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[PATCH] mkimage: powerpc: fix CHRP note descsz

From: Daniel Axtens
Subject: [PATCH] mkimage: powerpc: fix CHRP note descsz
Date: Tue, 7 Apr 2020 16:17:26 +1000

Currently, an image generated with 'grub-mkimage -n' causes an error when
read with 'readelf -a':

Displaying notes found at file offset 0x000106f0 with length 0x0000002c:
  Owner                Data size        Description
readelf: Warning: note with invalid namesz and/or descsz found at offset 0x0
readelf: Warning:  type: 0x1275, namesize: 0x00000008, descsize: 0x0000002c, 
alignment: 4

This is because the descsz of the CHRP note is set to
 sizeof (struct grub_ieee1275_note)
which is the size of the entire note, including name and elf header. The
desczs should contain only the contents, not the name and header sizes.

Set the descsz instead to 'sizeof (struct grub_ieee1275_note_desc)'

Resultant readelf output:

Displaying notes found at file offset 0x00010710 with length 0x0000002c:
  Owner                Data size        Description
  PowerPC              0x00000018       Unknown note type: (0x00001275)
   description data: ff ff ff ff 00 c0 00 00 ff ff ff ff ff ff ff ff ff ff ff 
ff 00 00 40 00

So far as I can tell this issue has existed for as long as the note
generation code has existed, but I guess nothing really checks descsz.

Signed-off-by: Daniel Axtens <address@hidden>


These days you can't (AFAICT) add a note section with grub-install, you
have to use grub-mkimage and install the binary manually, so the change is
unlikely to cause a regression. I also can't find any code in SLOF that
would read this note, so I guess it's only the proprietary IBM hypervisor
that looks for it. Nonetheless, it would be nice to have the fix: I ended
up duplicating the bug into some new code I'm writing to add a different
note section at the end of the binary and it cost me a fair bit of time.
 util/grub-mkimagexx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/util/grub-mkimagexx.c b/util/grub-mkimagexx.c
index d16ec63a16ff..ab6dfab79242 100644
--- a/util/grub-mkimagexx.c
+++ b/util/grub-mkimagexx.c
@@ -463,7 +463,7 @@ SUFFIX (grub_mkimage_generate_elf) (const struct 
       grub_util_info ("adding CHRP NOTE segment");
       note_ptr->header.n_namesz = grub_host_to_target32 (sizeof 
-      note_ptr->header.n_descsz = grub_host_to_target32 (note_size);
+      note_ptr->header.n_descsz = grub_host_to_target32 (sizeof (struct 
       note_ptr->header.n_type = grub_host_to_target32 
       strcpy (note_ptr->name, GRUB_IEEE1275_NOTE_NAME);
       note_ptr->descriptor.real_mode = grub_host_to_target32 (0xffffffff);

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