From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.202]) by ozlabs.org (Postfix) with ESMTP id F169B67C84 for ; Wed, 6 Jul 2005 02:36:52 +1000 (EST) Received: by wproxy.gmail.com with SMTP id 36so938274wra for ; Tue, 05 Jul 2005 09:36:51 -0700 (PDT) Message-ID: <4dd15d1805070509361339d08e@mail.gmail.com> Date: Tue, 5 Jul 2005 12:36:51 -0400 From: David Ho To: appro@fy.chalmers.se, linuxppc-embedded@ozlabs.org, openssl-dev@openssl.org In-Reply-To: <4dd15d1805070508451b76afae@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> 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: , First pass debugging results from gdb on ppc8xx. Executing ssh-keygen with following arguments. (gdb) show args Argument list to give program being debugged when it is started is "-t rsa1 -f /etc/ssh/ssh_host_key -N """. Program received signal SIGSEGV, Segmentation fault. BN_bn2dec (a=3D0x1002d9f0) at bn_print.c:136 136 *lp=3DBN_div_word(t,BN_DEC_CONV); (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 (gdb) p/x $pc $1 =3D 0xfef2058 0x0fef2058 : stw r3,0(r29) (gdb) x 0x10031000 0x10031000: Cannot access memory at address 0x10031000 On 7/5/05, David Ho wrote: > This is the second confirmed report of the same problem on the ppc8xx. >=20 > After reading my email. I must say I was the unfriendly one, I > apologize for that. >=20 > More debugging evidence to come. >=20 > ---------- Forwarded message ---------- > From: Murch, Christopher > Date: Jul 1, 2005 9:46 AM > Subject: RE: PPC bn_div_words routine rewrite > To: David Ho >=20 >=20 > David, > I had observed the same issue on ppc 8xx machines after upgrading to the = asm > version of the BN routines. Thank you very much for your work for the fi= x. > 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 simil= iar > problems? > Thanks. > Chris >=20 > -----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 >=20 >=20 > 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 >=20 > ssh-keygen -t rsa1 -f /etc/ssh/ssh_host_key -N "" >=20 > The program craps out when it tries to write the public key in ascii > decimal. >=20 > Regards, > David >=20 > 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 other > > 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_carry > > 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 >