[Qemu-devel] [RFC v2 2/4] elf-ops.h: Add get_elf_note_type()

[Liam Merwick]

Introduce a routine which, given a pointer to a range of ELF Notes,
searches through them looking for a note matching the type specified
and returns a pointer to the matching ELF note.

Signed-off-by: Liam Merwick <address@hidden>
---
 include/hw/elf_ops.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/include/hw/elf_ops.h b/include/hw/elf_ops.h
index 37d20a3800c1..ffbdfbe9c2d8 100644
--- a/include/hw/elf_ops.h
+++ b/include/hw/elf_ops.h
@@ -265,6 +265,49 @@ fail:
     return ret;
 }
 
+/* Given 'nhdr', a pointer to a range of ELF Notes, search through them
+ * for a note matching type 'elf_note_type' and return a pointer to
+ * the matching ELF note.
+ */
+static struct elf_note *glue(get_elf_note_type, SZ)(struct elf_note *nhdr,
+                                                    elf_word note_size,
+                                                    elf_word phdr_align,
+                                                    elf_word elf_note_type)
+{
+    elf_word nhdr_size = sizeof(struct elf_note);
+    elf_word elf_note_entry_offset = 0;
+    elf_word note_type;
+    elf_word nhdr_namesz;
+    elf_word nhdr_descsz;
+
+    if (nhdr == NULL) {
+        return NULL;
+    }
+
+    note_type = nhdr->n_type;
+    while (note_type != elf_note_type) {
+        nhdr_namesz = nhdr->n_namesz;
+        nhdr_descsz = nhdr->n_descsz;
+
+        elf_note_entry_offset = nhdr_size +
+            QEMU_ALIGN_UP(nhdr_namesz, phdr_align) +
+            QEMU_ALIGN_UP(nhdr_descsz, phdr_align);
+
+        /* If the offset calculated in this iteration exceeds the
+        * supplied size, we are done and no matching note was found.
+        */
+        if (elf_note_entry_offset > note_size) {
+            return NULL;
+        }
+
+        /* skip to the next ELF Note entry */
+        nhdr = (void *)nhdr + elf_note_entry_offset;
+        note_type = nhdr->n_type;
+    }
+
+    return nhdr;
+}
+
 static int glue(load_elf, SZ)(const char *name, int fd,
                               uint64_t (*elf_note_fn)(void *, void *, bool),
                               uint64_t (*translate_fn)(void *, uint64_t),
@@ -512,6 +555,13 @@ static int glue(load_elf, SZ)(const char *name, int fd,
                 }
             }
 
+           /* Search the ELF notes to find one with a type matching the
+            * value passed in via 'translate_opaque'
+            */
+            nhdr = (struct elf_note *)data;
+           assert(translate_opaque != NULL);
+            nhdr = glue(get_elf_note_type, SZ)(nhdr, file_size, ph->p_align,
+                                               *(uint64_t *)translate_opaque);
             if (nhdr != NULL) {
                 bool is64 =
                     sizeof(struct elf_note) == sizeof(struct elf64_note);
-- 
1.8.3.1