boot.h

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Author : guenther
Date : 2019-05-10 13:29:21
Hash : c0197e40
Message : ld.so boot cleanup support: - put functions and data which are only used before calling the executable's start function into their own page-aligned segments for unmapping (only done on amd64, arm64, armv7, powerpc, and sparc64 so far) - pass .init_array and .preinit_array functions an addition argument which is a callback to get a structure which includes a function that frees the boot text and data - sometimes delay doing RELRO processing: for a shared-object marked DF_1_INITFIRST do it after the object's .init_array, for the executable do it after the .preinit_array - improve test-ld.so to link against libpthread and trigger its initialization late libc changes to use this will come later ok kettenis@

lib/csu/boot.h

/*	$OpenBSD: boot.h,v 1.30 2019/05/10 13:29:21 guenther Exp $ */

/*
 * Copyright (c) 1998 Per Fogelstrom, Opsycon AB
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

/*
 * IMPORTANT: any functions below are NOT protected by SSP.  Please
 * do not add anything except what is required to reach GOT with
 * an adjustment.
 */

#define	_DYN_LOADER

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/exec.h>
#include <sys/sysctl.h>
#include <nlist.h>
#include <link.h>
#include <dlfcn.h>

#include "syscall.h"
#include "archdep.h"
#include "path.h"
#include "resolve.h"
#include "sod.h"
#include "stdlib.h"

/*
 * Use the internal, hidden name for any syscalls we need, to avoid
 * accidental override by application code
 */
#define REDIRECT_SYSCALL(x)	typeof(x) x asm("_libc_"#x) __dso_hidden
REDIRECT_SYSCALL(mprotect);

#ifdef RCRT0

#define	DT_PROC(n)	((n) - DT_LOPROC)

#if RELOC_TAG == DT_RELA
typedef	Elf_RelA	RELOC_TYPE;
#elif RELOC_TAG == DT_REL
typedef	Elf_Rel		RELOC_TYPE;
#else
# error "unknown RELOC_TAG"
#endif

/* The set of dynamic tags that we're interested in for bootstrapping */
struct boot_dyn {
	RELOC_TYPE	*dt_reloc;	/* DT_RELA   or DT_REL */
	Elf_Addr	dt_relocsz;	/* DT_RELASZ or DT_RELSZ */
	Elf_Addr	*dt_pltgot;
	Elf_Addr	dt_pltrelsz;
	const Elf_Sym	*dt_symtab;
	RELOC_TYPE	*dt_jmprel;
#if DT_PROCNUM > 0
	u_long		dt_proc[DT_PROCNUM];
#endif
};

static void *relro_addr;
static size_t relro_size;
#define RCRT0_RELRO()							\
	do {								\
		if (relro_addr != NULL && relro_size != 0)		\
			mprotect(relro_addr, relro_size, PROT_READ);	\
	} while (0)

/*
 * Local decls.
 */
void _dl_boot_bind(const long, long *, Elf_Dyn *);

void
_dl_boot_bind(const long sp, long *dl_data, Elf_Dyn *dynamicp)
{
	struct boot_dyn	dynld;		/* Resolver data for the loader */
	AuxInfo		*auxstack;
	long		*stack;
	Elf_Dyn		*dynp;
	int		n, argc;
	char		**argv, **envp;
	long		loff;
	RELOC_TYPE	*rp;
	Elf_Phdr	*phdp;
	Elf_Addr	i;

	/*
	 * Scan argument and environment vectors. Find dynamic
	 * data vector put after them.
	 */
	stack = (long *)sp;
	argc = *stack++;
	argv = (char **)stack;
	envp = &argv[argc + 1];
	stack = (long *)envp;
	while (*stack++ != 0L)
		;

	/*
	 * Zero out dl_data.
	 */
	for (n = 0; n <= AUX_entry; n++)
		dl_data[n] = 0;

	/*
	 * Dig out auxiliary data set up by exec call. Move all known
	 * tags to an indexed local table for easy access.
	 */
	for (auxstack = (AuxInfo *)stack; auxstack->au_id != AUX_null;
	    auxstack++) {
		if (auxstack->au_id > AUX_entry)
			continue;
		dl_data[auxstack->au_id] = auxstack->au_v;
	}
	loff = dl_data[AUX_base];	/* XXX assumes ld.so is linked at 0x0 */

	/*
	 * We need to do 'selfreloc' in case the code weren't
	 * loaded at the address it was linked to.
	 *
	 * Scan the DYNAMIC section for the loader.
	 * Cache the data for easier access.
	 */
	dynp = dynamicp;

	_dl_memset(&dynld, 0, sizeof(dynld));
	while (dynp->d_tag != DT_NULL) {
		/* first the tags that are pointers to be relocated */
		if (dynp->d_tag == DT_PLTGOT)
			dynld.dt_pltgot = (void *)(dynp->d_un.d_ptr + loff);
		else if (dynp->d_tag == DT_SYMTAB)
			dynld.dt_symtab = (void *)(dynp->d_un.d_ptr + loff);
		else if (dynp->d_tag == RELOC_TAG)	/* DT_{RELA,REL} */
			dynld.dt_reloc = (void *)(dynp->d_un.d_ptr + loff);
		else if (dynp->d_tag == DT_JMPREL)
			dynld.dt_jmprel = (void *)(dynp->d_un.d_ptr + loff);

		/* Now for the tags that are just sizes or counts */
		else if (dynp->d_tag == DT_PLTRELSZ)
			dynld.dt_pltrelsz = dynp->d_un.d_val;
		else if (dynp->d_tag == RELOC_TAG+1)	/* DT_{RELA,REL}SZ */
			dynld.dt_relocsz = dynp->d_un.d_val;
#if DT_PROCNUM > 0
		else if (dynp->d_tag >= DT_LOPROC &&
		    dynp->d_tag < DT_LOPROC + DT_PROCNUM)
			dynld.dt_proc[dynp->d_tag - DT_LOPROC] =
			    dynp->d_un.d_val;
#endif /* DT_PROCNUM */
		dynp++;
	}

	rp = dynld.dt_jmprel;
	for (i = 0; i < dynld.dt_pltrelsz; i += sizeof *rp) {
		const Elf_Sym *sp;

		sp = dynld.dt_symtab + ELF_R_SYM(rp->r_info);
		if (!ELF_R_SYM(rp->r_info) || sp->st_value != 0) {
#ifdef HAVE_JMPREL
			Elf_Addr *ra = (Elf_Addr *)(rp->r_offset + loff);
			RELOC_JMPREL(rp, sp, ra, loff, dynld.dt_pltgot);
#else
			_dl_exit(6);
#endif
		}
		rp++;
	}

	rp = dynld.dt_reloc;
	for (i = 0; i < dynld.dt_relocsz; i += sizeof *rp) {
		Elf_Addr *ra;
		const Elf_Sym *sp;

		sp = dynld.dt_symtab + ELF_R_SYM(rp->r_info);
		if (!ELF_R_SYM(rp->r_info) || sp->st_value != 0) {
			ra = (Elf_Addr *)(rp->r_offset + loff);
			RELOC_DYN(rp, sp, ra, loff);
		}
		rp++;
	}

	RELOC_GOT(&dynld, loff);

	/*
	 * we have been fully relocated here, so most things no longer
	 * need the loff adjustment
	 */

	/*
	 * No further changes to the PLT and/or GOT are needed so make
	 * them read-only.
	 */

	/* do any RWX -> RX fixups for executable PLTs and apply GNU_RELRO */
	phdp = (Elf_Phdr *)dl_data[AUX_phdr];
	for (i = 0; i < dl_data[AUX_phnum]; i++, phdp++) {
		switch (phdp->p_type) {
#if defined(__alpha__) || defined(__hppa__) || defined(__powerpc__) || \
    defined(__sparc64__)
		case PT_LOAD:
			if ((phdp->p_flags & (PF_X | PF_W)) != (PF_X | PF_W))
				break;
			mprotect((void *)(phdp->p_vaddr + loff), phdp->p_memsz,
			    PROT_READ);
			break;
#endif
		case PT_GNU_RELRO:
			relro_addr = (void *)(phdp->p_vaddr + loff);
			relro_size = phdp->p_memsz;
			/*
			 * GNU_RELRO (a) covers the GOT, and (b) comes after
			 * all LOAD sections, so if we found it then we're done
			 */
			break;
		}
	}
}

#endif /* RCRT0 */

IABSD.fr/src/lib/csu/boot.h

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IABSD.fr/src /lib/csu/boot.h