linux.git/arch/s390/kernel/vmlinux.lds.S, branch v6.16

s390/fpu: Add fpc exception handler / remove fixup section again

2025-01-26T16:24:04+00:00

The fixup section was added again by mistake when test_fp_ctl() was
removed. The reason for the removal of the fixup section is described in
commit 484a8ed8b7d1 ("s390/extable: add dedicated uaccess handler").
Remove it again for the same reason.

Add an exception handler which handles exceptions when the floating point
control register is attempted to be set to invalid values. The exception
handler sets the floating point control register to zero and continues
execution at the specified address.

The new sfpc inline assembly is open-coded to make back porting a bit
easier.

Fixes: 702644249d3e ("s390/fpu: get rid of test_fp_ctl()")
Cc: stable@vger.kernel.org
Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev

Merge tag 'asm-generic-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic

2024-09-26T18:54:40+00:00

Pull asm-generic updates from Arnd Bergmann:
 "These are only two small patches, one cleanup for arch/alpha and a
  preparation patch cleaning up the handling of runtime constants in the
  linker scripts"

* tag 'asm-generic-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic:
  runtime constants: move list of constants to vmlinux.lds.h
  alpha: no need to include asm/xchg.h twice

s390/boot: Fix KASLR base offset off by __START_KERNEL bytes

2024-08-22T17:24:13+00:00

Symbol offsets to the KASLR base do not match symbol address in
the vmlinux image. That is the result of setting the KASLR base
to the beginning of .text section as result of an optimization.

Revert that optimization and allocate virtual memory for the
whole kernel image including __START_KERNEL bytes as per the
linker script. That allows keeping the semantics of the KASLR
base offset in sync with other architectures.

Rename __START_KERNEL to TEXT_OFFSET, since it represents the
offset of the .text section within the kernel image, rather than
a virtual address.

Still skip mapping TEXT_OFFSET bytes to save memory on pgtables
and provoke exceptions in case an attempt to access this area is
made, as no kernel symbol may reside there.

In case CONFIG_KASAN is enabled the location counter might exceed
the value of TEXT_OFFSET, while the decompressor linker script
forcefully resets it to TEXT_OFFSET, which leads to a sections
overlap link failure. Use MAX() expression to avoid that.

Reported-by: Omar Sandoval 
Closes: https://lore.kernel.org/linux-s390/ZnS8dycxhtXBZVky@telecaster.dhcp.thefacebook.com/
Fixes: 56b1069c40c7 ("s390/boot: Rework deployment of the kernel image")
Signed-off-by: Alexander Gordeev 
Acked-by: Vasily Gorbik 
Signed-off-by: Vasily Gorbik

runtime constants: move list of constants to vmlinux.lds.h

2024-08-19T07:48:14+00:00

Refactor the list of constant variables into a macro.
This should make it easier to add more constants in the future.

Signed-off-by: Jann Horn 
Reviewed-by: Alexander Gordeev 
Reviewed-by: Thomas Gleixner 
Acked-by: Arnd Bergmann 
Acked-by: Will Deacon 
Signed-off-by: Arnd Bergmann

s390/vmlinux.lds.S: Move ro_after_init section behind rodata section

2024-07-31T14:30:20+00:00

The .data.rel.ro and .got section were added between the rodata and
ro_after_init data section, which adds an RW mapping in between all RO
mapping of the kernel image:

---[ Kernel Image Start ]---
0x000003ffe0000000-0x000003ffe0e00000        14M PMD RO X
0x000003ffe0e00000-0x000003ffe0ec7000       796K PTE RO X
0x000003ffe0ec7000-0x000003ffe0f00000       228K PTE RO NX
0x000003ffe0f00000-0x000003ffe1300000         4M PMD RO NX
0x000003ffe1300000-0x000003ffe1331000       196K PTE RO NX
0x000003ffe1331000-0x000003ffe13b3000       520K PTE RW NX <---
0x000003ffe13b3000-0x000003ffe13d5000       136K PTE RO NX
0x000003ffe13d5000-0x000003ffe1400000       172K PTE RW NX
0x000003ffe1400000-0x000003ffe1500000         1M PMD RW NX
0x000003ffe1500000-0x000003ffe1700000         2M PTE RW NX
0x000003ffe1700000-0x000003ffe1800000         1M PMD RW NX
0x000003ffe1800000-0x000003ffe187e000       504K PTE RW NX
---[ Kernel Image End ]---

Move the ro_after_init data section again right behind the rodata
section to prevent interleaving RO and RW mappings:

---[ Kernel Image Start ]---
0x000003ffe0000000-0x000003ffe0e00000        14M PMD RO X
0x000003ffe0e00000-0x000003ffe0ec7000       796K PTE RO X
0x000003ffe0ec7000-0x000003ffe0f00000       228K PTE RO NX
0x000003ffe0f00000-0x000003ffe1300000         4M PMD RO NX
0x000003ffe1300000-0x000003ffe1353000       332K PTE RO NX
0x000003ffe1353000-0x000003ffe1400000       692K PTE RW NX
0x000003ffe1400000-0x000003ffe1500000         1M PMD RW NX
0x000003ffe1500000-0x000003ffe1700000         2M PTE RW NX
0x000003ffe1700000-0x000003ffe1800000         1M PMD RW NX
0x000003ffe1800000-0x000003ffe187e000       504K PTE RW NX
---[ Kernel Image End ]---

Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/alternatives: Allow early alternative patching in decompressor

2024-07-23T14:02:31+00:00

Add the required code to patch alternatives early in the decompressor.
This is required for the upcoming lowcore relocation changes, where
alternatives for facility 193 need to get patched before lowcore
alternatives.

Reviewed-by: Alexander Gordeev 
Co-developed-by: Heiko Carstens 
Signed-off-by: Heiko Carstens 
Signed-off-by: Sven Schnelle 
Signed-off-by: Vasily Gorbik

s390: Add runtime constant support

2024-07-23T13:54:58+00:00

Implement the runtime constant infrastructure for s390, allowing the
dcache d_hash() function to be generated using as a constant for hash
table address followed by shift by a constant of the hash index.

This is the s390 variant of commit 94a2bc0f611c ("arm64: add 'runtime
constant' support") and commit e3c92e81711d ("runtime constants: add
x86 architecture support").

Signed-off-by: Heiko Carstens 
Acked-by: Vasily Gorbik 
Signed-off-by: Vasily Gorbik

s390: Compile kernel with -fPIC and link with -no-pie

2024-04-29T15:33:30+00:00

When the kernel is built with CONFIG_PIE_BUILD option enabled it
uses dynamic symbols, for which the linker does not allow more
than 64K number of entries. This can break features like kpatch.

Hence, whenever possible the kernel is built with CONFIG_PIE_BUILD
option disabled. For that support of unaligned symbols generated by
linker scripts in the compiler is necessary.

However, older compilers might lack such support. In that case the
build process resorts to CONFIG_PIE_BUILD option-enabled build.

Compile object files with -fPIC option and then link the kernel
binary with -no-pie linker option.

As result, the dynamic symbols are not generated and not only kpatch
feature succeeds, but also the whole CONFIG_PIE_BUILD option-enabled
code could be dropped.

[ agordeev: Reworded the commit message ]

Suggested-by: Ulrich Weigand 
Signed-off-by: Sumanth Korikkar 
Reviewed-by: Alexander Gordeev 
Signed-off-by: Alexander Gordeev

s390: vmlinux.lds.S: Drop .hash and .gnu.hash for !CONFIG_PIE_BUILD

2024-04-29T15:33:30+00:00

Sections .hash and .gnu.hash are only created when CONFIG_PIE_BUILD
option is enabled. Drop these for the case CONFIG_PIE_BUILD is disabled.

[ agordeev: Reworded the commit message ]

Fixes: 778666df60f0 ("s390: compile relocatable kernel without -fPIE")
Suggested-by: Alexander Gordeev 
Signed-off-by: Sumanth Korikkar 
Reviewed-by: Alexander Gordeev 
Signed-off-by: Alexander Gordeev

s390/boot: Rework deployment of the kernel image

2024-04-17T11:38:02+00:00

Rework deployment of kernel image for both compressed and
uncompressed variants as defined by CONFIG_KERNEL_UNCOMPRESSED
kernel configuration variable.

In case CONFIG_KERNEL_UNCOMPRESSED is disabled avoid uncompressing
the kernel to a temporary buffer and copying it to the target
address. Instead, uncompress it directly to the target destination.

In case CONFIG_KERNEL_UNCOMPRESSED is enabled avoid moving the
kernel to default 0x100000 location when KASLR is disabled or
failed. Instead, use the uncompressed kernel image directly.

In case KASLR is disabled or failed .amode31 section location in
memory is not randomized and precedes the kernel image. In case
CONFIG_KERNEL_UNCOMPRESSED is disabled that location overlaps the
area used by the decompression algorithm. That is fine, since that
area is not used after the decompression finished and the size of
.amode31 section is not expected to exceed BOOT_HEAP_SIZE ever.

There is no decompression in case CONFIG_KERNEL_UNCOMPRESSED is
enabled. Therefore, rename decompress_kernel() to deploy_kernel(),
which better describes both uncompressed and compressed cases.

Introduce AMODE31_SIZE macro to avoid immediate value of 0x3000
(the size of .amode31 section) in the decompressor linker script.
Modify the vmlinux linker script to force the size of .amode31
section to AMODE31_SIZE (the value of (_eamode31 - _samode31)
could otherwise differ as result of compiler options used).

Introduce __START_KERNEL macro that defines the kernel ELF image
entry point and set it to the currrent value of 0x100000.

Signed-off-by: Alexander Gordeev