May 2016 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

A question about kernel real-mode code's LMA & VMA
by 落痕 May 7, 2016

May 7, 2016

Hi, The following is extracted from Documentation/x86/boot.txt, which show's memory map when booting a kernel. 117 ~ ~ 118 | Protected-mode kernel | 119 100000 +------------------------+ 120 | I/O memory hole | 121 0A0000 +------------------------+ 122 | Reserved for BIOS | Leave as much as possible unused 123 ~ ~ 124 | Command line | (Can also be below the X+10000 mark) 125 X+10000 +------------------------+ 126 | Stack/heap | For use by the kernel real-mode code. 127 X+08000 +------------------------+ 128 | Kernel setup | The kernel real-mode code. 129 | Kernel boot sector | The kernel legacy boot sector. 130 X +------------------------+ 131 | Boot loader | <- Boot sector entry point 0000:7C00 132 001000 +------------------------+ 133 | Reserved for MBR/BIOS | 134 000800 +------------------------+ 135 | Typically used by MBR | 136 000600 +------------------------+ 137 | BIOS use only | 138 000000 +------------------------+where the address X is as low as the design of the boot loader 141 permits. The address X is not determined by kernel, so the kernel real-mode code's VMA may not equal to LMA, how kernel solved it?? One more question, in ld script, does the location counter ".", represent VMA?? Thanks.

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porting linux to new arm board
by Ahmed Soliman May 5, 2016

May 5, 2016

I want to port linux to new Ti tiva C TM4C123G it is 80MHZ 32-bit ARM cortex M4 board with FPU 256KB flash /32bit SRAM /2kb EEPROM I am interested on hacking into this board and turning it to micro server (for fun and learning) or so... I compiled linux kernel few times in the past, yet I am clueless on how to get started thanks in advance

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what is the rationale for all ethernet device vendors being "default y"?
by Robert P. J. Day May 4, 2016

May 4, 2016

just noticed that on my x86 system, when i do a: $ make defconfig under "Ethernet driver support", all the top-level vendor choices (3com, adaptec and so on) all have Kconfig entries with: default y reasonably, for each vendor, all of their cards are not "default y" (that would be kind of silly), but what is the logic behind making each vendor selection "default y"? i ask because i'm putting together some kernel configuration fragments that will contribute to a final .config file and, because of all that "default y" stuff, i explicitly have to add "is not set" lines to my fragments to turn off all the vendors in which i have no interest. admittedly, as i read it, leaving them as "default y" doesn't seem to generate any additional code unless you actually select a board from that vendor; still, is there a reason the Kconfig files are set up the way they are? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Kprobes: change the kernel's execution path?
by Sargun Dhillon May 4, 2016

May 4, 2016

I'm attempting to change the behaviour of the inet_get_local_port_range function in the kernel, I've created a kprobe that sets regs->ip = (unsigned long)&inet_get_local_port_range_handler_fake in the pre_handler, and returns 1. I've specified a post_handler to avoid kprobe optimization. Unfortunately, I get a fault immediately after this. I saw in an earlier mailing list post (http://lkml.iu.edu/hypermail/linux/kernel/1310.2/02545.html) suggesting to call reset_current_kprobe(), and preempt_enable_no_resched(). Unfortunately these are not exported to my module. Is there any other way to detour the kernel execution path?

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rules for interface naming for on-board cards
by Gadre Nayan May 3, 2016

May 3, 2016

Hi, I am trying to understand the way interface names are given. So one way is hard coding in net_device->name. If the name contains a %d format string, the first available device name with the given base is used; assigned numbers start at zero. On my base machine, I have 1 NIC card which is onboard, rest I can remove and plug. For the onboard card I get the interfaces as em1-4, while all the other cards I get names as p1p2, p3p4 etc. Does Udev know the difference. How are these names given, definitely there must be some configuration which is used to distinguish on-board card vs removable. Thanks.

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