imgact_elf: handle unaligned phdrs

Althought non-compliant, there are binaries which have the phdrs placed
unaligned in the image.  Since we have the code to allocate memory for
off-page phdrs, the same code path can be used to handle unaligned
phdrs.

Relax the requirement for both the activated image and interpreter.

PR:	295629
Reviewed by:	emaste, markj, olce
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D57498

sys/kern/imgact_elf.c

@@ -858,12 +858,12 @@ __elfN(load_file)(struct thread *td, const char *file, u_long *addr,
 		goto fail;
 	}
 
-	if (!aligned(imgp->image_header + hdr->e_phoff, Elf_Addr) ||
-	    hdr->e_phnum > __elfN(phnums)) {
+	if (hdr->e_phnum > __elfN(phnums)) {
 		error = ENOEXEC;
 		goto fail;
 	}
-	if (__elfN(phdr_in_zero_page)(hdr)) {
+	if (__elfN(phdr_in_zero_page)(hdr) &&
+	    aligned(imgp->image_header + hdr->e_phoff, Elf_Addr)) {
 		phdr = (const Elf_Phdr *)(imgp->image_header + hdr->e_phoff);
 	} else {
 		VOP_UNLOCK(imgp->vp);
@@ -1157,10 +1157,6 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp)
 	free_interp = false;
 	m_phdrs = NULL;
 
-	if (!aligned(imgp->image_header + hdr->e_phoff, Elf_Addr)) {
-		uprintf("Unaligned program headers\n");
-		return (ENOEXEC);
-	}
 	if (hdr->e_phoff + hdr->e_phnum * hdr->e_phentsize < hdr->e_phoff) {
 		uprintf("PHDRS wrap\n");
 		return (ENOEXEC);
@@ -1170,7 +1166,8 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp)
 		    hdr->e_phnum, __elfN(phnums));
 		return (ENOEXEC);
 	}
-	if (__elfN(phdr_in_zero_page)(hdr)) {
+	if (__elfN(phdr_in_zero_page)(hdr) &&
+	    aligned(imgp->image_header + hdr->e_phoff, Elf_Addr)) {
 		phdr = (const Elf_Phdr *)(imgp->image_header + hdr->e_phoff);
 	} else {
 		VOP_UNLOCK(imgp->vp);