[Xen-devel] [PATCH v2] libxc: elf_kernel loader: Remove check for shstrtab

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

This was probably useful as a sanity check when the "__xen_guest"
section were not legacy.  But now ELF notes are prefered and
"should live in a PT_NOTE segment" (elfnote.h).

This check is unnecessary as elf_xen_parse() from xen/common/libelf
will do the right thing and look for ELFNOTEs in the different places
in order of preference. elf_xen_parse() will still be able to also
look for the legacy "__xen_guest" section without the check in libxc.

This patch would allow to write a simpler ELF header for an OVMF blob
(which isn't an ELF) and allow it to be loaded as a PVH kernel. The
header only needs to declare two program segments:
- one to tell an ELF loader where to put the blob,
- one for a Xen ELFNOTE.

The ELFNOTE is to comply to the pvh design which wants the
XEN_ELFNOTE_PHYS32_ENTRY to declare a blob as compaptible with the PVH
boot ABI.

Note that without the ELFNOTE, libxc will load an ELF but with
the plain ELF loader, which doesn't check for shstrtab.

Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---

Notes:
    v2: Rework commit message, explain why the check is unnecessary.

 tools/libxc/xc_dom_elfloader.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/tools/libxc/xc_dom_elfloader.c b/tools/libxc/xc_dom_elfloader.c
index 82b5f2ee79..b327db219d 100644
--- a/tools/libxc/xc_dom_elfloader.c
+++ b/tools/libxc/xc_dom_elfloader.c
@@ -165,15 +165,6 @@ static elf_negerrnoval xc_dom_parse_elf_kernel(struct 
xc_dom_image *dom)
         return rc;
     }
 
-    /* Find the section-header strings table. */
-    if ( ELF_PTRVAL_INVALID(elf->sec_strtab) )
-    {
-        xc_dom_panic(dom->xch, XC_INVALID_KERNEL, "%s: ELF image"
-                     " has no shstrtab", __FUNCTION__);
-        rc = -EINVAL;
-        goto out;
-    }
-
     /* parse binary and get xen meta info */
     elf_parse_binary(elf);
     if ( elf_xen_parse(elf, &dom->parms) != 0 )
-- 
Anthony PERARD


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