[Ltrace-devel] [PATCH v2 3/8] Break out the symbol info gathering into a backend call

[edgar.iglesias at gmail.com]

From: "Edgar E. Iglesias" <edgar at axis.com>

No functional change. Will be used by the MIPS backend.

Signed-off-by: Edgar E. Iglesias <edgar at axis.com>
---
 backend.h    |   15 +++++++++++++++
 ltrace-elf.c |   54 ++++++++++++++++++++++++++++++++++--------------------
 2 files changed, 49 insertions(+), 20 deletions(-)

diff --git a/backend.h b/backend.h
index bae53bd..e241eab 100644
--- a/backend.h
+++ b/backend.h
@@ -266,6 +266,21 @@ void arch_process_destroy(struct Process *proc);
 int arch_process_clone(struct Process *retp, struct Process *proc);
 int arch_process_exec(struct Process *proc);
 
+/* The following callback has to be implemented in backend if arch.h
+ * defines ARCH_HAVE_GET_SYM_INFO.
+ *
+ * This is called for every PLT relocation R in ELF file LTE, that
+ * ltrace is about to add to it's internal representation of the
+ * program under trace.
+ * The corresponding PLT entry is for SYM_INDEX-th relocation in the file.
+ *
+ * The callback is responsible for initializing RELA and SYM.
+ *
+ * Return 0 if OK.
+ * Return a negative value if this symbol (SYM_INDEX) should be ignored.  */
+int arch_get_sym_info(struct ltelf *lte, const char *filename,
+		      size_t sym_index, GElf_Rela *rela, GElf_Sym *sym);
+
 enum plt_status {
 	plt_fail,
 	plt_ok,
diff --git a/ltrace-elf.c b/ltrace-elf.c
index bc99c6a..80f18df 100644
--- a/ltrace-elf.c
+++ b/ltrace-elf.c
@@ -510,35 +510,49 @@ do_close_elf(struct ltelf *lte) {
 	close(lte->fd);
 }
 
+#ifndef ARCH_HAVE_GET_SYMINFO
+int
+arch_get_sym_info(struct ltelf *lte, const char *filename,
+		  size_t sym_index, GElf_Rela *rela, GElf_Sym *sym)
+{
+	int i = sym_index;
+	GElf_Rel rel;
+	void *ret;
+
+	if (lte->relplt->d_type == ELF_T_REL) {
+		ret = gelf_getrel(lte->relplt, i, &rel);
+		rela->r_offset = rel.r_offset;
+		rela->r_info = rel.r_info;
+		rela->r_addend = 0;
+	} else {
+		ret = gelf_getrela(lte->relplt, i, rela);
+	}
+
+	if (ret == NULL
+	    || ELF64_R_SYM(rela->r_info) >= lte->dynsym_count
+	    || gelf_getsym(lte->dynsym, ELF64_R_SYM(rela->r_info),
+			   sym) == NULL) {
+		fprintf(stderr,
+			"Couldn't get relocation from \"%s\": %s\n",
+			filename, elf_errmsg(-1));
+		exit(EXIT_FAILURE);
+	}
+
+	return 0;
+}
+#endif
+
 static int
 populate_plt(struct Process *proc, const char *filename,
 	     struct ltelf *lte, struct library *lib)
 {
 	size_t i;
 	for (i = 0; i < lte->relplt_count; ++i) {
-		GElf_Rel rel;
 		GElf_Rela rela;
 		GElf_Sym sym;
-		void *ret;
-
-		if (lte->relplt->d_type == ELF_T_REL) {
-			ret = gelf_getrel(lte->relplt, i, &rel);
-			rela.r_offset = rel.r_offset;
-			rela.r_info = rel.r_info;
-			rela.r_addend = 0;
-		} else {
-			ret = gelf_getrela(lte->relplt, i, &rela);
-		}
 
-		if (ret == NULL
-		    || ELF64_R_SYM(rela.r_info) >= lte->dynsym_count
-		    || gelf_getsym(lte->dynsym, ELF64_R_SYM(rela.r_info),
-				   &sym) == NULL) {
-			fprintf(stderr,
-				"Couldn't get relocation from \"%s\": %s\n",
-				filename, elf_errmsg(-1));
-			exit(EXIT_FAILURE);
-		}
+		if (arch_get_sym_info(lte, filename, i, &rela, &sym) < 0)
+			continue; /* Skip this entry.  */
 
 		char const *name = lte->dynstr + sym.st_name;
 
-- 
1.7.8.6