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authorLaura Abbott <labbott@redhat.com>2018-07-05 17:49:37 -0700
committerMasahiro Yamada <yamada.masahiro@socionext.com>2018-07-18 01:18:05 +0900
commit9afb719e7046c4f2462278862ab3db2961cc141c (patch)
tree1c80da67479e528cddc6db97a0ed7397e2afc1a0
parent934193a654c1f4d0643ddbf4b2529b508cae926e (diff)
kbuild: Add build salt to the kernel and modules
In Fedora, the debug information is packaged separately (foo-debuginfo) and can be installed separately. There's been a long standing issue where only one version of a debuginfo info package can be installed at a time. There's been an effort for Fedora for parallel debuginfo to rectify this problem. Part of the requirement to allow parallel debuginfo to work is that build ids are unique between builds. The existing upstream rpm implementation ensures this by re-calculating the build-id using the version and release as a seed. This doesn't work 100% for the kernel because of the vDSO which is its own binary and doesn't get updated when embedded. Fix this by adding some data in an ELF note for both the kernel and modules. The data is controlled via a Kconfig option so distributions can set it to an appropriate value to ensure uniqueness between builds. Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
-rw-r--r--include/linux/build-salt.h20
-rw-r--r--init/Kconfig9
-rw-r--r--init/version.c3
-rw-r--r--scripts/mod/modpost.c3
4 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/build-salt.h b/include/linux/build-salt.h
new file mode 100644
index 000000000000..bb007bd05e7a
--- /dev/null
+++ b/include/linux/build-salt.h
@@ -0,0 +1,20 @@
+#ifndef __BUILD_SALT_H
+#define __BUILD_SALT_H
+
+#include <linux/elfnote.h>
+
+#define LINUX_ELFNOTE_BUILD_SALT 0x100
+
+#ifdef __ASSEMBLER__
+
+#define BUILD_SALT \
+ ELFNOTE(Linux, LINUX_ELFNOTE_BUILD_SALT, .asciz CONFIG_BUILD_SALT)
+
+#else
+
+#define BUILD_SALT \
+ ELFNOTE32("Linux", LINUX_ELFNOTE_BUILD_SALT, CONFIG_BUILD_SALT)
+
+#endif
+
+#endif /* __BUILD_SALT_H */
diff --git a/init/Kconfig b/init/Kconfig
index 041f3a022122..d39b31484c52 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -107,6 +107,15 @@ config LOCALVERSION_AUTO
which is done within the script "scripts/setlocalversion".)
+config BUILD_SALT
+ string "Build ID Salt"
+ default ""
+ help
+ The build ID is used to link binaries and their debug info. Setting
+ this option will use the value in the calculation of the build id.
+ This is mostly useful for distributions which want to ensure the
+ build is unique between builds. It's safe to leave the default.
+
config HAVE_KERNEL_GZIP
bool
diff --git a/init/version.c b/init/version.c
index bfb4e3f4955e..ef4012ec4375 100644
--- a/init/version.c
+++ b/init/version.c
@@ -7,6 +7,7 @@
*/
#include <generated/compile.h>
+#include <linux/build-salt.h>
#include <linux/export.h>
#include <linux/uts.h>
#include <linux/utsname.h>
@@ -49,3 +50,5 @@ const char linux_proc_banner[] =
"%s version %s"
" (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ")"
" (" LINUX_COMPILER ") %s\n";
+
+BUILD_SALT;
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 1663fb19343a..dc6d714e4dcb 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2125,10 +2125,13 @@ static int check_modname_len(struct module *mod)
**/
static void add_header(struct buffer *b, struct module *mod)
{
+ buf_printf(b, "#include <linux/build-salt.h>\n");
buf_printf(b, "#include <linux/module.h>\n");
buf_printf(b, "#include <linux/vermagic.h>\n");
buf_printf(b, "#include <linux/compiler.h>\n");
buf_printf(b, "\n");
+ buf_printf(b, "BUILD_SALT;\n");
+ buf_printf(b, "\n");
buf_printf(b, "MODULE_INFO(vermagic, VERMAGIC_STRING);\n");
buf_printf(b, "MODULE_INFO(name, KBUILD_MODNAME);\n");
buf_printf(b, "\n");