From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.203]) by ozlabs.org (Postfix) with ESMTP id AD77F67C14 for ; Wed, 6 Jul 2005 03:01:03 +1000 (EST) Received: by wproxy.gmail.com with SMTP id i6so921592wra for ; Tue, 05 Jul 2005 10:01:02 -0700 (PDT) Message-ID: <4dd15d1805070510015cdaac04@mail.gmail.com> Date: Tue, 5 Jul 2005 13:01:02 -0400 From: David Ho To: appro@fy.chalmers.se, linuxppc-embedded@ozlabs.org, openssl-dev@openssl.org In-Reply-To: <4dd15d1805070509361339d08e@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <19EE6EC66973A5408FBE4CB7772F6F0A02C8770E@ltnmail.xyplex.com> <4dd15d1805070508312427a0ba@mail.gmail.com> <4dd15d1805070508451b76afae@mail.gmail.com> <4dd15d1805070509361339d08e@mail.gmail.com> Subject: Re: PPC bn_div_words routine rewrite Reply-To: David Ho List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , I can tell you with certainty, with reference to the function BN_bn2dec, that since lp is a pointer, and within the while loop around bn_print.c:136 lp is being incremented. Because the test BN_is_zero(t) is always false, you have a pointer that is going off into the stratosphere, hence the segfault on ppc8xx. More analysis to come. On 7/5/05, David Ho wrote: > First pass debugging results from gdb on ppc8xx. Executing ssh-keygen > with following arguments. >=20 > (gdb) show args > Argument list to give program being debugged when it is started is > "-t rsa1 -f /etc/ssh/ssh_host_key -N """. >=20 > Program received signal SIGSEGV, Segmentation fault. > BN_bn2dec (a=3D0x1002d9f0) at bn_print.c:136 > 136 *lp=3DBN_div_word(t,BN_DEC_CONV); >=20 > (gdb) i r > r0 0x0 0 > r1 0x7fffd580 2147472768 > r2 0x30012868 805382248 > r3 0x80000000 2147483648 > r4 0xfef33fc 267334652 > r5 0x25 37 > r6 0xfccdef8 265084664 > r7 0x7fffd4c0 2147472576 > r8 0xfbad2887 4222429319 > r9 0x84044022 2214871074 > r10 0x0 0 > r11 0x2 2 > r12 0xfef2054 267329620 > r13 0x10030bc8 268635080 > r14 0x0 0 > r15 0x0 0 > r16 0x0 0 > r17 0x0 0 > r18 0x0 0 > r19 0x0 0 > r20 0x0 0 > r21 0x0 0 > r22 0x0 0 > r23 0x64 100 > r24 0x5 5 > r25 0x1002d438 268620856 > r26 0x1002d9f0 268622320 > r27 0x1002c578 268617080 > r28 0x1 1 > r29 0x10031000 268636160 > r30 0xffbf7d0 268171216 > r31 0x1002d9f0 268622320 > pc 0xfef2058 267329624 > ps 0xd032 53298 > cr 0x24044022 604258338 > lr 0xfef2054 267329620 > ctr 0xfccefa0 265088928 > xer 0x20000000 536870912 > fpscr 0x0 0 > vscr 0x0 0 > vrsave 0x0 0 >=20 > (gdb) p/x $pc > $1 =3D 0xfef2058 >=20 > 0x0fef2058 : stw r3,0(r29) >=20 > (gdb) x 0x10031000 > 0x10031000: Cannot access memory at address 0x10031000 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 >=20 > On 7/5/05, David Ho wrote: > > This is the second confirmed report of the same problem on the ppc8xx. > > > > After reading my email. I must say I was the unfriendly one, I > > apologize for that. > > > > More debugging evidence to come. > > > > ---------- Forwarded message ---------- > > From: Murch, Christopher > > Date: Jul 1, 2005 9:46 AM > > Subject: RE: PPC bn_div_words routine rewrite > > To: David Ho > > > > > > David, > > I had observed the same issue on ppc 8xx machines after upgrading to th= e asm > > version of the BN routines. Thank you very much for your work for the = fix. > > My question is, do you have high confidence in the other new asm ppc BN > > routines after observing this issue or do you think they might have sim= iliar > > problems? > > Thanks. > > Chris > > > > -----Original Message----- > > From: David Ho [mailto:davidkwho@gmail.com] > > Sent: Thursday, June 30, 2005 6:22 PM > > To: openssl-dev@openssl.org; linuxppc-embedded@ozlabs.org > > Subject: Re: PPC bn_div_words routine rewrite > > > > > > The reason I had to redo this routine, in case anyone is wondering, is > > because ssh-keygen segfaults when this assembly routine returns junk > > to the BN_div_word function. On a ppc, if you issue the command > > > > ssh-keygen -t rsa1 -f /etc/ssh/ssh_host_key -N "" > > > > The program craps out when it tries to write the public key in ascii > > decimal. > > > > Regards, > > David > > > > On 6/30/05, David Ho wrote: > > > Hi all, > > > > > > This is a rewrite of the bn_div_words routine for the PowerPC arch, > > > tested on a MPC8xx processor. > > > I initially thought there is maybe a small mistake in the code that > > > requires a one-liner change but it turns out I have to redo the > > > routine. > > > I guess this routine is not called very often as I see that most othe= r > > > routines are hand-crafted, whereas this routine is compiled from a C > > > function that apparently has not gone through a whole lot of testing. > > > > > > I wrote a C function to confirm correctness of the code. > > > > > > unsigned long div_words (unsigned long h, > > > unsigned long l, > > > unsigned long d) > > > { > > > unsigned long i_h; /* intermediate dividend */ > > > unsigned long i_q; /* quotient of i_h/d */ > > > unsigned long i_r; /* remainder of i_h/d */ > > > > > > unsigned long i_cntr; > > > unsigned long i_carry; > > > > > > unsigned long ret_q; /* return quotient */ > > > > > > /* cannot divide by zero */ > > > if (d =3D=3D 0) return 0xffffffff; > > > > > > /* do simple 32-bit divide */ > > > if (h =3D=3D 0) return l/d; > > > > > > i_q =3D h/d; > > > i_r =3D h - (i_q*d); > > > ret_q =3D i_q; > > > > > > i_cntr =3D 32; > > > > > > while (i_cntr--) > > > { > > > i_carry =3D (l & 0x80000000) ? 1:0; > > > l =3D l << 1; > > > > > > i_h =3D (i_r << 1) | i_carry; > > > i_q =3D i_h/d; > > > i_r =3D i_h - (i_q*d); > > > > > > ret_q =3D (ret_q << 1) | i_q; > > > } > > > > > > return ret_q; > > > } > > > > > > > > > Then I handcrafted the routine in PPC assembly. > > > The result is a 26 line assembly that is easy to understand and > > > predictable as opposed to a 81liner that I am still trying to > > > decipher... > > > If anyone is interested in incorporating this routine to the openssl > > > code I'll be happy to assist. > > > At this point I think I will be taking a bit of a break from this 3 > > > day debugging/fixing marathon. > > > > > > Regards, > > > David Ho > > > > > > > > > # > > > # Handcrafted version of bn_div_words > > > # > > > # r3 =3D h > > > # r4 =3D l > > > # r5 =3D d > > > > > > cmplwi 0,r5,0 # compare r5 and 0 > > > bc BO_IF_NOT,CR0_EQ,.Lppcasm_div1 # proceed if d!=3D0 > > > li r3,-1 # d=3D0 return -1 > > > bclr BO_ALWAYS,CR0_LT > > > .Lppcasm_div1: > > > cmplwi 0,r3,0 # compare r3 and 0 > > > bc BO_IF_NOT,CR0_EQ,.Lppcasm_div2 # proceed if h !=3D 0 > > > divwu r3,r4,r5 # ret_q =3D l/d > > > bclr BO_ALWAYS,CR0_LT # return result in r3 > > > .Lppcasm_div2: > > > divwu r9,r3,r5 # i_q =3D h/d > > > mullw r10,r9,r5 # i_r =3D h - (i_q*d) > > > subf r10,r10,r3 > > > mr r3,r9 # req_q =3D i_q > > > .Lppcasm_set_ctr: > > > li r12,32 # ctr =3D bitsizeof(d) > > > mtctr r12 > > > .Lppcasm_div_loop: > > > addc r4,r4,r4 # l =3D l << 1 -> i_carry > > > adde r11,r10,r10 # i_h =3D (i_r << 1) | i_carr= y > > > divwu r9,r11,r5 # i_q =3D i_h/d > > > mullw r10,r9,r5 # i_r =3D i_h - (i_q*d) > > > subf r10,r10,r11 > > > add r3,r3,r3 # ret_q =3D ret_q << 1 | i_q > > > add r3,r3,r9 > > > bc BO_dCTR_NZERO,CR0_EQ,.Lppcasm_div_loop > > > .Lppc_div_end: > > > bclr BO_ALWAYS,CR0_LT # return result in r3 > > > .long 0x00000000 > > > > > _______________________________________________ > > Linuxppc-embedded mailing list > > Linuxppc-embedded@ozlabs.org > > https://ozlabs.org/mailman/listinfo/linuxppc-embedded > > >