[PATCHv6 0/4] Salted build ids via ELF notes

[PATCHv6 0/4] Salted build ids via ELF notes

[Laura Abbott]

Hi,

This is v6 of the series to allow unique build ids. v6 is mostly minor
fixups and Acks for this to go through the kbuild tree.

Thanks,
Laura

Laura Abbott (4):
  kbuild: Add build salt to the kernel and modules
  x86: Add build salt to the vDSO
  powerpc: Add build salt to the vDSO
  arm64: Add build salt to the vDSO

 arch/arm64/kernel/vdso/note.S     |  3 +++
 arch/powerpc/kernel/vdso32/note.S |  3 +++
 arch/x86/entry/vdso/vdso-note.S   |  3 +++
 arch/x86/entry/vdso/vdso32/note.S |  3 +++
 include/linux/build-salt.h        | 20 ++++++++++++++++++++
 init/Kconfig                      |  9 +++++++++
 init/version.c                    |  3 +++
 scripts/mod/modpost.c             |  3 +++
 8 files changed, 47 insertions(+)
 create mode 100644 include/linux/build-salt.h

-- 
2.17.1

[PATCHv6 1/4] kbuild: Add build salt to the kernel and modules

[Laura Abbott]

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>
---
v6: Added more detail to the commit text about why exactly this feature
is useful. Default string now ""
---
 include/linux/build-salt.h | 20 ++++++++++++++++++++
 init/Kconfig               |  9 +++++++++
 init/version.c             |  3 +++
 scripts/mod/modpost.c      |  3 +++
 4 files changed, 35 insertions(+)
 create mode 100644 include/linux/build-salt.h

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");
-- 
2.17.1

[PATCHv6 2/4] x86: Add build salt to the vDSO

[Laura Abbott]

The vDSO needs to have a unique build id in a similar manner
to the kernel and modules. Use the build salt macro.

Acked-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v6: Ack from Andy
---
 arch/x86/entry/vdso/vdso-note.S   | 3 +++
 arch/x86/entry/vdso/vdso32/note.S | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/entry/vdso/vdso-note.S b/arch/x86/entry/vdso/vdso-note.S
index 79a071e4357e..79423170118f 100644
--- a/arch/x86/entry/vdso/vdso-note.S
+++ b/arch/x86/entry/vdso/vdso-note.S
@@ -3,6 +3,7 @@
  * Here we can supply some information useful to userland.
  */
 
+#include <linux/build-salt.h>
 #include <linux/uts.h>
 #include <linux/version.h>
 #include <linux/elfnote.h>
@@ -10,3 +11,5 @@
 ELFNOTE_START(Linux, 0, "a")
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
+
+BUILD_SALT
diff --git a/arch/x86/entry/vdso/vdso32/note.S b/arch/x86/entry/vdso/vdso32/note.S
index 9fd51f206314..e78047d119f6 100644
--- a/arch/x86/entry/vdso/vdso32/note.S
+++ b/arch/x86/entry/vdso/vdso32/note.S
@@ -4,6 +4,7 @@
  * Here we can supply some information useful to userland.
  */
 
+#include <linux/build-salt.h>
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
@@ -14,6 +15,8 @@ ELFNOTE_START(Linux, 0, "a")
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
 
+BUILD_SALT
+
 #ifdef CONFIG_XEN
 /*
  * Add a special note telling glibc's dynamic linker a fake hardware
-- 
2.17.1

[PATCHv6 3/4] powerpc: Add build salt to the vDSO

[Laura Abbott]

The vDSO needs to have a unique build id in a similar manner
to the kernel and modules. Use the build salt macro.

Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v6: Remove semi-colon
---
 arch/powerpc/kernel/vdso32/note.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kernel/vdso32/note.S b/arch/powerpc/kernel/vdso32/note.S
index d4b5be4f3d5f..227a7327399e 100644
--- a/arch/powerpc/kernel/vdso32/note.S
+++ b/arch/powerpc/kernel/vdso32/note.S
@@ -5,6 +5,7 @@
 
 #include <linux/uts.h>
 #include <linux/version.h>
+#include <linux/build-salt.h>
 
 #define ASM_ELF_NOTE_BEGIN(name, flags, vendor, type)			      \
 	.section name, flags;						      \
@@ -23,3 +24,5 @@
 	ASM_ELF_NOTE_BEGIN(".note.kernel-version", "a", UTS_SYSNAME, 0)
 	.long LINUX_VERSION_CODE
 	ASM_ELF_NOTE_END
+
+BUILD_SALT
-- 
2.17.1

[PATCHv6 4/4] arm64: Add build salt to the vDSO

[Laura Abbott]

The vDSO needs to have a unique build id in a similar manner
to the kernel and modules. Use the build salt macro.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
v6: Remove the semi-colon, Ack from Will
---
 arch/arm64/kernel/vdso/note.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/vdso/note.S b/arch/arm64/kernel/vdso/note.S
index b82c85e5d972..e20483b104d9 100644
--- a/arch/arm64/kernel/vdso/note.S
+++ b/arch/arm64/kernel/vdso/note.S
@@ -22,7 +22,10 @@
 #include <linux/uts.h>
 #include <linux/version.h>
 #include <linux/elfnote.h>
+#include <linux/build-salt.h>
 
 ELFNOTE_START(Linux, 0, "a")
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
+
+BUILD_SALT
-- 
2.17.1

Re: [PATCHv6 0/4] Salted build ids via ELF notes

[Masahiro Yamada]

2018-07-06 9:49 GMT+09:00 Laura Abbott <labbott@redhat.com>:
> Hi,
>
> This is v6 of the series to allow unique build ids. v6 is mostly minor
> fixups and Acks for this to go through the kbuild tree.


Applied to linux-kbuild. Thanks!


> Thanks,
> Laura
>
> Laura Abbott (4):
>   kbuild: Add build salt to the kernel and modules
>   x86: Add build salt to the vDSO
>   powerpc: Add build salt to the vDSO
>   arm64: Add build salt to the vDSO
>
>  arch/arm64/kernel/vdso/note.S     |  3 +++
>  arch/powerpc/kernel/vdso32/note.S |  3 +++
>  arch/x86/entry/vdso/vdso-note.S   |  3 +++
>  arch/x86/entry/vdso/vdso32/note.S |  3 +++
>  include/linux/build-salt.h        | 20 ++++++++++++++++++++
>  init/Kconfig                      |  9 +++++++++
>  init/version.c                    |  3 +++
>  scripts/mod/modpost.c             |  3 +++
>  8 files changed, 47 insertions(+)
>  create mode 100644 include/linux/build-salt.h
>
> --
> 2.17.1
>
> --
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-- 
Best Regards
Masahiro Yamada