From 2f51efc6b71dc7e47acd26e4610107905feb074b Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Wed, 6 Apr 2022 11:31:30 +0900 Subject: docs: bootconfig: Add how to embed the bootconfig into kernel Add a description how to embed the bootconfig file into kernel. Link: https://lkml.kernel.org/r/164921228987.1090670.16843569536974147213.stgit@devnote2 Cc: Padmanabha Srinivasaiah Cc: Jonathan Corbet Cc: Randy Dunlap Cc: Nick Desaulniers Cc: Sami Tolvanen Cc: Nathan Chancellor Cc: Masahiro Yamada Cc: Linux Kbuild mailing list Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (Google) --- Documentation/admin-guide/bootconfig.rst | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) (limited to 'Documentation') diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index a1860fc0ca88..d99994345d41 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -158,9 +158,15 @@ Each key-value pair is shown in each line with following style:: Boot Kernel With a Boot Config ============================== -Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file with padding, size, -checksum and 12-byte magic word as below. +There are two options to boot the kernel with bootconfig: attaching the +bootconfig to the initrd image or embedding it in the kernel itself. + +Attaching a Boot Config to Initrd +--------------------------------- + +Since the boot configuration file is loaded with initrd by default, +it will be added to the end of the initrd (initramfs) image file with +padding, size, checksum and 12-byte magic word as below. [initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n] @@ -196,6 +202,25 @@ To remove the config from the image, you can use -d option as below:: Then add "bootconfig" on the normal kernel command line to tell the kernel to look for the bootconfig at the end of the initrd file. +Embedding a Boot Config into Kernel +----------------------------------- + +If you can not use initrd, you can also embed the bootconfig file in the +kernel by Kconfig options. In this case, you need to recompile the kernel +with the following configs:: + + CONFIG_BOOT_CONFIG_EMBED=y + CONFIG_BOOT_CONFIG_EMBED_FILE="/PATH/TO/BOOTCONFIG/FILE" + +``CONFIG_BOOT_CONFIG_EMBED_FILE`` requires an absolute path or a relative +path to the bootconfig file from source tree or object tree. +The kernel will embed it as the default bootconfig. + +Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` +option on the kernel command line to enable the embedded bootconfig. + +Note that even if you set this option, you can override the embedded +bootconfig by another bootconfig which attached to the initrd. Kernel parameters via Boot Config ================================= -- cgit v1.2.3 From 4d1257bbc220603d9e5c5157552448c066111c71 Mon Sep 17 00:00:00 2001 From: Kurt Kanzenbach Date: Thu, 14 Apr 2022 11:18:05 +0200 Subject: tracing: Add documentation for trace clock tai Add documentation for newly introduced trace clock "tai". This clock corresponds to CLOCK_TAI. Link: https://lkml.kernel.org/r/20220414091805.89667-4-kurt@linutronix.de Signed-off-by: Kurt Kanzenbach Signed-off-by: Steven Rostedt (Google) --- Documentation/trace/ftrace.rst | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation') diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 45b8c56af67a..b37dc19e4d40 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -517,6 +517,18 @@ of ftrace. Here is a list of some of the key files: processing should be able to handle them. See comments in the ktime_get_boot_fast_ns() function for more information. + tai: + This is the tai clock (CLOCK_TAI) and is derived from the wall- + clock time. However, this clock does not experience + discontinuities and backwards jumps caused by NTP inserting leap + seconds. Since the clock access is designed for use in tracing, + side effects are possible. The clock access may yield wrong + readouts in case the internal TAI offset is updated e.g., caused + by setting the system time or using adjtimex() with an offset. + These effects are rare and post processing should be able to + handle them. See comments in the ktime_get_tai_fast_ns() + function for more information. + To set a clock, simply echo the clock name into this file:: # echo global > trace_clock -- cgit v1.2.3 From 4dd2aea24ed7613735664feadc9879d37f718c23 Mon Sep 17 00:00:00 2001 From: Daniel Bristot de Oliveira Date: Tue, 10 May 2022 11:45:24 +0200 Subject: tracing/timerlat: Print stacktrace in the IRQ handler if needed If print_stack and stop_tracing_us are set, and stop_tracing_us is hit with latency higher than or equal to print_stack, print the stack at the IRQ handler as it is useful to define the root cause for the IRQ latency. Link: https://lkml.kernel.org/r/fd04530ce98ae9270e41bb124ee5bf67b05ecfed.1652175637.git.bristot@kernel.org Cc: Juri Lelli Cc: Clark Williams Cc: Ingo Molnar Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (Google) --- Documentation/trace/timerlat-tracer.rst | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/trace/timerlat-tracer.rst b/Documentation/trace/timerlat-tracer.rst index 64d1fe6e9b93..d643c95c01eb 100644 --- a/Documentation/trace/timerlat-tracer.rst +++ b/Documentation/trace/timerlat-tracer.rst @@ -74,8 +74,9 @@ directory. The timerlat configs are: - stop_tracing_total_us: stop the system tracing if a timer latency at the *thread* context is higher than the configured value happens. Writing 0 disables this option. - - print_stack: save the stack of the IRQ occurrence, and print - it after the *thread context* event". + - print_stack: save the stack of the IRQ occurrence. The stack is printed + after the *thread context* event, or at the IRQ handler if *stop_tracing_us* + is hit. timerlat and osnoise ---------------------------- -- cgit v1.2.3