1 /*
2  * Dwarf abbreviation parsing code.
3  *
4  * The convention here is that calling dwarfgetabbrevs relinquishes
5  * access to any abbrevs returned previously.  Will have to add
6  * explicit reference counting if this turns out not to be acceptable.
7  */
8 
9 #include <u.h>
10 #include <libc.h>
11 #include <bio.h>
12 #include "elf.h"
13 #include "dwarf.h"
14 
15 static int parseabbrevs(Dwarf*, ulong, DwarfAbbrev*, DwarfAttr*, int*, int*);
16 DwarfAbbrev *dwarfgetabbrev(Dwarf*, ulong, ulong);
17 
18 static int
19 loadabbrevs(Dwarf *d, ulong off, DwarfAbbrev **aa)
20 {
21 	int nattr, nabbrev;
22 	DwarfAbbrev *abbrev;
23 	DwarfAttr *attr;
24 
25 	if(d->acache.off == off && d->acache.na){
26 		*aa = d->acache.a;
27 		return d->acache.na;
28 	}
29 
30 	/* two passes - once to count, then allocate, then a second to copy */
31 	if(parseabbrevs(d, off, nil, nil, &nabbrev, &nattr) < 0)
32 		return -1;
33 
34 	abbrev = malloc(nabbrev*sizeof(DwarfAbbrev) + nattr*sizeof(DwarfAttr));
35 	attr = (DwarfAttr*)(abbrev+nabbrev);
36 
37 	if(parseabbrevs(d, off, abbrev, attr, nil, nil) < 0){
38 		free(abbrev);
39 		return -1;
40 	}
41 
42 	free(d->acache.a);
43 	d->acache.a = abbrev;
44 	d->acache.na = nabbrev;
45 	d->acache.off = off;
46 
47 	*aa = abbrev;
48 	return nabbrev;
49 }
50 
51 static int
52 parseabbrevs(Dwarf *d, ulong off, DwarfAbbrev *abbrev, DwarfAttr *attr, int *pnabbrev, int *pnattr)
53 {
54 	int i, nabbrev, nattr, haskids;
55 	ulong num, tag, name, form;
56 	DwarfBuf b;
57 
58 	if(off >= d->abbrev.len){
59 		werrstr("bad abbrev section offset 0x%lux >= 0x%lux\n", off, d->abbrev.len);
60 		return -1;
61 	}
62 
63 	memset(&b, 0, sizeof b);
64 	b.p = d->abbrev.data + off;
65 	b.ep = d->abbrev.data + d->abbrev.len;
66 
67 	nabbrev = 0;
68 	nattr = 0;
69 	for(;;){
70 		if(b.p == nil){
71 			werrstr("malformed abbrev data");
72 			return -1;
73 		}
74 		num = dwarfget128(&b);
75 		if(num == 0)
76 			break;
77 		tag = dwarfget128(&b);
78 		haskids = dwarfget1(&b);
79 		for(i=0;; i++){
80 			name = dwarfget128(&b);
81 			form = dwarfget128(&b);
82 			if(name == 0 && form == 0)
83 				break;
84 			if(attr){
85 				attr[i].name = name;
86 				attr[i].form = form;
87 			}
88 		}
89 		if(abbrev){
90 			abbrev->num = num;
91 			abbrev->tag = tag;
92 			abbrev->haskids = haskids;
93 			abbrev->attr = attr;
94 			abbrev->nattr = i;
95 			abbrev++;
96 			attr += i;
97 		}
98 		nabbrev++;
99 		nattr += i;
100 	}
101 	if(pnabbrev)
102 		*pnabbrev = nabbrev;
103 	if(pnattr)
104 		*pnattr = nattr;
105 	return 0;
106 }
107 
108 static DwarfAbbrev*
109 findabbrev(DwarfAbbrev *a, int na, ulong num)
110 {
111 	int i;
112 
113 	for(i=0; i<na; i++)
114 		if(a[i].num == num)
115 			return &a[i];
116 	werrstr("abbrev not found");
117 	return nil;
118 }
119 
120 DwarfAbbrev*
121 dwarfgetabbrev(Dwarf *d, ulong off, ulong num)
122 {
123 	DwarfAbbrev *a;
124 	int na;
125 
126 	if((na = loadabbrevs(d, off, &a)) < 0){
127 		werrstr("loadabbrevs: %r");
128 		return nil;
129 	}
130 	return findabbrev(a, na, num);
131 }