From 7c57da24403033322792c810baff9ab564c97c26 Mon Sep 17 00:00:00 2001
From: Christian Hergert <chergert@redhat.com>
Date: Mon, 8 May 2023 14:25:27 -0700
Subject: [PATCH] libsysprof-analyze: add build-id to SysprofDocumentMmap

In anticipation of getting PERF_EVENT_MMAP2 events, assume we tack on the
build-id in hex after the filename like "filename\0@build-id\0" so that we
can use it when decoding frames. That will allow us to avoid doing inode
checks (which breaks when moving files between computers anyway) as well
as potentially supporting debuginfod in the future via build-id.
---
 .../sysprof-document-mmap.c                   | 41 ++++++++++++++++++-
 .../sysprof-document-mmap.h                   |  2 +
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/src/libsysprof-analyze/sysprof-document-mmap.c b/src/libsysprof-analyze/sysprof-document-mmap.c
index c5a2f85c..50bc5351 100644
--- a/src/libsysprof-analyze/sysprof-document-mmap.c
+++ b/src/libsysprof-analyze/sysprof-document-mmap.c
@@ -36,6 +36,7 @@ struct _SysprofDocumentMmapClass
 
 enum {
   PROP_0,
+  PROP_BUILD_ID,
   PROP_END_ADDRESS,
   PROP_FILE,
   PROP_FILE_INODE,
@@ -78,6 +79,10 @@ sysprof_document_mmap_get_property (GObject    *object,
       g_value_set_uint64 (value, sysprof_document_mmap_get_file_inode (self));
       break;
 
+    case PROP_BUILD_ID:
+      g_value_set_string (value, sysprof_document_mmap_get_build_id (self));
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
     }
@@ -115,6 +120,11 @@ sysprof_document_mmap_class_init (SysprofDocumentMmapClass *klass)
                          0, G_MAXUINT64, 0,
                          (G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
 
+  properties [PROP_BUILD_ID] =
+    g_param_spec_string ("build-id", NULL, NULL,
+                         NULL,
+                         (G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
+
   g_object_class_install_properties (object_class, N_PROPS, properties);
 }
 
@@ -176,9 +186,38 @@ sysprof_document_mmap_get_file (SysprofDocumentMmap *self)
 {
   const SysprofCaptureMap *mmap;
 
-  g_return_val_if_fail (SYSPROF_IS_DOCUMENT_MMAP (self), 0);
+  g_return_val_if_fail (SYSPROF_IS_DOCUMENT_MMAP (self), NULL);
 
   mmap = SYSPROF_DOCUMENT_FRAME_GET (self, SysprofCaptureMap);
 
   return SYSPROF_DOCUMENT_FRAME_CSTRING (self, mmap->filename);
 }
+
+const char *
+sysprof_document_mmap_get_build_id (SysprofDocumentMmap *self)
+{
+  const char *file;
+  const char *build_id;
+  gsize len;
+
+  g_return_val_if_fail (SYSPROF_IS_DOCUMENT_MMAP (self), NULL);
+
+  if (!(file = sysprof_document_mmap_get_file (self)))
+    return NULL;
+
+  /* The build-id may be tacked on after the filename if after the
+   * Nil byte we get '@'. SYSPROF_DOCUMENT_FRAME_CSTRING() will check
+   * for bounds so we can feed it a position we don't know is part
+   * of our frame or not. We expect "FILE\0@BUILD_ID_IN_HEX\0".
+   */
+
+  len = strlen (file);
+
+  if (!(build_id = SYSPROF_DOCUMENT_FRAME_CSTRING (self, &file[len+1])))
+    return NULL;
+
+  if (build_id[0] != '@')
+    return NULL;
+
+  return &build_id[1];
+}
diff --git a/src/libsysprof-analyze/sysprof-document-mmap.h b/src/libsysprof-analyze/sysprof-document-mmap.h
index 0bbe3deb..65451730 100644
--- a/src/libsysprof-analyze/sysprof-document-mmap.h
+++ b/src/libsysprof-analyze/sysprof-document-mmap.h
@@ -45,6 +45,8 @@ SYSPROF_AVAILABLE_IN_ALL
 guint64     sysprof_document_mmap_get_file_offset   (SysprofDocumentMmap *self);
 SYSPROF_AVAILABLE_IN_ALL
 const char *sysprof_document_mmap_get_file          (SysprofDocumentMmap *self);
+SYSPROF_AVAILABLE_IN_ALL
+const char *sysprof_document_mmap_get_build_id      (SysprofDocumentMmap *self);
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC (SysprofDocumentMmap, g_object_unref)