s390: add relocs tool

This 'relocs' tool is copied from the x86 version, ported for s390, and
greatly simplified to remove unnecessary features.

It reads vmlinux and outputs assembly to create a .vmlinux.relocs_64
section which contains the offsets of all R_390_64 relocations which
apply to allocatable sections.
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Link: https://lore.kernel.org/r/20240219132734.22881-3-sumanthk@linux.ibm.comSigned-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/tools/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 gen_facilities
 gen_opcode_table
+relocs

arch/s390/tools/Makefile

@@ -25,3 +25,8 @@ $(kapi)/facility-defs.h: $(obj)/gen_facilities FORCE
 
 $(kapi)/dis-defs.h: $(obj)/gen_opcode_table FORCE
 	$(call filechk,dis-defs.h)
+
+hostprogs	+= relocs
+PHONY		+= relocs
+relocs: $(obj)/relocs
+	@:

arch/s390/tools/relocs.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <elf.h>
+#include <byteswap.h>
+#define USE_BSD
+#include <endian.h>
+
+#define ELF_BITS 64
+
+#define ELF_MACHINE		EM_S390
+#define ELF_MACHINE_NAME	"IBM S/390"
+#define SHT_REL_TYPE		SHT_RELA
+#define Elf_Rel			Elf64_Rela
+
+#define ELF_CLASS		ELFCLASS64
+#define ELF_ENDIAN		ELFDATA2MSB
+#define ELF_R_SYM(val)		ELF64_R_SYM(val)
+#define ELF_R_TYPE(val)		ELF64_R_TYPE(val)
+#define ELF_ST_TYPE(o)		ELF64_ST_TYPE(o)
+#define ELF_ST_BIND(o)		ELF64_ST_BIND(o)
+#define ELF_ST_VISIBILITY(o)	ELF64_ST_VISIBILITY(o)
+
+#define ElfW(type)		_ElfW(ELF_BITS, type)
+#define _ElfW(bits, type)	__ElfW(bits, type)
+#define __ElfW(bits, type)	Elf##bits##_##type
+
+#define Elf_Addr		ElfW(Addr)
+#define Elf_Ehdr		ElfW(Ehdr)
+#define Elf_Phdr		ElfW(Phdr)
+#define Elf_Shdr		ElfW(Shdr)
+#define Elf_Sym			ElfW(Sym)
+
+static Elf_Ehdr		ehdr;
+static unsigned long	shnum;
+static unsigned int	shstrndx;
+
+struct relocs {
+	uint32_t	*offset;
+	unsigned long	count;
+	unsigned long	size;
+};
+
+static struct relocs relocs64;
+#define FMT PRIu64
+
+struct section {
+	Elf_Shdr	shdr;
+	struct section	*link;
+	Elf_Rel		*reltab;
+};
+
+static struct section *secs;
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+#define le16_to_cpu(val)	(val)
+#define le32_to_cpu(val)	(val)
+#define le64_to_cpu(val)	(val)
+#define be16_to_cpu(val)	bswap_16(val)
+#define be32_to_cpu(val)	bswap_32(val)
+#define be64_to_cpu(val)	bswap_64(val)
+#endif
+
+#if BYTE_ORDER == BIG_ENDIAN
+#define le16_to_cpu(val)	bswap_16(val)
+#define le32_to_cpu(val)	bswap_32(val)
+#define le64_to_cpu(val)	bswap_64(val)
+#define be16_to_cpu(val)	(val)
+#define be32_to_cpu(val)	(val)
+#define be64_to_cpu(val)	(val)
+#endif
+
+static uint16_t elf16_to_cpu(uint16_t val)
+{
+	if (ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
+		return le16_to_cpu(val);
+	else
+		return be16_to_cpu(val);
+}
+
+static uint32_t elf32_to_cpu(uint32_t val)
+{
+	if (ehdr.e_ident[EI_DATA] == ELFDATA2LSB)
+		return le32_to_cpu(val);
+	else
+		return be32_to_cpu(val);
+}
+
+#define elf_half_to_cpu(x)	elf16_to_cpu(x)
+#define elf_word_to_cpu(x)	elf32_to_cpu(x)
+
+static uint64_t elf64_to_cpu(uint64_t val)
+{
+	return be64_to_cpu(val);
+}
+
+#define elf_addr_to_cpu(x)	elf64_to_cpu(x)
+#define elf_off_to_cpu(x)	elf64_to_cpu(x)
+#define elf_xword_to_cpu(x)	elf64_to_cpu(x)
+
+static void die(char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+	exit(1);
+}
+
+static void read_ehdr(FILE *fp)
+{
+	if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
+		die("Cannot read ELF header: %s\n", strerror(errno));
+	if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0)
+		die("No ELF magic\n");
+	if (ehdr.e_ident[EI_CLASS] != ELF_CLASS)
+		die("Not a %d bit executable\n", ELF_BITS);
+	if (ehdr.e_ident[EI_DATA] != ELF_ENDIAN)
+		die("ELF endian mismatch\n");
+	if (ehdr.e_ident[EI_VERSION] != EV_CURRENT)
+		die("Unknown ELF version\n");
+
+	/* Convert the fields to native endian */
+	ehdr.e_type	 = elf_half_to_cpu(ehdr.e_type);
+	ehdr.e_machine	 = elf_half_to_cpu(ehdr.e_machine);
+	ehdr.e_version	 = elf_word_to_cpu(ehdr.e_version);
+	ehdr.e_entry	 = elf_addr_to_cpu(ehdr.e_entry);
+	ehdr.e_phoff	 = elf_off_to_cpu(ehdr.e_phoff);
+	ehdr.e_shoff	 = elf_off_to_cpu(ehdr.e_shoff);
+	ehdr.e_flags	 = elf_word_to_cpu(ehdr.e_flags);
+	ehdr.e_ehsize	 = elf_half_to_cpu(ehdr.e_ehsize);
+	ehdr.e_phentsize = elf_half_to_cpu(ehdr.e_phentsize);
+	ehdr.e_phnum	 = elf_half_to_cpu(ehdr.e_phnum);
+	ehdr.e_shentsize = elf_half_to_cpu(ehdr.e_shentsize);
+	ehdr.e_shnum	 = elf_half_to_cpu(ehdr.e_shnum);
+	ehdr.e_shstrndx  = elf_half_to_cpu(ehdr.e_shstrndx);
+
+	shnum = ehdr.e_shnum;
+	shstrndx = ehdr.e_shstrndx;
+
+	if ((ehdr.e_type != ET_EXEC) && (ehdr.e_type != ET_DYN))
+		die("Unsupported ELF header type\n");
+	if (ehdr.e_machine != ELF_MACHINE)
+		die("Not for %s\n", ELF_MACHINE_NAME);
+	if (ehdr.e_version != EV_CURRENT)
+		die("Unknown ELF version\n");
+	if (ehdr.e_ehsize != sizeof(Elf_Ehdr))
+		die("Bad Elf header size\n");
+	if (ehdr.e_phentsize != sizeof(Elf_Phdr))
+		die("Bad program header entry\n");
+	if (ehdr.e_shentsize != sizeof(Elf_Shdr))
+		die("Bad section header entry\n");
+
+	if (shnum == SHN_UNDEF || shstrndx == SHN_XINDEX) {
+		Elf_Shdr shdr;
+
+		if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0)
+			die("Seek to %" FMT " failed: %s\n", ehdr.e_shoff, strerror(errno));
+
+		if (fread(&shdr, sizeof(shdr), 1, fp) != 1)
+			die("Cannot read initial ELF section header: %s\n", strerror(errno));
+
+		if (shnum == SHN_UNDEF)
+			shnum = elf_xword_to_cpu(shdr.sh_size);
+
+		if (shstrndx == SHN_XINDEX)
+			shstrndx = elf_word_to_cpu(shdr.sh_link);
+	}
+
+	if (shstrndx >= shnum)
+		die("String table index out of bounds\n");
+}
+
+static void read_shdrs(FILE *fp)
+{
+	Elf_Shdr shdr;
+	int i;
+
+	secs = calloc(shnum, sizeof(struct section));
+	if (!secs)
+		die("Unable to allocate %ld section headers\n", shnum);
+
+	if (fseek(fp, ehdr.e_shoff, SEEK_SET) < 0)
+		die("Seek to %" FMT " failed: %s\n", ehdr.e_shoff, strerror(errno));
+
+	for (i = 0; i < shnum; i++) {
+		struct section *sec = &secs[i];
+
+		if (fread(&shdr, sizeof(shdr), 1, fp) != 1) {
+			die("Cannot read ELF section headers %d/%ld: %s\n",
+			    i, shnum, strerror(errno));
+		}
+
+		sec->shdr.sh_name      = elf_word_to_cpu(shdr.sh_name);
+		sec->shdr.sh_type      = elf_word_to_cpu(shdr.sh_type);
+		sec->shdr.sh_flags     = elf_xword_to_cpu(shdr.sh_flags);
+		sec->shdr.sh_addr      = elf_addr_to_cpu(shdr.sh_addr);
+		sec->shdr.sh_offset    = elf_off_to_cpu(shdr.sh_offset);
+		sec->shdr.sh_size      = elf_xword_to_cpu(shdr.sh_size);
+		sec->shdr.sh_link      = elf_word_to_cpu(shdr.sh_link);
+		sec->shdr.sh_info      = elf_word_to_cpu(shdr.sh_info);
+		sec->shdr.sh_addralign = elf_xword_to_cpu(shdr.sh_addralign);
+		sec->shdr.sh_entsize   = elf_xword_to_cpu(shdr.sh_entsize);
+
+		if (sec->shdr.sh_link < shnum)
+			sec->link = &secs[sec->shdr.sh_link];
+	}
+
+}
+
+static void read_relocs(FILE *fp)
+{
+	int i, j;
+
+	for (i = 0; i < shnum; i++) {
+		struct section *sec = &secs[i];
+
+		if (sec->shdr.sh_type != SHT_REL_TYPE)
+			continue;
+
+		sec->reltab = malloc(sec->shdr.sh_size);
+		if (!sec->reltab)
+			die("malloc of %" FMT " bytes for relocs 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->reltab, 1, sec->shdr.sh_size, fp) != sec->shdr.sh_size)
+			die("Cannot read symbol table: %s\n", strerror(errno));
+
+		for (j = 0; j < sec->shdr.sh_size / sizeof(Elf_Rel); j++) {
+			Elf_Rel *rel = &sec->reltab[j];
+
+			rel->r_offset = elf_addr_to_cpu(rel->r_offset);
+			rel->r_info   = elf_xword_to_cpu(rel->r_info);
+#if (SHT_REL_TYPE == SHT_RELA)
+			rel->r_addend = elf_xword_to_cpu(rel->r_addend);
+#endif
+		}
+	}
+}
+
+static void add_reloc(struct relocs *r, uint32_t offset)
+{
+	if (r->count == r->size) {
+		unsigned long newsize = r->size + 50000;
+		void *mem = realloc(r->offset, newsize * sizeof(r->offset[0]));
+
+		if (!mem)
+			die("realloc of %ld entries for relocs failed\n", newsize);
+
+		r->offset = mem;
+		r->size = newsize;
+	}
+	r->offset[r->count++] = offset;
+}
+
+static int do_reloc(struct section *sec, Elf_Rel *rel)
+{
+	unsigned int r_type = ELF64_R_TYPE(rel->r_info);
+	ElfW(Addr) offset = rel->r_offset;
+
+	switch (r_type) {
+	case R_390_NONE:
+	case R_390_PC32:
+	case R_390_PC64:
+	case R_390_PC16DBL:
+	case R_390_PC32DBL:
+	case R_390_PLT32DBL:
+	case R_390_GOTENT:
+		break;
+	case R_390_64:
+		add_reloc(&relocs64, offset);
+		break;
+	default:
+		die("Unsupported relocation type: %d\n", r_type);
+		break;
+	}
+
+	return 0;
+}
+
+static void walk_relocs(void)
+{
+	int i;
+
+	/* Walk through the relocations */
+	for (i = 0; i < shnum; i++) {
+		struct section *sec_applies;
+		int j;
+		struct section *sec = &secs[i];
+
+		if (sec->shdr.sh_type != SHT_REL_TYPE)
+			continue;
+
+		sec_applies = &secs[sec->shdr.sh_info];
+		if (!(sec_applies->shdr.sh_flags & SHF_ALLOC))
+			continue;
+
+		for (j = 0; j < sec->shdr.sh_size / sizeof(Elf_Rel); j++) {
+			Elf_Rel *rel = &sec->reltab[j];
+
+			do_reloc(sec, rel);
+		}
+	}
+}
+
+static int cmp_relocs(const void *va, const void *vb)
+{
+	const uint32_t *a, *b;
+
+	a = va; b = vb;
+	return (*a == *b) ? 0 : (*a > *b) ? 1 : -1;
+}
+
+static void sort_relocs(struct relocs *r)
+{
+	qsort(r->offset, r->count, sizeof(r->offset[0]), cmp_relocs);
+}
+
+static int print_reloc(uint32_t v)
+{
+	return fprintf(stdout, "\t.long 0x%08"PRIx32"\n", v) > 0 ? 0 : -1;
+}
+
+static void emit_relocs(void)
+{
+	int i;
+
+	walk_relocs();
+	sort_relocs(&relocs64);
+
+	printf(".section \".vmlinux.relocs_64\",\"a\"\n");
+	for (i = 0; i < relocs64.count; i++)
+		print_reloc(relocs64.offset[i]);
+}
+
+static void process(FILE *fp)
+{
+	read_ehdr(fp);
+	read_shdrs(fp);
+	read_relocs(fp);
+	emit_relocs();
+}
+
+static void usage(void)
+{
+	die("relocs vmlinux\n");
+}
+
+int main(int argc, char **argv)
+{
+	unsigned char e_ident[EI_NIDENT];
+	const char *fname;
+	FILE *fp;
+
+	fname = NULL;
+
+	if (argc != 2)
+		usage();
+
+	fname = argv[1];
+
+	fp = fopen(fname, "r");
+	if (!fp)
+		die("Cannot open %s: %s\n", fname, strerror(errno));
+
+	if (fread(&e_ident, 1, EI_NIDENT, fp) != EI_NIDENT)
+		die("Cannot read %s: %s", fname, strerror(errno));
+
+	rewind(fp);
+
+	process(fp);
+
+	fclose(fp);
+	return 0;
+}