November 2016 - Devel - lists.sel4.systems

Memory Management
by Mark Reus 22 Nov '16

22 Nov '16

Hi I have a general case about memory allocation in particular with that of the Vspace. I have been reading some documents and trying to compare how it is in Linux Kernel. Any program Virtual memory in a Linux kernel is as shown in picture below where all processes have 1GB of virtual memory which is mapped to kernel space for faster context switches and system calls. _____________________ | Kernel Space (1GB) | |_____________________| | | | User Mode Space | | (3 GB) | | | |_____________________| I have come across this this link http://os.inf.tu-dresden.de/pipermail/l4-hackers/2014/006262.html detailing a little about the sel4 memory management. But I haven't been able to completely comprehend it . I wanted to know if the seL4 kernel also has a similar mapping of kernel space. Regards Mark

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Syscall errors with musl
by Rinat Dobrokhotov 21 Nov '16

21 Nov '16

Hi all, I have written simple programme which gets system time. I get syscall errors when programm is calling gettimeofday function: *main.c:* #include <time.h> #include <sys/time.h> #include <stdlib.h> #include <stdio.h> int main(int argc, char *argv[]) { int iterations = 1000000; struct timeval start, end; gettimeofday(&start, NULL); for (int i = 0; i < iterations; i++) { } gettimeofday(&end, NULL); printf("%ld\n", ((end.tv_sec * 1000000 + end.tv_usec) - (start.tv_sec * 1000000 + start.tv_usec))); return 0; *Errors:* libsel4muslcsys: Error attempting syscall 263 libsel4muslcsys: Error attempting syscall 78 Could you tell me where I mistook? -- Best regards, Rinat Dobrokhotov

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seL4RPC vs seL4RPCCall?
by Andrew Gacek 18 Nov '16

18 Nov '16

What's the difference between seL4RPC and seL4RPCCall in CAmkES? Is there documentation on the various connectors somewhere? Thanks, Andrew

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Send input to seL4 in QEMU
by Andrew Gacek 18 Nov '16

18 Nov '16

Hi, We are developing an seL4 application that will process UDP packets coming in over a network connection. Eventually, we'll be running this on real hardware with real drivers, but for now we are using QEMU. We have a python script that can generate packet payloads. Is there a way to send this information into QEMU so that we can develop our seL4 application without having the drivers and hardware in place? If it matters, we are using CAmkES as well. Thanks, Andrew

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seL4 Kernel Profiler
by Chris Guikema 18 Nov '16

18 Nov '16

Hello, I am working on a Code Profiler for use in seL4 Systems. I see that the Kernel already has some form of profiling/benchmarking functionality built in. However, I do not see anything in the documentation that covers how this is used. Is there a guide that I can follow to get the kernel profile functional? Thanks Chris Guikema

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Will seL4_Word ever be anything but uintptr_t?
by Corey Richardson 17 Nov '16

17 Nov '16

I guess this is a somewhat philosophical question. It's come up a bit in the Rust libs I've been writing. Casting from pointer-sized things to *specifically* u32/u64 is bit tiresome for the places where I can't abstract over that. -- cmr http://octayn.net/ +16038524272

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seL4 on i.MX53
by Yevgeny Lavrov 15 Nov '16

15 Nov '16

Hello. I've multiple ARM devices at my disposal that I want to use to experiment with seL4, one of them is USB Armory (Architecture: ARMv7 Cortex-A8 Processor: i.MX53 800MHz). Before I get into it, I would like to know if seL4 supports this ARM device. Thanks

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Unable To Map Physical Frame
by Mark Reus 13 Nov '16

13 Nov '16

Hi I want to map the arm global timer which is located at memory location 0xF8F00200 . However, when I am trying to get the physical frame using : error = simple_get_frame_cap(&simple, (void*)global_timer_paddr, 12, &ep_cap_path); if (error) { ZF_LOGE("Failed to find frame at paddr %p\n", global_timer_paddr); return error; } I get the Error Statement on stduout as "main@main.c:209 Failed to find frame at paddr 0xf8f00200" If i print the bootinfo during bootup, I can see that I have access to this region 0xf8000000 | 00000012 | [520 <--> 521 ] Can someone help me as why this issue may be caused? I know that this global timer is said to be mapped in the private region. But I do not what exactly that means and if we cannot do it. Regards Mark

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malloc and SCHED0004
by Vasily A. Sartakov 05 Nov '16

05 Nov '16

Greetings. I am keep working, and now I would like to discuss my second memory-related issue. In contrast with first one, the second issue happens only in SCHED004 test, in malloc function: helper_thread_t **threads = (helper_thread_t **) malloc(sizeof(helper_thread_t*) * NUM_PRIOS); malloc dies because there is no record inside TLB. someone tries to write something to an address, for example, 0x54f1c8. This address is important because it is located outside of the virtual memory allocated for the test. Previous, elf_loader allocates a region and the region ends exactly on 0x54efff. I have experimented with different setups, added some debug functions, and each time I saw the same picture: malloc dies because tries to write to next page outside the allocated region. I know what is the function tries to write. It is a pretrim, part of libmuslc: static int pretrim(struct chunk *self, size_t n, int i, int j) { size_t n1; struct chunk *next, *split; /* We cannot pretrim if it would require re-binning. */ if (j < 40) return 0; if (j < i+3) { if (j != 63) return 0; n1 = CHUNK_SIZE(self); if (n1-n <= MMAP_THRESHOLD) return 0; } else { n1 = CHUNK_SIZE(self); } if (bin_index(n1-n) != j) return 0; next = NEXT_CHUNK(self); printf("next - %x, n1 = %x\n", next, n1); split = (void *)((char *)self + n); <————— the split points outside the allocated region split->prev = self->prev; <————— here we die split->next = self->next; split->prev->next = split; split->next->prev = split; split->psize = n | C_INUSE; split->csize = n1-n; next->psize = n1-n; self->csize = n | C_INUSE; return 1; } As a previous, I would like to ask, should I keep in mind something platform specific? maybe you have modified, like a_and asm functions or something else in libmuslc? Also, malloc itself raises questions: void *malloc(size_t n) { struct chunk *c; int i, j; if (adjust_size(&n) < 0) return 0; <….> i = bin_index_up(n); for (;;) { uint64_t mask = mal.binmap & -(1ULL<<i); mal.binmap is used uninitialised. also, when we set up bits inside it? Moreover, I have different values on ARM (0x80000000000) and MIPS (0x8000000000000000), I am not sure that it is ok Thank you! -- Vasily A. Sartakov sartakov(a)ksyslabs.org

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Timer for Performance Measurement
by Andrew Mine 04 Nov '16

04 Nov '16

Hi Is there any inbuilt library to get the time like get_time in seL4? I want to measure IPC performance and overheads for my tasks. Regards Andrew

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