kboot: Explicitly use host:/proc

When looking for the boot_params symbol we need to get the UEFI memory
map, use host: prefix. The short-circuit we have for this only works
when we have a filesystem. During the earliest parts of boot, we can
sometimes not have this yet, so making this explicit allows these
environments to function.

It's always in the host path. Print better
error messages, and add newlines in two palces.

Sponsored by:		Netflix

stand/kboot/libkboot/dfk.c

@@ -39,8 +39,13 @@
 #define ELF_TARG_DATA	ELFDATA2LSB
 #endif
 
+#ifndef _STANDALONE
 #define KCORE_PATH "/proc/kcore"
 #define KALLSYMS_PATH "/proc/kallsyms"
+#else
+#define KCORE_PATH "host:/proc/kcore"
+#define KALLSYMS_PATH "host:/proc/kallsyms"
+#endif
 
 struct elf_file
 {
@@ -135,8 +140,10 @@ symbol_addr(const char *symbol)
 	unsigned long addr;
 	char line[256];
 
-	if (!lb_init(&lb, KALLSYMS_PATH))
+	if (!lb_init(&lb, KALLSYMS_PATH)) {
+		printf("Cannot open symbol file %s\n", KALLSYMS_PATH);
 		return (0);
+	}
 	while (lb_1line(&lb, line, sizeof(line))) {
 		char *val, *name, *x, t;
 
@@ -259,11 +266,11 @@ data_from_kernel(const char *sym, void *buf, size_t len)
 
 	addr = symbol_addr(sym);
 	if (addr == 0) {
-		fprintf(stderr, "Can't find symbol %s", sym);
+		fprintf(stderr, "Can't find symbol %s\n", sym);
 		return (false);
 	}
 	if (!read_at_address(addr, buf, len)) {
-		fprintf(stderr, "Can't read from kernel");
+		fprintf(stderr, "Can't read from kernel\n");
 		return (false);
 	}
 	return (true);