kernel/arch/s390/include/asm/lowcore.h, branch linux-5.14.y

s390/smp: enable DAT before CPU restart callback is called

2021-09-15T08:02:06Z

[ Upstream commit 915fea04f9320d0f4ab6ecbb6bf759eebcd2c41d ] The restart interrupt is triggered whenever a secondary CPU is brought online, a remote function call dispatched from another CPU or a manual PSW restart is initiated and causes the system to kdump. The handling routine is always called with DAT turned off. It then initializes the stack frame and invokes a callback. The existing callbacks handle DAT as follows: * __do_restart() and __machine_kexec() turn in on upon entry; * __ipl_run(), __reipl_run() and __dump_run() do not turn it right away, but all of them call diag308() - which turns DAT on, but only if kasan is enabled; In addition to the described complexity all callbacks (and the functions they call) should avoid kasan instrumentation while DAT is off. This update enables DAT in the assembler restart handler and relieves any callbacks (which are mostly C functions) from dealing with DAT altogether. There are four types of CPU restart that initialize control registers in different ways: 1. Start of secondary CPU on boot - control registers are inherited from the IPL CPU; 2. Restart of online CPU - control registers of the CPU being restarted are kept; 3. Hotplug of offline CPU - control registers are inherited from the starting CPU; 4. Start of offline CPU triggered by manual PSW restart - the control registers are read from the absolute lowcore and contain the boot time IPL CPU values updated with all follow-up calls of smp_ctl_set_bit() and smp_ctl_clear_bit() routines; In first three cases contents of the control registers is the most recent. In the latter case control registers are good enough to facilitate successful completion of kdump operation. Suggested-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/lowcore: remove superfluous __packed annotations

2021-06-07T15:07:01Z

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

s390: use struct tpi_info in lowcore.h

2021-06-07T15:07:01Z

Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/traps: add struct to access transactional diagnostic block

2021-06-07T15:06:58Z

gcc-11 warns: arch/s390/kernel/traps.c: In function __do_pgm_check: arch/s390/kernel/traps.c:319:17: warning: memcpy reading 256 bytes from a region of size 0 [-Wstringop-overread] 319 | memcpy(¤t->thread.trap_tdb, &S390_lowcore.pgm_tdb, 256); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix this by adding a struct pgm_tdb to struct lowcore and copy that. Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/irq: add union/struct to access external interrupt parameters

2021-06-07T15:06:58Z

gcc-11 warns: arch/s390/kernel/irq.c: In function do_ext_irq: arch/s390/kernel/irq.c:175:9: warning: memcpy reading 4 bytes from a region of size 0 [-Wstringop-overread] 175 | memcpy(®s->int_code, &S390_lowcore.ext_cpu_addr, 4); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix this by adding a struct for int_code to struct lowcore. Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/facilities: move stfl information from lowcore to global data

2021-06-07T15:06:58Z

With gcc-11, there are a lot of warnings because the facility functions are accessing lowcore through a null pointer. Fix this by moving the facility arrays away from lowcore. Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/entry: use assignment to read intcode / asm to copy gprs

2021-06-07T15:06:58Z

arch/s390/kernel/syscall.c: In function __do_syscall: arch/s390/kernel/syscall.c:147:9: warning: memcpy reading 64 bytes from a region of size 0 [-Wstringop-overread] 147 | memcpy(®s->gprs[8], S390_lowcore.save_area_sync, 8 * sizeof(unsigned long)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/s390/kernel/syscall.c:148:9: warning: memcpy reading 4 bytes from a region of size 0 [-Wstringop-overread] 148 | memcpy(®s->int_code, &S390_lowcore.svc_ilc, sizeof(regs->int_code)); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Fix this by moving the gprs restore from C to assembly, and use a assignment for int_code instead of memcpy. Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390: add stack for machine check handler

2021-02-13T16:17:53Z

The previous code used the normal kernel stack for machine checks. This is problematic when a machine check interrupts a system call or interrupt handler right at the beginning where registers are set up. Assume system_call is interrupted at the first instruction and a machine check is triggered. The machine check handler is called, checks the PSW to see whether it is coming from user space, notices that it is already in kernel mode but %r15 still contains the user space stack. This would lead to a kernel crash. There are basically two ways of fixing that: Either using the 'critical cleanup' approach which compares the address in the PSW to see whether it is already at a point where the stack has been set up, or use an extra stack for the machine check handler. For simplicity, we will go with the second approach and allocate an extra stack. This adds some memory overhead for large systems, but usually large system have plenty of memory so this isn't really a concern. But it keeps the mchk stack setup simple and less error prone. Fixes: 0b0ed657fe00 ("s390: remove critical section cleanup from entry.S") Signed-off-by: Sven Schnelle Cc: # v5.8+ Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390: convert to generic entry

2021-01-19T11:29:26Z

This patch converts s390 to use the generic entry infrastructure from kernel/entry/*. There are a few special things on s390: - PIF_PER_TRAP is moved to TIF_PER_TRAP as the generic code doesn't know about our PIF flags in exit_to_user_mode_loop(). - The old code had several ways to restart syscalls: a) PIF_SYSCALL_RESTART, which was only set during execve to force a restart after upgrading a process (usually qemu-kvm) to pgste page table extensions. b) PIF_SYSCALL, which is set by do_signal() to indicate that the current syscall should be restarted. This is changed so that do_signal() now also uses PIF_SYSCALL_RESTART. Continuing to use PIF_SYSCALL doesn't work with the generic code, and changing it to PIF_SYSCALL_RESTART makes PIF_SYSCALL and PIF_SYSCALL_RESTART more unique. - On s390 calling sys_sigreturn or sys_rt_sigreturn is implemented by executing a svc instruction on the process stack which causes a fault. While handling that fault the fault code sets PIF_SYSCALL to hand over processing to the syscall code on exit to usermode. The patch introduces PIF_SYSCALL_RET_SET, which is set if ptrace sets a return value for a syscall. The s390x ptrace ABI uses r2 both for the syscall number and return value, so ptrace cannot set the syscall number + return value at the same time. The flag makes handling that a bit easier. do_syscall() will just skip executing the syscall if PIF_SYSCALL_RET_SET is set. CONFIG_DEBUG_ASCE was removd in favour of the generic CONFIG_DEBUG_ENTRY. CR1/7/13 will be checked both on kernel entry and exit to contain the correct asces. Signed-off-by: Sven Schnelle Signed-off-by: Vasily Gorbik

s390/mm: remove set_fs / rework address space handling

2020-11-23T11:01:12Z

Remove set_fs support from s390. With doing this rework address space handling and simplify it. As a result address spaces are now setup like this: CPU running in | %cr1 ASCE | %cr7 ASCE | %cr13 ASCE ----------------------------|-----------|-----------|----------- user space | user | user | kernel kernel, normal execution | kernel | user | kernel kernel, kvm guest execution | gmap | user | kernel To achieve this the getcpu vdso syscall is removed in order to avoid secondary address mode and a separate vdso address space in for user space. The getcpu vdso syscall will be implemented differently with a subsequent patch. The kernel accesses user space always via secondary address space. This happens in different ways: - with mvcos in home space mode and directly read/write to secondary address space - with mvcs/mvcp in primary space mode and copy from primary space to secondary space or vice versa - with e.g. cs in secondary space mode and access secondary space Switching translation modes happens with sacf before and after instructions which access user space, like before. Lazy handling of control register reloading is removed in the hope to make everything simpler, but at the cost of making kernel entry and exit a bit slower. That is: on kernel entry the primary asce is always changed to contain the kernel asce, and on kernel exit the primary asce is changed again so it contains the user asce. In kernel mode there is only one exception to the primary asce: when kvm guests are executed the primary asce contains the gmap asce (which describes the guest address space). The primary asce is reset to kernel asce whenever kvm guest execution is interrupted, so that this doesn't has to be taken into account for any user space accesses. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens