xref: /illumos-gate/usr/src/cmd/sgs/rtld/amd64/_setup.c (revision 56726c7e)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2018, Joyent, Inc.
 * Copyright 2022 Oxide Computer Company
 */

/*
 * amd64 specific setup routine  -  relocate ld.so's symbols, setup its
 * environment, map in loadable sections of the executable.
 *
 * Takes base address ld.so was loaded at, address of ld.so's dynamic
 * structure, address of process environment pointers, address of auxiliary
 * vector and * argv[0] (process name).
 * If errors occur, send process signal - otherwise
 * return executable's entry point to the bootstrap routine.
 */

#include	<signal.h>
#include	<stdlib.h>
#include	<sys/auxv.h>
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<link.h>
#include	<dlfcn.h>
#include	"_rtld.h"
#include	"_audit.h"
#include	"msg.h"

/*
 * Number of bytes to save for register usage.
 */
uint_t _plt_save_size;
void (*_plt_fp_save)(void *);
void (*_plt_fp_restore)(void *);

extern void _elf_rtbndr_fp_save_orig(void *);
extern void _elf_rtbndr_fp_restore_orig(void *);
extern void _elf_rtbndr_fp_fxsave(void *);
extern void _elf_rtbndr_fp_fxrestore(void *);
extern void _elf_rtbndr_fp_xsave(void *);
extern void _elf_rtbndr_fp_xrestore(void *);

/*
 * Based on what the kernel has told us, go through and set up the various
 * pointers that we'll need for elf_rtbndr for the FPU.
 */
static void
_setup_plt_fpu(int kind, size_t len)
{
	/*
	 * If we didn't get a length for some reason, fall back to the old
	 * implementation.
	 */
	if (len == 0)
		kind = -1;

	switch (kind) {
	case AT_386_FPINFO_FXSAVE:
		_plt_fp_save = _elf_rtbndr_fp_fxsave;
		_plt_fp_restore = _elf_rtbndr_fp_fxrestore;
		_plt_save_size = len;
		break;
	/*
	 * We can treat processors that don't correctly handle the exception
	 * information in xsave the same way we do others. The information
	 * that may or may not be properly saved and restored should not be
	 * relevant to us because of the ABI.
	 */
	case AT_386_FPINFO_XSAVE:
	case AT_386_FPINFO_XSAVE_AMD:
		_plt_fp_save = _elf_rtbndr_fp_xsave;
		_plt_fp_restore = _elf_rtbndr_fp_xrestore;
		_plt_save_size = len;
		break;
	default:
		_plt_fp_save = _elf_rtbndr_fp_save_orig;
		_plt_fp_restore = _elf_rtbndr_fp_restore_orig;
		/*
		 * The ABI says that 8 floating point registers are used for
		 * passing arguments (%xmm0 through %xmm7). Because these
		 * registers on some platforms may shadow the %ymm and %zmm
		 * registers, we end up needing to size this for the maximally
		 * sized register we care about, a 512-bit (64-byte) zmm
		 * register.
		 */
		_plt_save_size = 64 * 8;
		break;
	}
}

/* VARARGS */
unsigned long
_setup(Boot *ebp, Dyn *ld_dyn)
{
	ulong_t		reladdr, relacount, ld_base = 0;
	ulong_t		relaent = 0, pltrelsz = 0;
	ulong_t		strtab, soname, interp_base = 0;
	char		*_rt_name, **_envp, **_argv;
	int		_syspagsz = 0, fd = -1;
	uint_t		_flags = 0;
	uint_t		hwcap[3] = { 0, 0, 0 };
	Dyn		*dyn_ptr;
	Phdr		*phdr = NULL;
	Rt_map		*lmp;
	auxv_t		*auxv, *_auxv;
	uid_t		uid = (uid_t)-1, euid = (uid_t)-1;
	gid_t		gid = (gid_t)-1, egid = (gid_t)-1;
	char		*_platform = NULL, *_execname = NULL, *_emulator = NULL;
	int		auxflags = -1, fpkind = -1;
	size_t		fpsize = 0;

	/*
	 * Scan the bootstrap structure to pick up the basics.
	 */
	for (; ebp->eb_tag != EB_NULL; ebp++)
		switch (ebp->eb_tag) {
		case EB_LDSO_BASE:
			ld_base = (unsigned long)ebp->eb_un.eb_val;
			break;
		case EB_ARGV:
			_argv = (char **)ebp->eb_un.eb_ptr;
			break;
		case EB_ENVP:
			_envp = (char **)ebp->eb_un.eb_ptr;
			break;
		case EB_AUXV:
			_auxv = (auxv_t *)ebp->eb_un.eb_ptr;
			break;
		case EB_PAGESIZE:
			_syspagsz = (int)ebp->eb_un.eb_val;
			break;
		}

	/*
	 * Search the aux. vector for the information passed by exec.
	 */
	for (auxv = _auxv; auxv->a_type != AT_NULL; auxv++) {
		switch (auxv->a_type) {
		case AT_EXECFD:
			/* this is the old exec that passes a file descriptor */
			fd = (int)auxv->a_un.a_val;
			break;
		case AT_FLAGS:
			/* processor flags (MAU available, etc) */
			_flags = auxv->a_un.a_val;
			break;
		case AT_PAGESZ:
			/* system page size */
			_syspagsz = (int)auxv->a_un.a_val;
			break;
		case AT_PHDR:
			/* address of the segment table */
			phdr = (Phdr *)auxv->a_un.a_ptr;
			break;
		case AT_BASE:
			/* interpreter base address */
			if (ld_base == 0)
				ld_base = auxv->a_un.a_val;
			interp_base = auxv->a_un.a_val;
			break;
		case AT_SUN_UID:
			/* effective user id for the executable */
			euid = (uid_t)auxv->a_un.a_val;
			break;
		case AT_SUN_RUID:
			/* real user id for the executable */
			uid = (uid_t)auxv->a_un.a_val;
			break;
		case AT_SUN_GID:
			/* effective group id for the executable */
			egid = (gid_t)auxv->a_un.a_val;
			break;
		case AT_SUN_RGID:
			/* real group id for the executable */
			gid = (gid_t)auxv->a_un.a_val;
			break;
		case AT_SUN_PLATFORM:
			/* platform name */
			_platform = auxv->a_un.a_ptr;
			break;
		case AT_SUN_EXECNAME:
			/* full pathname of execed object */
			_execname = auxv->a_un.a_ptr;
			break;
		case AT_SUN_AUXFLAGS:
			/* auxiliary flags */
			auxflags = (int)auxv->a_un.a_val;
			break;
		case AT_SUN_HWCAP:
			/* hardware capabilities */
			hwcap[0] = (uint_t)auxv->a_un.a_val;
			break;
		case AT_SUN_HWCAP2:
			/* hardware capabilities */
			hwcap[1] = (uint_t)auxv->a_un.a_val;
			break;
		case AT_SUN_HWCAP3:
			/* hardware capabilities */
			hwcap[2] = (uint_t)auxv->a_un.a_val;
			break;
		case AT_SUN_EMULATOR:
			/* name of emulation library, if any */
			_emulator = auxv->a_un.a_ptr;
			break;
		case AT_SUN_FPTYPE:
			fpkind = (int)auxv->a_un.a_val;
			break;
		case AT_SUN_FPSIZE:
			fpsize = (size_t)auxv->a_un.a_val;
			break;
		}
	}

	/*
	 * Get needed info from ld.so's dynamic structure.
	 */
	/* LINTED */
	dyn_ptr = (Dyn *)((char *)ld_dyn + ld_base);
	for (ld_dyn = dyn_ptr; ld_dyn->d_tag != DT_NULL; ld_dyn++) {
		switch (ld_dyn->d_tag) {
		case DT_RELA:
			reladdr = ld_dyn->d_un.d_ptr + ld_base;
			break;
		case DT_RELACOUNT:
			relacount = ld_dyn->d_un.d_val;
			break;
		case DT_RELAENT:
			relaent = ld_dyn->d_un.d_val;
			break;
		case DT_PLTRELSZ:
			pltrelsz = ld_dyn->d_un.d_val;
			break;
		case DT_STRTAB:
			strtab = ld_dyn->d_un.d_ptr + ld_base;
			break;
		case DT_SONAME:
			soname = ld_dyn->d_un.d_val;
			break;
		}
	}
	_rt_name = (char *)strtab + soname;

	/*
	 * If we don't have a RELAENT, just assume the size.
	 */
	if (relaent == 0)
		relaent = sizeof (Rela);

	/*
	 * As all global symbol references within ld.so.1 are protected
	 * (symbolic), only RELATIVE and JMPSLOT relocations should be left
	 * to process at runtime.  Process all relocations now.
	 */
	relacount += (pltrelsz / relaent);
	for (; relacount; relacount--) {
		ulong_t	roffset;

		roffset = ((Rela *)reladdr)->r_offset + ld_base;
		*((ulong_t *)roffset) += ld_base +
		    ((Rela *)reladdr)->r_addend;
		reladdr += relaent;
	}

	/*
	 * If an emulation library is being used, use that as the linker's
	 * effective executable name. The real executable is not linked by this
	 * linker.
	 */
	if (_emulator != NULL) {
		_execname = _emulator;
		rtld_flags2 |= RT_FL2_BRANDED;
	}

	/*
	 * Initialize the dyn_plt_ent_size field.  It currently contains the
	 * size of the dyn_plt_template.  It still needs to be aligned and have
	 * space for the 'dyn_data' area added.
	 */
	dyn_plt_ent_size = ROUND(dyn_plt_ent_size, M_WORD_ALIGN) +
	    sizeof (uintptr_t) + sizeof (uintptr_t) + sizeof (ulong_t) +
	    sizeof (ulong_t) + sizeof (Sym);

	/*
	 * Initialize the amd64 specific PLT relocation constants based on the
	 * FP information that we have.
	 */
	_setup_plt_fpu(fpkind, fpsize);

	/*
	 * Continue with generic startup processing.
	 */
	if ((lmp = setup((char **)_envp, (auxv_t *)_auxv, _flags, _platform,
	    _syspagsz, _rt_name, ld_base, interp_base, fd, phdr,
	    _execname, _argv, uid, euid, gid, egid, auxflags,
	    hwcap)) == NULL) {
		rtldexit(&lml_main, 1);
	}

	return (LM_ENTRY_PT(lmp)());
}