tool/abi_symbols: omit known internal symbols

This patch prevents the abi_symbols tool from generating symbols that
are known to occur in shared objects but must not be part of a library
ABI. This saves a bit of time during library-porting work.

However, to avoid the accidental use of ABI symbol definitions that lack
any form of manual curation, the abi_symbols tool outputs a special
message, which is explicitly checked-for by the check_abi tool.

Fixes #3112

tool/abi_symbols

@@ -21,6 +21,14 @@ set demangled [exec c++filt << $symbols]
 
 set demangled_lines [split $demangled "\n"]
 
+# obtail list of blacklisted symbols
+set fd [open "[file dirname $argv0]/internal_abi.list"]
+set symbol_blacklist [split [read $fd] "\n"]
+close $fd
+
+# add notice that the symbols file hasn't undergone any manual inspection
+puts "# Please review the symbols and remove this line."
+
 set i 0
 set output_lines {}
 foreach line [split $symbols "\n"] {
@@ -78,6 +86,12 @@ foreach line [split $symbols "\n"] {
 	if {[regexp {W|V} $type] && ($name != $demangled_name)} {
 		set keep 0 }
 
+	#
+	# Drop blacklisted symbols
+	#
+	foreach blacklisted_symbol $symbol_blacklist {
+		if {$name == $blacklisted_symbol} { set keep 0 } }
+
 	# write result
 	if {$keep} {
 

tool/check_abi

@@ -31,6 +31,16 @@ proc report_error { message } {
 }
 
 
+#
+# Warn about an ABI symbol definition that was generated by the 'abi_symbols'
+# tool but hasn't undergone any manual review. This is most likely an
+# accidental omission.
+#
+foreach line $abi_content {
+	if {$line == "# Please review the symbols and remove this line."} {
+		report_error "attempt to use unreviewed $abi_name ABI\n       at $abi_path" } }
+
+
 #
 # Extract symbol list w/o comments and empty lines, check for trailing spaces
 #
@@ -57,26 +67,12 @@ foreach line $abi_content {
 #
 # Check for absence of Genode-internal linking artifacts from ABI
 #
-
-#
-# The following symbols may appear in shared objects but should not by part
+# The listed symbols may appear in shared objects but should not by part
 # of any ABI.
 #
-set symbol_blacklist {
-	__bss_start
-	__eh_frame_start__
-	__exidx_end
-	__exidx_start
-	__l4sys_invoke_indirect
-	_ctors_end
-	_ctors_start
-	_edata
-	_end
-	_init
-	_parent_cap
-	_parent_cap_local_name
-	_parent_cap_thread_id
-}
+set fd [open "[file dirname $argv0]/internal_abi.list"]
+set symbol_blacklist [split [read $fd] "\n"]
+close $fd
 
 foreach line $abi_symbols {
 	set name [lindex $line 0]

tool/internal_abi.list

@@ -0,0 +1,13 @@
+__bss_start
+__eh_frame_start__
+__exidx_end
+__exidx_start
+__l4sys_invoke_indirect
+_ctors_end
+_ctors_start
+_edata
+_end
+_init
+_parent_cap
+_parent_cap_local_name
+_parent_cap_thread_id