[PATCH 1/6] s390/tools: Pass symbol name to do_relocs()

[Heiko Carstens <hca@linux.ibm.com>]

Pass the symbol symbol name which corresponds to a relocation to
do_relocs(). This is preparation for kcfi support.

Given that the s390 specific relocs tool is a stripped down version of the
x86 version, add more code from the x86 version to the s390 version, while
keeping coding style, etc. in order to add the required functionality.

Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/s390/tools/relocs.c | 142 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 139 insertions(+), 3 deletions(-)

diff --git a/arch/s390/tools/relocs.c b/arch/s390/tools/relocs.c
index 30a732c808f3..a2774176d38f 100644
--- a/arch/s390/tools/relocs.c
+++ b/arch/s390/tools/relocs.c
@@ -41,6 +41,10 @@
 static Elf_Ehdr		ehdr;
 static unsigned long	shnum;
 static unsigned int	shstrndx;
+static unsigned int	shsymtabndx;
+static unsigned int	shxsymtabndx;
+
+static int sym_index(Elf_Sym *sym);
 
 struct relocs {
 	uint32_t	*offset;
@@ -54,11 +58,40 @@ static struct relocs relocs64;
 struct section {
 	Elf_Shdr	shdr;
 	struct section	*link;
+	Elf_Sym		*symtab;
+	Elf32_Word	*xsymtab;
 	Elf_Rel		*reltab;
+	char		*strtab;
 };
 
 static struct section *secs;
 
+static const char *sec_name(unsigned shndx)
+{
+	const char *sec_strtab;
+	const char *name = "<noname>";
+	sec_strtab = secs[shstrndx].strtab;
+
+	if (shndx < shnum)
+		name = sec_strtab + secs[shndx].shdr.sh_name;
+	else if (shndx == SHN_ABS)
+		name = "ABSOLUTE";
+	else if (shndx == SHN_COMMON)
+		name = "COMMON";
+	return name;
+}
+
+static const char *sym_name(const char *sym_strtab, Elf_Sym *sym)
+{
+	const char *name;
+
+	if (sym->st_name)
+		name = sym_strtab + sym->st_name;
+	else
+		name = sec_name(sym_index(sym));
+	return name;
+}
+
 #if BYTE_ORDER == LITTLE_ENDIAN
 #define le16_to_cpu(val)	(val)
 #define le32_to_cpu(val)	(val)
@@ -105,6 +138,23 @@ static uint64_t elf64_to_cpu(uint64_t val)
 #define elf_off_to_cpu(x)	elf64_to_cpu(x)
 #define elf_xword_to_cpu(x)	elf64_to_cpu(x)
 
+static int sym_index(Elf_Sym *sym)
+{
+	Elf_Sym *symtab = secs[shsymtabndx].symtab;
+	Elf32_Word *xsymtab = secs[shxsymtabndx].xsymtab;
+	unsigned long offset;
+	int index;
+
+	if (sym->st_shndx != SHN_XINDEX)
+		return sym->st_shndx;
+
+	/* calculate offset of sym from head of table. */
+	offset = (unsigned long)sym - (unsigned long)symtab;
+	index = offset / sizeof(*sym);
+
+	return elf32_to_cpu(xsymtab[index]);
+}
+
 static void die(char *fmt, ...)
 {
 	va_list ap;
@@ -216,6 +266,81 @@ static void read_shdrs(FILE *fp)
 
 }
 
+static void read_strtabs(FILE *fp)
+{
+	int i;
+
+	for (i = 0; i < shnum; i++) {
+		struct section *sec = &secs[i];
+
+		if (sec->shdr.sh_type != SHT_STRTAB)
+			continue;
+
+		sec->strtab = malloc(sec->shdr.sh_size);
+		if (!sec->strtab)
+			die("malloc of %" FMT " bytes for strtab failed\n", sec->shdr.sh_size);
+
+		if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0)
+			die("Seek to %" FMT " failed: %s\n", sec->shdr.sh_offset, strerror(errno));
+
+		if (fread(sec->strtab, 1, sec->shdr.sh_size, fp) != sec->shdr.sh_size)
+			die("Cannot read symbol table: %s\n", strerror(errno));
+	}
+}
+
+static void read_symtabs(FILE *fp)
+{
+	int i, j;
+
+	for (i = 0; i < shnum; i++) {
+		struct section *sec = &secs[i];
+		int num_syms;
+
+		switch (sec->shdr.sh_type) {
+		case SHT_SYMTAB_SHNDX:
+			sec->xsymtab = malloc(sec->shdr.sh_size);
+			if (!sec->xsymtab)
+				die("malloc of %" FMT " bytes for xsymtab failed\n", sec->shdr.sh_size);
+
+			if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0)
+				die("Seek to %" FMT " failed: %s\n", sec->shdr.sh_offset, strerror(errno));
+
+			if (fread(sec->xsymtab, 1, sec->shdr.sh_size, fp) != sec->shdr.sh_size)
+				die("Cannot read extended symbol table: %s\n", strerror(errno));
+
+			shxsymtabndx = i;
+			continue;
+
+		case SHT_SYMTAB:
+			num_syms = sec->shdr.sh_size / sizeof(Elf_Sym);
+
+			sec->symtab = malloc(sec->shdr.sh_size);
+			if (!sec->symtab)
+				die("malloc of %" FMT " bytes for symtab failed\n", sec->shdr.sh_size);
+
+			if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0)
+				die("Seek to %" FMT " failed: %s\n", sec->shdr.sh_offset, strerror(errno));
+
+			if (fread(sec->symtab, 1, sec->shdr.sh_size, fp) != sec->shdr.sh_size)
+				die("Cannot read symbol table: %s\n", strerror(errno));
+
+			for (j = 0; j < num_syms; j++) {
+				Elf_Sym *sym = &sec->symtab[j];
+
+				sym->st_name  = elf_word_to_cpu(sym->st_name);
+				sym->st_value = elf_addr_to_cpu(sym->st_value);
+				sym->st_size  = elf_xword_to_cpu(sym->st_size);
+				sym->st_shndx = elf_half_to_cpu(sym->st_shndx);
+			}
+			shsymtabndx = i;
+			continue;
+
+		default:
+			continue;
+		}
+	}
+}
+
 static void read_relocs(FILE *fp)
 {
 	int i, j;
@@ -263,7 +388,8 @@ static void add_reloc(struct relocs *r, uint32_t offset)
 	r->offset[r->count++] = offset;
 }
 
-static int do_reloc(struct section *sec, Elf_Rel *rel)
+static int do_reloc(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
+		    const char *symname)
 {
 	unsigned int r_type = ELF64_R_TYPE(rel->r_info);
 	ElfW(Addr) offset = rel->r_offset;
@@ -296,21 +422,29 @@ static void walk_relocs(void)
 
 	/* Walk through the relocations */
 	for (i = 0; i < shnum; i++) {
-		struct section *sec_applies;
+		char *sym_strtab;
+		Elf_Sym *sh_symtab;
+		struct section *sec_applies, *sec_symtab;
 		int j;
 		struct section *sec = &secs[i];
 
 		if (sec->shdr.sh_type != SHT_REL_TYPE)
 			continue;
 
+		sec_symtab  = sec->link;
 		sec_applies = &secs[sec->shdr.sh_info];
 		if (!(sec_applies->shdr.sh_flags & SHF_ALLOC))
 			continue;
 
+		sh_symtab = sec_symtab->symtab;
+		sym_strtab = sec_symtab->link->strtab;
+
 		for (j = 0; j < sec->shdr.sh_size / sizeof(Elf_Rel); j++) {
 			Elf_Rel *rel = &sec->reltab[j];
+			Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)];
+			const char *symname = sym_name(sym_strtab, sym);
 
-			do_reloc(sec, rel);
+			do_reloc(sec, rel, sym, symname);
 		}
 	}
 }
@@ -349,6 +483,8 @@ static void process(FILE *fp)
 {
 	read_ehdr(fp);
 	read_shdrs(fp);
+	read_strtabs(fp);
+	read_symtabs(fp);
 	read_relocs(fp);
 	emit_relocs();
 }
-- 
2.53.0