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linux/arch/s390/kernel/traps.c
Linus Torvalds f90f2145b2 s390 updates for 6.15 merge window 
- Add sorting of mcount locations at build time
 
 - Rework uaccess functions with C exception handling to shorten inline
   assembly size and enable full inlining. This yields near-optimal code
   for small constant copies with a ~40kb kernel size increase
 
 - Add support for a configurable STRICT_MM_TYPECHECKS which allows to
   generate better code, but also allows to have type checking for
   debug builds
 
 - Optimize get_lowcore() for common callers with alternatives that
   nearly revert to the pre-relocated lowcore code, while also slightly
   reducing syscall entry and exit time
 
 - Convert MACHINE_HAS_* checks for single facility tests into cpu_has_*
   style macros that call test_facility(), and for features with additional
   conditions, add a new ALT_TYPE_FEATURE alternative to provide a static
   branch via alternative patching. Also, move machine feature detection
   to the decompressor for early patching and add debugging functionality
   to easily show which alternatives are patched
 
 - Add exception table support to early boot / startup code to get rid
   of the open coded exception handling
 
 - Use asm_inline for all inline assemblies with EX_TABLE or ALTERNATIVE
   to ensure correct inlining and unrolling decisions
 
 - Remove 2k page table leftovers now that s390 has been switched to
   always allocate 4k page tables
 
 - Split kfence pool into 4k mappings in arch_kfence_init_pool() and
   remove the architecture-specific kfence_split_mapping()
 
 - Use READ_ONCE_NOCHECK() in regs_get_kernel_stack_nth() to silence
   spurious KASAN warnings from opportunistic ftrace argument tracing
 
 - Force __atomic_add_const() variants on s390 to always return void,
   ensuring compile errors for improper usage
 
 - Remove s390's ioremap_wt() and pgprot_writethrough() due to mismatched
   semantics and lack of known users, relying on asm-generic fallbacks
 
 - Signal eventfd in vfio-ap to notify userspace when the guest AP
   configuration changes, including during mdev removal
 
 - Convert mdev_types from an array to a pointer in vfio-ccw and vfio-ap
   drivers to avoid fake flex array confusion
 
 - Cleanup trap code
 
 - Remove references to the outdated linux390@de.ibm.com address
 
 - Other various small fixes and improvements all over the code
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Merge tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 updates from Vasily Gorbik:

 - Add sorting of mcount locations at build time

 - Rework uaccess functions with C exception handling to shorten inline
   assembly size and enable full inlining. This yields near-optimal code
   for small constant copies with a ~40kb kernel size increase

 - Add support for a configurable STRICT_MM_TYPECHECKS which allows to
   generate better code, but also allows to have type checking for debug
   builds

 - Optimize get_lowcore() for common callers with alternatives that
   nearly revert to the pre-relocated lowcore code, while also slightly
   reducing syscall entry and exit time

 - Convert MACHINE_HAS_* checks for single facility tests into cpu_has_*
   style macros that call test_facility(), and for features with
   additional conditions, add a new ALT_TYPE_FEATURE alternative to
   provide a static branch via alternative patching. Also, move machine
   feature detection to the decompressor for early patching and add
   debugging functionality to easily show which alternatives are patched

 - Add exception table support to early boot / startup code to get rid
   of the open coded exception handling

 - Use asm_inline for all inline assemblies with EX_TABLE or ALTERNATIVE
   to ensure correct inlining and unrolling decisions

 - Remove 2k page table leftovers now that s390 has been switched to
   always allocate 4k page tables

 - Split kfence pool into 4k mappings in arch_kfence_init_pool() and
   remove the architecture-specific kfence_split_mapping()

 - Use READ_ONCE_NOCHECK() in regs_get_kernel_stack_nth() to silence
   spurious KASAN warnings from opportunistic ftrace argument tracing

 - Force __atomic_add_const() variants on s390 to always return void,
   ensuring compile errors for improper usage

 - Remove s390's ioremap_wt() and pgprot_writethrough() due to
   mismatched semantics and lack of known users, relying on asm-generic
   fallbacks

 - Signal eventfd in vfio-ap to notify userspace when the guest AP
   configuration changes, including during mdev removal

 - Convert mdev_types from an array to a pointer in vfio-ccw and vfio-ap
   drivers to avoid fake flex array confusion

 - Cleanup trap code

 - Remove references to the outdated linux390@de.ibm.com address

 - Other various small fixes and improvements all over the code

* tag 's390-6.15-1' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (78 commits)
  s390: Use inline qualifier for all EX_TABLE and ALTERNATIVE inline assemblies
  s390/kfence: Split kfence pool into 4k mappings in arch_kfence_init_pool()
  s390/ptrace: Avoid KASAN false positives in regs_get_kernel_stack_nth()
  s390/boot: Ignore vmlinux.map
  s390/sysctl: Remove "vm/allocate_pgste" sysctl
  s390: Remove 2k vs 4k page table leftovers
  s390/tlb: Use mm_has_pgste() instead of mm_alloc_pgste()
  s390/lowcore: Use lghi instead llilh to clear register
  s390/syscall: Merge __do_syscall() and do_syscall()
  s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly
  s390/smp: Implement raw_smp_processor_id() with inline assembly
  s390/current: Implement current with inline assembly
  s390/lowcore: Use inline qualifier for get_lowcore() inline assembly
  s390: Move s390 sysctls into their own file under arch/s390
  s390/syscall: Simplify syscall_get_arguments()
  s390/vfio-ap: Notify userspace that guest's AP config changed when mdev removed
  s390: Remove ioremap_wt() and pgprot_writethrough()
  s390/mm: Add configurable STRICT_MM_TYPECHECKS
  s390/mm: Convert pgste_val() into function
  s390/mm: Convert pgprot_val() into function
  ...
2025-03-29 11:59:43 -07:00

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// SPDX-License-Identifier: GPL-2.0
/*
* S390 version
* Copyright IBM Corp. 1999, 2000
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
* Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
*
* Derived from "arch/i386/kernel/traps.c"
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/cpufeature.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/randomize_kstack.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/cpu.h>
#include <linux/entry-common.h>
#include <linux/kmsan.h>
#include <asm/asm-extable.h>
#include <asm/irqflags.h>
#include <asm/ptrace.h>
#include <asm/vtime.h>
#include <asm/fpu.h>
#include <asm/fault.h>
#include "entry.h"
static inline void __user *get_trap_ip(struct pt_regs *regs)
{
unsigned long address;
if (regs->int_code & 0x200)
address = current->thread.trap_tdb.data[3];
else
address = regs->psw.addr;
return (void __user *)(address - (regs->int_code >> 16));
}
#ifdef CONFIG_GENERIC_BUG
int is_valid_bugaddr(unsigned long addr)
{
return 1;
}
#endif
void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
if (user_mode(regs)) {
force_sig_fault(si_signo, si_code, get_trap_ip(regs));
report_user_fault(regs, si_signo, 0);
} else {
if (!fixup_exception(regs))
die(regs, str);
}
}
static void do_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
if (notify_die(DIE_TRAP, str, regs, 0, regs->int_code, si_signo) == NOTIFY_STOP)
return;
do_report_trap(regs, si_signo, si_code, str);
}
NOKPROBE_SYMBOL(do_trap);
void do_per_trap(struct pt_regs *regs)
{
if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
return;
if (!current->ptrace)
return;
force_sig_fault(SIGTRAP, TRAP_HWBKPT, (void __force __user *)current->thread.per_event.address);
}
NOKPROBE_SYMBOL(do_per_trap);
static void default_trap_handler(struct pt_regs *regs)
{
if (user_mode(regs)) {
report_user_fault(regs, SIGSEGV, 0);
force_exit_sig(SIGSEGV);
} else
die(regs, "Unknown program exception");
}
#define DO_ERROR_INFO(name, signr, sicode, str) \
static void name(struct pt_regs *regs) \
{ \
do_trap(regs, signr, sicode, str); \
}
DO_ERROR_INFO(addressing_exception, SIGILL, ILL_ILLADR, "addressing exception")
DO_ERROR_INFO(divide_exception, SIGFPE, FPE_INTDIV, "fixpoint divide exception")
DO_ERROR_INFO(execute_exception, SIGILL, ILL_ILLOPN, "execute exception")
DO_ERROR_INFO(hfp_divide_exception, SIGFPE, FPE_FLTDIV, "HFP divide exception")
DO_ERROR_INFO(hfp_overflow_exception, SIGFPE, FPE_FLTOVF, "HFP overflow exception")
DO_ERROR_INFO(hfp_significance_exception, SIGFPE, FPE_FLTRES, "HFP significance exception")
DO_ERROR_INFO(hfp_sqrt_exception, SIGFPE, FPE_FLTINV, "HFP square root exception")
DO_ERROR_INFO(hfp_underflow_exception, SIGFPE, FPE_FLTUND, "HFP underflow exception")
DO_ERROR_INFO(operand_exception, SIGILL, ILL_ILLOPN, "operand exception")
DO_ERROR_INFO(overflow_exception, SIGFPE, FPE_INTOVF, "fixpoint overflow exception")
DO_ERROR_INFO(privileged_op, SIGILL, ILL_PRVOPC, "privileged operation")
DO_ERROR_INFO(special_op_exception, SIGILL, ILL_ILLOPN, "special operation exception")
DO_ERROR_INFO(specification_exception, SIGILL, ILL_ILLOPN, "specification exception");
DO_ERROR_INFO(transaction_exception, SIGILL, ILL_ILLOPN, "transaction constraint exception")
static inline void do_fp_trap(struct pt_regs *regs, __u32 fpc)
{
int si_code = 0;
/* FPC[2] is Data Exception Code */
if ((fpc & 0x00000300) == 0) {
/* bits 6 and 7 of DXC are 0 iff IEEE exception */
if (fpc & 0x8000) /* invalid fp operation */
si_code = FPE_FLTINV;
else if (fpc & 0x4000) /* div by 0 */
si_code = FPE_FLTDIV;
else if (fpc & 0x2000) /* overflow */
si_code = FPE_FLTOVF;
else if (fpc & 0x1000) /* underflow */
si_code = FPE_FLTUND;
else if (fpc & 0x0800) /* inexact */
si_code = FPE_FLTRES;
}
do_trap(regs, SIGFPE, si_code, "floating point exception");
}
static void translation_specification_exception(struct pt_regs *regs)
{
/* May never happen. */
panic("Translation-Specification Exception");
}
static void illegal_op(struct pt_regs *regs)
{
int is_uprobe_insn = 0;
u16 __user *location;
int signal = 0;
u16 opcode;
location = get_trap_ip(regs);
if (user_mode(regs)) {
if (get_user(opcode, location))
return;
if (opcode == S390_BREAKPOINT_U16) {
if (current->ptrace)
force_sig_fault(SIGTRAP, TRAP_BRKPT, location);
else
signal = SIGILL;
#ifdef CONFIG_UPROBES
} else if (opcode == UPROBE_SWBP_INSN) {
is_uprobe_insn = 1;
#endif
} else {
signal = SIGILL;
}
}
/*
* This is either an illegal op in kernel mode, or user space trapped
* on a uprobes illegal instruction. See if kprobes or uprobes picks
* it up. If not, SIGILL.
*/
if (is_uprobe_insn || !user_mode(regs)) {
if (notify_die(DIE_BPT, "bpt", regs, 0, 3, SIGTRAP) != NOTIFY_STOP)
signal = SIGILL;
}
if (signal)
do_trap(regs, signal, ILL_ILLOPC, "illegal operation");
}
NOKPROBE_SYMBOL(illegal_op);
static void vector_exception(struct pt_regs *regs)
{
int si_code, vic;
/* get vector interrupt code from fpc */
save_user_fpu_regs();
vic = (current->thread.ufpu.fpc & 0xf00) >> 8;
switch (vic) {
case 1: /* invalid vector operation */
si_code = FPE_FLTINV;
break;
case 2: /* division by zero */
si_code = FPE_FLTDIV;
break;
case 3: /* overflow */
si_code = FPE_FLTOVF;
break;
case 4: /* underflow */
si_code = FPE_FLTUND;
break;
case 5: /* inexact */
si_code = FPE_FLTRES;
break;
default: /* unknown cause */
si_code = 0;
}
do_trap(regs, SIGFPE, si_code, "vector exception");
}
static void data_exception(struct pt_regs *regs)
{
save_user_fpu_regs();
if (current->thread.ufpu.fpc & FPC_DXC_MASK)
do_fp_trap(regs, current->thread.ufpu.fpc);
else
do_trap(regs, SIGILL, ILL_ILLOPN, "data exception");
}
static void space_switch_exception(struct pt_regs *regs)
{
/* Set user psw back to home space mode. */
if (user_mode(regs))
regs->psw.mask |= PSW_ASC_HOME;
/* Send SIGILL. */
do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");
}
static void monitor_event_exception(struct pt_regs *regs)
{
if (user_mode(regs))
return;
switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {
case BUG_TRAP_TYPE_NONE:
fixup_exception(regs);
break;
case BUG_TRAP_TYPE_WARN:
break;
case BUG_TRAP_TYPE_BUG:
die(regs, "monitor event");
break;
}
}
void kernel_stack_invalid(struct pt_regs *regs)
{
/*
* Normally regs are unpoisoned by the generic entry code, but
* kernel_stack_overflow() is a rare case that is called bypassing it.
*/
kmsan_unpoison_entry_regs(regs);
bust_spinlocks(1);
pr_emerg("Kernel stack pointer invalid\n");
show_regs(regs);
bust_spinlocks(0);
panic("Invalid kernel stack pointer, cannot continue");
}
NOKPROBE_SYMBOL(kernel_stack_invalid);
static void __init test_monitor_call(void)
{
int val = 1;
if (!IS_ENABLED(CONFIG_BUG))
return;
asm_inline volatile(
" mc 0,0\n"
"0: lhi %[val],0\n"
"1:\n"
EX_TABLE(0b, 1b)
: [val] "+d" (val));
if (!val)
panic("Monitor call doesn't work!\n");
}
void __init trap_init(void)
{
struct lowcore *lc = get_lowcore();
unsigned long flags;
struct ctlreg cr0;
local_irq_save(flags);
cr0 = local_ctl_clear_bit(0, CR0_LOW_ADDRESS_PROTECTION_BIT);
psw_bits(lc->external_new_psw).mcheck = 1;
psw_bits(lc->program_new_psw).mcheck = 1;
psw_bits(lc->svc_new_psw).mcheck = 1;
psw_bits(lc->io_new_psw).mcheck = 1;
local_ctl_load(0, &cr0);
local_irq_restore(flags);
local_mcck_enable();
test_monitor_call();
}
static void (*pgm_check_table[128])(struct pt_regs *regs);
void noinstr __do_pgm_check(struct pt_regs *regs)
{
struct lowcore *lc = get_lowcore();
irqentry_state_t state;
unsigned int trapnr;
union teid teid;
teid.val = lc->trans_exc_code;
regs->int_code = lc->pgm_int_code;
regs->int_parm_long = teid.val;
/*
* In case of a guest fault, short-circuit the fault handler and return.
* This way the sie64a() function will return 0; fault address and
* other relevant bits are saved in current->thread.gmap_teid, and
* the fault number in current->thread.gmap_int_code. KVM will be
* able to use this information to handle the fault.
*/
if (test_pt_regs_flag(regs, PIF_GUEST_FAULT)) {
current->thread.gmap_teid.val = regs->int_parm_long;
current->thread.gmap_int_code = regs->int_code & 0xffff;
return;
}
state = irqentry_enter(regs);
if (user_mode(regs)) {
update_timer_sys();
if (!cpu_has_bear()) {
if (regs->last_break < 4096)
regs->last_break = 1;
}
current->thread.last_break = regs->last_break;
}
if (lc->pgm_code & 0x0200) {
/* transaction abort */
current->thread.trap_tdb = lc->pgm_tdb;
}
if (lc->pgm_code & PGM_INT_CODE_PER) {
if (user_mode(regs)) {
struct per_event *ev = &current->thread.per_event;
set_thread_flag(TIF_PER_TRAP);
ev->address = lc->per_address;
ev->cause = lc->per_code_combined;
ev->paid = lc->per_access_id;
} else {
/* PER event in kernel is kprobes */
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
do_per_trap(regs);
goto out;
}
}
if (!irqs_disabled_flags(regs->psw.mask))
trace_hardirqs_on();
__arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
trapnr = regs->int_code & PGM_INT_CODE_MASK;
if (trapnr)
pgm_check_table[trapnr](regs);
out:
local_irq_disable();
irqentry_exit(regs, state);
}
/*
* The program check table contains exactly 128 (0x00-0x7f) entries. Each
* line defines the function to be called corresponding to the program check
* interruption code.
*/
static void (*pgm_check_table[128])(struct pt_regs *regs) = {
[0x00] = default_trap_handler,
[0x01] = illegal_op,
[0x02] = privileged_op,
[0x03] = execute_exception,
[0x04] = do_protection_exception,
[0x05] = addressing_exception,
[0x06] = specification_exception,
[0x07] = data_exception,
[0x08] = overflow_exception,
[0x09] = divide_exception,
[0x0a] = overflow_exception,
[0x0b] = divide_exception,
[0x0c] = hfp_overflow_exception,
[0x0d] = hfp_underflow_exception,
[0x0e] = hfp_significance_exception,
[0x0f] = hfp_divide_exception,
[0x10] = do_dat_exception,
[0x11] = do_dat_exception,
[0x12] = translation_specification_exception,
[0x13] = special_op_exception,
[0x14] = default_trap_handler,
[0x15] = operand_exception,
[0x16] = default_trap_handler,
[0x17] = default_trap_handler,
[0x18] = transaction_exception,
[0x19] = default_trap_handler,
[0x1a] = default_trap_handler,
[0x1b] = vector_exception,
[0x1c] = space_switch_exception,
[0x1d] = hfp_sqrt_exception,
[0x1e ... 0x37] = default_trap_handler,
[0x38] = do_dat_exception,
[0x39] = do_dat_exception,
[0x3a] = do_dat_exception,
[0x3b] = do_dat_exception,
[0x3c] = default_trap_handler,
[0x3d] = do_secure_storage_access,
[0x3e] = default_trap_handler,
[0x3f] = default_trap_handler,
[0x40] = monitor_event_exception,
[0x41 ... 0x7f] = default_trap_handler,
};
#define COND_TRAP(x) asm( \
".weak " __stringify(x) "\n\t" \
".set " __stringify(x) "," \
__stringify(default_trap_handler))
COND_TRAP(do_secure_storage_access);
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