[PATCH 5.15 v2 0/5] Fix Build ID on arm64 if CONFIG_MODVERSIONS=y

[PATCH 5.15 v2 0/5] Fix Build ID on arm64 if CONFIG_MODVERSIONS=y

[Tom Saeger]

Build ID is missing for arm64 with CONFIG_MODVERSIONS=y using ld >= 2.36
on 5.4, 5.10, and 5.15

Backport BuildID fixes.

I've build tested this on {x86_64, arm64, riscv, powerpc, s390, sh}.

  # view Build ID
  $ readelf -n vmlinux | grep "Build ID"

Changes for v2:
- rebase 5/5 c1c551bebf92 ("sh: define RUNTIME_DISCARD_EXIT") from upstream

Previous threads:
[1] https://lore.kernel.org/all/cover.1674851705.git.tom.saeger@oracle.com/
[2] https://lore.kernel.org/all/3df32572ec7016e783d37e185f88495831671f5d.1671143628.git.tom.saeger@oracle.com/
[3] https://lore.kernel.org/all/cover.1670358255.git.tom.saeger@oracle.com/

Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
Masahiro Yamada (2):
      arch: fix broken BuildID for arm64 and riscv
      s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36

Michael Ellerman (2):
      powerpc/vmlinux.lds: Define RUNTIME_DISCARD_EXIT
      powerpc/vmlinux.lds: Don't discard .rela* for relocatable builds

Tom Saeger (1):
      sh: define RUNTIME_DISCARD_EXIT

 arch/powerpc/kernel/vmlinux.lds.S | 6 +++++-
 arch/s390/kernel/vmlinux.lds.S    | 2 ++
 arch/sh/kernel/vmlinux.lds.S      | 1 +
 include/asm-generic/vmlinux.lds.h | 5 +++++
 4 files changed, 13 insertions(+), 1 deletion(-)
---
base-commit: 85d7786c66b69d3f07cc149ac2f78d8f330c7c11
change-id: 20230210-tsaeger-upstream-linux-stable-5-15-f7bf45952c23

Best regards,
-- 
Tom Saeger <tom.saeger@oracle.com>


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[PATCH 5.15 v2 1/5] arch: fix broken BuildID for arm64 and riscv

[Tom Saeger]

From: Masahiro Yamada <masahiroy@kernel.org>

commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.

Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
since commit 994b7ac1697b ("arm64: remove special treatment for the
link order of head.o").

The issue is that the type of .notes section, which contains the BuildID,
changed from NOTES to PROGBITS.

Ard Biesheuvel figured out that whichever object gets linked first gets
to decide the type of a section. The PROGBITS type is the result of the
compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.

While Ard provided a fix for arm64, I want to fix this globally because
the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
remove special treatment for the link order of head.o"). This problem
will happen in general for other architectures if they start to drop
unneeded entries from scripts/head-object-list.txt.

Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.

Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")
Reported-by: Dennis Gilmore <dennis@ausil.us>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 include/asm-generic/vmlinux.lds.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e28792ca25a1..8471717c5085 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -903,7 +903,12 @@
 #define PRINTK_INDEX
 #endif
 
+/*
+ * Discard .note.GNU-stack, which is emitted as PROGBITS by the compiler.
+ * Otherwise, the type of .notes section would become PROGBITS instead of NOTES.
+ */
 #define NOTES								\
+	/DISCARD/ : { *(.note.GNU-stack) }				\
 	.notes : AT(ADDR(.notes) - LOAD_OFFSET) {			\
 		__start_notes = .;					\
 		KEEP(*(.note.*))					\

-- 
2.39.1


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Re: [PATCH 5.15 v2 1/5] arch: fix broken BuildID for arm64 and riscv

[Greg Kroah-Hartman]

On Fri, Feb 10, 2023 at 01:18:40PM -0700, Tom Saeger wrote:
> From: Masahiro Yamada <masahiroy@kernel.org>
> 
> commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.
> 
> Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
> since commit 994b7ac1697b ("arm64: remove special treatment for the
> link order of head.o").
> 
> The issue is that the type of .notes section, which contains the BuildID,
> changed from NOTES to PROGBITS.
> 
> Ard Biesheuvel figured out that whichever object gets linked first gets
> to decide the type of a section. The PROGBITS type is the result of the
> compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.
> 
> While Ard provided a fix for arm64, I want to fix this globally because
> the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
> remove special treatment for the link order of head.o"). This problem
> will happen in general for other architectures if they start to drop
> unneeded entries from scripts/head-object-list.txt.
> 
> Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.
> 
> Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
> Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
> Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")

Why are we adding a commit to 5.15.y that fixes an issue that only
showed up in 6.1.y?

We need a good comment somewhere saying why this is needed...

thanks,

greg k-h

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Re: [PATCH 5.15 v2 1/5] arch: fix broken BuildID for arm64 and riscv

[Tom Saeger]

On Thu, Feb 23, 2023 at 10:51:45AM +0100, Greg Kroah-Hartman wrote:
> On Fri, Feb 10, 2023 at 01:18:40PM -0700, Tom Saeger wrote:
> > From: Masahiro Yamada <masahiroy@kernel.org>
> > 
> > commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.
> > 
> > Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
> > since commit 994b7ac1697b ("arm64: remove special treatment for the
> > link order of head.o").
> > 
> > The issue is that the type of .notes section, which contains the BuildID,
> > changed from NOTES to PROGBITS.
> > 
> > Ard Biesheuvel figured out that whichever object gets linked first gets
> > to decide the type of a section. The PROGBITS type is the result of the
> > compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.
> > 
> > While Ard provided a fix for arm64, I want to fix this globally because
> > the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
> > remove special treatment for the link order of head.o"). This problem
> > will happen in general for other architectures if they start to drop
> > unneeded entries from scripts/head-object-list.txt.
> > 
> > Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.
> > 
> > Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
> > Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
> > Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")
> 
> Why are we adding a commit to 5.15.y that fixes an issue that only
> showed up in 6.1.y?

Only in 6.1.y?  No, not true. It was just the
observed manifestation of 'ld' quirkiness at that time in mainline.

This same issue "missing Build ID in arm64 vmlinux"
also exists in stable with CONFIG_MODVERSIONS=y arm64 since:
5.15.60+
5.10.136+
5.4.210+

These all had backports of:
0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments")
which with CONFIG_MODVERSIONS=y brought about an observable 'ld' quirkiness.

Both are related to a behavior change in different versions of binutils ld and the
kernel's linker script.

99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
IS the mechanism which works-around the ld quirkiness, by adjusting
kernel's linker script.

a494398bde27 ("s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36")
Documents the binutils commit which changed ld's behavior.

The entire sequence (dependencies and fixes) IS the 5.4 patch series I sent.
It provides the kernel linker script mechanism and architecture hooks to
work with 'ld' versions before and after...

5.10, and 5.15 are similar, but already had dependency patches.

Please reconsider applying the 5.15, 5.10, and 5.4 series, as they fix a
real problem.

> 
> We need a good comment somewhere saying why this is needed...

Does the above suffice?

> 
> thanks,
> 
> greg k-h

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Re: [PATCH 5.15 v2 1/5] arch: fix broken BuildID for arm64 and riscv

[Tom Saeger]

On Thu, Feb 23, 2023 at 11:53:42AM -0600, Tom Saeger wrote:
> On Thu, Feb 23, 2023 at 10:51:45AM +0100, Greg Kroah-Hartman wrote:
> > On Fri, Feb 10, 2023 at 01:18:40PM -0700, Tom Saeger wrote:
> > > From: Masahiro Yamada <masahiroy@kernel.org>
> > > 
> > > commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.
> > > 
> > > Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
> > > since commit 994b7ac1697b ("arm64: remove special treatment for the
> > > link order of head.o").
> > > 
> > > The issue is that the type of .notes section, which contains the BuildID,
> > > changed from NOTES to PROGBITS.
> > > 
> > > Ard Biesheuvel figured out that whichever object gets linked first gets
> > > to decide the type of a section. The PROGBITS type is the result of the
> > > compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.
> > > 
> > > While Ard provided a fix for arm64, I want to fix this globally because
> > > the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
> > > remove special treatment for the link order of head.o"). This problem
> > > will happen in general for other architectures if they start to drop
> > > unneeded entries from scripts/head-object-list.txt.
> > > 
> > > Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.
> > > 
> > > Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
> > > Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
> > > Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")

Greg, how about something like this tacked onto backport of this commit?

[Tom: stable backport 5.15.y, 5.10.y, 5.4.y]

Though the above "Fixes:" commits are not in this kernel, the conditions
which lead to a missing Build ID in arm64 vmlinux are similar.

Evidence points to these conditions:
1. ld version > 2.36 (exact binutils commit documented in a494398bde27)
2. first object which gets linked (head.o) has a PROGBITS .note.GNU-stack segment

These conditions can be observed when:
- 5.15.60+ OR 5.10.136+ OR 5.4.210+
- AND ld version > 2.36
- AND arch=arm64
- AND CONFIG_MODVERSIONS=y

This was previously bisected to the stable backport of 0d362be5b142.
Follow-up experiments were discussed here: https://lore.kernel.org/all/20221221235413.xaisboqmr7dkqwn6@oracle.com/ 
which strongly hints at condition 2.


> > 
> > Why are we adding a commit to 5.15.y that fixes an issue that only
> > showed up in 6.1.y?

If you approve - I'll send v3 for 5.15, 5.10, and 5.4 (with style fixes).

Cheers,

--Tom

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Re: [PATCH 5.15 v2 1/5] arch: fix broken BuildID for arm64 and riscv

[Greg Kroah-Hartman]

On Thu, Feb 23, 2023 at 08:47:24PM -0600, Tom Saeger wrote:
> On Thu, Feb 23, 2023 at 11:53:42AM -0600, Tom Saeger wrote:
> > On Thu, Feb 23, 2023 at 10:51:45AM +0100, Greg Kroah-Hartman wrote:
> > > On Fri, Feb 10, 2023 at 01:18:40PM -0700, Tom Saeger wrote:
> > > > From: Masahiro Yamada <masahiroy@kernel.org>
> > > > 
> > > > commit 99cb0d917ffa1ab628bb67364ca9b162c07699b1 upstream.
> > > > 
> > > > Dennis Gilmore reports that the BuildID is missing in the arm64 vmlinux
> > > > since commit 994b7ac1697b ("arm64: remove special treatment for the
> > > > link order of head.o").
> > > > 
> > > > The issue is that the type of .notes section, which contains the BuildID,
> > > > changed from NOTES to PROGBITS.
> > > > 
> > > > Ard Biesheuvel figured out that whichever object gets linked first gets
> > > > to decide the type of a section. The PROGBITS type is the result of the
> > > > compiler emitting .note.GNU-stack as PROGBITS rather than NOTE.
> > > > 
> > > > While Ard provided a fix for arm64, I want to fix this globally because
> > > > the same issue is happening on riscv since commit 2348e6bf4421 ("riscv:
> > > > remove special treatment for the link order of head.o"). This problem
> > > > will happen in general for other architectures if they start to drop
> > > > unneeded entries from scripts/head-object-list.txt.
> > > > 
> > > > Discard .note.GNU-stack in include/asm-generic/vmlinux.lds.h.
> > > > 
> > > > Link: https://lore.kernel.org/lkml/CAABkxwuQoz1CTbyb57n0ZX65eSYiTonFCU8-LCQc=74D=xE=rA@mail.gmail.com/
> > > > Fixes: 994b7ac1697b ("arm64: remove special treatment for the link order of head.o")
> > > > Fixes: 2348e6bf4421 ("riscv: remove special treatment for the link order of head.o")
> 
> Greg, how about something like this tacked onto backport of this commit?
> 
> [Tom: stable backport 5.15.y, 5.10.y, 5.4.y]
> 
> Though the above "Fixes:" commits are not in this kernel, the conditions
> which lead to a missing Build ID in arm64 vmlinux are similar.
> 
> Evidence points to these conditions:
> 1. ld version > 2.36 (exact binutils commit documented in a494398bde27)
> 2. first object which gets linked (head.o) has a PROGBITS .note.GNU-stack segment
> 
> These conditions can be observed when:
> - 5.15.60+ OR 5.10.136+ OR 5.4.210+
> - AND ld version > 2.36
> - AND arch=arm64
> - AND CONFIG_MODVERSIONS=y
> 
> This was previously bisected to the stable backport of 0d362be5b142.
> Follow-up experiments were discussed here: https://lore.kernel.org/all/20221221235413.xaisboqmr7dkqwn6@oracle.com/ 
> which strongly hints at condition 2.
> 
> 
> > > 
> > > Why are we adding a commit to 5.15.y that fixes an issue that only
> > > showed up in 6.1.y?
> 
> If you approve - I'll send v3 for 5.15, 5.10, and 5.4 (with style fixes).

That would make more sense, thanks.

greg k-h

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[PATCH 5.15 v2 2/5] powerpc/vmlinux.lds: Define RUNTIME_DISCARD_EXIT

[Tom Saeger]

From: Michael Ellerman <mpe@ellerman.id.au>

commit 4b9880dbf3bdba3a7c56445137c3d0e30aaa0a40 upstream.

The powerpc linker script explicitly includes .exit.text, because
otherwise the link fails due to references from __bug_table and
__ex_table. The code is freed (discarded) at runtime along with
.init.text and data.

That has worked in the past despite powerpc not defining
RUNTIME_DISCARD_EXIT because DISCARDS appears late in the powerpc linker
script (line 410), and the explicit inclusion of .exit.text
earlier (line 280) supersedes the discard.

However commit 99cb0d917ffa ("arch: fix broken BuildID for arm64 and
riscv") introduced an earlier use of DISCARD as part of the RO_DATA
macro (line 136). With binutils < 2.36 that causes the DISCARD
directives later in the script to be applied earlier [1], causing
.exit.text to actually be discarded at link time, leading to build
errors:

  '.exit.text' referenced in section '__bug_table' of crypto/algboss.o: defined in
  discarded section '.exit.text' of crypto/algboss.o
  '.exit.text' referenced in section '__ex_table' of drivers/nvdimm/core.o: defined in
  discarded section '.exit.text' of drivers/nvdimm/core.o

Fix it by defining RUNTIME_DISCARD_EXIT, which causes the generic
DISCARDS macro to not include .exit.text at all.

1: https://lore.kernel.org/lkml/87fscp2v7k.fsf@igel.home/

Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230105132349.384666-1-mpe@ellerman.id.au
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 arch/powerpc/kernel/vmlinux.lds.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 1a63e37f336a..50a04347ab05 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -8,6 +8,7 @@
 #define BSS_FIRST_SECTIONS *(.bss.prominit)
 #define EMITS_PT_NOTE
 #define RO_EXCEPTION_TABLE_ALIGN	0
+#define RUNTIME_DISCARD_EXIT
 
 #define SOFT_MASK_TABLE(align)						\
 	. = ALIGN(align);						\

-- 
2.39.1


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[PATCH 5.15 v2 3/5] powerpc/vmlinux.lds: Don't discard .rela* for relocatable builds

[Tom Saeger]

From: Michael Ellerman <mpe@ellerman.id.au>

commit 07b050f9290ee012a407a0f64151db902a1520f5 upstream.

Relocatable kernels must not discard relocations, they need to be
processed at runtime. As such they are included for CONFIG_RELOCATABLE
builds in the powerpc linker script (line 340).

However they are also unconditionally discarded later in the
script (line 414). Previously that worked because the earlier inclusion
superseded the discard.

However commit 99cb0d917ffa ("arch: fix broken BuildID for arm64 and
riscv") introduced an earlier use of DISCARD as part of the RO_DATA
macro (line 137). With binutils < 2.36 that causes the DISCARD
directives later in the script to be applied earlier, causing .rela* to
actually be discarded at link time, leading to build warnings and a
kernel that doesn't boot:

  ld: warning: discarding dynamic section .rela.init.rodata

Fix it by conditionally discarding .rela* only when CONFIG_RELOCATABLE
is disabled.

Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Link: https://lore.kernel.org/r/20230105132349.384666-2-mpe@ellerman.id.au
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 arch/powerpc/kernel/vmlinux.lds.S | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 50a04347ab05..3a3ef558244a 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -400,9 +400,12 @@ SECTIONS
 	DISCARDS
 	/DISCARD/ : {
 		*(*.EMB.apuinfo)
-		*(.glink .iplt .plt .rela* .comment)
+		*(.glink .iplt .plt .comment)
 		*(.gnu.version*)
 		*(.gnu.attributes)
 		*(.eh_frame)
+#ifndef CONFIG_RELOCATABLE
+		*(.rela*)
+#endif
 	}
 }

-- 
2.39.1


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[PATCH 5.15 v2 4/5] s390: define RUNTIME_DISCARD_EXIT to fix link error with GNU ld < 2.36

[Tom Saeger]

From: Masahiro Yamada <masahiroy@kernel.org>

commit a494398bde273143c2352dd373cad8211f7d94b2 upstream.

Nathan Chancellor reports that the s390 vmlinux fails to link with
GNU ld < 2.36 since commit 99cb0d917ffa ("arch: fix broken BuildID
for arm64 and riscv").

It happens for defconfig, or more specifically for CONFIG_EXPOLINE=y.

  $ s390x-linux-gnu-ld --version | head -n1
  GNU ld (GNU Binutils for Debian) 2.35.2
  $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- allnoconfig
  $ ./scripts/config -e CONFIG_EXPOLINE
  $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu- olddefconfig
  $ make -s ARCH=s390 CROSS_COMPILE=s390x-linux-gnu-
  `.exit.text' referenced in section `.s390_return_reg' of drivers/base/dd.o: defined in discarded section `.exit.text' of drivers/base/dd.o
  make[1]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
  make: *** [Makefile:1252: vmlinux] Error 2

arch/s390/kernel/vmlinux.lds.S wants to keep EXIT_TEXT:

        .exit.text : {
                EXIT_TEXT
        }

But, at the same time, EXIT_TEXT is thrown away by DISCARD because
s390 does not define RUNTIME_DISCARD_EXIT.

I still do not understand why the latter wins after 99cb0d917ffa,
but defining RUNTIME_DISCARD_EXIT seems correct because the comment
line in arch/s390/kernel/vmlinux.lds.S says:

        /*
         * .exit.text is discarded at runtime, not link time,
         * to deal with references from __bug_table
         */

Nathan also found that binutils commit 21401fc7bf67 ("Duplicate output
sections in scripts") cured this issue, so we cannot reproduce it with
binutils 2.36+, but it is better to not rely on it.

Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
Link: https://lore.kernel.org/all/Y7Jal56f6UBh1abE@dev-arch.thelio-3990X/
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20230105031306.1455409-1-masahiroy@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 arch/s390/kernel/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
index 8ce1615c1046..cdc8b84b2db4 100644
--- a/arch/s390/kernel/vmlinux.lds.S
+++ b/arch/s390/kernel/vmlinux.lds.S
@@ -17,6 +17,8 @@
 /* Handle ro_after_init data on our own. */
 #define RO_AFTER_INIT_DATA
 
+#define RUNTIME_DISCARD_EXIT
+
 #define EMITS_PT_NOTE
 
 #include <asm-generic/vmlinux.lds.h>

-- 
2.39.1


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[PATCH 5.15 v2 5/5] sh: define RUNTIME_DISCARD_EXIT

[Tom Saeger]

commit c1c551bebf928889e7a8fef7415b44f9a64975f4 upstream.

sh vmlinux fails to link with GNU ld < 2.40 (likely < 2.36) since
commit 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv").

This is similar to fixes for powerpc and s390:
commit 4b9880dbf3bd ("powerpc/vmlinux.lds: Define RUNTIME_DISCARD_EXIT").
commit a494398bde27 ("s390: define RUNTIME_DISCARD_EXIT to fix link error
with GNU ld < 2.36").

  $ sh4-linux-gnu-ld --version | head -n1
  GNU ld (GNU Binutils for Debian) 2.35.2

  $ make ARCH=sh CROSS_COMPILE=sh4-linux-gnu- microdev_defconfig
  $ make ARCH=sh CROSS_COMPILE=sh4-linux-gnu-

  `.exit.text' referenced in section `__bug_table' of crypto/algboss.o:
  defined in discarded section `.exit.text' of crypto/algboss.o
  `.exit.text' referenced in section `__bug_table' of
  drivers/char/hw_random/core.o: defined in discarded section
  `.exit.text' of drivers/char/hw_random/core.o
  make[2]: *** [scripts/Makefile.vmlinux:34: vmlinux] Error 1
  make[1]: *** [Makefile:1252: vmlinux] Error 2

arch/sh/kernel/vmlinux.lds.S keeps EXIT_TEXT:

	/*
	 * .exit.text is discarded at runtime, not link time, to deal with
	 * references from __bug_table
	 */
	.exit.text : AT(ADDR(.exit.text)) { EXIT_TEXT }

However, EXIT_TEXT is thrown away by
DISCARD(include/asm-generic/vmlinux.lds.h) because
sh does not define RUNTIME_DISCARD_EXIT.

GNU ld 2.40 does not have this issue and builds fine.
This corresponds with Masahiro's comments in a494398bde27:
"Nathan [Chancellor] also found that binutils
commit 21401fc7bf67 ("Duplicate output sections in scripts") cured this
issue, so we cannot reproduce it with binutils 2.36+, but it is better
to not rely on it."

Link: https://lkml.kernel.org/r/9166a8abdc0f979e50377e61780a4bba1dfa2f52.1674518464.git.tom.saeger@oracle.com
Fixes: 99cb0d917ffa ("arch: fix broken BuildID for arm64 and riscv")
Link: https://lore.kernel.org/all/Y7Jal56f6UBh1abE@dev-arch.thelio-3990X/
Link: https://lore.kernel.org/all/20230123194218.47ssfzhrpnv3xfez@oracle.com/
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dennis Gilmore <dennis@ausil.us>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tom Saeger <tom.saeger@oracle.com>
---
 arch/sh/kernel/vmlinux.lds.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/sh/kernel/vmlinux.lds.S b/arch/sh/kernel/vmlinux.lds.S
index 3161b9ccd2a5..b6276a3521d7 100644
--- a/arch/sh/kernel/vmlinux.lds.S
+++ b/arch/sh/kernel/vmlinux.lds.S
@@ -4,6 +4,7 @@
  * Written by Niibe Yutaka and Paul Mundt
  */
 OUTPUT_ARCH(sh)
+#define RUNTIME_DISCARD_EXIT
 #include <asm/thread_info.h>
 #include <asm/cache.h>
 #include <asm/vmlinux.lds.h>

-- 
2.39.1


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Re: [PATCH 5.15 v2 0/5] Fix Build ID on arm64 if CONFIG_MODVERSIONS=y

[Greg Kroah-Hartman]

On Fri, Feb 10, 2023 at 01:18:39PM -0700, Tom Saeger wrote:
> Build ID is missing for arm64 with CONFIG_MODVERSIONS=y using ld >= 2.36
> on 5.4, 5.10, and 5.15
> 
> Backport BuildID fixes.

I do not understand why you are applying patches from 6.2 that "fix"
something that is not in this kernel (or the older ones).  Please
document that really well on your next set of submissions.

I've taken the 6.1.y series only and dropped all the others.

thanks,

greg k-h

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Re: [PATCH 5.15 v2 0/5] Fix Build ID on arm64 if CONFIG_MODVERSIONS=y

[Tom Saeger]

On Thu, Feb 23, 2023 at 10:55:39AM +0100, Greg Kroah-Hartman wrote:
> On Fri, Feb 10, 2023 at 01:18:39PM -0700, Tom Saeger wrote:
> > Build ID is missing for arm64 with CONFIG_MODVERSIONS=y using ld >= 2.36
> > on 5.4, 5.10, and 5.15
> > 
> > Backport BuildID fixes.
> 
> I do not understand why you are applying patches from 6.2 that "fix"
> something that is not in this kernel (or the older ones).  Please
> document that really well on your next set of submissions.

Build ID is missing for arm64 with CONFIG_MODVERSIONS=y using ld >= 2.36
That's it.

What is quirky is binutils 'ld'.
Where this can be fixed is the kernel linker script, which IS present.
Those are the patches.

> 
> I've taken the 6.1.y series only and dropped all the others.

All the others is where it's really broken.

> 
> thanks,
> 
> greg k-h

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