Stack trace

_.md

Usage:

$ ./stack-trace <number> [libunwind] [fp_chain]
$ # Example (Call pattern is different for different numbers)
$ ./stack-trace 52 libunwind fp_chain

Makefile

CFLAGS += -fno-omit-frame-pointer -funwind-tables
LDFLAGS += -lunwind

.PHONY: all
all: stack-trace

.PHONY: clean
clean:
	rm stack-trace

stack-trace.c

#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#define UNW_LOCAL_ONLY
#include <libunwind.h>

void print_stack_trace_libunwind() {

    printf("=== Stack trace from libunwind ===\n");

    unw_cursor_t cursor; unw_context_t uc;
    unw_word_t pc, sp;

    unw_getcontext(&uc);
    unw_init_local(&cursor, &uc);

    while (unw_step(&cursor) > 0) {
        unw_get_reg(&cursor, UNW_REG_IP, &pc);
        unw_get_reg(&cursor, UNW_REG_SP, &sp);

        printf("Program counter: 0x%016" PRIxPTR "\n", (uintptr_t) pc);
        printf("Stack pointer: 0x%016" PRIxPTR "\n", (uintptr_t) sp);
        printf("\n");
    }

    printf("=== End ===\n\n");
}

void print_stack_trace_fp_chain() {
    printf("=== Stack trace from fp chain ===\n");

    uintptr_t *fp;
    asm("mv %0, fp" : "=r"(fp) : : );

    // When should this stop?
    while (fp) {
        printf("Return address: 0x%016" PRIxPTR "\n", fp[-1]);
        printf("Old stack pointer: 0x%016" PRIxPTR "\n", fp[-2]);
        printf("\n");

        fp = (uintptr_t *) fp[-2];
    }
    printf("=== End ===\n\n");
}

int use_libunwind = 0, use_fp_chain = 0;

void flip(unsigned n);
void flap(unsigned n);

void flip(unsigned n) {
    if (n == 0) {
        if (use_libunwind)
            print_stack_trace_libunwind();

        if (use_fp_chain)
            print_stack_trace_fp_chain();
    } else if ((n & 1) == 0) {
        flip(n >> 1);
    } else if ((n & 1) == 1) {
        flap(n >> 1);
    }

    printf("flip %u\n", n);
}

void flap(unsigned n) {
    if ((n & 1) == 0) {
        flip(n >> 1);
    } else if ((n & 1) == 1) {
        flap(n >> 1);
    }

    printf("flap %u\n", n);
}

int main(int argc, char *argv[]) {
    unsigned input;
    sscanf(argv[1], "%u", &input);

    for (int i = 2; i < argc; i ++) {
        if (strcmp(argv[i], "libunwind") == 0)
            use_libunwind = 1;
        
        if (strcmp(argv[i], "fp_chain") == 0)
            use_fp_chain = 1;
    }

    flip(input);
    return 0;
}