[MINI-OS,01/12] kexec: add kexec framework

Commit Message

Jürgen Groß March 21, 2025, 9:24 a.m. UTC

Add a new config option CONFIG_KEXEC for support of kexec-ing into a
new mini-os kernel. Add a related kexec.c source and a kexec.h header.

For now allow CONFIG_KEXEC to be set only for PVH variant of mini-os.

Signed-off-by: Juergen Gross <[e-mail]>
---
 Config.mk                  |  1 +
 Makefile                   |  1 +
 arch/x86/testbuild/all-no  |  1 +
 arch/x86/testbuild/all-yes |  2 ++
 arch/x86/testbuild/kexec   |  4 +++
 include/kexec.h            |  7 +++++
 kexec.c                    | 62 ++++++++++++++++++++++++++++++++++++++
 7 files changed, 78 insertions(+)
 create mode 100644 arch/x86/testbuild/kexec
 create mode 100644 include/kexec.h
 create mode 100644 kexec.c

Patch

diff --git a/Config.mk b/Config.mk
index e493533a..e2afb1b4 100644
--- a/Config.mk
+++ b/Config.mk
@@ -204,6 +204,7 @@  CONFIG-n += CONFIG_LIBXENGUEST
 CONFIG-n += CONFIG_LIBXENTOOLCORE
 CONFIG-n += CONFIG_LIBXENTOOLLOG
 CONFIG-n += CONFIG_LIBXENMANAGE
+CONFIG-n += CONFIG_KEXEC
 # Setting CONFIG_USE_XEN_CONSOLE copies all print output to the Xen emergency
 # console apart of standard dom0 handled console.
 CONFIG-n += CONFIG_USE_XEN_CONSOLE
diff --git a/Makefile b/Makefile
index d094858a..a64913ad 100644
--- a/Makefile
+++ b/Makefile
@@ -51,6 +51,7 @@  src-y += gntmap.c
 src-y += gnttab.c
 src-y += hypervisor.c
 src-y += kernel.c
+src-$(CONFIG_KEXEC) += kexec.c
 src-y += lock.c
 src-y += main.c
 src-y += mm.c
diff --git a/arch/x86/testbuild/all-no b/arch/x86/testbuild/all-no
index 5b3e99ed..b2ee5ce8 100644
--- a/arch/x86/testbuild/all-no
+++ b/arch/x86/testbuild/all-no
@@ -18,3 +18,4 @@  CONFIG_LIBXS = n
 CONFIG_LWIP = n
 CONFIG_BALLOON = n
 CONFIG_USE_XEN_CONSOLE = n
+CONFIG_KEXEC = n
diff --git a/arch/x86/testbuild/all-yes b/arch/x86/testbuild/all-yes
index 8ae489a4..99ba75dd 100644
--- a/arch/x86/testbuild/all-yes
+++ b/arch/x86/testbuild/all-yes
@@ -19,3 +19,5 @@  CONFIG_BALLOON = y
 CONFIG_USE_XEN_CONSOLE = y
 # The following are special: they need support from outside
 CONFIG_LWIP = n
+# KEXEC only without PARAVIRT
+CONFIG_KEXEC = n
diff --git a/arch/x86/testbuild/kexec b/arch/x86/testbuild/kexec
new file mode 100644
index 00000000..ea17b4d9
--- /dev/null
+++ b/arch/x86/testbuild/kexec
@@ -0,0 +1,4 @@ 
+CONFIG_PARAVIRT = n
+CONFIG_BALLOON = y
+CONFIG_USE_XEN_CONSOLE = y
+CONFIG_KEXEC = y
diff --git a/include/kexec.h b/include/kexec.h
new file mode 100644
index 00000000..6fd96774
--- /dev/null
+++ b/include/kexec.h
@@ -0,0 +1,7 @@ 
+#ifndef _KEXEC_H
+#define _KEXEC_H
+
+int kexec(void *kernel, unsigned long kernel_size,
+          const char *cmdline);
+
+#endif /* _KEXEC_H */
diff --git a/kexec.c b/kexec.c
new file mode 100644
index 00000000..53528169
--- /dev/null
+++ b/kexec.c
@@ -0,0 +1,62 @@ 
+/******************************************************************************
+ * kexec.c
+ *
+ * Support of kexec (reboot locally into new mini-os kernel).
+ *
+ * Copyright (c) 2024, Juergen Gross, SUSE Linux GmbH
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifdef CONFIG_PARAVIRT
+#error "kexec support not implemented in PV variant"
+#endif
+
+#include <errno.h>
+#include <mini-os/os.h>
+#include <mini-os/lib.h>
+#include <mini-os/kexec.h>
+
+/*
+ * General approach for kexec support (PVH only) is as follows:
+ *
+ * - New kernel needs to be in memory in form of a ELF file in a virtual
+ *   memory region.
+ * - A new start_info structure is constructed in memory with the final
+ *   memory locations included.
+ * - All memory areas needed for kexec execution are being finalized.
+ * - From here on a graceful failure is no longer possible.
+ * - Grants and event channels are torn down.
+ * - A temporary set of page tables is constructed at a location where it
+ *   doesn't conflict with old and new kernel or start_info.
+ * - The final kexec execution stage is copied to a memory area below 4G which
+ *   doesn't conflict with the target areas of kernel etc.
+ * - Cr3 is switched to the new set of page tables.
+ * - Execution continues in the final execution stage.
+ * - All data is copied to its final addresses.
+ * - Processing is switched to 32-bit mode without address translation.
+ * - The new kernel is activated.
+ */
+
+int kexec(void *kernel, unsigned long kernel_size,
+          const char *cmdline)
+{
+    return ENOSYS;
+}
+EXPORT_SYMBOL(kexec);