Add symbolic backtraces and expose skiboot map to Linux

We use a double link technique, doing a first pass with a .o containing
a dummy symbol map, then re-linking with a new .o

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

12 files changed, 113 insertions, 32 deletions

diff --git a/Makefile.main b/Makefile.main
index aff145e8..129d38b0 100644
--- a/Makefile.main
+++ b/Makefile.main
@@ -119,14 +119,19 @@ OBJS += $(LIBPORE)
 endif
 OBJS += $(LIBC) $(CCAN) $(DEVSRC_OBJ) gitid.o
 
+OBJS_1 = $(OBJS) asm/dummy_map.o
+OBJS_2 = $(OBJS) asm/real_map.o
+
 $(TARGET).lid: $(TARGET).elf
 	$(call Q,OBJCOPY, $(OBJCOPY) -O binary -S $^ $@, $@)
 
-$(TARGET).elf: $(OBJS) $(TARGET).lds $(KERNEL)
-	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(OBJS) -o $@, $@)
+$(TARGET).tmp.elf: $(OBJS_1) $(TARGET).lds $(KERNEL)
+	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(OBJS_1) -o $@, $@)
+
+asm/real_map.o : $(TARGET).tmp.map
 
-$(TARGET).map: $(TARGET).elf
-	$(call Q,NM, $(NM) -n $< | grep -v '\( [aNUw] \)\|\(__crc_\)\|\( \$[adt]\)' > $@, $@)
+$(TARGET).elf: $(OBJS_2) $(TARGET).lds $(KERNEL)
+	$(call Q,LD, $(CC) $(LDFLAGS) -T $(TARGET).lds $(OBJS_2) -o $@, $@)
 
 $(SUBDIRS):
 	$(call Q,MKDIR,mkdir $@, $@)
@@ -165,7 +170,7 @@ cscope:
 
 clean:
 	$(RM) *.[odsa] $(SUBDIRS:%=%/*.[odsa])
-	$(RM) $(TARGET).elf $(TARGET).lid $(TARGET).map $(TARGET).lds
+	$(RM) *.elf $(TARGET).lid *.map $(TARGET).lds
 	$(RM) include/asm-offsets.h gitid.c
 
 distclean: clean
diff --git a/Makefile.rules b/Makefile.rules
index 200abcb4..3014c819 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -51,3 +51,6 @@ endef
 
 %.lds : %.lds.S
 	$(call Q,CC, $(CC) $(CPPFLAGS) -P -E $< -o $@, $@)
+
+%.map: %.elf
+	$(call Q,NM, $(NM) -n $< | grep -v '\( [aNUw] \)\|\(__crc_\)\|\( \$[adt]\)' > $@, $@)
diff --git a/asm/dummy_map.S b/asm/dummy_map.S
new file mode 100644
index 00000000..19a8d621
--- /dev/null
+++ b/asm/dummy_map.S
@@ -0,0 +1,3 @@
+	.section ".sym_map","a"
+	.byte	0
+
diff --git a/asm/real_map.S b/asm/real_map.S
new file mode 100644
index 00000000..fbbf2ccf
--- /dev/null
+++ b/asm/real_map.S
@@ -0,0 +1,20 @@
+/* Copyright 2013-2014 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * 	http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+ * implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+	.section ".sym_map","a"
+	.incbin "skiboot.tmp.map"
+ 
diff --git a/core/opal.c b/core/opal.c
index 7e534864..345d6193 100644
--- a/core/opal.c
+++ b/core/opal.c
@@ -119,6 +119,8 @@ static void add_opal_firmware_node(void)
 	dt_add_property_string(firmware, "compatible", "ibm,opal-firmware");
 	dt_add_property_string(firmware, "name", "firmware");
 	dt_add_property_string(firmware, "git-id", gitid);
+	dt_add_property(firmware, "symbol-map", __sym_map_start,
+			__sym_map_end - __sym_map_start);
 }
 
 void add_opal_node(void)
diff --git a/core/stack.c b/core/stack.c
index 15c6e54b..1341175f 100644
--- a/core/stack.c
+++ b/core/stack.c
@@ -20,8 +20,9 @@
 #include <cpu.h>
 #include <stack.h>
 #include <mem_region.h>
+#include <unistd.h>
 
-#define STACK_BUF_ENTRIES	20
+#define STACK_BUF_ENTRIES	60
 static struct bt_entry bt_buf[STACK_BUF_ENTRIES];
 
 extern uint32_t _stext, _etext;
@@ -47,27 +48,27 @@ void __nomcount __backtrace(struct bt_entry *entries, unsigned int *count)
 
 void __print_backtrace(unsigned int pir,
 		       struct bt_entry *entries, unsigned int count,
-		       char *out_buf, unsigned int *len)
+		       char *out_buf, unsigned int *len, bool symbols)
 {
+	static char bt_text_buf[4096];
 	int i, l = 0, max;
 	char *buf = out_buf;
-	unsigned long bottom, top, tbot, ttop;
+	unsigned long bottom, top, tbot, ttop, saddr = 0;
+	char *sym = NULL, *sym_end = NULL;
 	char mark;
 
-	if (len)
+	if (!out_buf) {
+		buf = bt_text_buf;
+		max = sizeof(bt_text_buf) - 16;
+	} else
 		max = *len - 1;
-	else
-		max = INT_MAX;
 
 	bottom = cpu_stack_bottom(pir);
 	top = cpu_stack_top(pir);
-	tbot = (unsigned long)&_stext;
+	tbot = SKIBOOT_BASE;
 	ttop = (unsigned long)&_etext;
 
-	if (buf)
-		l += snprintf(buf, max, "CPU %04x Backtrace:\n", pir);
-	else
-		l += printf("CPU %04x Backtrace:\n", pir);
+	l += snprintf(buf, max, "CPU %04x Backtrace:\n", pir);
 	for (i = 0; i < count && l < max; i++) {
 		if (entries->sp < bottom || entries->sp > top)
 			mark = '!';
@@ -75,19 +76,23 @@ void __print_backtrace(unsigned int pir,
 			mark = '*';
 		else
 			mark = ' ';
-		if (buf)
-			l += snprintf(buf + l, max - l,
-				      " S: %016lx R: %016lx %c\n",
-				      entries->sp, entries->pc, mark);
+		if (symbols)
+			saddr = get_symbol(entries->pc, &sym, &sym_end);
+		l += snprintf(buf + l, max - l,
+			      " S: %016lx R: %016lx %c ",
+			      entries->sp, entries->pc, mark);
+		while(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 += printf(" S: %016lx R: %016lx %c\n",
-				    entries->sp, entries->pc, mark);
+			l += snprintf(buf + l, max - l, "\n");
 		entries++;
 	}
-	if (buf)
-		buf[l++] = 0;
-	else
-		l++;
+	if (!out_buf)
+		write(stdout->fd, bt_text_buf, l);
+	buf[l++] = 0;
 	if (len)
 		*len = l;
 }
@@ -97,7 +102,7 @@ void backtrace(void)
 	unsigned int ents = STACK_BUF_ENTRIES;
 
 	__backtrace(bt_buf, &ents);
-	__print_backtrace(mfspr(SPR_PIR), bt_buf, ents, NULL, NULL);
+	__print_backtrace(mfspr(SPR_PIR), bt_buf, ents, NULL, NULL, true);
 }
 
 void __noreturn __nomcount __stack_chk_fail(void);
@@ -189,7 +194,7 @@ void check_stacks(void)
 		      lowest->pir, lowest->stack_bot_mark, lowest->stack_bot_pc,
 		      lowest->stack_bot_tok);
 		__print_backtrace(lowest->pir, lowest->stack_bot_bt,
-				  lowest->stack_bot_bt_count, NULL, NULL);
+				  lowest->stack_bot_bt_count, NULL, NULL, true);
 		unlock(&stack_check_lock);
 	}
 
diff --git a/core/utils.c b/core/utils.c
index 63046fcd..1a81ae2c 100644
--- a/core/utils.c
+++ b/core/utils.c
@@ -68,3 +68,30 @@ char __attrconst tohex(uint8_t nibble)
 	return __tohex[nibble];
 }
 
+unsigned long get_symbol(unsigned long addr, char **sym, char **sym_end)
+{
+	unsigned long prev = 0, next;
+	char *psym = NULL, *p = __sym_map_start;
+
+	*sym = *sym_end = NULL;
+	while(p < __sym_map_end) {
+		next = strtoul(p, &p, 16) | SKIBOOT_BASE;
+		if (next > addr && prev <= addr) {
+			p = psym + 3;;
+			if (p >= __sym_map_end)
+				return 0;
+			*sym = p;
+			while(p < __sym_map_end && *p != 10)
+				p++;
+			*sym_end = p;
+			return prev;
+		}
+		prev = next;
+		psym = p;
+		while(p < __sym_map_end && *p != 10)
+			p++;
+		p++;
+	}
+	return 0;
+}
+
diff --git a/hw/fsp/fsp-attn.c b/hw/fsp/fsp-attn.c
index 036962cd..02603a1b 100644
--- a/hw/fsp/fsp-attn.c
+++ b/hw/fsp/fsp-attn.c
@@ -109,7 +109,7 @@ void update_sp_attn_area(const char *msg)
 	__backtrace(bt_buf, &ent_cnt);
 	len = BT_FRAME_LEN;
 	__print_backtrace(mfspr(SPR_PIR), bt_buf, ent_cnt,
-			  ti_attn->msg.bt_buf, &len);
+			  ti_attn->msg.bt_buf, &len, false);
 	snprintf(ti_attn->msg.file_info, FILE_INFO_LEN, "%s", msg);
 
 	ti_attn->msg_len = GITID_LEN + BT_FRAME_LEN +
diff --git a/include/cpu.h b/include/cpu.h
index d7acd259..a8710737 100644
--- a/include/cpu.h
+++ b/include/cpu.h
@@ -65,7 +65,7 @@ struct cpu_thread {
 	int64_t				stack_bot_mark;
 	uint64_t			stack_bot_pc;
 	uint64_t			stack_bot_tok;
-#define CPU_BACKTRACE_SIZE	20
+#define CPU_BACKTRACE_SIZE	60
 	struct bt_entry			stack_bot_bt[CPU_BACKTRACE_SIZE];
 	unsigned int			stack_bot_bt_count;
 #endif
diff --git a/include/skiboot.h b/include/skiboot.h
index 8750c70a..79aece69 100644
--- a/include/skiboot.h
+++ b/include/skiboot.h
@@ -171,6 +171,12 @@ extern struct dt_node *dt_root;
 /* Generated git id. */
 extern const char gitid[];
 
+/* 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);
+
 /* Fast reboot support */
 extern void fast_reset(void);
 extern void __secondary_cpu_entry(void);
diff --git a/include/stack.h b/include/stack.h
index d6a06096..02f1fe6e 100644
--- a/include/stack.h
+++ b/include/stack.h
@@ -114,7 +114,7 @@ extern void __backtrace(struct bt_entry *entries, unsigned int *count);
 /* Convert a backtrace to ASCII */
 extern void __print_backtrace(unsigned int pir, struct bt_entry *entries,
 			      unsigned int count, char *out_buf,
-			      unsigned int *len);
+			      unsigned int *len, bool symbols);
 
 /* For use by debug code, create and print backtrace, uses a static buffer */
 extern void backtrace(void);
diff --git a/skiboot.lds.S b/skiboot.lds.S
index 4e905f87..a54ff5f0 100644
--- a/skiboot.lds.S
+++ b/skiboot.lds.S
@@ -125,7 +125,17 @@ SECTIONS
 	.dynsym : { *(.dynsym) }
 	.dynstr : { *(.dynstr) }
 
-	. = ALIGN(0x1000);
+	. = ALIGN(0x10);
+	.sym_map : {
+		__sym_map_start = . ;
+		KEEP(*(.sym_map))
+		__sym_map_end = . ;
+		KEEP(*(.sym_map))
+	}
+
+	/* We locate the BSS at 1M to leave room for the symbol map */
+	. = 0x100000;
+
 	_sbss = .;
 	.bss : {
 		*(.bss*)