PATH: use a linked list internallysyslinux-5.11-pre1

In retrospect, choosing the colon character as the entry separator for
the PATH directive was not a smart move, as that character is also used
in TFTP-style paths. This conflict manifests as PXELINUX being unable to
find and load files.

An example dnsmasq log looks like,

dnsmasq-tftp: sent /arch/boot/syslinux/lpxelinux.0 to 192.168.0.90
dnsmasq-tftp: file /arch/ldlinux.c32 not found
dnsmasq-tftp: file /arch//ldlinux.c32 not found
dnsmasq-tftp: file /arch//boot/isolinux/ldlinux.c32 not found
dnsmasq-tftp: file /arch//isolinux/ldlinux.c32 not found
dnsmasq-tftp: file /arch//boot/syslinuxldlinux.c32 not found
dnsmasq-tftp: sent /arch//boot/syslinux/ldlinux.c32 to 192.168.0.90
dnsmasq-tftp: error 0 No error, file close received from 192.168.0.90
dnsmasq-tftp: failed sending /arch//boot/syslinux/ldlinux.c32 to 192.168.0.90
dnsmasq-tftp: sent /arch/boot/syslinux/archiso.cfg to 192.168.0.90
dnsmasq-tftp: sent /arch/boot/syslinux/whichsys.c32 to 192.168.0.90
dnsmasq-tftp: file /arch/libcom32.c32 not found
dnsmasq-tftp: file /arch//libcom32.c32 not found
dnsmasq-tftp: file /arch/libcom32.c32 not found
dnsmasq-tftp: file /arch//arch//boot/syslinux/libcom32.c32 not found

The last line of the log is the indication that there's a problem.
Internally, Syslinux adds the location of ldlinux.c32 to PATH by
querying the current working directory once ldlinux.c32 is successfully
loaded. Under PXELINUX that means the initial PATH string will be,

   "::/arch/boot/syslinux/"

The PATH parsing code doesn't know how to correctly parse the "::"
string and hence, the file is searched for relative to the 210 dhcp
option directory - /arch/.

Implement PATH with a linked list which *greatly* simplifies the path
code, and means we no longer have to parse strings backwards and
forwards.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 12 insertions, 24 deletions

diff --git a/com32/lib/sys/module/common.c b/com32/lib/sys/module/common.c
index 8547036b..b763704e 100644
--- a/com32/lib/sys/module/common.c
+++ b/com32/lib/sys/module/common.c
@@ -59,40 +59,28 @@ void print_elf_symbols(struct elf_module *module) {
 
 FILE *findpath(char *name)
 {
+	struct path_entry *entry;
 	char path[FILENAME_MAX];
 	FILE *f;
-	char *p, *n;
-	int i;
 
 	f = fopen(name, "rb"); /* for full path */
 	if (f)
 		return f;
 
-	p = PATH;
-again:
-	i = 0;
-	while (*p && *p != ':' && i < FILENAME_MAX - 1) {
-		path[i++] = *p++;
-	}
-
-	if (*p == ':')
-		p++;
+	list_for_each_entry(entry, &PATH, list) {
+		bool slash = false;
 
-	/* Ensure we have a '/' separator */
-	if (path[i] != '/' && i < FILENAME_MAX - 1)
-		path[i++] = '/';
+		/* Ensure we have a '/' separator */
+		if (entry->str[strlen(entry->str) - 1] != '/')
+			slash = true;
 
-	n = name;
-	while (*n && i < FILENAME_MAX - 1)
-		path[i++] = *n++;
-	path[i] = '\0';
+		snprintf(path, sizeof(path), "%s%s%s",
+			 entry->str, slash ? "/" : "", name);
 
-	f = fopen(path, "rb");
-	if (f)
-		return f;
-
-	if (p >= PATH && p < PATH + strlen(PATH))
-		goto again;
+		f = fopen(path, "rb");
+		if (f)
+			return f;
+	}
 
 	return NULL;
 }