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6e057fc15a
When tweaking llvm optimizations, I found that selftest build failed
with the following error:
libbpf: elf: skipping unrecognized data section(6) .rodata.str1.1
libbpf: prog 'sysctl_tcp_mem': bad map relo against '.L__const.is_tcp_mem.tcp_mem_name'
in section '.rodata.str1.1'
Error: failed to open BPF object file: Relocation failed
make: *** [/work/net-next/tools/testing/selftests/bpf/test_sysctl_prog.skel.h] Error 255
make: *** Deleting file `/work/net-next/tools/testing/selftests/bpf/test_sysctl_prog.skel.h'
The local string constant "tcp_mem_name" is put into '.rodata.str1.1' section
which libbpf cannot handle. Using untweaked upstream llvm, "tcp_mem_name"
is completely inlined after loop unrolling.
Commit 7fb5eefd76 ("selftests/bpf: Fix test_sysctl_loop{1, 2}
failure due to clang change") solved a similar problem by defining
the string const as a global. Let us do the same here
for test_sysctl_prog.c so it can weather future potential llvm changes.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200910202718.956042-1-yhs@fb.com
73 lines
1.6 KiB
C
73 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2019 Facebook
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#include <stdint.h>
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#include <string.h>
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#include <linux/stddef.h>
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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/* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */
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#define MAX_ULONG_STR_LEN 0xF
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/* Max supported length of sysctl value string (pow2). */
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#define MAX_VALUE_STR_LEN 0x40
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#ifndef ARRAY_SIZE
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#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
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#endif
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const char tcp_mem_name[] = "net/ipv4/tcp_mem";
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static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
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{
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unsigned char i;
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char name[sizeof(tcp_mem_name)];
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int ret;
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memset(name, 0, sizeof(name));
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ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
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if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
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return 0;
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#pragma clang loop unroll(full)
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for (i = 0; i < sizeof(tcp_mem_name); ++i)
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if (name[i] != tcp_mem_name[i])
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return 0;
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return 1;
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}
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SEC("cgroup/sysctl")
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int sysctl_tcp_mem(struct bpf_sysctl *ctx)
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{
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unsigned long tcp_mem[3] = {0, 0, 0};
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char value[MAX_VALUE_STR_LEN];
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unsigned char i, off = 0;
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volatile int ret;
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if (ctx->write)
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return 0;
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if (!is_tcp_mem(ctx))
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return 0;
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ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
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if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
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return 0;
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#pragma clang loop unroll(full)
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for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
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ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
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tcp_mem + i);
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if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
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return 0;
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off += ret & MAX_ULONG_STR_LEN;
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}
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return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
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}
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char _license[] SEC("license") = "GPL";
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