kernel/arch/s390/boot/head.S, branch linux-rolling-stable

s390/boot: Add exception table support

2025-03-04T16:25:22Z

The early boot code contains various open-coded inline assemblies with exception handling. In order to handle possible exceptions each of them changes the program check new psw, and restores it. In order to simplify the various inline assemblies add simple exception table support: the program check handler is called with a fully populated pt_regs on the stack and may change the psw and register members. When the program check handler returns the psw and registers from pt_regs will be used to continue execution. The program check handler searches the exception table for an entry which matches the address of the program check. If such an entry is found the psw address within pt_regs on the stack is replaced with a fixup address, and execution continues at the new address. If no entry is found the psw is changed to a disabled wait psw and execution stops. Before entering the C part of the program check handler the address of the program check new psw is replaced to a minimalistic handler. This is supposed to help against program check loops. If an exception happens while in program check processing the register contents of the original exception are restored and a disabled wait psw is loaded. Acked-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/boot: Pass pt_regs to program check handler

2025-03-04T16:25:22Z

Setup a pt_regs structure on the stack, poplulate it in low level assembler code, and pass it to print_pgm_check_info(). This way there is no need to access then lowcore from print_pgm_check_info() anymore, and the function looks like a normal program check handler function. Acked-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/time: Convert MACHINE_HAS_SCC to machine_has_scc()

2025-03-04T16:18:06Z

Use static branch(es) to implement and use machine_has_scc() instead of a runtime check via MACHINE_HAS_SCC. This comes with a cleanup of early time initialization: the initial tod_clock_base value is now passed via the bootdata mechanism, instead of using absolute lowcore as transport vehicle from the decompressor to the kernel. Also the early tod clock initialization is moved to the decompressor which allows to use a static branch with machine_has_scc() within the kernel. Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/entry: Unify save_area_sync and save_area_async

2024-08-29T20:56:34Z

In the past two save areas existed because interrupt handlers and system call / program check handlers where entered with interrupts enabled. To prevent a handler from overwriting the save areas from the previous handler, interrupts used the async save area, while system call and program check handler used the sync save area. Since the removal of critical section cleanup from entry.S, handlers are entered with interrupts disabled. When the interrupts are re-enabled, the save area is no longer need. Therefore merge both save areas into one. Reviewed-by: Heiko Carstens Reviewed-by: Alexander Gordeev Signed-off-by: Sven Schnelle Signed-off-by: Vasily Gorbik

s390: fix various typos

2023-07-03T09:19:42Z

Fix various typos found with codespell. Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev

s390: consistently use .balign instead of .align

2023-06-28T11:57:09Z

The .align directive has inconsistent behavior across architectures. Use .balign instead everywhere. This is a no-op for s390, but with this there is no mix in using .align and .balign anymore. Future code is supposed to use only .balign. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Alexander Gordeev

s390/head: get rid of 31 bit leftovers

2022-05-18T11:31:07Z

Get rid of old 31 bit leftovers within ipl code: - convert everything to pc relative code - use 64 bit addressing mode as early as possible - use 64 bit arithmetics wherever possible This way the code doesn't look as odd as before anymore. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/boot: workaround llvm IAS bug

2022-05-17T13:16:29Z

For at least the mvc and clc instructions llvm's integrated assembler can generate incorrect code. In particular this happens with decompressor boot code. The reason seems to be that relocations for the second displacement of each instruction are at incorrect locations (-/+: gas vs llvm IAS): mvc __LC_IO_NEW_PSW(16),.Lnewpsw results in 4: d2 0f 01 f0 00 00 mvc 496(16,%r0),0 - 8: R_390_12 .head.text+0x10 + 6: R_390_12 .head.text+0x10 and clc 0(3,%r4),.L_hdr results in 258: d5 02 40 00 00 00 clc 0(3,%r4),0 - 25c: R_390_12 .head.text+0x324 + 25a: R_390_12 .head.text+0x324 Workaround this by writing the code in a different way. Tested-by: Nathan Chancellor Tested-by: Nick Desaulniers Link: https://github.com/llvm/llvm-project/issues/55411 Link: https://lore.kernel.org/r/20220511120532.2228616-7-hca@linux.ibm.com Signed-off-by: Heiko Carstens

s390/boot: convert parmarea to C

2022-05-06T18:45:15Z

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 Signed-off-by: Heiko Carstens

s390/boot: convert initial lowcore to C

2022-05-06T18:45:15Z

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