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Naresh reported this build error on linux-next:
s390x-linux-gnu-ld: Unexpected GOT/PLT entries detected!
make[3]: *** [/builds/linux/arch/s390/boot/Makefile:87:
arch/s390/boot/vmlinux.syms] Error 1
make[3]: Target 'arch/s390/boot/bzImage' not remade because of errors.
The reason for the build error is an incorrect/incomplete assertion which
checks the size of the .got.plt section. Similar to x86 the size is either
zero or 24 bytes (three entries).
See commit 262b5cae67a6 ("x86/boot/compressed: Move .got.plt entries out of
the .got section") for more details. The three reserved/additional entries
for s390 are described in chapter 3.2.2 of the s390x ABI [1] (thanks to
Andreas Krebbel for pointing this out!).
[1] https://github.com/IBM/s390x-abi/releases/download/v1.6.1/lzsabi_s390x.pdf
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Closes: https://lore.kernel.org/all/CA+G9fYvWp8TY-fMEvc3UhoVtoR_eM5VsfHj3+n+kexcfJJ+Cvw@mail.gmail.com
Fixes: 30226853d6ec ("s390: vmlinux.lds.S: explicitly handle '.got' and '.plt' sections")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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On s390, currently kernel uses the '-fPIE' compiler flag for compiling
vmlinux. This has a few problems:
- It uses dynamic symbols (.dynsym), for which the linker refuses to
allow more than 64k sections. This can break features which use
'-ffunction-sections' and '-fdata-sections', including kpatch-build
[1] and Function Granular KASLR.
- It unnecessarily uses GOT relocations, adding an extra layer of
indirection for many memory accesses.
Instead of using '-fPIE', resolve all the relocations at link time and
then manually adjust any absolute relocations (R_390_64) during boot.
This is done by first telling the linker to preserve all relocations
during the vmlinux link. (Note this is harmless: they are later
stripped in the vmlinux.bin link.)
Then use the 'relocs' tool to find all absolute relocations (R_390_64)
which apply to allocatable sections. The offsets of those relocations
are saved in a special section which is then used to adjust the
relocations during boot.
(Note: For some reason, Clang occasionally creates a GOT reference, even
without '-fPIE'. So Clang-compiled kernels have a GOT, which needs to
be adjusted.)
On my mostly-defconfig kernel, this reduces kernel text size by ~1.3%.
[1] https://github.com/dynup/kpatch/issues/1284
[2] https://gcc.gnu.org/pipermail/gcc-patches/2023-June/622872.html
[3] https://gcc.gnu.org/pipermail/gcc-patches/2023-August/625986.html
Compiler consideration:
Gcc recently implemented an optimization [2] for loading symbols without
explicit alignment, aligning with the IBM Z ELF ABI. This ABI mandates
symbols to reside on a 2-byte boundary, enabling the use of the larl
instruction. However, kernel linker scripts may still generate unaligned
symbols. To address this, a new -munaligned-symbols option has been
introduced [3] in recent gcc versions. This option has to be used with
future gcc versions.
Older Clang lacks support for handling unaligned symbols generated
by kernel linker scripts when the kernel is built without -fPIE. However,
future versions of Clang will include support for the -munaligned-symbols
option. When the support is unavailable, compile the kernel with -fPIE
to maintain the existing behavior.
In addition to it:
move vmlinux.relocs to safe relocation
When the kernel is built with CONFIG_KERNEL_UNCOMPRESSED, the entire
uncompressed vmlinux.bin is positioned in the bzImage decompressor
image at the default kernel LMA of 0x100000, enabling it to be executed
in-place. However, the size of .vmlinux.relocs could be large enough to
cause an overlap with the uncompressed kernel at the address 0x100000.
To address this issue, .vmlinux.relocs is positioned after the
.rodata.compressed in the bzImage. Nevertheless, in this configuration,
vmlinux.relocs will overlap with the .bss section of vmlinux.bin. To
overcome that, move vmlinux.relocs to a safe location before clearing
.bss and handling relocs.
Compile warning fix from Sumanth Korikkar:
When kernel is built with CONFIG_LD_ORPHAN_WARN and -fno-PIE, there are
several warnings:
ld: warning: orphan section `.rela.iplt' from
`arch/s390/kernel/head64.o' being placed in section `.rela.dyn'
ld: warning: orphan section `.rela.head.text' from
`arch/s390/kernel/head64.o' being placed in section `.rela.dyn'
ld: warning: orphan section `.rela.init.text' from
`arch/s390/kernel/head64.o' being placed in section `.rela.dyn'
ld: warning: orphan section `.rela.rodata.cst8' from
`arch/s390/kernel/head64.o' being placed in section `.rela.dyn'
Orphan sections are sections that exist in an object file but don't have
a corresponding output section in the final executable. ld raises a
warning when it identifies such sections.
Eliminate the warning by placing all .rela orphan sections in .rela.dyn
and raise an error when size of .rela.dyn is greater than zero. i.e.
Dont just neglect orphan sections.
This is similar to adjustment performed in x86, where kernel is built
with -fno-PIE.
commit 5354e84598f2 ("x86/build: Add asserts for unwanted sections")
[sumanthk@linux.ibm.com: rebased Josh Poimboeuf patches and move
vmlinux.relocs to safe location]
[hca@linux.ibm.com: merged compile warning fix from Sumanth]
Tested-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Link: https://lore.kernel.org/r/20240219132734.22881-4-sumanthk@linux.ibm.com
Link: https://lore.kernel.org/r/20240219132734.22881-5-sumanthk@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are several series of warnings
from the various discardable sections that the kernel adds for build
purposes that are not needed at runtime:
s390-linux-ld: warning: orphan section `.export_symbol' from `arch/s390/boot/decompressor.o' being placed in section `.export_symbol'
s390-linux-ld: warning: orphan section `.discard.addressable' from `arch/s390/boot/decompressor.o' being placed in section `.discard.addressable'
s390-linux-ld: warning: orphan section `.modinfo' from `arch/s390/boot/decompressor.o' being placed in section `.modinfo'
include/asm-generic/vmlinux.lds.h has a macro for easily discarding
these sections across the kernel named COMMON_DISCARDS, use it to clear
up the warnings.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-9-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there is a warning around the '.comment'
section for each file in arch/s390/boot
s390-linux-ld: warning: orphan section `.comment' from `arch/s390/boot/als.o' being placed in section `.comment'
s390-linux-ld: warning: orphan section `.comment' from `arch/s390/boot/startup.o' being placed in section `.comment'
s390-linux-ld: warning: orphan section `.comment' from `arch/s390/boot/physmem_info.o' being placed in section `.comment'
include/asm-generic/vmlinux.lds.h has a macro for required ELF sections
not related to debugging named ELF_DETAILS, use it to clear up the
warnings.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-8-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are several series of warnings for
each file in arch/s390/boot due to the boot linker script not handling
the DWARF debug sections:
s390-linux-ld: warning: orphan section `.debug_line' from `arch/s390/boot/head.o' being placed in section `.debug_line'
s390-linux-ld: warning: orphan section `.debug_info' from `arch/s390/boot/head.o' being placed in section `.debug_info'
s390-linux-ld: warning: orphan section `.debug_abbrev' from `arch/s390/boot/head.o' being placed in section `.debug_abbrev'
s390-linux-ld: warning: orphan section `.debug_aranges' from `arch/s390/boot/head.o' being placed in section `.debug_aranges'
s390-linux-ld: warning: orphan section `.debug_str' from `arch/s390/boot/head.o' being placed in section `.debug_str'
include/asm-generic/vmlinux.lds.h has a macro for DWARF debug sections
named DWARF_DEBUG, use it to clear up the warnings.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-7-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are several warnings from
arch/s390/boot/head.o due to the unhandled presence of '.rela' sections:
s390-linux-ld: warning: orphan section `.rela.iplt' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.head.text' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.got' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.data' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.data.rel.ro' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.iplt' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.head.text' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.got' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.data' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
s390-linux-ld: warning: orphan section `.rela.data.rel.ro' from `arch/s390/boot/head.o' being placed in section `.rela.dyn'
These sections are unneeded for the decompressor and they are not
emitted in the binary currently. In a manner similar to other
architectures, coalesce the sections into '.rela.dyn' and ensure it is
zero sized, which is a safe/tested approach versus full discard.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-6-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there is a warning about the presence of
an '.init.text' section in arch/s390/boot:
s390-linux-ld: warning: orphan section `.init.text' from `arch/s390/boot/sclp_early_core.o' being placed in section `.init.text'
arch/s390/boot/sclp_early_core.c includes a file from the main kernel
build, which picks up a usage of '__init' somewhere. For the
decompressed image, this section can just be coalesced into '.text'.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-5-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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When building with CONFIG_LD_ORPHAN_WARN after selecting
CONFIG_ARCH_HAS_LD_ORPHAN_WARN, there are a lot of warnings around the
GOT and PLT sections:
s390-linux-ld: warning: orphan section `.plt' from `arch/s390/kernel/head64.o' being placed in section `.plt'
s390-linux-ld: warning: orphan section `.got' from `arch/s390/kernel/head64.o' being placed in section `.got'
s390-linux-ld: warning: orphan section `.got.plt' from `arch/s390/kernel/head64.o' being placed in section `.got.plt'
s390-linux-ld: warning: orphan section `.iplt' from `arch/s390/kernel/head64.o' being placed in section `.iplt'
s390-linux-ld: warning: orphan section `.igot.plt' from `arch/s390/kernel/head64.o' being placed in section `.igot.plt'
s390-linux-ld: warning: orphan section `.iplt' from `arch/s390/boot/head.o' being placed in section `.iplt'
s390-linux-ld: warning: orphan section `.igot.plt' from `arch/s390/boot/head.o' being placed in section `.igot.plt'
s390-linux-ld: warning: orphan section `.got' from `arch/s390/boot/head.o' being placed in section `.got'
Currently, only the '.got' section is actually emitted in the final
binary. In a manner similar to other architectures, put the '.got'
section near the '.data' section and coalesce the PLT sections,
checking that the final section is zero sized, which is a safe/tested
approach versus full discard.
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240207-s390-lld-and-orphan-warn-v1-3-8a665b3346ab@kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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Currently several approaches for finding unused memory in decompressor
are utilized. While "safe_addr" grows towards higher addresses, vmem
code allocates paging structures top down. The former requires careful
ordering. In addition to that ipl report handling code verifies potential
intersections with secure boot certificates on its own. Neither of two
approaches are memory holes aware and consistent with each other in low
memory conditions.
To solve that, existing approaches are generalized and combined
together, as well as online memory ranges are now taken into
consideration.
physmem_info has been extended to contain reserved memory ranges. New
set of functions allow to handle reserves and find unused memory.
All reserves and memory allocations are "typed". In case of out of
memory condition decompressor fails with detailed info on current
reserved ranges and usable online memory.
Linux version 6.2.0 ...
Kernel command line: ... mem=100M
Our of memory allocating 100000 bytes 100000 aligned in range 0:5800000
Reserved memory ranges:
0000000000000000 0000000003e33000 DECOMPRESSOR
0000000003f00000 00000000057648a3 INITRD
00000000063e0000 00000000063e8000 VMEM
00000000063eb000 00000000063f4000 VMEM
00000000063f7800 0000000006400000 VMEM
0000000005800000 0000000006300000 KASAN
Usable online memory ranges (info source: sclp read info [3]):
0000000000000000 0000000006400000
Usable online memory total: 6400000 Reserved: 61b10a3 Free: 24ef5d
Call Trace:
(sp:000000000002bd58 [<0000000000012a70>] physmem_alloc_top_down+0x60/0x14c)
sp:000000000002bdc8 [<0000000000013756>] _pa+0x56/0x6a
sp:000000000002bdf0 [<0000000000013bcc>] pgtable_populate+0x45c/0x65e
sp:000000000002be90 [<00000000000140aa>] setup_vmem+0x2da/0x424
sp:000000000002bec8 [<0000000000011c20>] startup_kernel+0x428/0x8b4
sp:000000000002bf60 [<00000000000100f4>] startup_normal+0xd4/0xd4
physmem_alloc_range allows to find free memory in specified range. It
should be used for one time allocations only like finding position for
amode31 and vmlinux.
physmem_alloc_top_down can be used just like physmem_alloc_range, but
it also allows multiple allocations per type and tries to merge sequential
allocations together. Which is useful for paging structures allocations.
If sequential allocations cannot be merged together they are "chained",
allowing easy per type reserved ranges enumeration and migration to
memblock later. Extra "struct reserved_range" allocated for chaining are
not tracked or reserved but rely on the fact that both
physmem_alloc_range and physmem_alloc_top_down search for free memory
only below current top down allocator position. All reserved ranges
should be transferred to memblock before memblock allocations are
enabled.
The startup code has been reordered to delay any memory allocations until
online memory ranges are detected and occupied memory ranges are marked as
reserved to be excluded from follow-up allocations.
Ipl report certificates are a special case, ipl report certificates list
is checked together with other memory reserves until certificates are
saved elsewhere.
KASAN required memory for shadow memory allocation and mapping is reserved
as 1 large chunk which is later passed to KASAN early initialization code.
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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This patch enhances the kernel image adding a trailer as required for
secure boot by future firmware versions.
Cc: <stable@vger.kernel.org> # 5.2+
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
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Convert parmarea to C, which makes it much easier to initialize it. No need
to keep offsets in assembler code in sync with struct parmarea anymore.
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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Convert initial lowcore to C and use proper defines and structures to
initialize it. This should make the z/VM ipl procedure a bit less magic.
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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The final kernel image is created by linking decompressor object files with
a startup archive. The startup archive file however does not contain only
optional code and data which can be discarded if not referenced. It also
contains mandatory object data like head.o which must never be discarded,
even if not referenced.
Move the decompresser code and linker script to the boot directory and get
rid of the startup archive so everything is kept during link time.
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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