[debug] Allow debug messages to be initially disabled at runtime

Extend the DEBUG=... syntax to allow debug messages to be compiled in
but disabled by default.  For example:

  make bin/undionly.kpxe DEBUG=netdevice:3:1

would compile in the messages as for DEBUG=netdevice:3, but would set
the debug level mask so that only the DEBUG=netdevice:1 messages would
be displayed.

This allows for external code to selectively enable the additional
debug messages at runtime, without being overwhelmed by unwanted
initial noise.  For example, a developer of a new protocol may want to
temporarily enable tracing of all packets received: this can be done
by building with DEBUG=netdevice:3:1 and using

  // temporarily enable per-packet messages
  DBG_ENABLE_OBJECT ( netdevice, DBGLVL_EXTRA );
  ...
  // disable per-packet messages
  DBG_DISABLE_OBJECT ( netdevice, DBGLVL_EXTRA );

Note that unlike the usual DBG_ENABLE() and DBG_DISABLE() macros,
DBG_ENABLE_OBJECT() and DBG_DISABLE_OBJECT() will not be removed via
dead code elimination if debugging is disabled in the specified
object.  In particular, this means that using either of these macros
will always result in a symbol reference to the specified object.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/Makefile.housekeeping b/src/Makefile.housekeeping
index ceff814102d70874c06d55640fdcf578662fcd5a..264b9d0f949020fda568119caf72b7babc00685e 100644 (file)
--- a/src/Makefile.housekeeping
+++ b/src/Makefile.housekeeping
@@ -523,19 +523,25 @@ POST_O            :=
 POST_O_DEPS    :=
 endif
 
+# Debug level calculations
+#
+DBGLVL_MAX     = -DDBGLVL_MAX=$(firstword $(subst ., ,$(1)))
+DBGLVL_DFLT    = -DDBGLVL_DFLT=$(lastword $(subst ., ,$(1)))
+DBGLVL         = $(call DBGLVL_MAX,$(1)) $(call DBGLVL_DFLT,$(1))
+
 # Rules for specific object types.
 #
 COMPILE_c      = $(CC) $(CFLAGS) $(CFLAGS_c) $(OBJ_CFLAGS)
 RULE_c         = $(Q)$(COMPILE_c) -c $< -o $@ $(POST_O)
 RULE_c_to_ids.o = $(Q)$(ECHO_E) '$(OBJ_IDS_ASM_NL)' | $(ASSEMBLE_S) -o $@
-RULE_c_to_dbg%.o = $(Q)$(COMPILE_c) -DDBGLVL_MAX=$* -c $< -o $@ $(POST_O)
+RULE_c_to_dbg%.o= $(Q)$(COMPILE_c) $(call DBGLVL,$*) -c $< -o $@ $(POST_O)
 RULE_c_to_c    = $(Q)$(COMPILE_c) -E -c $< > $@
 RULE_c_to_s    = $(Q)$(COMPILE_c) -S -g0 -c $< -o $@
 
 PREPROCESS_S   = $(CPP) $(CFLAGS) $(CFLAGS_S) $(OBJ_CFLAGS)
 ASSEMBLE_S     = $(AS) $(ASFLAGS)
 RULE_S         = $(Q)$(PREPROCESS_S) $< | $(ASSEMBLE_S) -o $@
-RULE_S_to_dbg%.o = $(Q)$(PREPROCESS_S) -DDBGLVL_MAX=$* $< | $(ASSEMBLE_S) -o $@
+RULE_S_to_dbg%.o= $(Q)$(PREPROCESS_S) $(call DBGLVL,$*) $< | $(ASSEMBLE_S) -o $@
 RULE_S_to_s    = $(Q)$(PREPROCESS_S) $< > $@
 
 GENERIC_TARGETS        += ids.o dbg%.o c s
@@ -1019,10 +1025,12 @@ TGT_LD_FLAGS    = $(foreach SYM,$(TGT_LD_ENTRY) $(TGT_LD_DRIVERS) \
 # the target.
 #
 DEBUG_LIST     = $(subst $(COMMA), ,$(DEBUG))
-DEBUG_OBJ_LEVEL        = $(firstword $(word 2,$(subst :, ,$(1))) 1)
-DEBUG_OBJ_BASE = $(word 1,$(subst :, ,$(1))).dbg$(call DEBUG_OBJ_LEVEL,$(1))
-DEBUG_OBJ      = $(BIN)/$(call DEBUG_OBJ_BASE,$(1)).o
-DEBUG_ORIG_OBJ = $(BIN)/$(word 1,$(subst :, ,$(1))).o
+DEBUG_MAX      = $(firstword $(word 2,$(subst :, ,$(1))) 1)
+DEBUG_DFLT     = $(if $(word 3,$(subst :, ,$(1))),.$(word 3,$(subst :, ,$(1))))
+DEBUG_LEVEL    = $(call DEBUG_MAX,$(1))$(call DEBUG_DFLT,$(1))
+DEBUG_BASE     = $(firstword $(subst :, ,$(1))).dbg$(call DEBUG_LEVEL,$(1))
+DEBUG_OBJ      = $(BIN)/$(call DEBUG_BASE,$(1)).o
+DEBUG_ORIG_OBJ = $(BIN)/$(firstword $(subst :, ,$(1))).o
 DEBUG_OBJS     = $(foreach D,$(DEBUG_LIST),$(call DEBUG_OBJ,$(D)))
 DEBUG_ORIG_OBJS        = $(foreach D,$(DEBUG_LIST),$(call DEBUG_ORIG_OBJ,$(D)))
 BLIB_OBJS      = $(DEBUG_OBJS) $(filter-out $(DEBUG_ORIG_OBJS),$(BOBJS))

diff --git a/src/include/compiler.h b/src/include/compiler.h
index eae62c518c5f4f7001fca05a02919ea2c167d76f..4924c7ef51645dd51d4bda3faa4ff27a1a91734d 100644 (file)
--- a/src/include/compiler.h
+++ b/src/include/compiler.h
@@ -270,6 +270,10 @@ PROVIDE_SYMBOL ( OBJECT_SYMBOL );
 #define DBGLVL_MAX 0
 #endif
 
+#ifndef DBGLVL_DFLT
+#define DBGLVL_DFLT DBGLVL_MAX
+#endif
+
 #ifndef ASSEMBLY
 
 /** printf() for debugging */
@@ -286,7 +290,7 @@ extern void dbg_more ( void );
 
 /* Allow for selective disabling of enabled debug levels */
 #define __debug_disable( object ) _C2 ( __debug_disable_, object )
-char __debug_disable(OBJECT);
+char __debug_disable(OBJECT) = ( DBGLVL_MAX & ~DBGLVL_DFLT );
 #define DBG_DISABLE_OBJECT( object, level ) do {               \
        extern char __debug_disable(object);                    \
        __debug_disable(object) |= (level);                     \