From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: Stack Frame Calc Problem in head_4xx.S From: "Gary D. Thomas" To: jwalden@digitalatlantic.com Cc: Linux PPC embedded In-Reply-To: References: Content-Type: text/plain Message-Id: <1052000497.2537.5413.camel@hermes> Mime-Version: 1.0 Date: 03 May 2003 16:21:39 -0600 Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: On Sat, 2003-05-03 at 15:20, Jerry Walden wrote: > Greetings: > > I am having trouble understanding what is happening to my stack pointer. > > At line 1 r1 = 0x03f9_ebe8 > > After line 15 executes r1 = 0xc00f4ff0 > which seems fine so far (according to the map file it is pointing to the > proper location) > > After line 16 executes r1=0xc00f6ff0 > which is still within the bounds of init_task_union > > After line 17 execute r1 = 0xc00f6fe0 which seems like a problem to me, > because it is not with the > bounds of init_task_union - (see map file below) > Why do you think this? It seems that init_task_union comprises the space from 0xc00f4ff0..0xc00f6ff0. That value is certainly within that range. > I would expect r1 to be within the bounds of init_task_union after this code > is executed - > is my guess correct? If so how is it possible that line 17 comes up with > the result > that it did? Read how 'stwu' works. After the store takes place, r1 is updated with the new value. In other words stwu r0,-STACK_FRAME_OVERHEAD(r1) means [r1] = r0 r1 = r1 - STACK_FRAME_OVERHEAD(r1) which is exactly the results you are getting. > > TASK_UNION_SIZE = 8192 > STACK_FRAME_OVERHEAD = 16 > > Thanks for any help > > Jerry > > 1 start_here: > 2 > 3 /* ptr to current */ > 4 lis r2,init_task_union@h > 5 ori r2,r2,init_task_union@l > 6 > 7 /* ptr to phys current thread */ > 8 tophys(r4,r2) > 9 addi r4,r4,THREAD /* init task's THREAD */ > 10 mtspr SPRG3,r4 > 11 li r3,0 > 12 mtspr SPRG2,r3 /* 0 => r1 has kernel sp */ > 13 > 14 /* stack */ > 15 addi r1,r2,TASK_UNION_SIZE > 16 li r0,0 > 17 stwu r0,-STACK_FRAME_OVERHEAD(r1) > > > c00f4ff0 D init_task_union > c00f6ff0 d aligninfo > c00f70f0 D cpuinfo_op > c00f7100 D cpu_specs > c00f7280 D ppc_htab_operations > > > > Jerry Walden > Program Manager > Digital Atlantic Inc > http://www.digitalatlantic.com > jwalden@digitalatlantic.com > 1-877-494-6073 x407 > cell - 703-431-2413 > > -- Gary D. Thomas ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/