v4.19.13 snapshot.
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 0000000..39b13d7
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dynamic function tracer architecture backend.
+ *
+ * Copyright IBM Corp. 2009,2014
+ *
+ * Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
+ * Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/moduleloader.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/kprobes.h>
+#include <trace/syscall.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include <asm/set_memory.h>
+#include "entry.h"
+
+/*
+ * The mcount code looks like this:
+ * stg %r14,8(%r15) # offset 0
+ * larl %r1,<&counter> # offset 6
+ * brasl %r14,_mcount # offset 12
+ * lg %r14,8(%r15) # offset 18
+ * Total length is 24 bytes. Only the first instruction will be patched
+ * by ftrace_make_call / ftrace_make_nop.
+ * The enabled ftrace code block looks like this:
+ * > brasl %r0,ftrace_caller # offset 0
+ * larl %r1,<&counter> # offset 6
+ * brasl %r14,_mcount # offset 12
+ * lg %r14,8(%r15) # offset 18
+ * The ftrace function gets called with a non-standard C function call ABI
+ * where r0 contains the return address. It is also expected that the called
+ * function only clobbers r0 and r1, but restores r2-r15.
+ * For module code we can't directly jump to ftrace caller, but need a
+ * trampoline (ftrace_plt), which clobbers also r1.
+ * The return point of the ftrace function has offset 24, so execution
+ * continues behind the mcount block.
+ * The disabled ftrace code block looks like this:
+ * > jg .+24 # offset 0
+ * larl %r1,<&counter> # offset 6
+ * brasl %r14,_mcount # offset 12
+ * lg %r14,8(%r15) # offset 18
+ * The jg instruction branches to offset 24 to skip as many instructions
+ * as possible.
+ * In case we use gcc's hotpatch feature the original and also the disabled
+ * function prologue contains only a single six byte instruction and looks
+ * like this:
+ * > brcl 0,0 # offset 0
+ * To enable ftrace the code gets patched like above and afterwards looks
+ * like this:
+ * > brasl %r0,ftrace_caller # offset 0
+ */
+
+unsigned long ftrace_plt;
+
+static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
+{
+#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
+ /* brcl 0,0 */
+ insn->opc = 0xc004;
+ insn->disp = 0;
+#else
+ /* stg r14,8(r15) */
+ insn->opc = 0xe3e0;
+ insn->disp = 0xf0080024;
+#endif
+}
+
+static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+ if (insn->opc == BREAKPOINT_INSTRUCTION)
+ return 1;
+#endif
+ return 0;
+}
+
+static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+ insn->opc = BREAKPOINT_INSTRUCTION;
+ insn->disp = KPROBE_ON_FTRACE_NOP;
+#endif
+}
+
+static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+ insn->opc = BREAKPOINT_INSTRUCTION;
+ insn->disp = KPROBE_ON_FTRACE_CALL;
+#endif
+}
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ return 0;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+{
+ struct ftrace_insn orig, new, old;
+
+ if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
+ return -EFAULT;
+ if (addr == MCOUNT_ADDR) {
+ /* Initial code replacement */
+ ftrace_generate_orig_insn(&orig);
+ ftrace_generate_nop_insn(&new);
+ } else if (is_kprobe_on_ftrace(&old)) {
+ /*
+ * If we find a breakpoint instruction, a kprobe has been
+ * placed at the beginning of the function. We write the
+ * constant KPROBE_ON_FTRACE_NOP into the remaining four
+ * bytes of the original instruction so that the kprobes
+ * handler can execute a nop, if it reaches this breakpoint.
+ */
+ ftrace_generate_kprobe_call_insn(&orig);
+ ftrace_generate_kprobe_nop_insn(&new);
+ } else {
+ /* Replace ftrace call with a nop. */
+ ftrace_generate_call_insn(&orig, rec->ip);
+ ftrace_generate_nop_insn(&new);
+ }
+ /* Verify that the to be replaced code matches what we expect. */
+ if (memcmp(&orig, &old, sizeof(old)))
+ return -EINVAL;
+ s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+ return 0;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ struct ftrace_insn orig, new, old;
+
+ if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
+ return -EFAULT;
+ if (is_kprobe_on_ftrace(&old)) {
+ /*
+ * If we find a breakpoint instruction, a kprobe has been
+ * placed at the beginning of the function. We write the
+ * constant KPROBE_ON_FTRACE_CALL into the remaining four
+ * bytes of the original instruction so that the kprobes
+ * handler can execute a brasl if it reaches this breakpoint.
+ */
+ ftrace_generate_kprobe_nop_insn(&orig);
+ ftrace_generate_kprobe_call_insn(&new);
+ } else {
+ /* Replace nop with an ftrace call. */
+ ftrace_generate_nop_insn(&orig);
+ ftrace_generate_call_insn(&new, rec->ip);
+ }
+ /* Verify that the to be replaced code matches what we expect. */
+ if (memcmp(&orig, &old, sizeof(old)))
+ return -EINVAL;
+ s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+ return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ return 0;
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+ return 0;
+}
+
+#ifdef CONFIG_MODULES
+
+static int __init ftrace_plt_init(void)
+{
+ unsigned int *ip;
+
+ ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
+ if (!ftrace_plt)
+ panic("cannot allocate ftrace plt\n");
+ ip = (unsigned int *) ftrace_plt;
+ ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
+ ip[1] = 0x100a0004;
+ ip[2] = 0x07f10000;
+ ip[3] = FTRACE_ADDR >> 32;
+ ip[4] = FTRACE_ADDR & 0xffffffff;
+ set_memory_ro(ftrace_plt, 1);
+ return 0;
+}
+device_initcall(ftrace_plt_init);
+
+#endif /* CONFIG_MODULES */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Hook the return address and push it in the stack of return addresses
+ * in current thread info.
+ */
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
+{
+ if (unlikely(ftrace_graph_is_dead()))
+ goto out;
+ if (unlikely(atomic_read(¤t->tracing_graph_pause)))
+ goto out;
+ ip -= MCOUNT_INSN_SIZE;
+ if (!function_graph_enter(parent, ip, 0, NULL))
+ parent = (unsigned long) return_to_handler;
+out:
+ return parent;
+}
+NOKPROBE_SYMBOL(prepare_ftrace_return);
+
+/*
+ * Patch the kernel code at ftrace_graph_caller location. The instruction
+ * there is branch relative on condition. To enable the ftrace graph code
+ * block, we simply patch the mask field of the instruction to zero and
+ * turn the instruction into a nop.
+ * To disable the ftrace graph code the mask field will be patched to
+ * all ones, which turns the instruction into an unconditional branch.
+ */
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ u8 op = 0x04; /* set mask field to zero */
+
+ s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
+ return 0;
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ u8 op = 0xf4; /* set mask field to all ones */
+
+ s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
+ return 0;
+}
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */