kernel.git/arch/s390/tools, branch linux-6.10.y

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

2024-08-29T15:36:06Z

[ Upstream commit 1642285e511c2a40b14e87a41aa8feace6123036 ] 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 Signed-off-by: Sasha Levin

s390/boot: Rework deployment of the kernel image

2024-04-17T11:38:02Z

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

s390: Map kernel at fixed location when KASLR is disabled

2024-04-17T11:38:02Z

Since kernel virtual and physical address spaces are uncoupled the kernel is mapped at the top of the virtual address space in case KASLR is disabled. That does not pose any issue with regard to the kernel booting and operation, but makes it difficult to use a generated vmlinux with some debugging tools (e.g. gdb), because the exact location of the kernel image in virtual memory is unknown. Make that location known and introduce CONFIG_KERNEL_IMAGE_BASE configuration option. A custom CONFIG_KERNEL_IMAGE_BASE value that would break the virtual memory layout leads to a build error. The kernel image size is defined by KERNEL_IMAGE_SIZE macro and set to 512 MB, by analogy with x86. Suggested-by: Vasily Gorbik Signed-off-by: Alexander Gordeev

s390/tools: handle rela R_390_GOTPCDBL/R_390_GOTOFF64

2024-03-07T16:02:05Z

lkp test robot reported unhandled relocation type: R_390_GOTPCDBL, when kernel is built with -fno-PIE. relocs tool reads vmlinux and handles absolute relocations. PC relative relocs doesn't need adjustment. Also, the R_390_GOTPCDBL/R_390_GOTOFF64 relocations are present currently only when KASAN is enabled. The following program can create a R_390_GOTPCDBL/R_390_GOTOFF64 reloc (with fPIE/fPIC). void funcb(int *b) { *b = *b + 100; } void gen_gotoff(void) { int b = 10; funcb (&b); } gcc -c sample.c -fPIC -fsanitize=kernel-address --param asan-stack=1 The above example (built with -fPIC) was linked to one of the built-in.a (built with -fno-PIE) and checked for correctness with kaslr enabled. Both the relocs turns out relative and can be skipped. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202402221404.T2TGs8El-lkp@intel.com/ Fixes: 55dc65b46023 ("s390: add relocs tool") Signed-off-by: Sumanth Korikkar Acked-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390: add relocs tool

2024-02-20T13:37:33Z

This 'relocs' tool is copied from the x86 version, ported for s390, and greatly simplified to remove unnecessary features. It reads vmlinux and outputs assembly to create a .vmlinux.relocs_64 section which contains the offsets of all R_390_64 relocations which apply to allocatable sections. Acked-by: Vasily Gorbik Signed-off-by: Josh Poimboeuf Signed-off-by: Sumanth Korikkar Link: https://lore.kernel.org/r/20240219132734.22881-3-sumanthk@linux.ibm.com Signed-off-by: Heiko Carstens

s390/als: add vector facility to z13 architecture level set

2023-12-11T13:33:07Z

Add the vector facility to the z13 architecture level set (ALS). All hypervisors support the vector facility since many years. Adding the facility to the ALS allows for compile time optimizations of the kernel: if the kernel is compiled for z13 or later, all tests which verify if the vector facility is present can return "true". This will be implemented with a subsequent patch. Reviewed-by: Hendrik Brueckner Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev

KVM: s390: Add facility 197 to the allow list

2022-07-13T13:25:25Z

z16 also provides facility 197 (The processor-activity-instrumentation extension 1). Let's add it to KVM. Signed-off-by: Christian Borntraeger Link: https://lore.kernel.org/r/20220711115108.6494-1-borntraeger@linux.ibm.com Acked-by: Thomas Huth Reviewed-by: Claudio Imbrenda

s390: raise minimum supported machine generation to z10

2022-03-10T14:58:17Z

Machine generations up to z9 (released in May 2006) have been officially out of service for several years now (z9 end of service - January 31, 2019). No distributions build kernels supporting those old machine generations anymore, except Debian, which seems to pick the oldest supported generation. The team supporting Debian on s390 has been notified about the change. Raising minimum supported machine generation to z10 helps to reduce maintenance cost and effectively remove code, which is not getting enough testing coverage due to lack of older hardware and distributions support. Besides that this unblocks some optimization opportunities and allows to use wider instruction set in asm files for future features implementation. Due to this change spectre mitigation and usercopy implementations could be drastically simplified and many newer instructions could be converted from ".insn" encoding to instruction names. Acked-by: Ilya Leoshkevich Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/nospec: add an option to use thunk-extern

2022-03-10T14:58:17Z

Currently with -mindirect-branch=thunk and -mfunction-return=thunk compiler options expoline thunks are put into individual COMDAT group sections. s390 is the only architecture which has group sections and it has implications for kpatch and objtool tools support. Using -mindirect-branch=thunk-extern and -mfunction-return=thunk-extern is an alternative, which comes with a need to generate all required expoline thunks manually. Unfortunately modules area is too far away from the kernel image, and expolines from the kernel image cannon be used. But since all new distributions (except Debian) build kernels for machine generations newer than z10, where "exrl" instruction is available, that leaves only 16 expolines thunks possible. Provide an option to build the kernel with -mindirect-branch=thunk-extern and -mfunction-return=thunk-extern for z10 or newer. This also requires to postlink expoline thunks into all modules explicitly. Currently modules already contain most expolines anyhow. Unfortunately -mindirect-branch=thunk-extern and -mfunction-return=thunk-extern options support is broken in gcc <= 11.2. Additional compile test is required to verify proper gcc support. Acked-by: Ilya Leoshkevich Co-developed-by: Sumanth Korikkar Signed-off-by: Sumanth Korikkar Signed-off-by: Vasily Gorbik

s390/disassembler: update opcode table

2021-12-16T18:58:07Z

Sync with binutils: update opcode table to reflect the instruction format update of the lpswey instruction, and add the qpaci instruction. Signed-off-by: Heiko Carstens