kldxref: Workaround incorrect PT_DYNAMIC in existing powerpc kernels

Existing powerpc kernels include additional sections beyond .dynamic
in the PT_DYNAMIC segment.  Relax the requirement for an exact size
match of the section and segment for PowerPC files as a workaround.

Reported by:	jrtc27
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D43123

usr.sbin/kldxref/ef.c

@@ -252,8 +252,17 @@ ef_parse_dynamic(elf_file_t ef, const GElf_Phdr *phdyn)
 	dynamic_idx = -1;
 	for (i = 0; i < nshdr; i++) {
 		if (shdr[i].sh_type == SHT_DYNAMIC) {
+			/*
+			 * PowerPC kernels contain additional sections
+			 * beyond .dynamic in PT_DYNAMIC due to a linker
+			 * script bug.  Permit a section with a smaller
+			 * size as a workaround.
+			 */
 			if (shdr[i].sh_offset != phdyn->p_offset ||
-			    shdr[i].sh_size != phdyn->p_filesz) {
+			    ((elf_machine(ef->ef_efile) == EM_PPC ||
+			    elf_machine(ef->ef_efile) == EM_PPC64) ?
+			    shdr[i].sh_size > phdyn->p_filesz :
+			    shdr[i].sh_size != phdyn->p_filesz)) {
 				warnx(".dynamic section doesn't match phdr");
 				error = EFTYPE;
 				goto out;

usr.sbin/kldxref/ef.h

@@ -130,6 +130,7 @@ struct elf_file {
 	bool ef_cheriabi;
 };
 
+#define	elf_machine(ef)		((ef)->ef_hdr.e_machine)
 #define	elf_class(ef)		((ef)->ef_hdr.e_ident[EI_CLASS])
 #define	elf_encoding(ef)	((ef)->ef_hdr.e_ident[EI_DATA])
 #define	elf_machine(ef)		((ef)->ef_hdr.e_machine)