August 2018 - kernelnewbies@kernelnewbies.org

How to unwind stack to seek for specific caller?
by Lev Olshvang Aug. 4, 2018

Aug. 4, 2018

Hello all I know that I can print stack of function using dump_stack() But I need to find out whether my function y() was called from linux kernel function x().\ I see that kmsg_dump_get_buffer() function can get kernel messages but it is not clear for me should I use it bedore calling dump_stack or I need to do additional setup before calling for these 2 functions? Regards, Lev

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First patch
by Arkadiusz Lis Aug. 3, 2018

Aug. 3, 2018

Hi guys, I created my first patch. Could you please take a look and check for mistakes? It's a small clean up removing checkpatch.pl warnings. It was generated using 'git format-patch master..<mybranch>'. See below: >From 231fa77d595536cdaacf364b02dd64fd45a6adc4 Mon Sep 17 00:00:00 2001 From: Arkadiusz Lis <areklis909(a)gmail.com> Date: Thu, 2 Aug 2018 23:38:17 +0200 Subject: [PATCH] Staging: One Laptop Per Child: fix coding style and license issues Add argument names to the function pointers in struct dcon_platform_data. Add SPDX-License-Identifiers to the source files. Signed-off-by: Arkadiusz Lis <areklis909(a)gmail.com> --- drivers/staging/olpc_dcon/olpc_dcon.c | 1 + drivers/staging/olpc_dcon/olpc_dcon.h | 6 +++--- drivers/staging/olpc_dcon/olpc_dcon_xo_1.c | 1 + drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c | 1 + 4 files changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/staging/olpc_dcon/olpc_dcon.c b/drivers/staging/olpc_dcon/olpc_dcon.c index 2744c9f..318adc4 100644 --- a/drivers/staging/olpc_dcon/olpc_dcon.c +++ b/drivers/staging/olpc_dcon/olpc_dcon.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0 /* * Mainly by David Woodhouse, somewhat modified by Jordan Crouse * diff --git a/drivers/staging/olpc_dcon/olpc_dcon.h b/drivers/staging/olpc_dcon/olpc_dcon.h index fa89bb9..0ce1a7a 100644 --- a/drivers/staging/olpc_dcon/olpc_dcon.h +++ b/drivers/staging/olpc_dcon/olpc_dcon.h @@ -91,10 +91,10 @@ struct dcon_priv { }; struct dcon_platform_data { - int (*init)(struct dcon_priv *); + int (*init)(struct dcon_priv *dcon); void (*bus_stabilize_wiggle)(void); - void (*set_dconload)(int); - int (*read_status)(u8 *); + void (*set_dconload)(int val); + int (*read_status)(u8 *status); }; #include <linux/interrupt.h> diff --git a/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c b/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c index 633c58c..c72f492 100644 --- a/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c +++ b/drivers/staging/olpc_dcon/olpc_dcon_xo_1.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0 /* * Mainly by David Woodhouse, somewhat modified by Jordan Crouse * diff --git a/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c b/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c index 6458442..07b70eb 100644 --- a/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c +++ b/drivers/staging/olpc_dcon/olpc_dcon_xo_1_5.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0 /* * Copyright (c) 2009,2010 One Laptop per Child * -- 1.9.1

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Sharing memory between two kernel module - Better approach
by Abhinav Misra Aug. 2, 2018

Aug. 2, 2018

Hi, I want to know is there any alternative for sharing the memory between two modules. The approach which I can think of is taking a global pointer, using kmalloc and assigning start of memory to the global pointer and then in 2nd module use extern for using the same pointer. Is there any better way of doing the same ? BR, Abhinav

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(no subject)
by TU PHUNG VAN Aug. 2, 2018

Aug. 2, 2018

S.ư www

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Need Suggestions
by Athul Joy Aug. 2, 2018

Aug. 2, 2018

Dear friends, I am new to the Linux kernel development. Can anyone help me how to start my journey in order to build my own kernel?

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virtual address space allocation
by Babis Chalios Aug. 1, 2018

Aug. 1, 2018

Dear kernel hackers, I am working on the runtime system of a distributed memory programming language. For some reason we need to create a big hole on the address space of the application. We are trying to do so by using an mmap during the initialization of the runtime and then the runtime handles itself those addresses. This scenario works properly when the system allows memory overcommitment. More specifically, we seem to be fine if the /proc/sys/vm/overcommit_memory contains the values 0 or 1. However, we do have problems if memory overcommitment is disabled. So here goes the question: Is there any other mechanism to allow us to do what we want to? Things I 've thought so far: 1) To do my mmaps using PROT_NONE assuming that maybe those pages are not accounted for when calculating overcommitment. I did some tests and it seems that this assumption is wrong. 2) The possibility that there are addresses that are highly unlikely to be mapped in the address space of my application. If there is such an address range I could potentially relax the requirement that I should map all the address space at the beginning of the execution and instead try to mmap it progressively at runtime on a per-need basis. Any thoughts would be helpful. Cheers, Babis

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how to best ioremap() the ranges part of a "simple-bus" device?
by rpjday＠crashcourse.ca Aug. 1, 2018

Aug. 1, 2018

another (i suspect) fairly simple question, i've just never had the occasion to mess around in this part of the code. if i have a device tree source file containing the snippet: slave0: slave0-fubar@90000000 { compatible = "simple-bus"; ranges = <0x0 0x90000000 0x10000000>; #address-cells = <1>; #size-cells = <1>; }; slave1: slave1-fubar@a0000000 { compatible = "simple-bus"; ranges = <0x0 0xa0000000 0x10000000>; #address-cells = <1>; #size-cells = <1>; }; those two ranges actually represent physical addresses within an FPGA and, when certain events occur, i want some driver code to read/write some registers in slave0's address space, so obviously i'll need to access that device tree entry and effectively ioremap() slave0's physical address to a usable virtual address. is there a canonical way to do this? short of manually extracting the appropriate device tree node and reading that property and calling ioremap()? is there a wrapper for that sort of operation, which i imagine must be fairly common? oh, and a pointer to a good example in the current kernel source would, of course, be useful. rday

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