Bug 219732

When profiling a simple C program with nested function calls using DWARF
call graphs, perf report shows incorrect call graph relationships,
including impossible self-calls (merge -> merge) and skipped stack
frames (merge_all directly calling spinlock).

Reproducer code:



#include <stdint.h>

#define VOLATILE_ACCESS(x) (*(volatile typeof(x)*)&(x))

__attribute__((noinline))
void spinlock(void) {
    const uint64_t ITERATIONS = 1000;
    uint64_t counter = 0;
    
    while (counter < ITERATIONS) {
        VOLATILE_ACCESS(counter);
        counter += 1;
    }
}

__attribute__((noinline))
void merge(void) {
    for (int i = 0; i < 100; i++) {
        spinlock();
    }
}

__attribute__((noinline))
void merge_all(void) {
    for (int i = 0; i < 1000; i++) {
        merge();
    }
}

int main(void) {
    for (int i = 0; i < 10; i++) {
        merge_all();
    }
    return 0;
}



Build & reproduce:

1. gcc -O3 perf_test.c -o perf_test
2. perf record --call-graph dwarf ./perf_test
3. perf report

Actual output:


-   99.94%     0.00%  main     main                  [.] _start
     _start
     __libc_start_main@@GLIBC_2.34
     __libc_start_call_main
     main
   - merge_all
      - 98.73% merge
           98.23% spinlock
           0.50% merge
        1.22% spinlock


Expected call hierarchy:


main
  ─ merge_all
      ─ merge
          ─ spinlock


Instead, the call graph shows merge calling itself and merge_all directly
calling spinlock, which is impossible given the code structure.

System details:
perf version: 6.12.9-100.fc40.x86_64
kernel version: 6.9.7-200.fc40.x86_64
gcc version: 14.1.1 20240701 (Red Hat 14.1.1-7)