1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2019 Facebook 3 4 #include <linux/ptrace.h> 5 #include <linux/bpf.h> 6 #include <bpf/bpf_helpers.h> 7 #include "bpf_misc.h" 8 9 const struct { 10 unsigned a[4]; 11 /* 12 * if the struct's size is multiple of 16, compiler will put it into 13 * .rodata.cst16 section, which is not recognized by libbpf; work 14 * around this by ensuring we don't have 16-aligned struct 15 */ 16 char _y; 17 } rdonly_values = { .a = {2, 3, 4, 5} }; 18 19 struct { 20 unsigned did_run; 21 unsigned iters; 22 unsigned sum; 23 } res = {}; 24 25 SEC("raw_tracepoint/sys_enter:skip_loop") 26 int skip_loop(struct pt_regs *ctx) 27 { 28 /* prevent compiler to optimize everything out */ 29 unsigned * volatile p = (void *)&rdonly_values.a; 30 unsigned iters = 0, sum = 0; 31 32 /* we should never enter this loop */ 33 while (*p & 1) { 34 iters++; 35 sum += *p; 36 p++; 37 } 38 res.did_run = 1; 39 res.iters = iters; 40 res.sum = sum; 41 return 0; 42 } 43 44 SEC("raw_tracepoint/sys_enter:part_loop") 45 int part_loop(struct pt_regs *ctx) 46 { 47 /* prevent compiler to optimize everything out */ 48 unsigned * volatile p = (void *)&rdonly_values.a; 49 unsigned iters = 0, sum = 0; 50 51 /* validate verifier can derive loop termination */ 52 while (*p < 5) { 53 iters++; 54 sum += *p; 55 p++; 56 } 57 res.did_run = 1; 58 res.iters = iters; 59 res.sum = sum; 60 return 0; 61 } 62 63 SEC("raw_tracepoint/sys_enter:full_loop") 64 int full_loop(struct pt_regs *ctx) 65 { 66 /* prevent compiler to optimize everything out */ 67 unsigned * volatile p = (void *)&rdonly_values.a; 68 int i = ARRAY_SIZE(rdonly_values.a); 69 unsigned iters = 0, sum = 0; 70 71 /* validate verifier can allow full loop as well */ 72 while (i > 0 ) { 73 iters++; 74 sum += *p; 75 p++; 76 i--; 77 } 78 res.did_run = 1; 79 res.iters = iters; 80 res.sum = sum; 81 return 0; 82 } 83 84 char _license[] SEC("license") = "GPL"; 85