#include <stdlib.h> #include <signal.h> #include <unistd.h> #include <linux/compiler.h> #include "../tests.h" typedef struct _buf { char data1; char reserved[55]; char data2; } buf __attribute__((aligned(64))); /* volatile to try to avoid the compiler seeing reserved as unused. */ static volatile buf workload_datasym_buf1 = { /* to have this in the data section */ .reserved[0] = 1, }; static volatile sig_atomic_t done; static void sighandler(int sig __maybe_unused) { done = 1; } static int datasym(int argc, const char **argv) { int sec = 1; if (argc > 0) sec = atoi(argv[0]); signal(SIGINT, sighandler); signal(SIGALRM, sighandler); alarm(sec); while (!done) { workload_datasym_buf1.data1++; if (workload_datasym_buf1.data1 == 123) { /* * Add some 'noise' in the loop to work around errata * 1694299 on Arm N1. * * Bias exists in SPE sampling which can cause the load * and store instructions to be skipped entirely. This * comes and goes randomly depending on the offset the * linker places the datasym loop at in the Perf binary. * With an extra branch in the middle of the loop that * isn't always taken, the instruction stream is no * longer a continuous repeating pattern that interacts * badly with the bias. */ workload_datasym_buf1.data1++; } workload_datasym_buf1.data2 += workload_datasym_buf1.data1; } return 0; } DEFINE_WORKLOAD(datasym);