rtld_machine.c

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Author : guenther
Date : 2019-12-07 22:57:47
Hash : d9337de3
Message : Disable ltrace for objects linked with -znow, as at least on amd64, linking that was deletes the lazy relocation trampoline which ltrace currently depends on problem reported by tb@ directional feedback kettenis@ ok mpi@
libexec/ld.so/alpha/rtld_machine.c
/*	$OpenBSD: rtld_machine.c,v 1.70 2019/12/07 22:57:47 guenther Exp $ */

/*
 * Copyright (c) 1999 Dale Rahn
 * Copyright (c) 2001 Niklas Hallqvist
 * Copyright (c) 2001 Artur Grabowski
 *
 * 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.
 *
 */

#define _DYN_LOADER

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/exec.h>
#include <sys/syscall.h>
#include <sys/unistd.h>
#include <machine/pal.h>

#include <nlist.h>
#include <link.h>

#include "syscall.h"
#include "archdep.h"
#include "resolve.h"

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

int64_t pcookie __attribute__((section(".openbsd.randomdata"))) __dso_hidden;

int
_dl_md_reloc(elf_object_t *object, int rel, int relasz)
{
	long	i;
	long	numrela;
	long	relrel;
	int	fails = 0;
	Elf_Addr loff;
	Elf_Addr prev_value = 0;
	const Elf_Sym *prev_sym = NULL;
	Elf_RelA  *relas;

	loff = object->obj_base;
	numrela = object->Dyn.info[relasz] / sizeof(Elf_RelA);
	relrel = rel == DT_RELA ? object->relacount : 0;
	relas = (Elf_RelA *)(object->Dyn.info[rel]);

	if (relas == NULL)
		return 0;

	if (relrel > numrela)
		_dl_die("relacount > numrel: %ld > %ld", relrel, numrela);

	if (! object->Dyn.info[DT_PROC(DT_ALPHA_PLTRO)])
		_dl_die("unsupported insecure PLT object");

	/* tight loop for leading RELATIVE relocs */
	for (i = 0; i < relrel; i++, relas++) {
		Elf_Addr *r_addr;

		r_addr = (Elf_Addr *)(relas->r_offset + loff);

		/* Handle unaligned RELATIVE relocs */
		if ((((Elf_Addr)r_addr) & 0x7) != 0) {
			Elf_Addr tmp;
			_dl_bcopy(r_addr, &tmp, sizeof(Elf_Addr));
			tmp += loff;
			_dl_bcopy(&tmp, r_addr, sizeof(Elf_Addr));
		} else
			*r_addr += loff;
	}
	for (; i < numrela; i++, relas++) {
		Elf_Addr *r_addr;
		struct sym_res sr;
		const Elf_Sym *sym;
		const char *symn;

		r_addr = (Elf_Addr *)(relas->r_offset + loff);

		if (ELF_R_SYM(relas->r_info) == 0xffffffff)
			continue;


		sym = object->dyn.symtab;
		sym += ELF_R_SYM(relas->r_info);
		symn = object->dyn.strtab + sym->st_name;

		switch (ELF_R_TYPE(relas->r_info)) {
		case R_TYPE(REFQUAD):
			sr = _dl_find_symbol(symn,
			    SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_NOTPLT,
			    sym, object);
			if (sr.sym == NULL)
				goto resolve_failed;
			*r_addr += sr.obj->obj_base + sr.sym->st_value +
			    relas->r_addend;
			break;
		case R_TYPE(RELATIVE):
			/*
			 * There is a lot of unaligned RELATIVE
			 * relocs generated by gcc in the exception handlers.
			 */
			if ((((Elf_Addr) r_addr) & 0x7) != 0) {
				Elf_Addr tmp;
#if 0
_dl_printf("unaligned RELATIVE: %p type: %d %s 0x%lx -> 0x%lx\n", r_addr,
    ELF_R_TYPE(relas->r_info), object->load_name, *r_addr, *r_addr+loff);
#endif
				_dl_bcopy(r_addr, &tmp, sizeof(Elf_Addr));
				tmp += loff;
				_dl_bcopy(&tmp, r_addr, sizeof(Elf_Addr));
			} else
				*r_addr += loff;
			break;
		case R_TYPE(JMP_SLOT):
			sr = _dl_find_symbol(symn,
			    SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT,
			    sym, object);
			if (sr.sym == NULL)
				goto resolve_failed;
			*r_addr = sr.obj->obj_base + sr.sym->st_value +
			    relas->r_addend;
			break;
		case R_TYPE(GLOB_DAT):
			if (sym == prev_sym) {
				*r_addr = prev_value + relas->r_addend;
				break;
			}
			sr = _dl_find_symbol(symn,
			    SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_NOTPLT,
			    sym, object);
			if (sr.sym == NULL)
				goto resolve_failed;
			prev_sym = sym;
			prev_value = sr.obj->obj_base + sr.sym->st_value;
			*r_addr = prev_value + relas->r_addend;
			break;
		case R_TYPE(NONE):
			break;
		default:
			_dl_die("%s: unsupported relocation '%s' %lld at %p",
			    object->load_name, symn,
			    ELF_R_TYPE(relas->r_info), (void *)r_addr);
		}
		continue;
resolve_failed:
		if (ELF_ST_BIND(sym->st_info) != STB_WEAK)
			fails++;
	}
	__asm volatile("imb" : : : "memory");

	return fails;
}

/*
 * Resolve a symbol at run-time.
 */
Elf_Addr
_dl_bind(elf_object_t *object, int reloff)
{
	Elf_RelA *rela;
	struct sym_res sr;
	const Elf_Sym *sym;
	const char *symn;
	uint64_t cookie = pcookie;
	struct {
		struct __kbind param;
		Elf_Addr newval;
	} buf;

	rela = (Elf_RelA *)(object->Dyn.info[DT_JMPREL] + reloff);

	sym = object->dyn.symtab;
	sym += ELF_R_SYM(rela->r_info);
	symn = object->dyn.strtab + sym->st_name;

	sr = _dl_find_symbol(symn, SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT,
	    sym, object);
	if (sr.sym == NULL)
		_dl_die("lazy binding failed!");

	buf.newval = sr.obj->obj_base + sr.sym->st_value + rela->r_addend;

	if (__predict_false(sr.obj->traced) && _dl_trace_plt(sr.obj, symn))
		return buf.newval;

	buf.param.kb_addr = (Elf_Addr *)(object->obj_base + rela->r_offset);
	buf.param.kb_size = sizeof(Elf_Addr);

	/* directly code the syscall, so that it's actually inline here */
	{
		register long syscall_num __asm("$0") /* v0 */ = SYS_kbind;
		register void *arg1 __asm("$16") /* a0 */ = &buf;
		register long  arg2 __asm("$17") /* a1 */ = sizeof(buf);
		register long  arg3 __asm("$18") /* a2 */ = cookie;

		__asm volatile( "call_pal %1" : "+r" (syscall_num)
		    : "i" (PAL_OSF1_callsys), "r" (arg1), "r" (arg2),
		    "r" (arg3) : "$19", "$20", "memory");
	}

	return buf.newval;
}

void _dl_bind_start(void) __dso_hidden;	/* XXX */

/*
 *	Relocate the Global Offset Table (GOT).
 */
int
_dl_md_reloc_got(elf_object_t *object, int lazy)
{
	int	fails = 0;
	Elf_Addr *pltgot;

	if (object->Dyn.info[DT_PLTREL] != DT_RELA)
		return 0;

	pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT];

	if (!lazy || pltgot == NULL) {
		fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ);
	} else {
		if (object->obj_base != 0) {
			int i, size;
			Elf_Addr *addr;
			Elf_RelA *rela;

			size = object->Dyn.info[DT_PLTRELSZ] /
			    sizeof(Elf_RelA);
			rela = (Elf_RelA *)(object->Dyn.info[DT_JMPREL]);

			for (i = 0; i < size; i++) {
				addr = (Elf_Addr *)(object->obj_base +
				    rela[i].r_offset);
				*addr += object->obj_base;
			}
		}
		pltgot[0] = (Elf_Addr)_dl_bind_start;
		pltgot[1] = (Elf_Addr)object;
	}

	return fails;
}
IABSD.fr/src/libexec/ld.so/alpha/rtld_machine.c

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IABSD.fr/src /libexec/ld.so/alpha/rtld_machine.c
