9d592830a7 Mon Sep 17 00:00:00 2001 From: Johan Almbladh Date: Tue, 14 Sep 2021 11:18:42 +0200 Subject: bpf/tests: Add tail call limit test with external function call This patch adds a tail call limit test where the program also emits a BPF_CALL to an external function prior to the tail call. Mainly testing that JITed programs preserve its internal register state, for example tail call count, across such external calls. Signed-off-by: Johan Almbladh Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210914091842.4186267-15-johan.almbladh@anyfinetworks.com --- lib/test_bpf.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 83 insertions(+), 3 deletions(-) (limited to 'lib/test_bpf.c') diff --git a/lib/test_bpf.c b/lib/test_bpf.c index a94ab634f947..08f438e6fe9e 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -12208,6 +12208,30 @@ struct tail_call_test { offset, TAIL_CALL_MARKER), \ BPF_JMP_IMM(BPF_TAIL_CALL, 0, 0, 0) +/* + * A test function to be called from a BPF program, clobbering a lot of + * CPU registers in the process. A JITed BPF program calling this function + * must save and restore any caller-saved registers it uses for internal + * state, for example the current tail call count. + */ +BPF_CALL_1(bpf_test_func, u64, arg) +{ + char buf[64]; + long a = 0; + long b = 1; + long c = 2; + long d = 3; + long e = 4; + long f = 5; + long g = 6; + long h = 7; + + return snprintf(buf, sizeof(buf), + "%ld %lu %lx %ld %lu %lx %ld %lu %x", + a, b, c, d, e, f, g, h, (int)arg); +} +#define BPF_FUNC_test_func __BPF_FUNC_MAX_ID + /* * Tail call tests. Each test case may call any other test in the table, * including itself, specified as a relative index offset from the calling @@ -12267,6 +12291,28 @@ static struct tail_call_test tail_call_tests[] = { .flags = FLAG_NEED_STATE | FLAG_RESULT_IN_STATE, .result = (MAX_TAIL_CALL_CNT + 1 + 1) * MAX_TESTRUNS, }, + { + "Tail call count preserved across function calls", + .insns = { + BPF_LDX_MEM(BPF_W, R2, R1, 0), + BPF_ALU64_IMM(BPF_ADD, R2, 1), + BPF_STX_MEM(BPF_W, R1, R2, 0), + BPF_STX_MEM(BPF_DW, R10, R1, -8), + BPF_CALL_REL(BPF_FUNC_get_numa_node_id), + BPF_CALL_REL(BPF_FUNC_ktime_get_ns), + BPF_CALL_REL(BPF_FUNC_ktime_get_boot_ns), + BPF_CALL_REL(BPF_FUNC_ktime_get_coarse_ns), + BPF_CALL_REL(BPF_FUNC_jiffies64), + BPF_CALL_REL(BPF_FUNC_test_func), + BPF_LDX_MEM(BPF_DW, R1, R10, -8), + BPF_ALU32_REG(BPF_MOV, R0, R1), + TAIL_CALL(0), + BPF_EXIT_INSN(), + }, + .stack_depth = 8, + .flags = FLAG_NEED_STATE | FLAG_RESULT_IN_STATE, + .result = (MAX_TAIL_CALL_CNT + 1 + 1) * MAX_TESTRUNS, + }, { "Tail call error path, NULL target", .insns = { @@ -12345,17 +12391,19 @@ static __init int prepare_tail_call_tests(struct bpf_array **pprogs) /* Relocate runtime tail call offsets and addresses */ for (i = 0; i < len; i++) { struct bpf_insn *insn = &fp->insnsi[i]; - - if (insn->imm != TAIL_CALL_MARKER) - continue; + long addr = 0; switch (insn->code) { case BPF_LD | BPF_DW | BPF_IMM: + if (insn->imm != TAIL_CALL_MARKER) + break; insn[0].imm = (u32)(long)progs; insn[1].imm = ((u64)(long)progs) >> 32; break; case BPF_ALU | BPF_MOV | BPF_K: + if (insn->imm != TAIL_CALL_MARKER) + break; if (insn->off == TAIL_CALL_NULL) insn->imm = ntests; else if (insn->off == TAIL_CALL_INVALID) @@ -12363,6 +12411,38 @@ static __init int prepare_tail_call_tests(struct bpf_array **pprogs) else insn->imm = which + insn->off; insn->off = 0; + break; + + case BPF_JMP | BPF_CALL: + if (insn->src_reg != BPF_PSEUDO_CALL) + break; + switch (insn->imm) { + case BPF_FUNC_get_numa_node_id: + addr = (long)&numa_node_id; + break; + case BPF_FUNC_ktime_get_ns: + addr = (long)&ktime_get_ns; + break; + case BPF_FUNC_ktime_get_boot_ns: + addr = (long)&ktime_get_boot_fast_ns; + break; + case BPF_FUNC_ktime_get_coarse_ns: + addr = (long)&ktime_get_coarse_ns; + break; + case BPF_FUNC_jiffies64: + addr = (long)&get_jiffies_64; + break; + case BPF_FUNC_test_func: + addr = (long)&bpf_test_func; + break; + default: + err = -EFAULT; + goto out_err; + } + *insn = BPF_EMIT_CALL(BPF_CAST_CALL(addr)); + if ((long)__bpf_call_base + insn->imm != addr) + *insn = BPF_JMP_A(0); /* Skip: NOP */ + break; } } -- cgit v1.2.3-59-g8ed1b