dwarfget.c

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/*
 * Dwarf data format parsing routines.
 */

#include <precomp.h>

#define NDEBUG
#include <debug.h>

ulong
dwarfget1(DwarfBuf *b)
{
    if(b->p==nil || b->p+1 > b->ep){
        b->p = nil;
        return 0;
    }
    return *b->p++;
}

int
dwarfgetn(DwarfBuf *b, uchar *a, int n)
{
    if(b->p==nil || b->p+n > b->ep){
        b->p = nil;
        memset(a, 0, n);
        return -1;
    }
    memmove(a, b->p, n);
    b->p += n;
    return 0;
}

uchar*
dwarfgetnref(DwarfBuf *b, ulong n)
{
    uchar *p;

    if(b->p==nil || b->p+n > b->ep){
        b->p = nil;
        return nil;
    }
    p = b->p;
    b->p += n;
    return p;
}

char*
dwarfgetstring(DwarfBuf *b)
{
    char *s;

    if(b->p == nil)
        return nil;
    s = (char*)b->p;
    while(b->p < b->ep && *b->p)
        b->p++;
    if(b->p >= b->ep){
        b->p = nil;
        return nil;
    }
    b->p++;
    return s;
}

void
dwarfskip(DwarfBuf *b, int n)
{
    if(b->p==nil || b->p+n > b->ep)
        b->p = nil;
    else
        b->p += n;
}

ulong
dwarfget2(DwarfBuf *b)
{
    ulong v;

    if(b->p==nil || b->p+2 > b->ep){
        b->p = nil;
        return 0;
    }
    v = b->d->pe->e2(b->p);
    b->p += 2;
    return v;
}

ulong
dwarfget4(DwarfBuf *b)
{
    ulong v;

    if(b->p==nil || b->p+4 > b->ep){
        b->p = nil;
        return 0;
    }
    v = b->d->pe->e4(b->p);
    b->p += 4;
    return v;
}

uvlong
dwarfget8(DwarfBuf *b)
{
    uvlong v;

    if(b->p==nil || b->p+8 > b->ep){
        b->p = nil;
        return 0;
    }
    v = b->d->pe->e8(b->p);
    b->p += 8;
    return v;
}

ulong
dwarfgetaddr(DwarfBuf *b)
{
    static int nbad;

    if(b->addrsize == 0)
        b->addrsize = b->d->addrsize;

    switch(b->addrsize){
    case 1:
        return dwarfget1(b);
    case 2:
        return dwarfget2(b);
    case 4:
        return dwarfget4(b);
    case 8:
        return dwarfget8(b);
    default:
        if(++nbad == 1)
            werrstr("dwarf: unexpected address size %lud in dwarfgetaddr", b->addrsize);
        b->p = nil;
        return 0;
    }
}

int n1, n2, n3, n4, n5;

/* An inline function picks off the calls to dwarfget128 for 1-byte encodings,
 * more than by far the common case (99.999% on most binaries!). */
ulong
dwarfget128(DwarfBuf *b)
{
    static int nbad;
    ulong c, d;

    if(b->p == nil)
        return 0;
    c = *b->p++;
    if(!(c&0x80))
{n1++;
        return c;
}
    c &= ~0x80;
    d = *b->p++;
    c |= (d&0x7F)<<7;
    if(!(d&0x80))
{n2++;
        return c;
}
    d = *b->p++;
    c |= (d&0x7F)<<14;
    if(!(d&0x80))
{n3++;
        return c;
}
    d = *b->p++;
    c |= (d&0x7F)<<21;
    if(!(d&0x80))
{n4++;
        return c;
}
    d = *b->p++;
    c |= (d&0x7F)<<28;
    if(!(d&0x80))
{n5++;
        return c;
}
    while(b->p<b->ep && *b->p&0x80)
        b->p++;
    if(++nbad == 1)
        werrstr("dwarf: overflow during parsing of uleb128 integer");
    return c;
}

long
dwarfget128s(DwarfBuf *b)
{
    int nb, c;
    ulong v;
    static int nbad;

    v = 0;
    nb = 0;
    if(b->p==nil)
        return 0;
    while(b->p<b->ep){
        c = *b->p++;
        v |= (c & 0x7F)<<nb;
        nb += 7;
        if(!(c&0x80))
            break;
    }
    if(v&(1<<(nb-1)))
        v |= ~(((ulong)1<<nb)-1);
    if(nb > 8*sizeof(ulong)){
        if(0)
        if(++nbad == 1)
            werrstr("dwarf: overflow during parsing of sleb128 integer: got %d bits", nb);
    }
    return v;
}