x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux

PATCH Applied Fangrui Song 6 participants 8 messages May 20, 2020 – May 22, 2020

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Fangrui Song

author

2020-05-20 18:21 UTC #0 lore raw

PATCH 1/1 x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux

In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o

.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.

% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''

Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable

Reported-by kbuild test robot <[email protected]>

Signed-off-by Fangrui Song <[email protected]>

---
 arch/x86/boot/compressed/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

arch/x86/boot/compressed/vmlinux.lds.S +2 -0

index 0dc5c2b9614b..8f1025d1f681 100644
@@ -74,4 +74,6 @@ SECTIONS
 #endif
 	. = ALIGN(PAGE_SIZE);	/* keep ZO size page aligned */
 	_end = .;
+
+	DISCARDS
 }

Signature · 1 line

2.26.2.761.g0e0b3e54be-goog

Arvind Sankar

Tested-by on v1 1/1

2020-05-20 19:19 UTC #1 lore raw

Quoted 36 lines · Fangrui Song

In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>
---
 arch/x86/boot/compressed/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)
arch/x86/boot/compressed/vmlinux.lds.S +2 -0
index 0dc5c2b9614b..8f1025d1f681 100644
@@ -74,4 +74,6 @@ SECTIONS
 #endif
 	. = ALIGN(PAGE_SIZE);	/* keep ZO size page aligned */
 	_end = .;
+
+	DISCARDS
 }
Signature · 1 line
2.26.2.761.g0e0b3e54be-goog

Thanks! Maybe add a note in the commit message that the section is generated from unreachable() annotations when CONFIG_STACK_VALIDATION is enabled.

Tested-by Arvind Sankar <[email protected]>

Kees Cook

Reviewed-by on v1 1/1

2020-05-22 02:42 UTC #2 lore raw

In reply to Fangrui Song

Quoted 11 lines · Fangrui Song' via Clang Built Linux

In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.

Quoted 7 lines

% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>

Yay macro usage! :)

Reviewed-by Kees Cook <[email protected]>

Signature · 1 line

Kees Cook

Sedat Dilek

Tested-by

2020-05-22 06:51 UTC #3 lore raw

Quoted 16 lines · Kees Cook

Quoted 14 lines · Fangrui Song' via Clang Built Linux
In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''

Quoted 9 lines

Quoted 4 lines
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>
Yay macro usage! :)
Reviewed-by Kees Cook <[email protected]>

Feel free to add...

Tested-by Sedat Dilek <[email protected]> # build and boot on

Linux v5.7-rc6+ with Clang and LLD v10.0.1-rc1

...together with one more patches in the x86/boot area:

x86/boot: Correct relocation destination on old linkers

Next run will include:

x86/boot: Add .text.startup to setup.ld (v2)

- Sedat -

[1] https://github.com/llvm/llvm-project/releases/tag/llvmorg-10.0.1-rc1

Ard Biesheuvel

maintainer

2020-05-22 15:54 UTC #4 lore raw

Quoted 37 lines · Sedat Dilek

Quoted 16 lines · Kees Cook
Quoted 14 lines · Fangrui Song' via Clang Built Linux
In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Quoted 9 lines
Quoted 4 lines
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>
Yay macro usage! :)
Reviewed-by Kees Cook <[email protected]>
Feel free to add...
Tested-by Sedat Dilek <[email protected]> # build and boot on
Linux v5.7-rc6+ with Clang and LLD v10.0.1-rc1
...together with one more patches in the x86/boot area:
x86/boot: Correct relocation destination on old linkers

Quoted 7 lines

Next run will include:
x86/boot: Add .text.startup to setup.ld (v2)
- Sedat -
[1] https://github.com/llvm/llvm-project/releases/tag/llvmorg-10.0.1-rc1

Thanks, I'll queue this up.

Sedat Dilek

2020-05-22 15:57 UTC #5 lore raw

Quoted 41 lines · Ard Biesheuvel

Quoted 39 lines · Sedat Dilek
Quoted 16 lines · Kees Cook
Quoted 14 lines · Fangrui Song' via Clang Built Linux
In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Quoted 9 lines
Quoted 4 lines
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>
Yay macro usage! :)
Reviewed-by Kees Cook <[email protected]>
Feel free to add...
Tested-by Sedat Dilek <[email protected]> # build and boot on
Linux v5.7-rc6+ with Clang and LLD v10.0.1-rc1
...together with one more patches in the x86/boot area:
x86/boot: Correct relocation destination on old linkers
Next run will include:

Quoted 7 lines

Quoted 5 lines
x86/boot: Add .text.startup to setup.ld (v2)
- Sedat -
[1] https://github.com/llvm/llvm-project/releases/tag/llvmorg-10.0.1-rc1
Thanks, I'll queue this up.

Just FYI:
It's in tip.git#x86/build already.

- Sedat -

[1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=x86/build&id=d6ee6529436a15a0541aff6e1697989ee7dc2c44

Ard Biesheuvel

maintainer

2020-05-22 15:59 UTC #6 lore raw

Quoted 49 lines · Sedat Dilek

Quoted 47 lines · Ard Biesheuvel
Quoted 44 lines · Sedat Dilek
Quoted 16 lines · Kees Cook
Quoted 14 lines · Fangrui Song' via Clang Built Linux
In the latest efi tree, ce5e3f909fc0ed67e58367b9c56a54c20a51080b "efi/printf: Add 64-bit and 8-bit integer support", arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section from drivers/firmware/efi/libstub/vsprintf.stub.o
.discard.unreachable contains an R_X86_64_PC32 relocation, which will be warned by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time.
% ld.lld -m elf_x86_64 -T arch/x86/boot/compressed/vmlinux.lds ... -o arch/x86/boot/compressed/vmlinux ld.lld: warning: vsprintf.c:(.discard.unreachable+0x0): has non-ABS relocation R_X86_64_PC32 against symbol ''
Quoted 9 lines
Quoted 4 lines
Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable
Reported-by kbuild test robot <[email protected]>
Signed-off-by Fangrui Song <[email protected]>
Yay macro usage! :)
Reviewed-by Kees Cook <[email protected]>
Feel free to add...
Tested-by Sedat Dilek <[email protected]> # build and boot on
Linux v5.7-rc6+ with Clang and LLD v10.0.1-rc1
...together with one more patches in the x86/boot area:
x86/boot: Correct relocation destination on old linkers
Next run will include:
x86/boot: Add .text.startup to setup.ld (v2)
- Sedat -
[1] https://github.com/llvm/llvm-project/releases/tag/llvmorg-10.0.1-rc1

Quoted 8 lines

Quoted 1 line
Thanks, I'll queue this up.
Just FYI:
It's in tip.git#x86/build already.
- Sedat -
[1] https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=x86/build&id=d6ee6529436a15a0541aff6e1697989ee7dc2c44

Thanks for the head's up. I'll remove it from my branch again.

tip-bot2 for Fangrui Song

merge bot Applied

2020-05-22 12:40 UTC #7 lore raw

In reply to Fangrui Song

The following commit has been merged into the x86/build branch of tip:

Commit-ID:     d6ee6529436a15a0541aff6e1697989ee7dc2c44
Gitweb:        https://git.kernel.org/tip/d6ee6529436a15a0541aff6e1697989ee7dc2c44
Author:        Fangrui Song <[email protected]>
AuthorDate:    Wed, 20 May 2020 11:20:10 -07:00
Committer:     Borislav Petkov <[email protected]>
CommitterDate: Fri, 22 May 2020 12:42:07 +02:00

x86/boot: Discard .discard.unreachable for arch/x86/boot/compressed/vmlinux

With commit

ce5e3f909fc0 ("efi/printf: Add 64-bit and 8-bit integer support")

arch/x86/boot/compressed/vmlinux may have an undesired .discard.unreachable section coming from drivers/firmware/efi/libstub/vsprintf.stub.o. That section gets generated from unreachable() annotations when CONFIG_STACK_VALIDATION is enabled.

.discard.unreachable contains an R_X86_64_PC32 relocation which will be warned about by LLD: a non-SHF_ALLOC section (.discard.unreachable) is not part of the memory image, thus conceptually the distance between a non-SHF_ALLOC and a SHF_ALLOC is not a constant which can be resolved at link time:

Reuse the DISCARDS macro which includes .discard.* to drop .discard.unreachable.

[ bp: Massage and complete the commit message. ]

Reported-by kbuild test robot <[email protected]>

Signed-off-by Fangrui Song <[email protected]>

Signed-off-by Borislav Petkov <[email protected]>

Reviewed-by Kees Cook <[email protected]>

Tested-by Arvind Sankar <[email protected]>

Tested-by Sedat Dilek <[email protected]>

Link https://lkml.kernel.org/r/[email protected] open here

---
 arch/x86/boot/compressed/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

arch/x86/boot/compressed/vmlinux.lds.S +2 -0

index 508cfa6..1031af1 100644
@@ -73,4 +73,6 @@ SECTIONS
 #endif
 	. = ALIGN(PAGE_SIZE);	/* keep ZO size page aligned */
 	_end = .;
+
+	DISCARDS
 }