jump label: Add s390 support
Implement the architecture backend for jump label support on s390. For a shared kernel booted from a NSS silently disable jump labels because the NSS is read-only. Therefore jump labels will be disabled in a shared kernel and can't be activated. Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com> LKML-Reference: <6935d2c41ce111e1719176ed4bbd3dbe4de80855.1300299760.git.jbaron@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -88,6 +88,7 @@ config S390
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select HAVE_KERNEL_XZ
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select HAVE_GET_USER_PAGES_FAST
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select HAVE_ARCH_MUTEX_CPU_RELAX
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select HAVE_ARCH_JUMP_LABEL if !MARCH_G5
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select ARCH_INLINE_SPIN_TRYLOCK
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select ARCH_INLINE_SPIN_TRYLOCK_BH
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select ARCH_INLINE_SPIN_LOCK
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@ -0,0 +1,37 @@
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#ifndef _ASM_S390_JUMP_LABEL_H
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#define _ASM_S390_JUMP_LABEL_H
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#include <linux/types.h>
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#define JUMP_LABEL_NOP_SIZE 6
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#ifdef CONFIG_64BIT
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#define ASM_PTR ".quad"
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#define ASM_ALIGN ".balign 8"
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#else
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#define ASM_PTR ".long"
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#define ASM_ALIGN ".balign 4"
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#endif
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static __always_inline bool arch_static_branch(struct jump_label_key *key)
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{
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asm goto("0: brcl 0,0\n"
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".pushsection __jump_table, \"aw\"\n"
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ASM_ALIGN "\n"
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ASM_PTR " 0b, %l[label], %0\n"
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".popsection\n"
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: : "X" (key) : : label);
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return false;
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label:
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return true;
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}
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typedef unsigned long jump_label_t;
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struct jump_entry {
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jump_label_t code;
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jump_label_t target;
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jump_label_t key;
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};
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#endif
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@ -23,7 +23,7 @@ CFLAGS_sysinfo.o += -Iinclude/math-emu -Iarch/s390/math-emu -w
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obj-y := bitmap.o traps.o time.o process.o base.o early.o setup.o \
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processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o \
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s390_ext.o debug.o irq.o ipl.o dis.o diag.o mem_detect.o \
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vdso.o vtime.o sysinfo.o nmi.o sclp.o
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vdso.o vtime.o sysinfo.o nmi.o sclp.o jump_label.o
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obj-y += $(if $(CONFIG_64BIT),entry64.o,entry.o)
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obj-y += $(if $(CONFIG_64BIT),reipl64.o,reipl.o)
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@ -0,0 +1,59 @@
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/*
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* Jump label s390 support
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*
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* Copyright IBM Corp. 2011
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* Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
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*/
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <linux/stop_machine.h>
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#include <linux/jump_label.h>
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#include <asm/ipl.h>
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#ifdef HAVE_JUMP_LABEL
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struct insn {
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u16 opcode;
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s32 offset;
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} __packed;
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struct insn_args {
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unsigned long *target;
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struct insn *insn;
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ssize_t size;
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};
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static int __arch_jump_label_transform(void *data)
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{
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struct insn_args *args = data;
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int rc;
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rc = probe_kernel_write(args->target, args->insn, args->size);
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WARN_ON_ONCE(rc < 0);
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return 0;
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}
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void arch_jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type)
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{
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struct insn_args args;
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struct insn insn;
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if (type == JUMP_LABEL_ENABLE) {
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/* brcl 15,offset */
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insn.opcode = 0xc0f4;
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insn.offset = (entry->target - entry->code) >> 1;
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} else {
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/* brcl 0,0 */
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insn.opcode = 0xc004;
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insn.offset = 0;
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}
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args.target = (void *) entry->code;
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args.insn = &insn;
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args.size = JUMP_LABEL_NOP_SIZE;
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stop_machine(__arch_jump_label_transform, &args, NULL);
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}
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#endif
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