create-klp-module: get rid of redundant kpatch_relocation.offset field

kpatch_relocation's 'dest' addend and 'offset' fields are redundant.  In
fact, the 'offset' field isn't always accurate because it doesn't have a
relocation, so its value doesn't adjust when multiple .o files are
combined.  Just use the 'dest' addend instead.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

kpatch-build/create-diff-object.c

@@ -2517,7 +2517,6 @@ static void kpatch_create_intermediate_sections(struct kpatch_elf *kelf,
 			krelas[index].addend = rela->addend;
 			krelas[index].type = rela->type;
 			krelas[index].external = external;
-			krelas[index].offset = rela->offset;
 
 			/* add rela to fill in krelas[index].dest field */
 			ALLOC_LINK(rela2, &krela_sec->rela->relas);

kpatch-build/create-klp-module.c

@@ -160,7 +160,7 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 	struct symbol *sym, *dest;
 	struct rela *rela;
 	char *objname;
-	int nr, index, offset, toc_offset;
+	int nr, index, offset, dest_off;
 
 	krelas = krelasec->data->d_buf;
 	nr = krelasec->data->d_size / sizeof(*krelas);
@@ -168,48 +168,16 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 	for (index = 0; index < nr; index++) {
 		offset = index * sizeof(*krelas);
 
-		/* Get the base section to which the rela applies */
+		/* Get the rela dest sym + offset */
 		rela = find_rela_by_offset(krelasec->rela,
 					   offset + offsetof(struct kpatch_relocation, dest));
 		if (!rela)
 			ERROR("find_rela_by_offset");
 
-		/*
-		 * Patched file:
-		 * Relocation section '.rela.toc' at offset 0x46358 contains 60 entries:
-		 *     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
-		 *     0000000000000000  000001ee00000026 R_PPC64_ADDR64         0000000000000000 jiffies + 0
-		 *     0000000000000008  0000009400000026 R_PPC64_ADDR64         0000000000000000 __tracepoints + 0
-		 *     0000000000000010  000001db00000026 R_PPC64_ADDR64         0000000000000000 __cpu_online_mask + 0
-		 *     0000000000000018  0000009c00000026 R_PPC64_ADDR64         0000000000000000 .data..percpu + 0
-		 *     0000000000000020  000001ac00000026 R_PPC64_ADDR64         0000000000000000 __per_cpu_offset + 0
-		 *     0000000000000028  0000006900000026 R_PPC64_ADDR64         0000000000000000 .rodata.str1.8 + 0
-		 *     [...]
-		 *
-		 * Output file:
-		 * Relocation section '.rela.toc' at offset 0x1270 contains 58 entries:
-		 *     Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
-		 *     0000000000000000  0000000700000026 R_PPC64_ADDR64         0000000000000000 .data + 0
-		 *     0000000000000008  0000003c00000026 R_PPC64_ADDR64         0000000000000000 __kpatch_funcs + 0
-		 *     0000000000000010  0000005300000026 R_PPC64_ADDR64         0000000000000000 kmalloc_caches + 0
-		 *     0000000000000018  0000001100000026 R_PPC64_ADDR64         0000000000000000 .rodata.str1.8 + 0
-		 *     0000000000000020  0000001600000026 R_PPC64_ADDR64         0000000000000000 .bss + 0
-		 *     0000000000000028  0000004200000026 R_PPC64_ADDR64         0000000000000038 __kpatch_funcs_end + 0
-		 *     0000000000000030  0000003400000026 R_PPC64_ADDR64         0000000000000000 __this_module + 0
-		 *     0000000000000038  0000004d00000026 R_PPC64_ADDR64         0000000000000000 jiffies + 0
-		 *     0000000000000048  0000004500000026 R_PPC64_ADDR64         0000000000000000 __cpu_online_mask + 0
-		 *     0000000000000058  0000003900000026 R_PPC64_ADDR64         0000000000000000 __per_cpu_offset + 0
-		 *     [...]
-		 *
-		 * On ppc64le, when .o files are linked together, the .toc
-		 * entries might get re-arranged.  Capture the new .toc rela
-		 * offset value, which is used below to set the rela->addend.
-		 */
-		toc_offset = rela->addend;
-
 		dest = rela->sym;
+		dest_off = rela->addend;
 
-		/* Get the name of the object the rela belongs to */
+		/* Get the name of the object the dest belongs to */
 		rela = find_rela_by_offset(krelasec->rela,
 					   offset + offsetof(struct kpatch_relocation, objname));
 		if (!rela)
@@ -219,31 +187,31 @@ static void create_klp_relasecs_and_syms(struct kpatch_elf *kelf, struct section
 		if (!objname)
 			ERROR("strdup");
 
-		/* Get the corresponding .kpatch.symbol entry */
+		/* Get the .kpatch.symbol entry for the rela src */
 		rela = find_rela_by_offset(krelasec->rela,
 					   offset + offsetof(struct kpatch_relocation, ksym));
 		if (!rela)
 			ERROR("find_rela_by_offset");
 
-		/* Create (or find) a real symbol out of the .kpatch.symbol entry */
+		/* Create (or find) a klp symbol from the rela src entry */
 		sym = find_or_add_ksym_to_symbols(kelf, ksymsec, strings, rela->addend);
 		if (!sym)
 			ERROR("error finding or adding ksym to symtab");
 
-		/* Create (or find) the .klp.rela. section for this dest sec and object */
+		/* Create (or find) the .klp.rela. section for the dest sec and object */
 		klp_relasec = find_or_add_klp_relasec(kelf, dest->sec, objname);
 		if (!klp_relasec)
 			ERROR("error finding or adding klp relasec");
 
-		/* Add the rela to the .klp.rela. section */
+		/* Add the klp rela to the .klp.rela. section */
 		ALLOC_LINK(rela, &klp_relasec->relas);
+		rela->type = krelas[index].type;
 		rela->sym = sym;
 		rela->addend = krelas[index].addend;
-		rela->type = krelas[index].type;
 		if (!strcmp(dest->sec->name, ".toc"))
-			rela->offset = toc_offset;
+			rela->offset = dest_off;
 		else
-			rela->offset = krelas[index].offset + dest->sym.st_value;
+			rela->offset = dest_off + dest->sym.st_value;
 	}
 }
 

kpatch-build/kpatch-intermediate.h

@@ -36,7 +36,6 @@ struct kpatch_relocation {
 	unsigned long dest;
 	unsigned int type;
 	int addend;
-	int offset;
 	int external;
 	char *objname; /* object to which this rela applies to */
 	struct kpatch_symbol *ksym;