libmach

1 files changed, 129 insertions, 0 deletions

diff --git a/src/libmach/dwarfabbrev.c b/src/libmach/dwarfabbrev.c
new file mode 100644
index 00000000..2db418dd
--- /dev/null
+++ b/src/libmach/dwarfabbrev.c
@@ -0,0 +1,129 @@
+/*
+ * Dwarf abbreviation parsing code.
+ *
+ * The convention here is that calling dwarfgetabbrevs relinquishes
+ * access to any abbrevs returned previously.  Will have to add 
+ * explicit reference counting if this turns out not to be acceptable.
+ */
+
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include "elf.h"
+#include "dwarf.h"
+
+static int parseabbrevs(Dwarf*, ulong, DwarfAbbrev*, DwarfAttr*, int*, int*);
+DwarfAbbrev *dwarfgetabbrev(Dwarf*, ulong, ulong);
+
+static int
+loadabbrevs(Dwarf *d, ulong off, DwarfAbbrev **aa)
+{
+	int nattr, nabbrev;
+	DwarfAbbrev *abbrev;
+	DwarfAttr *attr;
+
+	if(d->acache.off == off && d->acache.na){
+		*aa = d->acache.a;
+		return d->acache.na;
+	}
+
+	/* two passes - once to count, then allocate, then a second to copy */
+	if(parseabbrevs(d, off, nil, nil, &nabbrev, &nattr) < 0)
+		return -1;
+
+	abbrev = malloc(nabbrev*sizeof(DwarfAbbrev) + nattr*sizeof(DwarfAttr));
+	attr = (DwarfAttr*)(abbrev+nabbrev);
+
+	if(parseabbrevs(d, off, abbrev, attr, nil, nil) < 0){
+		free(abbrev);
+		return -1;
+	}
+
+	free(d->acache.a);
+	d->acache.a = abbrev;
+	d->acache.na = nabbrev;
+	d->acache.off = off;
+
+	*aa = abbrev;
+	return nabbrev;
+}
+
+static int
+parseabbrevs(Dwarf *d, ulong off, DwarfAbbrev *abbrev, DwarfAttr *attr, int *pnabbrev, int *pnattr)
+{
+	int i, nabbrev, nattr, haskids;
+	ulong num, tag, name, form;
+	DwarfBuf b;
+
+	if(off >= d->abbrev.len){
+		werrstr("bad abbrev section offset 0x%lux >= 0x%lux\n", off, d->abbrev.len);
+		return -1;
+	}
+
+	memset(&b, 0, sizeof b);
+	b.p = d->abbrev.data + off;
+	b.ep = d->abbrev.data + d->abbrev.len;
+
+	nabbrev = 0;
+	nattr = 0;
+	for(;;){
+		if(b.p == nil){
+			werrstr("malformed abbrev data");
+			return -1;
+		}
+		num = dwarfget128(&b);
+		if(num == 0)
+			break;
+		tag = dwarfget128(&b);
+		haskids = dwarfget1(&b);
+		for(i=0;; i++){
+			name = dwarfget128(&b);
+			form = dwarfget128(&b);
+			if(name == 0 && form == 0)
+				break;
+			if(attr){
+				attr[i].name = name;
+				attr[i].form = form;
+			}
+		}
+		if(abbrev){
+			abbrev->num = num;
+			abbrev->tag = tag;
+			abbrev->haskids = haskids;
+			abbrev->attr = attr;
+			abbrev->nattr = i;
+			abbrev++;
+			attr += i;
+		}
+		nabbrev++;
+		nattr += i;
+	}
+	if(pnabbrev)
+		*pnabbrev = nabbrev;
+	if(pnattr)
+		*pnattr = nattr;
+	return 0;
+}
+
+static DwarfAbbrev*
+findabbrev(DwarfAbbrev *a, int na, ulong num)
+{
+	int i;
+
+	for(i=0; i<na; i++)
+		if(a[i].num == num)
+			return &a[i];
+	return nil;
+}
+
+DwarfAbbrev*
+dwarfgetabbrev(Dwarf *d, ulong off, ulong num)
+{
+	DwarfAbbrev *a;
+	int na;
+
+	if((na = loadabbrevs(d, off, &a)) < 0)
+		return nil;
+	return findabbrev(a, na, num);
+}
+