In arm/shared/startup/linkcmds.base these barriers are used to add gaps in the memory layout at link-time to accommodate for the size requirements of the MMU. xbarrier aligns the executable region, robarrier aligns the read-only memory, and rwbarrier aligns the read-write memory.
On Tue, Aug 4, 2015 at 6:23 PM, Rohini Kulkarni <krohini1...@gmail.com> wrote: > > > On Wed, Aug 5, 2015 at 1:47 AM, Gedare Bloom <ged...@gwu.edu> wrote: >> >> On Tue, Aug 4, 2015 at 2:18 PM, Rohini Kulkarni <krohini1...@gmail.com> >> wrote: >> > >> > >> > On Tue, Jul 28, 2015 at 5:51 AM, Pavel Pisa <ppisa4li...@pikron.com> >> > wrote: >> >> >> >> Hello Rohini and Gedare, >> >> >> >> On Friday 24 of July 2015 15:33:03 Gedare Bloom wrote: >> >> > What are the values of bsp_section_bss_begin, and >> >> > bsp_section_bss_size? >> >> > >> >> > Apparently, the memset is trying to write into the .text (code) >> >> > section, which is a very bad thing to do indeed. >> >> > >> >> >> >> Qiao Yang in RPi 1 BSP now works in the similar >> >> area to enable right graphic memory mapping. >> >> >> >> So my guess is that there could be problem caused >> >> by used MMU mode granularity, which is is 1 MB so >> >> if RO and RW sections are present in the same 1MB >> >> aligned block ten there can be problem. It depends >> >> which section is filled the first. If data and then >> >> text (RO) the troubles begin. If the order is vice >> >> versa then some part of text can be RW instead of RO, >> >> but it should work and cache should not be a problem. >> >> >> >> But I have not dig into this case too much. >> >> Only short glimpse. >> >> >> >> One option is to define 1 MB alignment between text >> >> ad data for RPi case. There is quite a lot of memory >> >> when compared to most RTEMS embedded targets to the >> >> waste is not so important. >> > >> > >> > I didn't quite get what this means. I have no clue on how to proceed >> > with >> > this. >> The MMU defines memory regions in 1MB chunks. Each chunk can have its >> own permissions (read-only, or read-write) set. If the .text and .data >> (or some other section) overlaps in the same 1MB chunk, and the wrong >> permission gets set, then there can be a problem e.g. part of .data >> might be RO or part of .text might be RW. >> >> Did you try the code Sebastian posted? to change the robarrier to >> rwbarrier? > > > What exactly are these barriers? >> >> >> Gedare >> >> >> >> >> >> >> Best wishes, >> >> >> >> Pavel >> >> >> >> On Friday 24 of July 2015 21:55:00 Rohini Kulkarni wrote: >> >> > Hi, >> >> > >> >> > I have attached the report containing outputs of arm-rtems4.11-size >> >> > and >> >> > arm-rtems4.11-nm -S. >> >> > >> >> > From arm-rtems4.11-nm -S I don't see how memset() is accessing .text >> >> > section. The start and end values for both are not overlapping. >> >> > >> >> > On Fri, Jul 24, 2015 at 7:03 PM, Gedare Bloom <ged...@gwu.edu> wrote: >> >> > > On Fri, Jul 24, 2015 at 3:30 AM, Rohini Kulkarni >> >> > > <krohini1...@gmail.com> >> >> > > >> >> > > wrote: >> >> > > > On 24 Jul 2015 12:35, "Sebastian Huber" < >> >> > > >> >> > > sebastian.hu...@embedded-brains.de> >> >> > > >> >> > > > wrote: >> >> > > >> On 23/07/15 23:24, Rohini Kulkarni wrote: >> >> > > >>> I could finally get back to this issue. I used Pi 1 for >> >> > > >>> debugging, >> >> > > >>> but the reason for this problem will apply to Pi 2 also. >> >> > > >>> With text section set to ARMV7_MMU_CODE_CACHED ( which implies >> >> > > >>> read >> >> > > >> >> > > only) >> >> > > >> >> > > >>> , a data abort exception occurs with memset() inside >> >> > > >> >> > > bsp_start_clear_bss() >> >> > > >> >> > > >>> function. An illegal write access to an address according to >> >> > > >>> me. >> >> > > >> >> >> > > >> Which exception and which address? Something is not working >> >> > > >> here. >> >> > > > >> >> > > > This is a part of the debugging output. When I used >> >> > > >> >> > > ARMV7_MMU_CODE_CACHED. >> >> > > >> >> > > > (gdb) s >> >> > > > bsp_start_clear_bss () >> >> > > > at >> >> > > > ../../../../../.././raspberrypi/lib/include/bsp/start.h:126 >> >> > > > 126 memset(bsp_section_bss_begin, 0, (size_t) >> >> > > > bsp_section_bss_size); >> >> > > >> >> > > What are the values of bsp_section_bss_begin, and >> >> > > bsp_section_bss_size? >> >> > > >> >> > > Apparently, the memset is trying to write into the .text (code) >> >> > > section, which is a very bad thing to do indeed. >> >> > > >> >> > > > (gdb) s >> >> > > > memset (m=0x1157e0, c=0, n=64176) >> >> > > > at ../../../../../gcc-4.9.2/newlib/libc/string/memset.c:59 >> >> > > > 59 ../../../../../gcc-4.9.2/newlib/libc/string/memset.c: No >> >> > > > such >> >> > > > file >> >> > > >> >> > > or >> >> > > >> >> > > > directory. >> >> > > > (gdb) s >> >> > > > 49 in ../../../../../gcc-4.9.2/newlib/libc/string/memset.c >> >> > > > (gdb) s >> >> > > > _ARMV4_Exception_data_abort_default () >> >> > > > at >> >> > > >> >> > > >> >> > > >> >> > > ../../../../../../../../rtems-local/rtems/c/src/../../cpukit/score/cpu/ar >> >> > >m/armv4-exception-default.S:71 >> >> > > >> >> > > > 71 sub sp, #MORE_CONTEXT_SIZE >> >> > > > >> >> > > > When I set text section flag to ARMV7_MMU_READ_WRITE, the system >> >> > > > starts >> >> > > > successfully. >> >> > > > >> >> > > >> -- >> >> > > >> Sebastian Huber, embedded brains GmbH >> >> > > >> >> >> > > >> Address : Dornierstr. 4, D-82178 Puchheim, Germany >> >> > > >> Phone : +49 89 189 47 41-16 >> >> > > >> Fax : +49 89 189 47 41-09 >> >> > > >> E-Mail : sebastian.hu...@embedded-brains.de >> >> > > >> PGP : Public key available on request. >> >> > > >> >> >> > > >> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des >> >> > > >> EHUG. >> >> > > > >> >> > > > _______________________________________________ >> >> > > > devel mailing list >> >> > > > devel@rtems.org >> >> > > > http://lists.rtems.org/mailman/listinfo/devel >> >> >> > >> > >> > >> > -- >> > Rohini Kulkarni >> > >> > _______________________________________________ >> > devel mailing list >> > devel@rtems.org >> > http://lists.rtems.org/mailman/listinfo/devel > > > > > -- > Rohini Kulkarni _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel