* [PATCHv3 0/2] Salted build ids via linker sections @ 2018-05-23 0:19 Laura Abbott 2018-05-23 0:19 ` [PATCHv3 1/2] kbuild: Introduce build-salt linker script Laura Abbott 2018-05-23 0:19 ` [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO Laura Abbott 0 siblings, 2 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-23 0:19 UTC (permalink / raw) To: Andy Lutomirski, mjw, H . J . Lu, Masahiro Yamada Cc: Laura Abbott, Linus Torvalds, X86 ML, linux-kernel, Nick Clifton, Cary Coutant, linux-kbuild Hi, This is v3 of the series to allow unique build-ids in the kernel. As a reminder of the context: "" 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. Mark Wielaard made an effort for Fedora 27 to allow parallel installation of debuginfo (see https://fedoraproject.org/wiki/Changes/ParallelInstallableDebuginfo for more details) Part of the requirement to allow this 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. After poking holes in a few of my ideas, there was a discussion with some people from the binutils team about adding --build-id-salt to let ld do the calculation debugedit is doing. There was a counter proposal made about adding some extra information via a .comment which will affect the build id calculation but just get stripped out. "" I mentioned in the previous version that there were problems with sporadic build failures. v3 switches to generating the linker script directly instead of a header + a linker script to avoid this problem. I also dropped the Kconfig completely (I can add it back as a guard if this seems not small enough to want all the time). I've also dropped the RFC tag since it's well formed enough at this point. Laura Abbott (2): kbuild: Introduce build-salt linker script x86/vdso: Add build salt to the vDSO Makefile | 4 +++- arch/x86/entry/vdso/Makefile | 4 +++- scripts/.gitignore | 1 + scripts/Makefile | 9 ++++++++- scripts/gensalt | 22 ++++++++++++++++++++++ scripts/link-vmlinux.sh | 3 ++- 6 files changed, 39 insertions(+), 4 deletions(-) create mode 100755 scripts/gensalt -- 2.17.0 ^ permalink raw reply [flat|nested] 13+ messages in thread
* [PATCHv3 1/2] kbuild: Introduce build-salt linker script 2018-05-23 0:19 [PATCHv3 0/2] Salted build ids via linker sections Laura Abbott @ 2018-05-23 0:19 ` Laura Abbott 2018-05-23 0:19 ` [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO Laura Abbott 1 sibling, 0 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-23 0:19 UTC (permalink / raw) To: Andy Lutomirski, mjw, H . J . Lu, Masahiro Yamada Cc: Laura Abbott, Linus Torvalds, X86 ML, linux-kernel, Nick Clifton, Cary Coutant, linux-kbuild The build id generated from --build-id can be generated in several different ways, with the default being the sha1 on the output of the linked file. For distributions, it can be useful to make sure this ID is unique, even if the actual file contents don't change. The easiest way to do this is to insert a comment section with some data. Introduce a generated linker script to link against the kernel/modules. This puts the kernel version in a .comment section which will generate a unique build id if the kernel version changes. Signed-off-by: Laura Abbott <labbott@redhat.com> --- v3: Generate the linker script directly instead of just a header. --- Makefile | 4 +++- scripts/.gitignore | 1 + scripts/Makefile | 9 ++++++++- scripts/gensalt | 22 ++++++++++++++++++++++ scripts/link-vmlinux.sh | 3 ++- 5 files changed, 36 insertions(+), 3 deletions(-) create mode 100755 scripts/gensalt diff --git a/Makefile b/Makefile index ec6f45928fd4..87fe8992afd8 100644 --- a/Makefile +++ b/Makefile @@ -428,7 +428,8 @@ KBUILD_AFLAGS_KERNEL := KBUILD_CFLAGS_KERNEL := KBUILD_AFLAGS_MODULE := -DMODULE KBUILD_CFLAGS_MODULE := -DMODULE -KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds +KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds \ + -T $(obj)/scripts/build-salt.lds LDFLAGS := GCC_PLUGINS_CFLAGS := @@ -997,6 +998,7 @@ export KBUILD_VMLINUX_INIT := $(head-y) $(init-y) export KBUILD_VMLINUX_MAIN := $(core-y) $(libs-y2) $(drivers-y) $(net-y) $(virt-y) export KBUILD_VMLINUX_LIBS := $(libs-y1) export KBUILD_LDS := arch/$(SRCARCH)/kernel/vmlinux.lds +export EXTRA_LDS := scripts/build-salt.lds export LDFLAGS_vmlinux # used by scripts/package/Makefile export KBUILD_ALLDIRS := $(sort $(filter-out arch/%,$(vmlinux-alldirs)) arch Documentation include samples scripts tools) diff --git a/scripts/.gitignore b/scripts/.gitignore index 0442c06eefcb..1c840ef4f0c8 100644 --- a/scripts/.gitignore +++ b/scripts/.gitignore @@ -13,3 +13,4 @@ asn1_compiler extract-cert sign-file insert-sys-cert +build-salt.lds diff --git a/scripts/Makefile b/scripts/Makefile index 25ab143cbe14..019b0749ff46 100644 --- a/scripts/Makefile +++ b/scripts/Makefile @@ -25,7 +25,14 @@ HOSTCFLAGS_asn1_compiler.o = -I$(srctree)/include HOSTLOADLIBES_sign-file = -lcrypto HOSTLOADLIBES_extract-cert = -lcrypto -always := $(hostprogs-y) $(hostprogs-m) +always := $(hostprogs-y) $(hostprogs-m) build-salt.lds + +define filechk_build-salt.lds + ($(CONFIG_SHELL) $(srctree)/scripts/gensalt $(KERNELRELEASE)) +endef + +$(obj)/build-salt.lds: $(src)/gensalt FORCE + $(call filechk,build-salt.lds) # The following hostprogs-y programs are only build on demand hostprogs-y += unifdef diff --git a/scripts/gensalt b/scripts/gensalt new file mode 100755 index 000000000000..846c0407cc43 --- /dev/null +++ b/scripts/gensalt @@ -0,0 +1,22 @@ +#!/bin/sh + +if [[ $1 = "" ]]; then + echo "#define BUILD_ID_SALT" + exit 0 +fi + +BUILD_ID_SALT=$1 + +echo "SECTIONS {" +echo ".comment (INFO) :" +echo " {" + +_TAG=`echo $BUILD_ID_SALT | sed -e 's/\(.\)/\1 /g'` +for c in $_TAG; do + _HEX=`echo -n $c | od -A n -t x1 | tr -d ' ' ` + echo "BYTE(0x$_HEX);" +done +echo "BYTE(0x00);" + +echo " } " +echo " } " diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index 9045823c7be7..588946dde658 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -84,6 +84,7 @@ modpost_link() vmlinux_link() { local lds="${objtree}/${KBUILD_LDS}" + local extra_lds="${objtree}/${EXTRA_LDS}" local objects if [ "${SRCARCH}" != "um" ]; then @@ -96,7 +97,7 @@ vmlinux_link() ${1}" ${LD} ${LDFLAGS} ${LDFLAGS_vmlinux} -o ${2} \ - -T ${lds} ${objects} + -T ${lds} -T ${extra_lds} ${objects} else objects="-Wl,--whole-archive \ built-in.a \ -- 2.17.0 ^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 0:19 [PATCHv3 0/2] Salted build ids via linker sections Laura Abbott 2018-05-23 0:19 ` [PATCHv3 1/2] kbuild: Introduce build-salt linker script Laura Abbott @ 2018-05-23 0:19 ` Laura Abbott 2018-05-23 0:33 ` Andy Lutomirski 2018-05-24 1:55 ` Masahiro Yamada 1 sibling, 2 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-23 0:19 UTC (permalink / raw) To: Andy Lutomirski, mjw, H . J . Lu, Masahiro Yamada Cc: Laura Abbott, Linus Torvalds, X86 ML, linux-kernel, Nick Clifton, Cary Coutant, linux-kbuild The vDSO is linked separately from the kernel and modules. Ensure it picks up the comment section, if available. Signed-off-by: Laura Abbott <labbott@redhat.com> --- v3: Invoke the generated linker script. The ".." nightmare is pretty ugly but I didn't see an easier way to pick up the generated file. That was actually part of my motivation for using an #include since paths for those are standardized. --- arch/x86/entry/vdso/Makefile | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index d998a487c9b1..f54aa97dc9f0 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -162,7 +162,9 @@ $(obj)/vdso32.so.dbg: FORCE \ quiet_cmd_vdso = VDSO $@ cmd_vdso = $(CC) -nostdlib -o $@ \ $(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \ - -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \ + -Wl,-T,$(filter %.lds,$^) \ + -Wl,-T$(obj)/../../../../scripts/build-salt.lds \ + $(filter %.o,$^) && \ sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@' VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=both) \ -- 2.17.0 ^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 0:19 ` [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO Laura Abbott @ 2018-05-23 0:33 ` Andy Lutomirski 2018-05-23 1:23 ` Laura Abbott 2018-05-23 22:53 ` Laura Abbott 2018-05-24 1:55 ` Masahiro Yamada 1 sibling, 2 replies; 13+ messages in thread From: Andy Lutomirski @ 2018-05-23 0:33 UTC (permalink / raw) To: Laura Abbott Cc: Andrew Lutomirski, Mark Wielaard, H. J. Lu, Masahiro Yamada, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, linux-kbuild On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: > The vDSO is linked separately from the kernel and modules. Ensure it picks > up the comment section, if available. Did you end up preferring this to just sticking the kernel version in a .comment in the vDSO for some reason? ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 0:33 ` Andy Lutomirski @ 2018-05-23 1:23 ` Laura Abbott 2018-05-23 22:53 ` Laura Abbott 1 sibling, 0 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-23 1:23 UTC (permalink / raw) To: Andy Lutomirski Cc: Mark Wielaard, H. J. Lu, Masahiro Yamada, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, linux-kbuild On 05/22/2018 05:33 PM, Andy Lutomirski wrote: > On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: > > >> The vDSO is linked separately from the kernel and modules. Ensure it picks >> up the comment section, if available. > > Did you end up preferring this to just sticking the kernel version in a > .comment in the vDSO for some reason? > That's a good idea I hadn't considered. I'll do that for the next version. Thanks, Laura ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 0:33 ` Andy Lutomirski 2018-05-23 1:23 ` Laura Abbott @ 2018-05-23 22:53 ` Laura Abbott 2018-05-23 23:55 ` Linus Torvalds 2018-05-24 0:11 ` Masahiro Yamada 1 sibling, 2 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-23 22:53 UTC (permalink / raw) To: Andy Lutomirski Cc: Mark Wielaard, H. J. Lu, Masahiro Yamada, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, linux-kbuild On 05/22/2018 05:33 PM, Andy Lutomirski wrote: > On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: > > >> The vDSO is linked separately from the kernel and modules. Ensure it picks >> up the comment section, if available. > > Did you end up preferring this to just sticking the kernel version in a > .comment in the vDSO for some reason? > Actually I remember now why this is necessary: there is not a simple way to encode a string into a linker file as it has to be spit out byte by byte. The autogeneration was the easiest way to make that happen. Maybe there's some horrific c preprocessing or other generation that could happen but I doubt that's any worse than the generated linker script. Thanks, Laura ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 22:53 ` Laura Abbott @ 2018-05-23 23:55 ` Linus Torvalds 2018-05-24 0:01 ` Andy Lutomirski 2018-05-24 0:11 ` Masahiro Yamada 1 sibling, 1 reply; 13+ messages in thread From: Linus Torvalds @ 2018-05-23 23:55 UTC (permalink / raw) To: Laura Abbott Cc: Andrew Lutomirski, mjw, H.J. Lu, Masahiro Yamada, the arch/x86 maintainers, Linux Kernel Mailing List, nickc, ccoutant, Linux Kbuild mailing list On Wed, May 23, 2018 at 3:53 PM Laura Abbott <labbott@redhat.com> wrote: > Actually I remember now why this is necessary: there is not a simple way > to encode a string into a linker file as it has to be spit out byte > by byte. I think you can use the "fill" thing to basically add any random data to a section. So you can do something like . = ALIGN(16); .salt : AT(ADDR(.salt) - LOAD_OFFSET) { LONG(0xffaa5500); . = ALIGN(16); } =0x01234567890abcdef in the lds file, and you'll get a section that looks like this: [torvalds@i7 linux]$ objdump -h vmlinux -j .salt -s vmlinux: file format elf64-x86-64 Sections: Idx Name Size VMA LMA File off Algn 15 .salt 00000010 ffffffff8432b000 000000000432b000 0352b000 2**0 CONTENTS, ALLOC, LOAD, DATA Contents of section .salt: ffffffff8432b000 0055aaff 00123456 7890abcd ef001234 .U....4Vx......4 Now whether that is sufficient for your needs, I dunno. Linus ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 23:55 ` Linus Torvalds @ 2018-05-24 0:01 ` Andy Lutomirski [not found] ` <CA+55aFxXCWc5qCAsuRmrCGqL7ws4f6B_zy1WR98kHgr_XZs3fw@mail.gmail.com> 0 siblings, 1 reply; 13+ messages in thread From: Andy Lutomirski @ 2018-05-24 0:01 UTC (permalink / raw) To: Linus Torvalds Cc: Laura Abbott, Andrew Lutomirski, mjw, H.J. Lu, Masahiro Yamada, the arch/x86 maintainers, Linux Kernel Mailing List, nickc, ccoutant, Linux Kbuild mailing list > On May 23, 2018, at 4:55 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > >> On Wed, May 23, 2018 at 3:53 PM Laura Abbott <labbott@redhat.com> wrote: >> >> Actually I remember now why this is necessary: there is not a simple way >> to encode a string into a linker file as it has to be spit out byte >> by byte. > > I think you can use the "fill" thing to basically add any random data to a > section. > > So you can do something like > > . = ALIGN(16); > .salt : AT(ADDR(.salt) - LOAD_OFFSET) { > LONG(0xffaa5500); > . = ALIGN(16); > } =0x01234567890abcdef > > in the lds file, and you'll get a section that looks like this: > > [torvalds@i7 linux]$ objdump -h vmlinux -j .salt -s > > vmlinux: file format elf64-x86-64 > > Sections: > Idx Name Size VMA LMA File off > Algn > 15 .salt 00000010 ffffffff8432b000 000000000432b000 0352b000 > 2**0 > CONTENTS, ALLOC, LOAD, DATA > Contents of section .salt: > ffffffff8432b000 0055aaff 00123456 7890abcd ef001234 .U....4Vx......4 > > Now whether that is sufficient for your needs, I dunno. > I don’t know whether I’m missing something obvious, but can’t this be in C? asm (“.pushsection \”.comment\”; .ascii \”” WHATEVER “\”; .popsection”); Or the .S equivalent. ^ permalink raw reply [flat|nested] 13+ messages in thread
[parent not found: <CA+55aFxXCWc5qCAsuRmrCGqL7ws4f6B_zy1WR98kHgr_XZs3fw@mail.gmail.com>]
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO [not found] ` <CA+55aFxXCWc5qCAsuRmrCGqL7ws4f6B_zy1WR98kHgr_XZs3fw@mail.gmail.com> @ 2018-05-24 1:36 ` Laura Abbott 0 siblings, 0 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-24 1:36 UTC (permalink / raw) To: Linus Torvalds, Andy Lutomirski Cc: Andrew Lutomirski, mjw, H.J. Lu, Masahiro Yamada, the arch/x86 maintainers, Linux Kernel Mailing List, nickc, ccoutant, Linux Kbuild mailing list On 05/23/2018 05:06 PM, Linus Torvalds wrote: > > > On Wed, May 23, 2018, 17:01 Andy Lutomirski <luto@amacapital.net <mailto:luto@amacapital.net>> wrote: > > > I don’t know whether I’m missing something obvious, but can’t this be in C? > > > Yes, but I thought Laura wanted to limit it to linker file tricks (this thread has gone on for so long that I've forgotten the details of why). > > Linus > > So we have to update the kernel and every module and the easiest way to do that was the linker script. I was assuming I'd just use the same approach for the vDSO but you're right that there's no reason we can't apply a different technique. I notice there's already a vdso-note.S which adds LINUX_VERSION_CODE as a note. This doesn't include the extra version so it doesn't quite meet our needs. There's no reason why we can't throw something else in there for good measure. Thanks, Laura ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 22:53 ` Laura Abbott 2018-05-23 23:55 ` Linus Torvalds @ 2018-05-24 0:11 ` Masahiro Yamada 2018-05-24 1:43 ` Masahiro Yamada 1 sibling, 1 reply; 13+ messages in thread From: Masahiro Yamada @ 2018-05-24 0:11 UTC (permalink / raw) To: Laura Abbott Cc: Andy Lutomirski, Mark Wielaard, H. J. Lu, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, Linux Kbuild mailing list 2018-05-24 7:53 GMT+09:00 Laura Abbott <labbott@redhat.com>: > On 05/22/2018 05:33 PM, Andy Lutomirski wrote: >> >> On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: >> >> >>> The vDSO is linked separately from the kernel and modules. Ensure it >>> picks >>> up the comment section, if available. >> >> >> Did you end up preferring this to just sticking the kernel version in a >> .comment in the vDSO for some reason? >> > > Actually I remember now why this is necessary: there is not a simple way > to encode a string into a linker file as it has to be spit out byte > by byte. The autogeneration was the easiest way to make that happen. > Maybe there's some horrific c preprocessing or other generation that > could happen but I doubt that's any worse than the generated linker > script. > I am personally prefer CONFIG option (as you did in v2) to KERNELVERSION. If you use "hex" type instead of "string" type in Kconfig, and LONG() instead of BYTE() in the script script, this can be much simpler, right? config BUILD_ID_SALT hex "Build ID Salt" help ... Then, in scripts/Makefile, define filechk_build-salt.lds { \ echo "SECTIONS {"; \ echo ".comment (INFO) : { LONG($(CONFIG_BUILD_ID_SALT)); }"; \ echo "}"; \ } endef $(obj)/build-salt.lds: $(src)/Makefile FORCE $(call filechk,build-salt.lds) This is now so simple that we can even remove the shell script. -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-24 0:11 ` Masahiro Yamada @ 2018-05-24 1:43 ` Masahiro Yamada 2018-05-24 2:16 ` Laura Abbott 0 siblings, 1 reply; 13+ messages in thread From: Masahiro Yamada @ 2018-05-24 1:43 UTC (permalink / raw) To: Laura Abbott Cc: Andy Lutomirski, Mark Wielaard, H. J. Lu, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, Linux Kbuild mailing list 2018-05-24 9:11 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > 2018-05-24 7:53 GMT+09:00 Laura Abbott <labbott@redhat.com>: >> On 05/22/2018 05:33 PM, Andy Lutomirski wrote: >>> >>> On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: >>> >>> >>>> The vDSO is linked separately from the kernel and modules. Ensure it >>>> picks >>>> up the comment section, if available. >>> >>> >>> Did you end up preferring this to just sticking the kernel version in a >>> .comment in the vDSO for some reason? >>> >> >> Actually I remember now why this is necessary: there is not a simple way >> to encode a string into a linker file as it has to be spit out byte >> by byte. The autogeneration was the easiest way to make that happen. >> Maybe there's some horrific c preprocessing or other generation that >> could happen but I doubt that's any worse than the generated linker >> script. >> > > > I am personally prefer CONFIG option (as you did in v2) to KERNELVERSION. > > > If you use "hex" type instead of "string" type in Kconfig, > and LONG() instead of BYTE() in the script script, > this can be much simpler, right? > > > > > > config BUILD_ID_SALT > hex "Build ID Salt" > help > ... > > > > > Then, in scripts/Makefile, > > > define filechk_build-salt.lds > { \ > echo "SECTIONS {"; \ > echo ".comment (INFO) : { LONG($(CONFIG_BUILD_ID_SALT)); }"; \ > echo "}"; \ > } > endef > > $(obj)/build-salt.lds: $(src)/Makefile FORCE > $(call filechk,build-salt.lds) > > > > > This is now so simple that we can even remove the shell script. I had not noticed the comments from Linus and Andy before I posted mine. Maybe, we should not add binary data into the .comment section. -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-24 1:43 ` Masahiro Yamada @ 2018-05-24 2:16 ` Laura Abbott 0 siblings, 0 replies; 13+ messages in thread From: Laura Abbott @ 2018-05-24 2:16 UTC (permalink / raw) To: Masahiro Yamada Cc: Andy Lutomirski, Mark Wielaard, H. J. Lu, Linus Torvalds, X86 ML, LKML, Nick Clifton, Cary Coutant, Linux Kbuild mailing list On 05/23/2018 06:43 PM, Masahiro Yamada wrote: > 2018-05-24 9:11 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: >> 2018-05-24 7:53 GMT+09:00 Laura Abbott <labbott@redhat.com>: >>> On 05/22/2018 05:33 PM, Andy Lutomirski wrote: >>>> >>>> On Tue, May 22, 2018 at 5:19 PM Laura Abbott <labbott@redhat.com> wrote: >>>> >>>> >>>>> The vDSO is linked separately from the kernel and modules. Ensure it >>>>> picks >>>>> up the comment section, if available. >>>> >>>> >>>> Did you end up preferring this to just sticking the kernel version in a >>>> .comment in the vDSO for some reason? >>>> >>> >>> Actually I remember now why this is necessary: there is not a simple way >>> to encode a string into a linker file as it has to be spit out byte >>> by byte. The autogeneration was the easiest way to make that happen. >>> Maybe there's some horrific c preprocessing or other generation that >>> could happen but I doubt that's any worse than the generated linker >>> script. >>> >> >> >> I am personally prefer CONFIG option (as you did in v2) to KERNELVERSION. >> >> >> If you use "hex" type instead of "string" type in Kconfig, >> and LONG() instead of BYTE() in the script script, >> this can be much simpler, right? >> >> >> >> >> >> config BUILD_ID_SALT >> hex "Build ID Salt" >> help >> ... >> >> >> >> >> Then, in scripts/Makefile, >> >> >> define filechk_build-salt.lds >> { \ >> echo "SECTIONS {"; \ >> echo ".comment (INFO) : { LONG($(CONFIG_BUILD_ID_SALT)); }"; \ >> echo "}"; \ >> } >> endef >> >> $(obj)/build-salt.lds: $(src)/Makefile FORCE >> $(call filechk,build-salt.lds) >> >> >> >> >> This is now so simple that we can even remove the shell script. > > > > I had not noticed the comments from Linus and Andy > before I posted mine. > > > Maybe, we should not add binary data into the .comment section. > > > The comments from Linus and Andy apply to the vDSO but I don't think they work for the kernel/modules. We need something that can apply to every module and the kernel and the linker script seems like easiest way to do that. The vDSO is a self-contained binary so it makes sense to not use the linker script there and instead throw something in one of the existing files. I'm kind of iffy about making the build-id salt a hex string since that requires bit more work to generate. I'll experiment in a new version. Thanks, Laura ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO 2018-05-23 0:19 ` [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO Laura Abbott 2018-05-23 0:33 ` Andy Lutomirski @ 2018-05-24 1:55 ` Masahiro Yamada 1 sibling, 0 replies; 13+ messages in thread From: Masahiro Yamada @ 2018-05-24 1:55 UTC (permalink / raw) To: Laura Abbott Cc: Andy Lutomirski, Mark Wielaard, H . J . Lu, Linus Torvalds, X86 ML, Linux Kernel Mailing List, Nick Clifton, Cary Coutant, Linux Kbuild mailing list 2018-05-23 9:19 GMT+09:00 Laura Abbott <labbott@redhat.com>: > > The vDSO is linked separately from the kernel and modules. Ensure it picks > up the comment section, if available. > > Signed-off-by: Laura Abbott <labbott@redhat.com> > --- > v3: Invoke the generated linker script. The ".." nightmare is pretty > ugly but I didn't see an easier way to pick up the generated file. > That was actually part of my motivation for using an #include since > paths for those are standardized. Maybe, you found a different approach. FWIW, If you use the linker script approach, you could simply use scripts/build-salt.lds instead of $(obj)/../../../../scripts/build-salt.lds -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2018-05-24 2:16 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
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2018-05-23 0:19 [PATCHv3 0/2] Salted build ids via linker sections Laura Abbott
2018-05-23 0:19 ` [PATCHv3 1/2] kbuild: Introduce build-salt linker script Laura Abbott
2018-05-23 0:19 ` [PATCHv3 2/2] x86/vdso: Add build salt to the vDSO Laura Abbott
2018-05-23 0:33 ` Andy Lutomirski
2018-05-23 1:23 ` Laura Abbott
2018-05-23 22:53 ` Laura Abbott
2018-05-23 23:55 ` Linus Torvalds
2018-05-24 0:01 ` Andy Lutomirski
[not found] ` <CA+55aFxXCWc5qCAsuRmrCGqL7ws4f6B_zy1WR98kHgr_XZs3fw@mail.gmail.com>
2018-05-24 1:36 ` Laura Abbott
2018-05-24 0:11 ` Masahiro Yamada
2018-05-24 1:43 ` Masahiro Yamada
2018-05-24 2:16 ` Laura Abbott
2018-05-24 1:55 ` Masahiro Yamada
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