From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kenneth Johansson Date: Tue, 27 Jul 2004 19:31:46 +0200 Subject: [U-Boot-Users] how does stack work? In-Reply-To: References: Message-ID: <41069182.6030704@ericsson.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Seingier Fran?ois-Xavier wrote: >hello, >I'm trying to understand how the initial stack works on a ppc4xx. According to start.S this is how the layout looks to me: > ___________ > | | > | | > | | > | gd_t | > |___________| > | 0 | > |___________| > | 0 | > |___________|<-+ > | reset_vec | | >SP ->|___________| | > | |--+ > |___________|<-+ > | | | > |___________| | > | |--+ > |___________| > | ... | > >I can't figure out precisely how the last stack frame works: >- /* clear final stack frame so that */ > /* stack backtraces terminate cleanly */ >I'm not sure to understand the "terminate cleanly". > > Some debug tool that get confused ?? >- why will the reset_vec be used in case of a stack underflow? >I tried to find an answer in the "PowerPC compiler writer's guide" about the ABI, but I am not even sure gcc uses an AIX or System V implementation... > > You can not return from the first function but for some unknown reason you do that what should happen ?? a reboot is probably as good as anything. The ABI for u-boot is eabi ftp://ftp.funet.fi/pub/mirrors/sourceware.cygnus.com/pub/binutils/ppc-docs/