perf symbol: Look for ImageBase in PE file to compute .text offset

Instead of using the file offset in the debug file.

This fixes a regression from 00a3423 ("perf symbols: Make
dso__load_bfd_symbols() load PE files from debug cache only"), causing
incorrect symbol resolution when debug file have been stripped from
non-debug sections (in which case its .text section is empty and doesn't
have any file position).

The debug files could also be created with a different file alignment,
and have different file positions from the mmap-ed binary, or have the
section reordered.

This instead looks for the file image base, using the corresponding bfd
*ABS* symbols. As PE symbols only have 4 bytes, it also needs to keep
.text section vma high bits.

Signed-off-by: Remi Bernon <rbernon@codeweavers.com>
Fixes: 00a3423 ("perf symbols: Make dso__load_bfd_symbols() load PE files from debug cache only")
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Nicholas Fraser <nfraser@codeweavers.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210909192637.4139125-1-rbernon@codeweavers.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: rbernon

tools/perf/util/symbol.c

@@ -1581,10 +1581,6 @@ int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
 	if (bfd_get_flavour(abfd) == bfd_target_elf_flavour)
 		goto out_close;
 
-	section = bfd_get_section_by_name(abfd, ".text");
-	if (section)
-		dso->text_offset = section->vma - section->filepos;
-
 	symbols_size = bfd_get_symtab_upper_bound(abfd);
 	if (symbols_size == 0) {
 		bfd_close(abfd);
@@ -1602,6 +1598,22 @@ int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
 	if (symbols_count < 0)
 		goto out_free;
 
+	section = bfd_get_section_by_name(abfd, ".text");
+	if (section) {
+		for (i = 0; i < symbols_count; ++i) {
+			if (!strcmp(bfd_asymbol_name(symbols[i]), "__ImageBase") ||
+			    !strcmp(bfd_asymbol_name(symbols[i]), "__image_base__"))
+				break;
+		}
+		if (i < symbols_count) {
+			/* PE symbols can only have 4 bytes, so use .text high bits */
+			dso->text_offset = section->vma - (u32)section->vma;
+			dso->text_offset += (u32)bfd_asymbol_value(symbols[i]);
+		} else {
+			dso->text_offset = section->vma - section->filepos;
+		}
+	}
+
 	qsort(symbols, symbols_count, sizeof(asymbol *), bfd_symbols__cmpvalue);
 
 #ifdef bfd_get_section