kernel.git/arch/s390/kernel/early.c, branch linux-6.4.y

s390/kasan: move shadow mapping to decompressor

2023-03-20T10:02:51Z

Since regular paging structs are initialized in decompressor already move KASAN shadow mapping to decompressor as well. This helps to avoid allocating KASAN required memory in 1 large chunk, de-duplicate paging structs creation code and start the uncompressed kernel with KASAN instrumentation right away. This also allows to avoid all pitfalls accidentally calling KASAN instrumented code during KASAN initialization. Acked-by: Heiko Carstens Reviewed-by: Alexander Gordeev Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/boot: remove non-functioning image bootable check

2023-03-20T10:02:50Z

check_image_bootable() has been introduced with commit 627c9b62058e ("s390/boot: block uncompressed vmlinux booting attempts") to make sure that users don't try to boot uncompressed vmlinux ELF image in qemu. It used to be possible quite some time ago. That commit prevented confusion with uncompressed vmlinux image starting to boot and even printing kernel messages until it crashed. Users might have tried to report the problem without realizing they are doing something which was not intended. Since commit f1d3c5323772 ("s390/boot: move sclp early buffer from fixed address in asm to C") check_image_bootable() doesn't function properly anymore, as well as booting uncompressed vmlinux image in qemu doesn't really produce any output and crashes. Moving forward it doesn't make sense to fix check_image_bootable() anymore, so simply remove it. Acked-by: Alexander Gordeev Acked-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/setup: do not complain about parameters handled in decompressor

2023-02-27T14:29:36Z

Currently there are several kernel command line parameters which are only parsed and handled in decompressor and not known to the kernel. This leads to the following error message during kernel boot: Unknown kernel command line parameters "mem=3G nokaslr", will be passed to user space. To avoid confusion, register those parameters with an empty stub so that kernel does not complain about them. Reported-by: Gerald Schaefer Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/mm: add support for RDP (Reset DAT-Protection)

2023-02-14T10:45:39Z

RDP instruction allows to reset DAT-protection bit in a PTE, with less CPU synchronization overhead than IPTE instruction. In particular, IPTE can cause machine-wide synchronization overhead, and excessive IPTE usage can negatively impact machine performance. RDP can be used instead of IPTE, if the new PTE only differs in SW bits and _PAGE_PROTECT HW bit, for PTE protection changes from RO to RW. SW PTE bit changes are allowed, e.g. for dirty and young tracking, but none of the other HW-defined part of the PTE must change. This is because the architecture forbids such changes to an active and valid PTE, which is why invalidation with IPTE is always used first, before writing a new entry. The RDP optimization helps mainly for fault-driven SW dirty-bit tracking. Writable PTEs are initially always mapped with HW _PAGE_PROTECT bit set, to allow SW dirty-bit accounting on first write protection fault, where the DAT-protection would then be reset. The reset is now done with RDP instead of IPTE, if RDP instruction is available. RDP cannot always guarantee that the DAT-protection reset is propagated to all CPUs immediately. This means that spurious TLB protection faults on other CPUs can now occur. For this, common code provides a flush_tlb_fix_spurious_fault() handler, which will now be used to do a CPU-local TLB flush. However, this will clear the whole TLB of a CPU, and not just the affected entry. For more fine-grained flushing, by simply doing a (local) RDP again, flush_tlb_fix_spurious_fault() would need to also provide the PTE pointer. Note that spurious TLB protection faults cannot really be distinguished from racing pagetable updates, where another thread already installed the correct PTE. In such a case, the local TLB flush would be unnecessary overhead, but overall reduction of CPU synchronization overhead by not using IPTE is still expected to be beneficial. Reviewed-by: Alexander Gordeev Signed-off-by: Gerald Schaefer Signed-off-by: Heiko Carstens

s390/mm: start kernel with DAT enabled

2023-01-13T13:15:05Z

The setup of the kernel virtual address space is spread throughout the sources, boot stages and config options like this: 1. The available physical memory regions are queried and stored as mem_detect information for later use in the decompressor. 2. Based on the physical memory availability the virtual memory layout is established in the decompressor; 3. If CONFIG_KASAN is disabled the kernel paging setup code populates kernel pgtables and turns DAT mode on. It uses the information stored at step [1]. 4. If CONFIG_KASAN is enabled the kernel early boot kasan setup populates kernel pgtables and turns DAT mode on. It uses the information stored at step [1]. The kasan setup creates early_pg_dir directory and directly overwrites swapper_pg_dir entries to make shadow memory pages available. Move the kernel virtual memory setup to the decompressor and start the kernel with DAT turned on right from the very first istruction. That completely eliminates the boot phase when the kernel runs in DAT-off mode, simplies the overall design and consolidates pgtables setup. The identity mapping is created in the decompressor, while kasan shadow mappings are still created by the early boot kernel code. Share with decompressor the existing kasan memory allocator. It decreases the size of a newly requested memory block from pgalloc_pos and ensures that kernel image is not overwritten. pgalloc_low and pgalloc_pos pointers are made preserved boot variables for that. Use the bootdata infrastructure to setup swapper_pg_dir and invalid_pg_dir directories used by the kernel later. The interim early_pg_dir directory established by the kasan initialization code gets eliminated as result. As the kernel runs in DAT-on mode only the PSW_KERNEL_BITS define gets PSW_MASK_DAT bit by default. Additionally, the setup_lowcore_dat_off() and setup_lowcore_dat_on() routines get merged, since there is no DAT-off mode stage anymore. The memory mappings are created with RW+X protection that allows the early boot code setting up all necessary data and services for the kernel being booted. Just before the paging is enabled the memory protection is changed to RO+X for text, RO+NX for read-only data and RW+NX for kernel data and the identity mapping. Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Heiko Carstens

s390/early: fix sclp_early_sccb variable lifetime

2023-01-13T13:15:04Z

Commit ada1da31ce34 ("s390/sclp: sort out physical vs virtual pointers usage") fixed the notion of virtual address for sclp_early_sccb pointer. However, it did not take into account that kasan_early_init() can also output messages and sclp_early_sccb should be adjusted by the time kasan_early_init() is called. Currently it is not a problem, since virtual and physical addresses on s390 are the same. Nevertheless, should they ever differ, this would cause an invalid pointer access. Fixes: ada1da31ce34 ("s390/sclp: sort out physical vs virtual pointers usage") Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Heiko Carstens

s390: move from strlcpy with unused retval to strscpy

2022-08-30T20:00:33Z

Follow the advice of the below link and prefer 'strscpy' in this subsystem. Conversion is 1:1 because the return value is not used. Generated by a coccinelle script. Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/ Signed-off-by: Wolfram Sang Acked-by: Jakub Kicinski Acked-by: Benjamin Block Acked-by: Alexandra Winter Link: https://lore.kernel.org/r/20220818205948.6360-1-wsa+renesas@sang-engineering.com Link: https://lore.kernel.org/r/20220818210102.7301-1-wsa+renesas@sang-engineering.com [gor@linux.ibm.com: squashed two changes linked above together] Signed-off-by: Vasily Gorbik

s390: simplify early program check handler

2022-05-25T09:46:02Z

Due to historic reasons the base program check handler calls a configurable function. Given that there is only the early program check handler left, simplify the code by directly calling that function. The only other user was removed with commit d485235b0054 ("s390: assume diag308 set always works"). Also rename all functions and the asm file to reflect this. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/extable: add and use fixup_exception helper function

2022-03-07T23:33:00Z

Add and use fixup_exception helper function in order to remove the duplicated exception handler fixup code at several places. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/base: pass pt_regs to early program check handler

2022-03-07T23:33:00Z

Pass pt_regs to early program check handler like it is done for every other interrupt and exception handler. Also the passed pt_regs can be changed by the called function and the changes register contents and psw contents will be taken into account when returning. In addition the return psw will not be copied to the program check old psw in lowcore, but to the usual return psw location, like it is also done by the regular program check handler. This allows also to get rid of the code that disabled lowcore protection when changing the return address. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik