[PATCH v8 08/12] xen: add /buildinfo/config entry to hypervisor filesystem

[Juergen Gross <jgross@xxxxxxxx>]

Add the /buildinfo/config entry to the hypervisor filesystem. This
entry contains the .config file used to build the hypervisor.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V3:
- store data in gzip format
- use binfile mechanism to create data file
- move code to kernel.c

V6:
- add config item for the /buildinfo/config (Jan Beulich)
- make config related variables const in kernel.h (Jan Beulich)

V7:
- update doc (Jan Beulich)
- use "rm -f" in Makefile (Jan Beulich)

V8:
- add dependency top CONFIG_HYPFS
- use macro for definition of leaf (Jan Beulich)

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 .gitignore                   |  2 ++
 docs/misc/hypfs-paths.pandoc |  4 ++++
 xen/common/Kconfig           | 11 +++++++++++
 xen/common/Makefile          | 12 ++++++++++++
 xen/common/kernel.c          | 11 +++++++++++
 xen/include/xen/kernel.h     |  3 +++
 6 files changed, 43 insertions(+)

diff --git a/.gitignore b/.gitignore
index ce3ef23d45..a58de1fd4a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -298,6 +298,8 @@ xen/arch/*/efi/boot.c
 xen/arch/*/efi/compat.c
 xen/arch/*/efi/efi.h
 xen/arch/*/efi/runtime.c
+xen/common/config_data.S
+xen/common/config.gz
 xen/include/headers*.chk
 xen/include/asm
 xen/include/asm-*/asm-offsets.h
diff --git a/docs/misc/hypfs-paths.pandoc b/docs/misc/hypfs-paths.pandoc
index d730caf394..9a76bc383b 100644
--- a/docs/misc/hypfs-paths.pandoc
+++ b/docs/misc/hypfs-paths.pandoc
@@ -135,6 +135,10 @@ Information about the compile domain.
 
 The compiler used to build Xen.
 
+#### /buildinfo/config = STRING [CONFIG_HYPFS_CONFIG]
+
+The contents of the `xen/.config` file at the time of the hypervisor build.
+
 #### /buildinfo/version/
 
 A directory containing version information of the hypervisor.
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index 2515e053c8..b36cd74a24 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -127,6 +127,17 @@ config HYPFS
 
          If unsure, say Y.
 
+config HYPFS_CONFIG
+       bool "Provide hypervisor .config via hypfs entry"
+       default y
+       depends on HYPFS
+       ---help---
+         When enabled the contents of the .config file used to build the
+         hypervisor are provided via the hypfs entry /buildinfo/config.
+
+         Disable this option in case you want to spare some memory or you
+         want to hide the .config contents from dom0.
+
 config KEXEC
        bool "kexec support"
        default y
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 98b7904dcd..d6d7bad2a9 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -1,6 +1,7 @@
 obj-$(CONFIG_ARGO) += argo.o
 obj-y += bitmap.o
 obj-y += bsearch.o
+obj-$(CONFIG_HYPFS_CONFIG) += config_data.o
 obj-$(CONFIG_CORE_PARKING) += core_parking.o
 obj-y += cpu.o
 obj-$(CONFIG_DEBUG_TRACE) += debugtrace.o
@@ -73,3 +74,14 @@ obj-$(CONFIG_UBSAN) += ubsan/
 
 obj-$(CONFIG_NEEDS_LIBELF) += libelf/
 obj-$(CONFIG_HAS_DEVICE_TREE) += libfdt/
+
+config.gz: ../.config
+       gzip -c $< >$@
+
+config_data.o: config.gz
+
+config_data.S: $(XEN_ROOT)/xen/tools/binfile
+       $(XEN_ROOT)/xen/tools/binfile $@ config.gz xen_config_data
+
+clean::
+       rm -f config_data.S config.gz 2>/dev/null
diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index db7bd23fcb..f8f41820d5 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -390,6 +390,10 @@ static HYPFS_STRING_INIT(compile_date, "compile_date");
 static HYPFS_STRING_INIT(compile_domain, "compile_domain");
 static HYPFS_STRING_INIT(extra, "extra");
 
+#ifdef CONFIG_HYPFS_CONFIG
+static HYPFS_STRING_INIT(config, "config");
+#endif
+
 static int __init buildinfo_init(void)
 {
     hypfs_add_dir(&hypfs_root, &buildinfo, true);
@@ -415,6 +419,13 @@ static int __init buildinfo_init(void)
     hypfs_add_leaf(&version, &major, true);
     hypfs_add_leaf(&version, &minor, true);
 
+#ifdef CONFIG_HYPFS_CONFIG
+    config.e.encoding = XEN_HYPFS_ENC_GZIP;
+    config.e.size = xen_config_data_size;
+    config.content = &xen_config_data;
+    hypfs_add_leaf(&buildinfo, &config, true);
+#endif
+
     return 0;
 }
 __initcall(buildinfo_init);
diff --git a/xen/include/xen/kernel.h b/xen/include/xen/kernel.h
index 548b64da9f..02e3281f52 100644
--- a/xen/include/xen/kernel.h
+++ b/xen/include/xen/kernel.h
@@ -100,5 +100,8 @@ extern enum system_state {
 
 bool_t is_active_kernel_text(unsigned long addr);
 
+extern const char xen_config_data;
+extern const unsigned int xen_config_data_size;
+
 #endif /* _LINUX_KERNEL_H */
 
-- 
2.26.1