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
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