elf: Add optional function ptr to load_elf() to parse ELF notes

This patch adds an optional function pointer, 'elf_note_fn', to
load_elf() which causes load_elf() to additionally parse any
ELF program headers of type PT_NOTE and check to see if the ELF
Note is of the type specified by the 'translate_opaque' arg.
If a matching ELF Note is found then the specfied function pointer
is called to process the ELF note.

Passing a NULL function pointer results in ELF Notes being skipped.

The first consumer of this functionality is the PVHboot support
which needs to read the XEN_ELFNOTE_PHYS32_ENTRY ELF Note while
loading the uncompressed kernel binary in order to discover the
boot entry address for the x86/HVM direct boot ABI.

Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 17 insertions, 9 deletions

diff --git a/hw/core/generic-loader.c b/hw/core/generic-loader.c
index fbae05fb3b..3695dd439c 100644
--- a/hw/core/generic-loader.c
+++ b/hw/core/generic-loader.c
@@ -136,7 +136,7 @@ static void generic_loader_realize(DeviceState *dev, Error **errp)
         AddressSpace *as = s->cpu ? s->cpu->as :  NULL;
 
         if (!s->force_raw) {
-            size = load_elf_as(s->file, NULL, NULL, &entry, NULL, NULL,
+            size = load_elf_as(s->file, NULL, NULL, NULL, &entry, NULL, NULL,
                                big_endian, 0, 0, 0, as);
 
             if (size < 0) {
diff --git a/hw/core/loader.c b/hw/core/loader.c
index c4f62fe427..3a000d576b 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -396,37 +396,42 @@ fail:
 }
 
 /* return < 0 if error, otherwise the number of bytes loaded in memory */
-int load_elf(const char *filename, uint64_t (*translate_fn)(void *, uint64_t),
+int load_elf(const char *filename,
+             uint64_t (*elf_note_fn)(void *, void *, bool),
+             uint64_t (*translate_fn)(void *, uint64_t),
              void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
              uint64_t *highaddr, int big_endian, int elf_machine,
              int clear_lsb, int data_swab)
 {
-    return load_elf_as(filename, translate_fn, translate_opaque, pentry,
-                       lowaddr, highaddr, big_endian, elf_machine, clear_lsb,
-                       data_swab, NULL);
+    return load_elf_as(filename, elf_note_fn, translate_fn, translate_opaque,
+                       pentry, lowaddr, highaddr, big_endian, elf_machine,
+                       clear_lsb, data_swab, NULL);
 }
 
 /* return < 0 if error, otherwise the number of bytes loaded in memory */
 int load_elf_as(const char *filename,
+                uint64_t (*elf_note_fn)(void *, void *, bool),
                 uint64_t (*translate_fn)(void *, uint64_t),
                 void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
                 uint64_t *highaddr, int big_endian, int elf_machine,
                 int clear_lsb, int data_swab, AddressSpace *as)
 {
-    return load_elf_ram(filename, translate_fn, translate_opaque,
+    return load_elf_ram(filename, elf_note_fn, translate_fn, translate_opaque,
                         pentry, lowaddr, highaddr, big_endian, elf_machine,
                         clear_lsb, data_swab, as, true);
 }
 
 /* return < 0 if error, otherwise the number of bytes loaded in memory */
 int load_elf_ram(const char *filename,
+                 uint64_t (*elf_note_fn)(void *, void *, bool),
                  uint64_t (*translate_fn)(void *, uint64_t),
                  void *translate_opaque, uint64_t *pentry, uint64_t *lowaddr,
                  uint64_t *highaddr, int big_endian, int elf_machine,
                  int clear_lsb, int data_swab, AddressSpace *as,
                  bool load_rom)
 {
-    return load_elf_ram_sym(filename, translate_fn, translate_opaque,
+    return load_elf_ram_sym(filename, elf_note_fn,
+                            translate_fn, translate_opaque,
                             pentry, lowaddr, highaddr, big_endian,
                             elf_machine, clear_lsb, data_swab, as,
                             load_rom, NULL);
@@ -434,6 +439,7 @@ int load_elf_ram(const char *filename,
 
 /* return < 0 if error, otherwise the number of bytes loaded in memory */
 int load_elf_ram_sym(const char *filename,
+                     uint64_t (*elf_note_fn)(void *, void *, bool),
                      uint64_t (*translate_fn)(void *, uint64_t),
                      void *translate_opaque, uint64_t *pentry,
                      uint64_t *lowaddr, uint64_t *highaddr, int big_endian,
@@ -476,11 +482,13 @@ int load_elf_ram_sym(const char *filename,
 
     lseek(fd, 0, SEEK_SET);
     if (e_ident[EI_CLASS] == ELFCLASS64) {
-        ret = load_elf64(filename, fd, translate_fn, translate_opaque, must_swab,
+        ret = load_elf64(filename, fd, elf_note_fn,
+                         translate_fn, translate_opaque, must_swab,
                          pentry, lowaddr, highaddr, elf_machine, clear_lsb,
                          data_swab, as, load_rom, sym_cb);
     } else {
-        ret = load_elf32(filename, fd, translate_fn, translate_opaque, must_swab,
+        ret = load_elf32(filename, fd, elf_note_fn,
+                         translate_fn, translate_opaque, must_swab,
                          pentry, lowaddr, highaddr, elf_machine, clear_lsb,
                          data_swab, as, load_rom, sym_cb);
     }