core: arm64: support relocation type R_AARCH64_ABS64 (257)

If a 64-bit TA contains relocations of type R_AARCH64_ABS64, OP-TEE
refuses to load it and logs the following error:

  ERROR:   TEE-CORE: Unknown relocation type 257

This relocation type does not seem to happen in our test applications,
but someone has experienced the issue after linking a TA against a
third-party static library [1]. I could reproduce the issue by
compiling the hello_world TA with -fPIC instead of -fpie. This simple
change generates *one* R_AARCH64_ABS64 in the TA ELF file.

This commit adds the necessary code to support R_AARCH64_ABS64.

[1] OP-TEE#1399

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Tested-by: Jerome Forissier <jerome.forissier@linaro.org> (qemu_v8)
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

core/arch/arm/kernel/elf_common.h

@@ -645,6 +645,7 @@ typedef struct {
 #define	R_386_TLS_TPOFF32	37	/* GOT entry of -ve static TLS offset */
 #define	R_386_IRELATIVE		42	/* PLT entry resolved indirectly at runtime */
 
+#define	R_AARCH64_ABS64		257
 #define	R_AARCH64_RELATIVE 	1027
 
 #define	R_ARM_NONE		0	/* No relocation. */

core/arch/arm/kernel/elf_load.c

@@ -499,16 +499,41 @@ static TEE_Result e32_process_rel(struct elf_load_state *state, size_t rel_sidx,
 static TEE_Result e64_process_rel(struct elf_load_state *state,
 			size_t rel_sidx, vaddr_t vabase)
 {
+	Elf64_Ehdr *ehdr = state->ehdr;
 	Elf64_Shdr *shdr = state->shdr;
 	Elf64_Rela *rela;
 	Elf64_Rela *rela_end;
+	size_t sym_tab_idx;
+	Elf64_Sym *sym_tab = NULL;
+	size_t num_syms = 0;
 
 	if (shdr[rel_sidx].sh_type != SHT_RELA)
 		return TEE_ERROR_NOT_IMPLEMENTED;
 
 	if (shdr[rel_sidx].sh_entsize != sizeof(Elf64_Rela))
 		return TEE_ERROR_BAD_FORMAT;
 
+	sym_tab_idx = shdr[rel_sidx].sh_link;
+	if (sym_tab_idx) {
+		if (sym_tab_idx >= ehdr->e_shnum)
+			return TEE_ERROR_BAD_FORMAT;
+
+		if (shdr[sym_tab_idx].sh_entsize != sizeof(Elf64_Sym))
+			return TEE_ERROR_BAD_FORMAT;
+
+		/* Check the address is inside TA memory */
+		if (shdr[sym_tab_idx].sh_addr > state->vasize ||
+		    (shdr[sym_tab_idx].sh_addr +
+				shdr[sym_tab_idx].sh_size) > state->vasize)
+			return TEE_ERROR_BAD_FORMAT;
+
+		sym_tab = (Elf64_Sym *)(vabase + shdr[sym_tab_idx].sh_addr);
+		if (!ALIGNMENT_IS_OK(sym_tab, Elf64_Sym))
+			return TEE_ERROR_BAD_FORMAT;
+
+		num_syms = shdr[sym_tab_idx].sh_size / sizeof(Elf64_Sym);
+	}
+
 	/* Check the address is inside TA memory */
 	if (shdr[rel_sidx].sh_addr >= state->vasize)
 		return TEE_ERROR_BAD_FORMAT;
@@ -522,6 +547,7 @@ static TEE_Result e64_process_rel(struct elf_load_state *state,
 	rela_end = rela + shdr[rel_sidx].sh_size / sizeof(Elf64_Rela);
 	for (; rela < rela_end; rela++) {
 		Elf64_Addr *where;
+		size_t sym_idx;
 
 		/* Check the address is inside TA memory */
 		if (rela->r_offset >= state->vasize)
@@ -532,6 +558,13 @@ static TEE_Result e64_process_rel(struct elf_load_state *state,
 			return TEE_ERROR_BAD_FORMAT;
 
 		switch (ELF64_R_TYPE(rela->r_info)) {
+		case R_AARCH64_ABS64:
+			sym_idx = ELF64_R_SYM(rela->r_info);
+			if (sym_idx > num_syms)
+				return TEE_ERROR_BAD_FORMAT;
+			*where = rela->r_addend + sym_tab[sym_idx].st_value +
+				 vabase;
+			break;
 		case R_AARCH64_RELATIVE:
 			*where = rela->r_addend + vabase;
 			break;