[PATCH] x86/build: make linking work again with ld incapable of generating build ID

[PATCH] x86/build: make linking work again with ld incapable of generating build ID

[Jan Beulich]

The retaining of .note.* in a PT_NOTE segment requires a matching
program header to be present in the first place. Drop the respective
conditional and adjust mkelf32 to deal with (ignore) the potentially
present but empty extra segment (but have the new code be generic by
dropping any excess trailing entirely empty segments).

Fixes: dedb0aa42c6d ("x86/build: use --orphan-handling linker option if available")
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/boot/mkelf32.c
+++ b/xen/arch/x86/boot/mkelf32.c
@@ -320,6 +320,19 @@ int main(int argc, char **argv)
                 (int)in64_ehdr.e_phentsize, (int)sizeof(in64_phdr));
         return 1;
     }
+
+    /* Ignore entirely empty trailing program headers. */
+    while ( in64_ehdr.e_phnum > num_phdrs )
+    {
+        (void)lseek(infd,
+                    in64_ehdr.e_phoff + in64_ehdr.e_phnum * sizeof(in64_phdr),
+                    SEEK_SET);
+        do_read(infd, &in64_phdr, sizeof(in64_phdr));
+        endianadjust_phdr64(&in64_phdr);
+        if ( in64_phdr.p_memsz )
+            break;
+        --in64_ehdr.e_phnum;
+    }
     if ( in64_ehdr.e_phnum != num_phdrs )
     {
         fprintf(stderr, "Expect precisly %d program header; found %d.\n",
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -40,9 +40,7 @@ OUTPUT_ARCH(i386:x86-64)
 PHDRS
 {
   text PT_LOAD ;
-#if defined(BUILD_ID) || defined(CONFIG_PVH_GUEST)
   note PT_NOTE ;
-#endif
 }
 #define PHDR(x) :x
 #else

Re: [PATCH] x86/build: make linking work again with ld incapable of generating build ID

[Andrew Cooper]

On 21/04/2022 11:40, Jan Beulich wrote:
> The retaining of .note.* in a PT_NOTE segment requires a matching
> program header to be present in the first place. Drop the respective
> conditional and adjust mkelf32 to deal with (ignore) the potentially
> present but empty extra segment (but have the new code be generic by
> dropping any excess trailing entirely empty segments).
>
> Fixes: dedb0aa42c6d ("x86/build: use --orphan-handling linker option if available")
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>