[coreboot-gerrit] New patch to review for coreboot: 01d8971 Poor man's ftrace from akaros

[Ronald G. Minnich (rminnich@gmail.com)]

Ronald G. Minnich (rminnich at gmail.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/7116

-gerrit

commit 01d897167dca04113c64110e56b0df1a31f98f26
Author: Ronald G. Minnich <rminnich at gmail.com>
Date:   Sat Oct 18 06:09:24 2014 +0000

    Poor man's ftrace from akaros
    
    This is the
    poor man's ftrace from Akaros
    (just search for that term)
    
    To use:
    suppose you want to trace all file entry and exit in some piece of code, e.g.
    cbfs.
    
    Just:
    spatch --in-place --sp-file scripts/spatch/poor-ftrace.coci src/lib/cbfs*.c
    Build as usual.
    
    When you run, you'll see function calls, and they will be spaced in
    according to their call depth, e.g.:
    a
    	b
    		c
    	b
    		d
    	b
    a
    
    It's incredibly useful for debugging. We have been able to very quickly zero in on
    bugs in Akaros with this code. I print at BIOS_EMERG so you're sure
    to take it out when done (just git checkout the files you're tracing or
    reverse the spatch.)
    
    For example, on riscv, I know it's dying, I don't know where.
    
    spatch --sp-file util/spatch/poor-ftrace.cocci src/arch/riscv/*.c src/lib/cbfs.c
    
    I get this:
    
    Find fallback
    cbfs_load_stage() in src/lib/cbfs.c
    	init_default_cbfs_media() in src/arch/riscv/rom_media.c
    	---- init_default_cbfs_media()
    	init_rom_media_cbfs() in src/arch/riscv/rom_media.c
    
    And I know where to start.
    
    You do need spatch installed.
    
    Change-Id: I69c3c20d30ebd666c0e859cea906a3fd5a094441
    Signed-off-by: Ronald G. Minnich <rminnich at gmail.com>
---
 src/console/printk.c          | 24 ++++++++++++++++++++++++
 src/include/console/console.h |  6 ++++++
 util/spatch/poor-ftrace.cocci | 18 ++++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/src/console/printk.c b/src/console/printk.c
index b6777e1..edfeb60 100644
--- a/src/console/printk.c
+++ b/src/console/printk.c
@@ -12,6 +12,7 @@
 #include <smp/node.h>
 #include <stddef.h>
 #include <trace.h>
+#include <stdlib.h>
 
 DECLARE_SPIN_LOCK(console_lock)
 
@@ -62,3 +63,26 @@ void do_vtxprintf(const char *fmt, va_list args)
 	console_tx_flush();
 }
 #endif /* CONFIG_CHROMEOS */
+
+int tab_depth = 0;
+
+void __print_func_entry(const char *func, const char *file)
+{
+	char tentabs[] = "\t\t\t\t\t\t\t\t\t\t"; // ten tabs and a \0
+	char *ourtabs = &tentabs[10 - MIN(tab_depth, 10)];
+	printk(BIOS_EMERG, "%s%s() in %s\n", ourtabs, func, file);
+	tab_depth++;
+}
+/* for tracing. You can call these on func entry and exit.
+ * Or, better, you can use the spatch in utils to add
+ * such tracing.
+ */
+void __print_func_exit(const char *func, const char *file)
+{
+	char tentabs[] = "\t\t\t\t\t\t\t\t\t\t"; // ten tabs and a \0
+	char *ourtabs;
+	tab_depth--;
+	ourtabs = &tentabs[10 - MIN(tab_depth, 10)];
+	printk(BIOS_EMERG, "%s---- %s()\n", ourtabs, func);
+}
+
diff --git a/src/include/console/console.h b/src/include/console/console.h
index 9e98bfc..d5ec2f3 100644
--- a/src/include/console/console.h
+++ b/src/include/console/console.h
@@ -75,6 +75,12 @@ static inline void do_vtxprintf(const char *fmt, va_list args) {};
  */
 #include <console/early_print.h>
 
+/* for the poor man's ftrace. */
+void __print_func_entry(const char *func, const char *file);
+void __print_func_exit(const char *func, const char *file);
+#define print_func_entry() __print_func_entry(__FUNCTION__, __FILE__)
+#define print_func_exit() __print_func_exit(__FUNCTION__, __FILE__)
+
 #else /* __ROMCC__ */
 
 #include "arch/x86/lib/romcc_console.c"
diff --git a/util/spatch/poor-ftrace.cocci b/util/spatch/poor-ftrace.cocci
new file mode 100644
index 0000000..3754374
--- /dev/null
+++ b/util/spatch/poor-ftrace.cocci
@@ -0,0 +1,18 @@
+// prints entry/exit when entering/leaving a function
+
+// for example, spatch with:
+// $ for i in kern/src/ns/ kern/src/net kern/drivers/; do \
+//       spatch --sp-file scripts/spatch/poor-ftrace.cocci  --in-place $i; done
+// if you have functions you want to ignore, add them to the blacklist in
+// kern/src/kdebug.c
+@@
+type t;
+function f;
+@@
+t f(...) {
++print_func_entry();
+<...
++print_func_exit();
+return ...;
+...>
+}