#include <stdint.h>
#include "kernel.h"

void debug_stack_trace(unsigned int max_frames)
{
    DEBUG("*** begin stack trace ***");
    // Thanks GCC :)
    uintptr_t* rbp = (uintptr_t*)__builtin_frame_address(0);

    for (unsigned int frame=0; frame<max_frames && rbp != NULL; frame++)
    {
        // Return address, 1 word above saved rbp
        uintptr_t rip = rbp[1];
        uintptr_t offset = 0;
        const char* name = debug_find_symbol(rip, &offset);
        DEBUG("[%u] <0x%p> (%s+0x%x)", frame, (void*)rip, name, offset);

        uintptr_t* next_rbp = (uintptr_t*)rbp[0];

        // invalid rbp or we're at the end
        if (next_rbp <= rbp || next_rbp == NULL)
        {
            break;
        }

        rbp = next_rbp;
    }
    DEBUG("*** end stack trace ***");
}

typedef struct
{
    uint64_t addr;
    const char *name;
} __attribute__((packed)) kernel_symbol_t;

__attribute__((weak)) extern kernel_symbol_t symbol_table[];
__attribute__((weak)) extern uint64_t symbol_count;

// binary search
const char* debug_find_symbol(uintptr_t rip, uintptr_t* offset)
{
    if (!symbol_table || symbol_count == 0)
    {
        if (offset) *offset = 0;
        return "???";
    }

    int low = 0, high = (int)symbol_count - 1;
    int best = -1;

    while (low <= high)
    {
        int mid = (low + high) / 2;
        if (symbol_table[mid].addr <= rip)
        {
            best = mid;
            low = mid + 1;
        } else {
            high = mid - 1;
        }
    }

    if (best != -1)
    {
        if (offset)
        {
            *offset = rip - symbol_table[best].addr;
        }
        return symbol_table[best].name;
    }

    if (offset) *offset = 0;
    return "unknown";
}