/* $NetBSD: rtld_start.S,v 1.25 2024/08/03 21:59:59 riastradh Exp $ */ /* * Copyright 1996 Matt Thomas <matt@3am-software.com> * Portions copyright 2002, 2003 Charles M. Hannum <root@ihack.net> * All rights reserved. * * 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. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * 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. */ #include <machine/asm.h> /* R9 contains the address of PS_STRINGS and since its caller saved, * we can just use it. R6 has a backup copy of the stack pointer which * we can use as well. */ ENTRY(_rtld_start, 0) /* Allocate space on the stack for the cleanup and obj_main * entries that _rtld() will provide for us. */ clrl %fp subl2 $8,%sp movab _DYNAMIC,%r0 subl3 _GLOBAL_OFFSET_TABLE_,%r0,%r10 pushl %r10 /* relocbase */ pushl %r0 /* &_DYNAMIC */ calls $2,_rtld_relocate_nonplt_self pushl %r10 /* relocbase */ pushal 4(%sp) /* sp */ calls $2,_rtld /* entry = _rtld(sp, relocbase) */ movq (%sp)+,%r7 /* grab cleanup and obj_main into %r7/%r8 */ jmp 2(%r0) /* jump to entry point + 2 */ END(_rtld_start) /* * Lazy binding entry point, called via PLT via JMP into pltgot[1]. * SP+4: address to relocation offset * SP+0: obj entry points */ ALTENTRY(_rtld_bind_start) pushl %r1 /* need to preserve r1 */ movq -8(%fp),%r0 /* get addresses of plt.got & reloc index */ pushl (%r1) /* push relocation offset */ pushl %r0 /* push address of obj entry */ calls $2,_rtld_bind /* * This code checks to see if we got called via a call{s,g} $n,*pcrel32 * This is by far the most common case (a call indirectly via the PLT). */ subl3 $7,16(%fp),%r1 /* return address */ bicb3 $1,(%r1),%r2 /* fetch opcode of instruction */ cmpb $0xfa,%r2 /* is it calls/callg */ jneq 20f /* no it isn't */ cmpb $0xff,2(%r1) /* and deferred 32-bit PC displacement? */ jneq 20f /* no it isn't */ /* * This makes sure the longword with the PLT's address has been updated * to point to the routine's address. If it hasn't, then returning * would put us in an infinite loop. Instead we punt and fake up a * callframe. */ movl 3(%r1),%r3 /* get displacement */ addl2 16(%fp),%r3 /* add ending location */ cmpl (%r3),%r0 /* does it contain the routine address? */ #ifdef DEBUG jneq 30f /* no it doesn't, die */ #else jneq 20f /* no it doesn't, go fake a new callframe */ #endif 11: movl %r1,16(%fp) /* backup to the calls/callg */ jbc $29,4(%fp),12f /* skip if this was a callg */ clrl (%ap) /* clear argument count */ 12: movl (%sp)+,%r1 /* restore r1 */ ret /* return and redo the call */ #if 1 20: /* * Since the calling standard says only r6-r11 should be saved, * that simplies things for us. That means we can use r0-r5 as * temporaries without worrying about preserving them. This means * can hold the current fixed callframe in r2-r5 as we build the * callframe without having to worry about overwriting the existing * callframe. */ extzv $0,$12,(%r0),%r1/* get routine's save mask */ bitw $0x3f,%r1 /* does the routine use r0-r5? */ jneq 30f /* yes, that sucks */ jbc $29,4(%fp),27f /* handle callg */ movq 4(%fp),%r2 /* fetch callframe status & saved AP */ movq 12(%fp),%r4 /* fetch callframe saved FP & PC */ insv %r1,$16,$12,%r2 /* update save mask */ movl (%sp)+,%fp /* use fp to keep saved r1 */ movl %ap,%sp /* reset stack to top of callframe */ 22: pushr %r1 /* push registers */ movq %r4,-(%sp) /* push callframe saved FP & PC */ movq %r2,-(%sp) /* push callframe status & saved AP */ pushl $0 /* push condition handler */ movl %fp,%r1 /* restore r1 */ movl %sp,%fp /* sp == fp now */ #if 1 jmp 2(%r0) /* jump past entry mask */ #else /* * More correct but IV/DV are never set so ignore doing this for now. */ movpsl -(%sp) /* push PSL */ clrb (%sp) /* clear user flags */ jbc $14,(%r0),24f /* IV need to be set? */ bisb2 $0x20,(%sp) /* yes, set it. */ 24: jbc $15,(%r0),25f /* DV need to be set? */ bisb2 $0x80,(%sp) /* yes, set it. */ 25: pushab 2(%r0) /* push address of first instruction */ rei /* and go to it (updating PSW) */ #endif /* * Count how many registers are being used for callg. */ 27: movl $0x32212110,%r3 /* bit counts */ extzv $6,$3,%r1,%r2 /* extract bits 6-8 */ ashl $2,%r2,%r2 /* shift by 2 */ extzv %r2,$4,%r3,%r4 /* extract count */ extzv $9,$3,%r1,%r2 /* extract bits 9-11 */ ashl $2,%r2,%r2 /* shift by 2 */ extzv %r2,$4,%r3,%r5 /* extract count */ movq 4(%fp),%r2 /* fetch callframe status & saved AP */ insv %r1,$16,$12,%r2 /* update save mask */ addl3 %r4,%r5,%r1 /* add counts and discard them */ movq 12(%fp),%r4 /* fetch callframe saved FP & PC */ moval 20(%fp)[%r1],%sp/* pop callframe */ extzv $16,$12,%r2,%r1 /* get save mask back */ jbr 22b /* now build the new callframe */ 30: calls $0,_C_LABEL(_rtld_die) #else /* * Check to see if called via call? $n,w^off(reg) */ 20: addl2 $2,%r1 /* 16-bit displacement */ bicb3 $1,(%r1),%r2 /* fetch opcode of instruction */ cmpb $0xfa,%r2 /* is it calls/callg */ jneq 30f /* no it isn't */ bicb3 $0x1f,2(%r1),%r3/* extract addressing mode */ cmpb $0xc0,%r3 /* 16-bit displacement? */ jeql 11b /* yes, redo the call */ halt /* * Check to see if called via call? $n,b^off(reg) */ 30: incl %r1 /* 8-bit displacement */ bicb3 $1,(%r1),%r2 /* fetch opcode of instruction */ cmpb $0xfa,%r2 /* is it calls/callg */ jneq 40f /* no it isn't */ bicb3 $0x1f,2(%r1),%r3/* extract addressing mode */ cmpb $0xa0,%r3 /* 8-bit displacement? */ jeql 11b /* yes, redo the call */ halt /* * Check to see if called via call? $n,(reg) */ 40: incl %r1 /* no displacement */ bicb3 $1,(%r1),%r2 /* fetch opcode of instruction */ cmpb $0xfa,%r2 /* is it calls/callg */ jeql 41f /* yes it is */ halt /* no, die die die */ 41: bicb3 $0x0f,2(%r1),%r2/* extract addressing mode */ bicb3 $0xf0,2(%r1),%r3/* extract register */ extzv $0,$12,6(%fp),%r4/* extract saved mask */ cmpb $0x60,%r2 /* register deferred? */ jeql 42f /* yes, deal with it */ cmpb $0x90,%r2 /* autoincrement deferred? */ jeql 70f /* yes, deal with it */ halt /* no, die die die */ 42: cmpw %r4,$0xffc /* did we save r2-r11? */ jneq 50f /* no, deal with it */ jbc %r3,%r4,43f /* is the register in the saved mask? */ /* * We saved r2-r11, so it's easy to replace the saved register with * the right value by indexing into saved register (offset by 8). */ movl %r0,(20-8)(%fp)[%r3] /* replace address in saved registers */ jbr 11b /* go back and redo call */ /* * Must have been called via r0 or r1 which are saved locally. * So move the routine address in the appropriate slot on the stack. */ 43: movl %r0,(%sp)[%r3] jbr 11b /* go back and redo call */ 50: jbs %r3,%r4,60f /* is the register in the saved mask? */ jbs %r3,$0x3f,43b /* is it r0-r5? */ /* * The register used for the call was not saved so we need to move * the new function address into it so the re-call will use the new * address. */ pushl %r0 /* save function address on the stack */ ashl %r5,$1,%r0 /* create a bitmask for the register */ popr %r0 /* pop it off the stack. */ jbr 11b /* and redo the call */ 60: clrl %r2 /* starting offset into saved registers */ clrl %r5 /* start with register 0 */ 61: cmpl %r2,%r3 /* is the register to save? */ jneq 62f /* no, advance to next */ movl %r0,20(%fp)[%r5]/* yes, save return address in saved reg */ jbr 11b /* and return the call */ 62: jbc %r5,%r4,63f /* is this register saved? */ incl %r5 /* yes, account for it */ 63: incl %r2 /* increment register number */ jbr 61b /* and loop */ 70: cmpb %r3,$12 blss 71f halt 71: cmpw %r4,$0xffc /* did we save r2-r11? */ jneq 72f /* no, deal with it */ subl2 $4,(20-8)(%fp)[%r3] /* backup incremented register */ jbr 11b /* and redo the call. 72: jbs %r3,%r4,80f jbs %r3,%3f,74f ashl %r5,$1,%r0 /* create a bitmask for the register */ pushr %r0 /* pop it off the stack. */ subl2 $4,(%sp) /* backup incremented register */ popr %r0 /* pop it off the stack. */ jbr 11b /* and redo the call. 73: subl2 %4,(%sp)[%r3] /* backup incremented register */ jbr 11b /* and redo the call. 80: clrl %r2 /* starting offset into saved registers */ clrl %r5 /* start with register 0 */ 81: cmpl %r2,%r3 /* is the register to save? */ jneq 82f /* no, advance to next */ subl $4,20(%fp)[%r5] /* yes, backup incremented register */ jbr 11b /* and return the call */ 82: jbc %r5,%r4,83f /* is this register saved? */ incl %r5 /* yes, account for it */ 83: incl %r2 /* increment register number */ jbr 81b /* and loop */ #endif END(_rtld_bind_start)
