scc

commit 099548f9e14488bce21d9f894637e9a2905c3efe
parent a960beadc92a005fd0c0b38c70d95c6e5e8b2976
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Fri, 17 Jan 2025 17:38:28 +0100

libmach: Add support for long section names

This is a common extension and it makes sense to apply the
same hack that is done for ent and aux entries.

Diffstat:
M
include/bits/scc/coff32/scnhdr.h
 | 
12
+++++++++++-
M
src/libmach/coff32/coff32getsec.c
 | 
11
++++++++++-
M
src/libmach/coff32/coff32read.c
 | 
5
+++++
M
src/libmach/coff32/coff32setsec.c
 | 
27
++++++++++++++++++++++++++-
M
src/libmach/coff32/coff32write.c
 | 
64
++++++++++++++++++++++++++++++++++++----------------------------

5 files changed, 88 insertions(+), 31 deletions(-)
diff --git a/include/bits/scc/coff32/scnhdr.h b/include/bits/scc/coff32/scnhdr.h
@@ -2,8 +2,18 @@
 
 #define SCNNMLEN 8
 
+#define s_name       _s._s_name
+#define s_zeroes     _s._s_s._s_zeroes
+#define s_offset     _s._s_s._s_offset
+
 struct scnhdr {
-	char s_name[SCNNMLEN];    /* section name */
+	union {
+		char _s_name[SCNNMLEN];    /* section name */
+		struct {
+			long _s_zeroes;        /* if _s_name[0-3] == 0 */
+			long _s_offset;        /* offset into string table */
+		} _s_s;
+	} _s;
 	long s_paddr;             /* physical address */
 	long s_vaddr;             /* virtual address */
 	long s_size;              /* section size */
diff --git a/src/libmach/coff32/coff32getsec.c b/src/libmach/coff32/coff32getsec.c
@@ -5,6 +5,15 @@
 #include "../libmach.h"
 #include "coff32.h"
 
+static char *
+secname(Coff32 *coff, SCNHDR *scn)
+{
+	if (scn->s_zeroes != 0)
+		return scn->s_name;
+
+	return &coff->strtbl[scn->s_offset];
+}
+
 Section *
 coff32getsec(Obj *obj, int *idx, Section *sec)
 {
@@ -79,7 +88,7 @@ coff32getsec(Obj *obj, int *idx, Section *sec)
 		break;
 	}
 
-	sec->name = scn->s_name;
+	sec->name = secname(coff, scn);
 	sec->index = n;
 	sec->size = scn->s_size;
 	sec->base = scn->s_vaddr;
diff --git a/src/libmach/coff32/coff32read.c b/src/libmach/coff32/coff32read.c
@@ -46,6 +46,7 @@ static void
 unpack_scn(int order, unsigned char *buf, SCNHDR *scn)
 {
 	int n;
+	char *s;
 
 	n = unpack(order,
 	          buf,
@@ -61,6 +62,10 @@ unpack_scn(int order, unsigned char *buf, SCNHDR *scn)
 	          &scn->s_nlnno,
 	          &scn->s_flags);
 	assert(n == SCNHSZ);
+
+	s = scn->s_name;
+	if (!s[0] && !s[1] && !s[2] && !s[3])
+		unpack(order, buf, "ll", &scn->s_zeroes, &scn->s_offset);
 }
 
 static void
diff --git a/src/libmach/coff32/coff32setsec.c b/src/libmach/coff32/coff32setsec.c
@@ -8,6 +8,29 @@
 #include "../libmach.h"
 #include "coff32.h"
 
+static char *
+secname(Coff32 *coff, SCNHDR *scn, Section *sec)
+{
+	char *p;
+	unsigned long siz = strlen(sec->name);
+
+	if (siz < SCNNMLEN)
+		return strncpy(scn->s_name, sec->name, SCNNMLEN);
+
+	if (coff->strsiz > ULONG_MAX - siz - 1)
+		return NULL;
+
+	siz += coff->strsiz + 1;
+	if ((p = realloc(coff->strtbl, siz)) == NULL)
+		return NULL;
+	coff->strtbl = p;
+
+	scn->s_zeroes = 0;
+	scn->s_offset = coff->strsiz;
+	coff->strsiz += siz;
+	return strcpy(&coff->strtbl[scn->s_offset], sec->name);
+}
+
 Section *
 coff32setsec(Obj *obj, int *idx, Section *sec)
 {
@@ -65,9 +88,11 @@ coff32setsec(Obj *obj, int *idx, Section *sec)
 		coff->scns = scn;
 		hdr->f_nscns = n + 1;
 	}
+
 	scn = &coff->scns[n];
+	if (!secname(coff, scn, sec))
+		return NULL;
 
-	strncpy(scn->s_name, sec->name, SCNNMLEN);
 	scn->s_paddr = 0;
 	scn->s_vaddr = sec->base;
 	scn->s_size = sec->size;
diff --git a/src/libmach/coff32/coff32write.c b/src/libmach/coff32/coff32write.c
@@ -38,10 +38,14 @@ pack_scn(int order, unsigned char *buf, SCNHDR *scn)
 {
 	int n;
 
+	if (scn->s_zeroes == 0)
+		pack(order, buf, "ll", scn->s_zeroes, scn->s_offset);
+	else
+		memcpy(buf, scn->s_name, 8);
+
 	n = pack(order,
-	         buf,
-	         "'8llllllssl",
-	         scn->s_name,
+	         buf + 8,
+	         "llllllssl",
 	         scn->s_paddr,
 	         scn->s_vaddr,
 	         scn->s_size,
@@ -51,6 +55,7 @@ pack_scn(int order, unsigned char *buf, SCNHDR *scn)
 	         scn->s_nrelloc,
 	         scn->s_nlnno,
 	         scn->s_flags);
+	n += 8;
 	assert(n == SCNHSZ);
 }
 
@@ -58,7 +63,6 @@ static void
 pack_ent(int order, unsigned char *buf, SYMENT *ent)
 {
 	int n;
-	char *s;
 
 	if (ent->n_zeroes == 0)
 		pack(order, buf, "ll", ent->n_zeroes, ent->n_offset);
@@ -66,7 +70,7 @@ pack_ent(int order, unsigned char *buf, SYMENT *ent)
 		memcpy(buf, ent->n_name, 8);
 
 	n = pack(order,
-	         buf,
+	         buf + 8,
 	         "lsscc",
 		     ent->n_value,
 		     ent->n_scnum,
@@ -224,28 +228,6 @@ writehdr(Obj *obj, FILE *fp)
 }
 
 static int
-writescns(Obj *obj, FILE *fp)
-{
-	int i;
-	SCNHDR *scn;
-	FILHDR *hdr;
-	struct coff32 *coff;
-	unsigned char buf[SCNHSZ];
-
-	coff  = obj->data;
-	hdr = &coff->hdr;
-
-	for (i = 0; i < hdr->f_nscns; i++) {
-		scn = &coff->scns[i];
-		pack_scn(ORDER(obj->type), buf, scn);
-		if (fwrite(buf, SCNHSZ, 1, fp) != 1)
-			return 0;
-	}
-
-	return 1;
-}
-
-static int
 allocstring(struct coff32 *coff, long off, struct strtbl *tbl)
 {
 	char *s, *name;
@@ -269,6 +251,32 @@ allocstring(struct coff32 *coff, long off, struct strtbl *tbl)
 }
 
 static int
+writescns(Obj *obj, FILE *fp, struct strtbl *tbl)
+{
+	int i;
+	SCNHDR *scn;
+	FILHDR *hdr;
+	struct coff32 *coff;
+	unsigned char buf[SCNHSZ];
+
+	coff  = obj->data;
+	hdr = &coff->hdr;
+
+	for (i = 0; i < hdr->f_nscns; i++) {
+		scn = &coff->scns[i];
+		if (scn->s_zeroes == 0) {
+			if (!allocstring(coff, scn->s_offset, tbl))
+				return 0;
+		}
+		pack_scn(ORDER(obj->type), buf, scn);
+		if (fwrite(buf, SCNHSZ, 1, fp) != 1)
+			return 0;
+	}
+
+	return 1;
+}
+
+static int
 writeents(Obj *obj, FILE *fp, struct strtbl *tbl)
 {
 	long i;
@@ -510,7 +518,7 @@ coff32write(Obj *obj, Map *map, FILE *fp)
 		goto err;
 	if (!writeaout(obj, fp))
 		goto err;
-	if (!writescns(obj, fp))
+	if (!writescns(obj, fp, &tbl))
 		goto err;
 	if (!writedata(obj, map, fp))
 		goto err;