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