dt_link.c

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/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only.
 * See the file usr/src/LICENSING.NOTICE in this distribution or
 * http://www.opensolaris.org/license/ for details.
 */

#pragma ident	"@(#)dt_link.c	1.7	05/01/07 SMI"

#define	ELF_TARGET_ALL
#include <elf.h>

#include <sys/types.h>
#include <sys/sysmacros.h>

#include <unistd.h>
#include <strings.h>
#include <alloca.h>
#include <limits.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <wait.h>
#include <assert.h>

#include <dt_impl.h>
#include <dt_provider.h>
#include <dt_string.h>

#define	ESHDR_NULL	0
#define	ESHDR_SHSTRTAB	1
#define	ESHDR_DOF	2
#define	ESHDR_STRTAB	3
#define	ESHDR_SYMTAB	4
#define	ESHDR_REL	5
#define	ESHDR_NUM	6

#define	PWRITE_SCN(index, data) \
	(lseek64(fd, (off64_t)elf_file.shdr[(index)].sh_offset, SEEK_SET) != \
	(off64_t)elf_file.shdr[(index)].sh_offset || \
	dt_write(dtp, fd, (data), elf_file.shdr[(index)].sh_size) != \
	elf_file.shdr[(index)].sh_size)

static const char DTRACE_SHSTRTAB32[] = "\0"
".shstrtab\0"		/* 1 */
".SUNW_dof\0"		/* 11 */
".strtab\0"		/* 21 */
".symtab\0"		/* 29 */
#ifdef __sparc
".rela.SUNW_dof";	/* 37 */
#else
".rel.SUNW_dof";	/* 37 */
#endif

static const char DTRACE_SHSTRTAB64[] = "\0"
".shstrtab\0"		/* 1 */
".SUNW_dof\0"		/* 11 */
".strtab\0"		/* 21 */
".symtab\0"		/* 29 */
".rela.SUNW_dof";	/* 37 */

static const char DOFSTR[] = "__SUNW_dof";
static const char DOFLAZYSTR[] = "___SUNW_dof";

typedef struct dof_elf32 {
	uint32_t de_nrel;	/* relocation count */
#ifdef __sparc
	Elf32_Rela *de_rel;	/* array of relocations for sparc */
#else
	Elf32_Rel *de_rel;	/* array of relocations for x86 */
#endif
	uint32_t de_nsym;	/* symbol count */
	Elf32_Sym *de_sym;	/* array of symbols */
	uint32_t de_strlen;	/* size of of string table */
	char *de_strtab;	/* string table */
	uint32_t de_global;	/* index of the first global symbol */
} dof_elf32_t;

static int
prepare_elf32(dtrace_hdl_t *dtp, const dof_hdr_t *dof, dof_elf32_t *dep)
{
	dof_sec_t *dofs, *s;
	dof_relohdr_t *dofrh;
	dof_relodesc_t *dofr;
	char *strtab;
	int i, j, nrel;
	size_t strtabsz = 1;
	uint32_t count = 0;
	size_t base;
	Elf32_Sym *sym;
#ifdef __sparc
	Elf32_Rela *rel;
#else
	Elf32_Rel *rel;
#endif

	/*LINTED*/
	dofs = (dof_sec_t *)((char *)dof + dof->dofh_secoff);

	/*
	 * First compute the size of the string table and the number of
	 * relocations present in the DOF.
	 */
	for (i = 0; i < dof->dofh_secnum; i++) {
		if (dofs[i].dofs_type != DOF_SECT_URELHDR)
			continue;

		/*LINTED*/
		dofrh = (dof_relohdr_t *)((char *)dof + dofs[i].dofs_offset);

		s = &dofs[dofrh->dofr_strtab];
		strtab = (char *)dof + s->dofs_offset;
		assert(strtab[0] == '\0');
		strtabsz += s->dofs_size - 1;

		s = &dofs[dofrh->dofr_relsec];
		/*LINTED*/
		dofr = (dof_relodesc_t *)((char *)dof + s->dofs_offset);
		count += s->dofs_size / s->dofs_entsize;
	}

	dep->de_strlen = strtabsz;
	dep->de_nrel = count;
	dep->de_nsym = count + 1; /* the first symbol is always null */

	if (dtp->dt_lazyload) {
		dep->de_strlen += sizeof (DOFLAZYSTR);
		dep->de_nsym++;
	} else {
		dep->de_strlen += sizeof (DOFSTR);
		dep->de_nsym++;
	}

	if ((dep->de_rel = calloc(dep->de_nrel,
	    sizeof (dep->de_rel[0]))) == NULL) {
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	if ((dep->de_sym = calloc(dep->de_nsym, sizeof (Elf32_Sym))) == NULL) {
		free(dep->de_rel);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	if ((dep->de_strtab = calloc(dep->de_strlen, 1)) == NULL) {
		free(dep->de_rel);
		free(dep->de_sym);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	count = 0;
	strtabsz = 1;
	dep->de_strtab[0] = '\0';
	rel = dep->de_rel;
	sym = dep->de_sym;
	dep->de_global = 1;

	/*
	 * The first symbol table entry must be zeroed and is always ignored.
	 */
	bzero(sym, sizeof (Elf32_Sym));
	sym++;

	/*
	 * Take a second pass through the DOF sections filling in the
	 * memory we allocated.
	 */
	for (i = 0; i < dof->dofh_secnum; i++) {
		if (dofs[i].dofs_type != DOF_SECT_URELHDR)
			continue;

		/*LINTED*/
		dofrh = (dof_relohdr_t *)((char *)dof + dofs[i].dofs_offset);

		s = &dofs[dofrh->dofr_strtab];
		strtab = (char *)dof + s->dofs_offset;
		bcopy(strtab + 1, dep->de_strtab + strtabsz, s->dofs_size);
		base = strtabsz;
		strtabsz += s->dofs_size - 1;

		s = &dofs[dofrh->dofr_relsec];
		/*LINTED*/
		dofr = (dof_relodesc_t *)((char *)dof + s->dofs_offset);
		nrel = s->dofs_size / s->dofs_entsize;

		s = &dofs[dofrh->dofr_tgtsec];

		for (j = 0; j < nrel; j++) {
#if defined(__i386) || defined(__amd64)
			rel->r_offset = s->dofs_offset +
			    dofr[j].dofr_offset;
			rel->r_info = ELF32_R_INFO(count + dep->de_global,
			    R_386_32);
#elif defined(__sparc)
			/*
			 * Add 4 bytes to hit the low half of this 64-bit
			 * big-endian address.
			 */
			rel->r_offset = s->dofs_offset +
			    dofr[j].dofr_offset + 4;
			rel->r_info = ELF32_R_INFO(count + dep->de_global,
			    R_SPARC_32);
#else
#error unknown ISA
#endif

			sym->st_name = base + dofr[j].dofr_name - 1;
			sym->st_value = 0;
			sym->st_size = 0;
			sym->st_info = ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE);
			sym->st_other = 0;
			sym->st_shndx = SHN_UNDEF;

			rel++;
			sym++;
			count++;
		}
	}

	/*
	 * Add a symbol for the DOF itself. We use a different symbol for
	 * lazily and actively loaded DOF to make them easy to distinguish.
	 */
	sym->st_name = strtabsz;
	sym->st_value = 0;
	sym->st_size = dof->dofh_filesz;
	sym->st_info = ELF32_ST_INFO(STB_GLOBAL, STT_OBJECT);
	sym->st_other = 0;
	sym->st_shndx = ESHDR_DOF;
	sym++;

	if (dtp->dt_lazyload) {
		bcopy(DOFLAZYSTR, dep->de_strtab + strtabsz,
		    sizeof (DOFLAZYSTR));
		strtabsz += sizeof (DOFLAZYSTR);
	} else {
		bcopy(DOFSTR, dep->de_strtab + strtabsz, sizeof (DOFSTR));
		strtabsz += sizeof (DOFSTR);
	}

	assert(count == dep->de_nrel);
	assert(strtabsz == dep->de_strlen);

	return (0);
}


typedef struct dof_elf64 {
	uint32_t de_nrel;
	Elf64_Rela *de_rel;
	uint32_t de_nsym;
	Elf64_Sym *de_sym;

	uint32_t de_strlen;
	char *de_strtab;

	uint32_t de_global;
} dof_elf64_t;

static int
prepare_elf64(dtrace_hdl_t *dtp, const dof_hdr_t *dof, dof_elf64_t *dep)
{
	dof_sec_t *dofs, *s;
	dof_relohdr_t *dofrh;
	dof_relodesc_t *dofr;
	char *strtab;
	int i, j, nrel;
	size_t strtabsz = 1;
	uint32_t count = 0;
	size_t base;
	Elf64_Sym *sym;
	Elf64_Rela *rel;

	/*LINTED*/
	dofs = (dof_sec_t *)((char *)dof + dof->dofh_secoff);

	/*
	 * First compute the size of the string table and the number of
	 * relocations present in the DOF.
	 */
	for (i = 0; i < dof->dofh_secnum; i++) {
		if (dofs[i].dofs_type != DOF_SECT_URELHDR)
			continue;

		/*LINTED*/
		dofrh = (dof_relohdr_t *)((char *)dof + dofs[i].dofs_offset);

		s = &dofs[dofrh->dofr_strtab];
		strtab = (char *)dof + s->dofs_offset;
		assert(strtab[0] == '\0');
		strtabsz += s->dofs_size - 1;

		s = &dofs[dofrh->dofr_relsec];
		/*LINTED*/
		dofr = (dof_relodesc_t *)((char *)dof + s->dofs_offset);
		count += s->dofs_size / s->dofs_entsize;
	}

	dep->de_strlen = strtabsz;
	dep->de_nrel = count;
	dep->de_nsym = count + 1; /* the first symbol is always null */

	if (dtp->dt_lazyload) {
		dep->de_strlen += sizeof (DOFLAZYSTR);
		dep->de_nsym++;
	} else {
		dep->de_strlen += sizeof (DOFSTR);
		dep->de_nsym++;
	}

	if ((dep->de_rel = calloc(dep->de_nrel,
	    sizeof (dep->de_rel[0]))) == NULL) {
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	if ((dep->de_sym = calloc(dep->de_nsym, sizeof (Elf64_Sym))) == NULL) {
		free(dep->de_rel);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	if ((dep->de_strtab = calloc(dep->de_strlen, 1)) == NULL) {
		free(dep->de_rel);
		free(dep->de_sym);
		return (dt_set_errno(dtp, EDT_NOMEM));
	}

	count = 0;
	strtabsz = 1;
	dep->de_strtab[0] = '\0';
	rel = dep->de_rel;
	sym = dep->de_sym;
	dep->de_global = 1;

	/*
	 * The first symbol table entry must be zeroed and is always ignored.
	 */
	bzero(sym, sizeof (Elf64_Sym));
	sym++;

	/*
	 * Take a second pass through the DOF sections filling in the
	 * memory we allocated.
	 */
	for (i = 0; i < dof->dofh_secnum; i++) {
		if (dofs[i].dofs_type != DOF_SECT_URELHDR)
			continue;

		/*LINTED*/
		dofrh = (dof_relohdr_t *)((char *)dof + dofs[i].dofs_offset);

		s = &dofs[dofrh->dofr_strtab];
		strtab = (char *)dof + s->dofs_offset;
		bcopy(strtab + 1, dep->de_strtab + strtabsz, s->dofs_size);
		base = strtabsz;
		strtabsz += s->dofs_size - 1;

		s = &dofs[dofrh->dofr_relsec];
		/*LINTED*/
		dofr = (dof_relodesc_t *)((char *)dof + s->dofs_offset);
		nrel = s->dofs_size / s->dofs_entsize;

		s = &dofs[dofrh->dofr_tgtsec];

		for (j = 0; j < nrel; j++) {
#if defined(__i386) || defined(__amd64)
			rel->r_offset = s->dofs_offset +
			    dofr[j].dofr_offset;
			rel->r_info = ELF64_R_INFO(count + dep->de_global,
			    R_AMD64_64);
#elif defined(__sparc)
			rel->r_offset = s->dofs_offset +
			    dofr[j].dofr_offset;
			rel->r_info = ELF64_R_INFO(count + dep->de_global,
			    R_SPARC_64);
#else
#error unknown ISA
#endif

			sym->st_name = base + dofr[j].dofr_name - 1;
			sym->st_value = 0;
			sym->st_size = 0;
			sym->st_info = ELF64_ST_INFO(STB_GLOBAL, STT_NOTYPE);
			sym->st_other = 0;
			sym->st_shndx = SHN_UNDEF;

			rel++;
			sym++;
			count++;
		}
	}

	/*
	 * Add a symbol for the DOF itself. We use a different symbol for
	 * lazily and actively loaded DOF to make them easy to distinguish.
	 */
	sym->st_name = strtabsz;
	sym->st_value = 0;
	sym->st_size = dof->dofh_filesz;
	sym->st_info = ELF64_ST_INFO(STB_GLOBAL, STT_OBJECT);
	sym->st_other = 0;
	sym->st_shndx = ESHDR_DOF;
	sym++;

	if (dtp->dt_lazyload) {
		bcopy(DOFLAZYSTR, dep->de_strtab + strtabsz,
		    sizeof (DOFLAZYSTR));
		strtabsz += sizeof (DOFLAZYSTR);
	} else {
		bcopy(DOFSTR, dep->de_strtab + strtabsz, sizeof (DOFSTR));
		strtabsz += sizeof (DOFSTR);
	}

	assert(count == dep->de_nrel);
	assert(strtabsz == dep->de_strlen);

	return (0);
}

/*
 * Write out an ELF32 file prologue consisting of a header, section headers,
 * and a section header string table.  The DOF data will follow this prologue
 * and complete the contents of the given ELF file.
 */
static int
dump_elf32(dtrace_hdl_t *dtp, const dof_hdr_t *dof, int fd)
{
	struct {
		Elf32_Ehdr ehdr;
		Elf32_Shdr shdr[ESHDR_NUM];
	} elf_file;

	Elf32_Shdr *shp;
	Elf32_Off off;
	dof_elf32_t de;
	int ret = 0;
	uint_t nshdr;

	if (prepare_elf32(dtp, dof, &de) != 0)
		return (-1); /* errno is set for us */

	/*
	 * If there are no relocations, we only need enough sections for
	 * the shstrtab and the DOF.
	 */
	nshdr = de.de_nrel == 0 ? ESHDR_SYMTAB + 1 : ESHDR_NUM;

	bzero(&elf_file, sizeof (elf_file));

	elf_file.ehdr.e_ident[EI_MAG0] = ELFMAG0;
	elf_file.ehdr.e_ident[EI_MAG1] = ELFMAG1;
	elf_file.ehdr.e_ident[EI_MAG2] = ELFMAG2;
	elf_file.ehdr.e_ident[EI_MAG3] = ELFMAG3;
	elf_file.ehdr.e_ident[EI_VERSION] = EV_CURRENT;
	elf_file.ehdr.e_ident[EI_CLASS] = ELFCLASS32;
#if defined(_BIG_ENDIAN)
	elf_file.ehdr.e_ident[EI_DATA] = ELFDATA2MSB;
#elif defined(_LITTLE_ENDIAN)
	elf_file.ehdr.e_ident[EI_DATA] = ELFDATA2LSB;
#endif
	elf_file.ehdr.e_type = ET_REL;
#if defined(__sparc)
	elf_file.ehdr.e_machine = EM_SPARC;
#elif defined(__i386) || defined(__amd64)
	elf_file.ehdr.e_machine = EM_386;
#endif
	elf_file.ehdr.e_version = EV_CURRENT;
	elf_file.ehdr.e_shoff = sizeof (Elf32_Ehdr);
	elf_file.ehdr.e_ehsize = sizeof (Elf32_Ehdr);
	elf_file.ehdr.e_phentsize = sizeof (Elf32_Phdr);
	elf_file.ehdr.e_shentsize = sizeof (Elf32_Shdr);
	elf_file.ehdr.e_shnum = nshdr;
	elf_file.ehdr.e_shstrndx = ESHDR_SHSTRTAB;
	off = sizeof (elf_file) + nshdr * sizeof (Elf32_Shdr);

	shp = &elf_file.shdr[ESHDR_SHSTRTAB];
	shp->sh_name = 1; /* DTRACE_SHSTRTAB32[1] = ".shstrtab" */
	shp->sh_type = SHT_STRTAB;
	shp->sh_offset = off;
	shp->sh_size = sizeof (DTRACE_SHSTRTAB32);
	shp->sh_addralign = sizeof (char);
	off = P2ROUNDUP(shp->sh_offset + shp->sh_size, 8);

	shp = &elf_file.shdr[ESHDR_DOF];
	shp->sh_name = 11; /* DTRACE_SHSTRTAB32[11] = ".SUNW_dof" */
	shp->sh_flags = SHF_ALLOC;
	shp->sh_type = SHT_SUNW_dof;
	shp->sh_offset = off;
	shp->sh_size = dof->dofh_filesz;
	shp->sh_addralign = 8;
	off = shp->sh_offset + shp->sh_size;

	shp = &elf_file.shdr[ESHDR_STRTAB];
	shp->sh_name = 21; /* DTRACE_SHSTRTAB32[21] = ".strtab" */
	shp->sh_flags = SHF_ALLOC;
	shp->sh_type = SHT_STRTAB;
	shp->sh_offset = off;
	shp->sh_size = de.de_strlen;
	shp->sh_addralign = sizeof (char);
	off = P2ROUNDUP(shp->sh_offset + shp->sh_size, 4);

	shp = &elf_file.shdr[ESHDR_SYMTAB];
	shp->sh_name = 29; /* DTRACE_SHSTRTAB32[29] = ".symtab" */
	shp->sh_flags = SHF_ALLOC;
	shp->sh_type = SHT_SYMTAB;
	shp->sh_entsize = sizeof (Elf32_Sym);
	shp->sh_link = ESHDR_STRTAB;
	shp->sh_offset = off;
	shp->sh_info = de.de_global;
	shp->sh_size = de.de_nsym * sizeof (Elf32_Sym);
	shp->sh_addralign = 4;
	off = P2ROUNDUP(shp->sh_offset + shp->sh_size, 4);

	if (de.de_nrel == 0) {
		if (dt_write(dtp, fd, &elf_file,
		    sizeof (elf_file)) != sizeof (elf_file) ||
		    PWRITE_SCN(ESHDR_SHSTRTAB, DTRACE_SHSTRTAB32) ||
		    PWRITE_SCN(ESHDR_STRTAB, de.de_strtab) ||
		    PWRITE_SCN(ESHDR_SYMTAB, de.de_sym) ||
		    PWRITE_SCN(ESHDR_DOF, dof)) {
			ret = dt_set_errno(dtp, errno);
		}
	} else {
		shp = &elf_file.shdr[ESHDR_REL];
		shp->sh_name = 37; /* DTRACE_SHSTRTAB32[37] = ".rel.SUNW_dof" */
		shp->sh_flags = SHF_ALLOC;
#ifdef __sparc
		shp->sh_type = SHT_RELA;
#else
		shp->sh_type = SHT_REL;
#endif
		shp->sh_entsize = sizeof (de.de_rel[0]);
		shp->sh_link = ESHDR_SYMTAB;
		shp->sh_info = ESHDR_DOF;
		shp->sh_offset = off;
		shp->sh_size = de.de_nrel * sizeof (de.de_rel[0]);
		shp->sh_addralign = 4;

		if (dt_write(dtp, fd, &elf_file,
		    sizeof (elf_file)) != sizeof (elf_file) ||
		    PWRITE_SCN(ESHDR_SHSTRTAB, DTRACE_SHSTRTAB32) ||
		    PWRITE_SCN(ESHDR_STRTAB, de.de_strtab) ||
		    PWRITE_SCN(ESHDR_SYMTAB, de.de_sym) ||
		    PWRITE_SCN(ESHDR_REL, de.de_rel) ||
		    PWRITE_SCN(ESHDR_DOF, dof)) {
			ret = dt_set_errno(dtp, errno);
		}
	}

	free(de.de_strtab);
	free(de.de_sym);
	free(de.de_rel);

	return (ret);