adding rt patch

diff --git a/kbuild-rt/.gitignore b/kbuild-rt/.gitignore
new file mode 100644 (file)
index 0000000..edc579e
--- /dev/null
+++ b/kbuild-rt/.gitignore
@@ -0,0 +1,3 @@
+*.tar.gz
+linux-*
+*.patch.*
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diff --git a/kbuild-rt/README.md b/kbuild-rt/README.md
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index 0000000..509a305
--- /dev/null
+++ b/kbuild-rt/README.md
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+# how to patch linux kernel? example using realtime patch for linux kernel 
+
+
+```shell
+$ sudo apt update
+$ sudo apt install build-essential git libssl-dev libelf-dev flex bison debhelper-compat bc
+
+```
+
+```shell
+
+$ uname -a
+Linux ubuntu24-server 6.8.0-71-generic #71-Ubuntu SMP PREEMPT_DYNAMIC Tue Jul 22 16:52:38 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
+
+
+```
+
+
+```shell
+$ curl -L https://mirrors.edge.kernel.org/pub/linux/kernel/v6.x/linux-6.8.tar.gz -o linux-6.8.tar.gz
+
+$ tar xzf linux-6.8.tar.gz
+```
+
+```shell
+$ curl -L https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/6.8/patch-6.8.2-rt11.patch.xz -o patch-6.8.2-rt11.patch.xz
+
+$ curl -L https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patch-6.8-rt8.patch.xz -o patch-6.8-rt8.patch.xz
+
+$ cd linux-6.8
+
+```
+
+
+```shell
+$ xzcat ../patch-6.8.2-rt11.patch.xz | patch -p1
+1 out of 23 hunks FAILED -- saving rejects to file net/core/dev.c.rej
+
+$ cd ../
+
+$ rm -r linux-6.8
+```
+
+```shell
+$ xzcat ../patch-6.8-rt8.patch.xz | patch -p1
+...
+patching file kernel/time/tick-sched.c
+patching file kernel/time/timer.c
+patching file kernel/trace/trace.c
+patching file kernel/trace/trace_output.c
+patching file lib/dump_stack.c
+patching file localversion-rt
+patching file net/core/dev.c
+patching file net/core/skbuff.c
+
+```
+
+```shell
+$ cp /boot/config-6.8.0-71-generic .config
+$ make oldconfig
+```
+
+```shell
+# choose 5
+Preemption Model
+  1. No Forced Preemption (Server) (PREEMPT_NONE)
+> 2. Voluntary Kernel Preemption (Desktop) (PREEMPT_VOLUNTARY)
+  3. Preemptible Kernel (Low-Latency Desktop) (PREEMPT)
+  4. Automagic preemption mode with runtime tweaking support (PREEMPT_AUTO) (NEW)
+  5. Fully Preemptible Kernel (Real-Time) (PREEMPT_RT) (NEW)
+choice[1-5?]:
+
+# hit enter until the end
+Undefined behaviour sanity checker (UBSAN) [Y/n/?] y
+  Abort on Sanitizer warnings (smaller kernel but less verbose) (UBSAN_TRAP) [N/y/?] n
+  Perform array index bounds checking (UBSAN_BOUNDS) [Y/n/?] y
+  Perform checking for bit-shift overflows (UBSAN_SHIFT) [Y/n/?] y
+  Perform checking for integer divide-by-zero (UBSAN_DIV_ZERO) [N/y/?] n
+  Perform checking for non-boolean values used as boolean (UBSAN_BOOL) [Y/n/?] y
+  Perform checking for out of bounds enum values (UBSAN_ENUM) [Y/n/?] y
+  Perform checking for misaligned pointer usage (UBSAN_ALIGNMENT) [N/y/?] n
+  Enable instrumentation for the entire kernel (UBSAN_SANITIZE_ALL) [Y/n/?] (NEW) 
+  Module for testing for undefined behavior detection (TEST_UBSAN) [N/m/?] n
+#
+# configuration written to .config
+#
+```
+
+```shell
+# delete value as below
+
+CONFIG_SYSTEM_TRUSTED_KEYS=""
+CONFIG_MODULE_SIG_KEY=""
+CONFIG_SYSTEM_REVOCATION_KEYS=""
+
+# comment out
+
+CONFIG_MODULE_SIG_FORCE
+CONFIG_DEBUG_INFO_BTF
+CONFIG_MODULE_SIG_ALL
+
+```
+
+```shell
+$ nproc
+4
+```
+
+```shell
+
+# $ make -j2 deb-pkg
+$ make -j2 bindeb-pkg
+```
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