f80f88f0e2
The BPF program for the snprintf selftest runs on all syscall entries.
On busy multicore systems this can cause concurrency issues.
For example it was observed that sometimes the userspace part of the
test reads " 4 0000" instead of " 4 000" (extra '0' at the end)
which seems to happen just before snprintf on another core sets
end[-1] = '\0'.
This patch adds a pid filter to the test to ensure that no
bpf_snprintf() will write over the test's output buffers while the
userspace reads the values.
Fixes: c2e39c6bdc ("selftests/bpf: Add a series of tests for bpf_snprintf")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Florent Revest <revest@chromium.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210428152501.1024509-1-revest@chromium.org
78 lines
1.9 KiB
C
78 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2021 Google LLC. */
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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__u32 pid = 0;
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char num_out[64] = {};
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long num_ret = 0;
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char ip_out[64] = {};
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long ip_ret = 0;
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char sym_out[64] = {};
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long sym_ret = 0;
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char addr_out[64] = {};
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long addr_ret = 0;
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char str_out[64] = {};
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long str_ret = 0;
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char over_out[6] = {};
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long over_ret = 0;
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char pad_out[10] = {};
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long pad_ret = 0;
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char noarg_out[64] = {};
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long noarg_ret = 0;
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long nobuf_ret = 0;
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extern const void schedule __ksym;
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SEC("raw_tp/sys_enter")
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int handler(const void *ctx)
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{
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/* Convenient values to pretty-print */
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const __u8 ex_ipv4[] = {127, 0, 0, 1};
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const __u8 ex_ipv6[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
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static const char str1[] = "str1";
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static const char longstr[] = "longstr";
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if ((int)bpf_get_current_pid_tgid() != pid)
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return 0;
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/* Integer types */
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num_ret = BPF_SNPRINTF(num_out, sizeof(num_out),
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"%d %u %x %li %llu %lX",
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-8, 9, 150, -424242, 1337, 0xDABBAD00);
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/* IP addresses */
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ip_ret = BPF_SNPRINTF(ip_out, sizeof(ip_out), "%pi4 %pI6",
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&ex_ipv4, &ex_ipv6);
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/* Symbol lookup formatting */
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sym_ret = BPF_SNPRINTF(sym_out, sizeof(sym_out), "%ps %pS %pB",
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&schedule, &schedule, &schedule);
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/* Kernel pointers */
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addr_ret = BPF_SNPRINTF(addr_out, sizeof(addr_out), "%pK %px %p",
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0, 0xFFFF00000ADD4E55, 0xFFFF00000ADD4E55);
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/* Strings embedding */
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str_ret = BPF_SNPRINTF(str_out, sizeof(str_out), "%s %+05s",
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str1, longstr);
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/* Overflow */
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over_ret = BPF_SNPRINTF(over_out, sizeof(over_out), "%%overflow");
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/* Padding of fixed width numbers */
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pad_ret = BPF_SNPRINTF(pad_out, sizeof(pad_out), "%5d %0900000X", 4, 4);
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/* No args */
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noarg_ret = BPF_SNPRINTF(noarg_out, sizeof(noarg_out), "simple case");
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/* No buffer */
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nobuf_ret = BPF_SNPRINTF(NULL, 0, "only interested in length %d", 60);
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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