84 lines
1.7 KiB
C
84 lines
1.7 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2019 Facebook
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#include <linux/ptrace.h>
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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const struct {
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unsigned a[4];
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/*
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* if the struct's size is multiple of 16, compiler will put it into
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* .rodata.cst16 section, which is not recognized by libbpf; work
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* around this by ensuring we don't have 16-aligned struct
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*/
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char _y;
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} rdonly_values = { .a = {2, 3, 4, 5} };
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struct {
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unsigned did_run;
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unsigned iters;
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unsigned sum;
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} res = {};
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SEC("raw_tracepoint/sys_enter:skip_loop")
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int skip_loop(struct pt_regs *ctx)
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{
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/* prevent compiler to optimize everything out */
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unsigned * volatile p = (void *)&rdonly_values.a;
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unsigned iters = 0, sum = 0;
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/* we should never enter this loop */
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while (*p & 1) {
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iters++;
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sum += *p;
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p++;
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}
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res.did_run = 1;
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res.iters = iters;
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res.sum = sum;
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return 0;
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}
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SEC("raw_tracepoint/sys_enter:part_loop")
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int part_loop(struct pt_regs *ctx)
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{
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/* prevent compiler to optimize everything out */
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unsigned * volatile p = (void *)&rdonly_values.a;
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unsigned iters = 0, sum = 0;
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/* validate verifier can derive loop termination */
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while (*p < 5) {
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iters++;
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sum += *p;
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p++;
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}
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res.did_run = 1;
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res.iters = iters;
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res.sum = sum;
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return 0;
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}
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SEC("raw_tracepoint/sys_enter:full_loop")
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int full_loop(struct pt_regs *ctx)
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{
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/* prevent compiler to optimize everything out */
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unsigned * volatile p = (void *)&rdonly_values.a;
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int i = sizeof(rdonly_values.a) / sizeof(rdonly_values.a[0]);
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unsigned iters = 0, sum = 0;
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/* validate verifier can allow full loop as well */
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while (i > 0 ) {
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iters++;
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sum += *p;
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p++;
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i--;
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}
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res.did_run = 1;
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res.iters = iters;
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res.sum = sum;
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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