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=x... 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 [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

There are notable differences in the vmlinux elf files produced before(bad) and after(good) applying this series.

Good: p_type:PT_NOTE segment exists. Bad: p_type:PT_NOTE segment is missing.

Good: sh_name_str:.notes section has sh_type:SHT_NOTE Bad: sh_name_str:.notes section has sh_type:SHT_PROGBITS

`readelf -n` (as of v2.40) searches for Build Id by processing only the very first note in sh_type:SHT_NOTE sections.

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. 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 d233f9e4b9c6..44103f9487c9 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -906,7 +906,12 @@ #define TRACEDATA #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.*)) \

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 e3984389f8ef..fabe6cf10bd2 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -379,9 +379,12 @@ 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 } }

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/9166a8abdc0f979e50377e61780a4bba1dfa2f52.167451846... 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>