s390/kaslr: add support for R_390_GLOB_DAT relocation type

Commit "bpf: Process in-kernel BTF" in linux-next introduced an undefined __weak symbol, which results in an R_390_GLOB_DAT relocation type. That is not yet handled by the KASLR relocation code, and the kernel stops with the message "Unknown relocation type". Add code to detect and handle R_390_GLOB_DAT relocation types and undefined symbols. Fixes: 805bc0b ("s390/kernel: build a relocatable kernel") Cc: <[email protected]> # v5.2+ Acked-by: Heiko Carstens <[email protected]> Signed-off-by: Gerald Schaefer <[email protected]> Signed-off-by: Vasily Gorbik <[email protected]>
ashr · Oct 22, 2019 · ac49303 · ac49303
1 parent 388bb19
commit ac49303
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Showing 2 changed files with 12 additions and 3 deletions.
diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
@@ -101,10 +101,18 @@ static void handle_relocs(unsigned long offset)
 	dynsym = (Elf64_Sym *) vmlinux.dynsym_start;
 	for (rela = rela_start; rela < rela_end; rela++) {
 		loc = rela->r_offset + offset;
-		val = rela->r_addend + offset;
+		val = rela->r_addend;
 		r_sym = ELF64_R_SYM(rela->r_info);
-		if (r_sym)
-			val += dynsym[r_sym].st_value;
+		if (r_sym) {
+			if (dynsym[r_sym].st_shndx != SHN_UNDEF)
+				val += dynsym[r_sym].st_value + offset;
+		} else {
+			/*
+			 * 0 == undefined symbol table index (STN_UNDEF),
+			 * used for R_390_RELATIVE, only add KASLR offset
+			 */
+			val += offset;
+		}
 		r_type = ELF64_R_TYPE(rela->r_info);
 		rc = arch_kexec_do_relocs(r_type, (void *) loc, val, 0);
 		if (rc)

diff --git a/arch/s390/kernel/machine_kexec_reloc.c b/arch/s390/kernel/machine_kexec_reloc.c
@@ -27,6 +27,7 @@ int arch_kexec_do_relocs(int r_type, void *loc, unsigned long val,
 		*(u32 *)loc = val;
 		break;
 	case R_390_64:		/* Direct 64 bit.  */
+	case R_390_GLOB_DAT:
 		*(u64 *)loc = val;
 		break;
 	case R_390_PC16:	/* PC relative 16 bit.	*/