core/utils: add snprintf_symbol

get_symbol is difficult to use. Add snprintf_symbol helper which
prints a symbol into a buffer with length, and returns the number
of bytes used, similarly to snprintf. Use this in the stack dumping
code rather than open-coding it.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

core/stack.c

@@ -59,8 +59,7 @@ void __print_backtrace(unsigned int pir,
 	static char bt_text_buf[4096];
 	int i, l = 0, max;
 	char *buf = out_buf;
-	unsigned long bottom, top, tbot, ttop, saddr = 0;
-	char *sym = NULL, *sym_end = NULL;
+	unsigned long bottom, top, tbot, ttop;
 	char mark;
 
 	if (!out_buf) {
@@ -82,20 +81,12 @@ void __print_backtrace(unsigned int pir,
 			mark = '*';
 		else
 			mark = ' ';
-		if (symbols)
-			saddr = get_symbol(entries->pc, &sym, &sym_end);
-		else
-			saddr = 0;
 		l += snprintf(buf + l, max - l,
 			      " S: %016lx R: %016lx %c ",
 			      entries->sp, entries->pc, mark);
-		while(saddr && sym < sym_end && l < max)
-			buf[l++] = *(sym++);
-		if (sym && l < max)
-			l += snprintf(buf + l, max - l, "+0x%lx\n",
-				      entries->pc - saddr);
-		else
-			l += snprintf(buf + l, max - l, "\n");
+		if (symbols)
+			l += snprintf_symbol(buf + l, max - l, entries->pc);
+		l += snprintf(buf + l, max - l, "\n");
 		entries++;
 	}
 	if (!out_buf)

core/utils.c

@@ -61,7 +61,7 @@ char __attrconst tohex(uint8_t nibble)
 	return __tohex[nibble];
 }
 
-unsigned long get_symbol(unsigned long addr, char **sym, char **sym_end)
+static unsigned long get_symbol(unsigned long addr, char **sym, char **sym_end)
 {
 	unsigned long prev = 0, next;
 	char *psym = NULL, *p = __sym_map_start;
@@ -88,3 +88,27 @@ unsigned long get_symbol(unsigned long addr, char **sym, char **sym_end)
 	return 0;
 }
 
+size_t snprintf_symbol(char *buf, size_t len, uint64_t addr)
+{
+	unsigned long saddr;
+	char *sym, *sym_end;
+	size_t l;
+
+	saddr = get_symbol(addr, &sym, &sym_end);
+	if (!saddr)
+		return 0;
+
+	if (len > sym_end - sym)
+		l = sym_end - sym;
+	else
+		l = len - 1;
+	memcpy(buf, sym, l);
+
+	/*
+	 * This snprintf will insert the terminating NUL even if the
+	 * symbol has used up the entire buffer less 1.
+	 */
+	l += snprintf(buf + l, len - l, "+0x%llx", addr - saddr);
+
+	return l;
+}

include/skiboot.h

@@ -204,8 +204,7 @@ extern const char version[];
 /* Debug support */
 extern char __sym_map_start[];
 extern char __sym_map_end[];
-extern unsigned long get_symbol(unsigned long addr,
-				char **sym, char **sym_end);
+extern size_t snprintf_symbol(char *buf, size_t len, uint64_t addr);
 
 /* Direct controls */
 extern void direct_controls_init(void);