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Recursive call to malloc crash system
by Fabrizio Bertocci 27 Jul '17

27 Jul '17

Hi all, I have a system configured to use dynamic heap through the vspace. I'm working with 5.2.0 and using pc99 simulator through qemu. Everything is occurring in the root task, as I haven't even completed my bootstrapping code. In this configuration, whenever my code calls malloc() and there is a low memory condition (where there is not enough space on the heap to fulfill my request), malloc() end up calling __expand_heap(). Here it first attempts to expand the heap through brk syscall, then if fails uses mmap() to attempt to get more pages from the virtual memory. In both cases (brk and mmap) end up calling a function in the vspace that attempts to make available new pages. Unfortunately the code in the libself4utils/src/vspace/vspace.c, end up calling malloc() for the sel4utils_res structure. As you expect, we are already in a no-memory condition, so a subsequent call to malloc() might end up calling __expand_heap() and so on... (depending on the bytes left on the heap, this nested malloc might succeed if the initial block was larger than the size of sel4utils_res structure). So, everything loops until the whole system crash because of stack overflow. Why vspace uses malloc() to dynamically allocate those structures, causing the whole system to fail? To test, I have changed the implementation in vspace.c to use a static buffer pool, and it seems it solve my issue, but am I doing something wrong in the bootstrap code ? Any help is appreciated, Regards, Fabrizio Bertocci Real-Time Innovations, Inc. Sunnyvale, CA

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Invalid package ID: "array-0.5.1.1 base-4.9.0.0 binary-0.8.3.0 bytestring-0.10.8.1"
by tj5527 23 Jul '17

23 Jul '17

Another problem when making sel4. The make program complains Invalid package ID: "array-0.5.1.1 base-4.9.0.0 binary-0.8.3.0 bytestring-0.10.8.1". [parse-capDL] building... make: Entering directory '/path/to/sel4/projects/capdl/capDL-tool' stack setup stack will use a locally installed GHC For more information on paths, see 'stack path' and 'stack exec env' To use this GHC and packages outside of a project, consider using: stack ghc, stack ghci, stack runghc, or stack exec stack build --only-dependencies Invalid package ID: "array-0.5.1.1 base-4.9.0.0 binary-0.8.3.0 bytestring-0.10.8.1" Makefile:39: recipe for target 'sandbox' failed make: *** [sandbox] Error 1 How can I fix this? Thank you. Ubuntu 16.04 LTS GNU Make 4.1 gcc version 5.4.0 20160609

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Sydney `taste of seL4' miniconference/developer day
by Peter.Chubb＠data61.csiro.au 19 Jul '17

19 Jul '17

Hi Folks, Next January 22--26, linux.conf.au will be in Sydney, Australia. We're planning on submitting a proposal for a one-day miniconference to be held in conjunction with the main conference. We'd like to line up potential speakers now, before submitting. If you are doing something cool and open source with seL4, and would like to speak at that miniconference, please let me know. linux.conf.au is one of the best grass-roots open-source and Linux conferences around; if you're doing anything cool that's open source with seL4 (or with Linux), then I'd encourage you to submit a proposal to the main conference as well, at https://linux.conf.au/ Peter Chubb -- Dr Peter Chubb Tel: +61 2 9490 5852 http://ts.data61.csiro.au/ Trustworthy Systems Group Data61 (formerly NICTA)

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Question on endpoint cap write permission
by Jimmy Brush 13 Jul '17

13 Jul '17

Hello, in the 6.0 manual section 3.1.4 the table shows that Write permission on an endpoint cap permits sending to the endpoint. however, in section 4.2.2 it says without the Write permission on the RECEIVING endpoint cap, any cap sent over IPC gets diminished. Am I missing something? It seems the Write permission is overloaded to mean two different things. This would seem to imply that to receive an undiminished capability via IPC you must have both send and receive permission to the endpoint you are receiving against. Which would mean if you wanted to limit someone to only receiving and never sending against an endpoint by giving them an endpoint cap with only Read permission, they would necessarily also NEVER be able to receive an undiminished capability. Thanks, JB

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Compile problems about camkes-vm project
by deng.chao1＠zte.com.cn 11 Jul '17

11 Jul '17

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L4Re IPC share memory that share file in one Linux filesystem and be visible to other Linuxes
by Joyce Peng(彭美僑) 05 Jul '17

05 Jul '17

Hi L4, I want to share a file in one Linux filesystem and be visible to other Linuxes that all run on top Fiasco.OC. It seems an IPC communication between L4re vm tasks. And access a file in Linux filesystem is a mechanism with kernel block device driver. But I only notice two char device drivers that use L4re library l4shmc in L4linux. It is l4ser_shm and l4shmnet. May you give some information about this work how to work. Thanks. Joyce Peng(彭美僑)

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malloc & errno
by Fabrizio Bertocci 05 Jul '17

05 Jul '17

Hi all, I am facing a puzzling problem related to muslc. While running some tests with the ia32 simulator (qemu), have noticed that whenever I call malloc() and I run out of memory (because my morecore buffer is too small), I am getting some kernel crash. I have traced the issue to the place where errno is set to -ENOMEM. Referencing to errno is platform-dependent and end up calling a function that retrieve the struct pthread associated and access errno as one of the field of the struct pthread. What is the correct process to set up a heap from the root task in such a way that we can call malloc() and correctly handle error conditions through errno? I am pretty sure I am doing something wrong in my initialization code (I have based my main(0 on the code from the tutorials), because I am also having other problems with malloc(). (even after I increase my heap area). For example, in some cases a call to malloc() end up calling a cascade of functions that eventually (from inside muslc) end up calling again malloc(). As consequence it enters in an infinite loop that stop only after it exhaust the initial stack. I could not find any clear example that show how to correctly set up a system to use muslc. Can anyone point me to a good example that shows how to bootstrap a system for the 5.2.0 branch? Regards, Fabrizio Bertocci Real-Time Innovations, Inc. Sunnyvale, CA

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make: stack: Command not found
by tj5527 04 Jul '17

04 Jul '17

A newbie question. I follow the link [1] trying to build sel4 with qemu. But when `make`ing the binary, it throws error message `make: stack: Command not found`. I `apt-get install stacks` but it still fails with the same error. What packages should I install for making sel4 with Ubuntu 16.04 LTS, GNU Make 4.1, and gcc version 5.4.0 20160609? Thanks [Error Message] -- Build files have been written to: /path/to/sel4/stage/x86/pc99/accelerator ninja: no work to do. [apps/vm] building... [HEADERS] [STAGE] autoconf.h [apps/vm] done. [parse-capDL] building... make: Entering directory '/path/to/sel4/projects/capdl/capDL-tool' stack setup make: stack: Command not found Makefile:39: recipe for target 'sandbox' failed make: *** [sandbox] Error 127 make: Leaving directory '/path/to/sel4/projects/capdl/capDL-tool' Makefile:53: recipe for target '/path/to/sel4/stage/x86/pc99/parse-capDL/parse-capDL' failed make: *** [/path/to/sel4/stage/x86/pc99/parse-capDL/parse-capDL] Error 2 [1] https://wiki.sel4.systems/Hardware/Qemu

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elfloader-tool
by Yevgeny Lavrov 30 Jun '17

30 Jun '17

Hi Is there any instruction on how to compile and use elfloader-tool? More specifically: I want to link seL4 image with other image to try out on i.MX6 platform. Thanks

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vmm documentation
by Mike Clark 29 Jun '17

29 Jun '17

Is there any documentation on how the VMM works? If I wanted to start hacking on the VMM and extend its capability, where should I start looking to learn how it works, etc? That might be a pretty broad topic, because there are lots of ways the VMM can be extended, I'm sure. Broad is fine, until I get things more figured out.

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