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crt0 uses a helper function in a MD src/libexec/ld.so .h file (rather than
reproducing the relevant defines and code in a different place) to perform
minor relocations.  If things go very wrong, it would call _dl_exit() --
a locally defined crt0 function which is syscall exit(2).  We don't need
to call exit(2) for this obscure case which doesn't happen and provides no
debugging information. An 'abort' is going to provide better information.
So let's change the function name to _dso_abort() and make it a single
illegal instruction.
ok guenther

/*	$OpenBSD: boot.h,v 1.35 2023/11/18 16:26:15 deraadt 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/exec_elf.h>
#include <sys/mman.h>

#include <machine/reloc.h>

__dead
void _csu_abort(void);

#include "archdep.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);
REDIRECT_SYSCALL(mimmutable);

#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

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);	\
			mimmutable(relro_addr, relro_size);		\
		}							\
	} 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 *dynp)
{
	AuxInfo		*auxstack;
	long		*stack;
	int		n, argc;
	char		**argv, **envp;
	long		loff;
	RELOC_TYPE	*dt_reloc, *rend;	/* DT_RELA   or DT_REL */
	Elf_Word	dt_relocsz;		/* DT_RELASZ or DT_RELSZ */
	const Elf_Sym	*dt_symtab;
	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 */

	/*
	 * Scan the DYNAMIC section for the items we need
	 */
	dt_reloc = NULL;
	dt_relocsz = 0;
	while (dynp->d_tag != DT_NULL) {
		/* first the tags that are pointers to be relocated */
		if (dynp->d_tag == DT_SYMTAB)
			dt_symtab = (void *)(dynp->d_un.d_ptr + loff);
		else if (dynp->d_tag == RELOC_TAG)	/* DT_{RELA,REL} */
			dt_reloc = (void *)(dynp->d_un.d_ptr + loff);

		/* Now for the tags that are just sizes or counts */
		else if (dynp->d_tag == RELOC_TAG+1)	/* DT_{RELA,REL}SZ */
			dt_relocsz = dynp->d_un.d_val;
		dynp++;
	}

	rend = (RELOC_TYPE *)((char *)dt_reloc + dt_relocsz);
	for (; dt_reloc < rend; dt_reloc++) {
		Elf_Addr *ra;
		const Elf_Sym *sp;

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

	/* 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(__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;
		}
	}
}