Debug user space application with MMU

This may be related to troubles debugging. I am trying to print a stack trace from within the program, but that doesn't work either. I tried with a very simple non-threaded C program:

#include <stdio.h>
# include <execinfo.h>
# include <stdlib.h>
void print_trace() {
  void *array;
  size_t size;
  // get void*'s for all entries on the stack
  size = backtrace(array, 10);
  // print out all the frames to stderr
  fprintf(stderr, "trace size %zu:\n", size);
  backtrace_symbols_fd(array, size, 2);
  exit(1);
}
void baz() {
  print_trace();
}
void bar() { baz(); }
void foo() { bar(); }
int main(int argc, char **argv) {
  foo();
}

trace size 7:
./test_bt(print_trace+0x19)
./test_bt(baz+0xe)
./test_bt(bar+0xe)
./test_bt(foo+0xe)
./test_bt(main+0x19)
/lib/libc.so.6(__libc_start_main+0xfe)
./test_bt

trace size 1:

warning: Couldn't find general-purpose registers in core file.
# 0  0x00000000 in ?? ()

-#define ELF_NGREG (sizeof (struct pt_regs) / sizeof(elf_greg_t))
+#define ELF_NGREG ((sizeof(struct pt_regs) + sizeof(struct switch_stack)) / sizeof(elf_greg_t))

Tobias, I just saw this fix in the commit log and was surprised to see a link back to my report here because I missed your response in the thread. I will try this fix!

# define _GNU_SOURCE
# include <stdio.h># include <inttypes.h># include <stdint.h># include <ucontext.h># include <dlfcn.h># include <string.h>
struct frame {
    void *fp; // frame pointer
    void *ra; // return address
};
void print_symbol(void *address) {
    Dl_info info;
    char    library;
    char    function;
    void   *symbol_address;
    if (dladdr(address, &info) == 0) {
        strncpy(function, "???", sizeof(function));
        strncpy(library, "???", sizeof(library));
        symbol_address = 0;
    } else {
        strncpy(function, info.dli_sname, sizeof(function));
        strncpy(library, info.dli_fname, sizeof(library));
        symbol_address = info.dli_saddr;
    }
    printf("0x%08X %s: %s\n", (uint32_t) symbol_address, library, function);
}
void backtrace() {
    struct frame *frame;
    // frame = CURRENT_FRAME_POINTER
    __asm("mov %0,r28" : "=r"(frame));
    // Last frames
    while (frame && frame->fp) {
        printf("fp = 0x%08X ra = 0x%08X\n", (uint32_t) frame->fp, (uint32_t) frame->ra);
        print_symbol((void *) frame->ra);
        frame = (struct frame *) frame->fp;
    }
}
void test3() {
    backtrace();
}
void test2() {
    test3();
}
void test1() {
    test2();
}
int main(int argc, char *argv) {
    test1();
    return 0;
}

CC             = nios2-linux-gnu-gcc
CFLAGS         = -Wall -fno-omit-frame-pointer
LDFLAGS        = -rdynamic -ldl
SOURCES = stackframe.c
OBJECTS = $(SOURCES:%.c=%.o)
PROGRAM = stackframe
.PHONY: all clean
all: $(PROGRAM)
clean:
    rm -rf $(OBJECTS) $(PROGRAM)
build: clean all
$(PROGRAM): $(OBJECTS)
    $(CC) -o $@ $(OBJECTS) $(LDFLAGS)
%.o: %.c
    $(CC) $(CFLAGS) -c $<

$ make
nios2-linux-gnu-gcc -Wall -fno-omit-frame-pointer -c stackframe.c
nios2-linux-gnu-gcc -o stackframe stackframe.o -rdynamic -ldl

# stackframe
fp = 0x7FE81D24 ra = 0x00001838
0x00001824 stackframe: test3
fp = 0x7FE81D2C ra = 0x00001860
0x0000184C stackframe: test2
fp = 0x7FE81D34 ra = 0x00001888
0x00001874 stackframe: test1
fp = 0x7FE81D44 ra = 0x000018B8
0x0000189C stackframe: main