[openbeosnetteam] Re: debug code

"Marcus Overhagen" <dos4gw@xxxxxx> wrote:
>Untested debug code for debugging buffer overruns when they happen

Tested code! does work 

#include <OS.h>
#include <stdio.h>

void panic(char*);

void panic(char*p)
{
        printf("%s\n",p);
        fflush(0);
//      exit(-1); //commented out to see all tests 
}

void *dbg_malloc(size_t size)
{
        static char *startaddr = 0;
        char *adr;
        size_t realsize;
        area_id id;
        
        //aquire lock sem here
        
        if (startaddr == 0) {
                //find a start address that is unused
                area_id id1;
                area_id id2;
                void *adr1;
                size_t size1 = 4000 * B_PAGE_SIZE; // about 16 MB
                size_t size2 = 30000 * B_PAGE_SIZE; // about 120 MB
                id1 = create_area("",(void 
**)&adr1,B_ANY_KERNEL_ADDRESS,size1,B_NO_LOCK,B_READ_AREA | B_WRITE_AREA);
                id2 = create_area("",(void 
**)&startaddr,B_ANY_KERNEL_ADDRESS,size2,B_NO_LOCK,B_READ_AREA | B_WRITE_AREA);
                if (id1 < 0 || id2 < 0)
                        panic("out of memory in init code");
                delete_area(id1);               
                delete_area(id2);
        }
        
        size += 4;
        
        realsize = (size + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);
        adr = startaddr;
        
        // next start address is one unmapped page away
        startaddr += realsize + B_PAGE_SIZE;
        
        id = create_area("memory",(void 
**)&adr,B_EXACT_ADDRESS,realsize,B_NO_LOCK,B_READ_AREA | B_WRITE_AREA);
        if (id < 0)
                panic("out of memory or address space");
        
        // align it to make the first byte after (adr + size) to be in an 
unallocated page
        adr += realsize - size;
        
        *(uint32*)adr = 0xDEADC0DE;
        adr += 4;
        
        // release lock sem
        
        return adr;
}

void dbg_free(void *ptr)
{
        char *p = (char *)ptr;
        area_id id;
        
        p -= 4;
        if (*(uint32*)p != 0xDEADC0DE) 
                panic("buffer underrun");

        id = area_for(p);
        if (id < 0)
                panic("no area for buffer");

        delete_area(id);
}

int main()
{
        char *p;

        printf("!1\n");
        p = (char *)dbg_malloc(1);
        dbg_free(p);

        printf("!2\n");
        p = (char *)dbg_malloc(1);
        p[0] = 0;
        dbg_free(p);

        printf("!3\n");
        p = (char *)dbg_malloc(1);
        p[-1] = 0;
        dbg_free(p);

        printf("!4\n");
        p = (char *)dbg_malloc(1);
        p[1] = 0;
        dbg_free(p);

}

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