[PATCH v2 5/5] symbols: prefer symbols which have a type

[Jan Beulich <jbeulich@suse.com>]

... and thus typically also a size. Using global vs local is undesirable
in certain situations, e.g. when a "real" symbol is local and at the
same address as a section start/end one (which are all global).

Note that for xen.efi the checking for "Function" is only forward-
looking at this point: The function-ness of symbols (much like their
size) is lost when linking PE/COFF binaries from ELF objects with GNU ld
up to at least 2.44.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
I didn't see much reason to also check for "Pointer" and "Array" or any
of the basic types. While nm reports pointers and arrays (but not the
basic types) for PE/COFF, making those up when linker input is ELF would
be impossible without further auxiliary (and non-standard) data in the
ELF symbol table. Transforming STT_FUNC, otoh, is in principle possible.

Implicit from the above: Until GNU ld properly transforms STT_FUNC,
symbol conflicts will be resolved differently for functions. Symbol
conflicts will always be resolved differently for data. xen.efi stack
traces may therefore be less informative than xen-syms ones.
---
v2: New.

--- a/xen/tools/symbols.c
+++ b/xen/tools/symbols.c
@@ -45,6 +45,7 @@ struct sym_entry {
 	unsigned int addr_idx;
 	unsigned int stream_offset;
 	unsigned char type;
+	bool typed;
 };
 #define SYMBOL_NAME(s) ((char *)(s)->sym + 1)
 
@@ -180,6 +181,9 @@ static int read_symbol(FILE *in, struct
 		s->type = stype; /* As s->sym[0] ends mangled. */
 	}
 	s->sym[0] = stype;
+	s->typed = strcmp(type, "FUNC") == 0 ||
+	           strcmp(type, "OBJECT") == 0 ||
+	           strcmp(type, "Function") == 0;
 	rc = 0;
 
  skip_tail:
@@ -613,6 +617,13 @@ static int compare_value(const void *p1,
 		return -1;
 	if (sym1->addr > sym2->addr)
 		return +1;
+
+	/* Prefer symbols which have a type. */
+	if (sym1->typed && !sym2->typed)
+		return -1;
+	if (sym2->typed && !sym1->typed)
+		return +1;
+
 	/* Prefer global symbols. */
 	if (isupper(*sym1->sym))
 		return -1;