1 files changed, 241 insertions, 0 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 000000000..923ecccae
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,241 @@
+// 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
+ */
+
+void *ftrace_func __read_mostly = ftrace_stub;
+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
+}
+
+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 (copy_from_kernel_nofault(&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 {
+		/* 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 (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
+		return -EFAULT;
+	/* 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)
+{
+	ftrace_func = 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 ra, unsigned long sp,
+				    unsigned long ip)
+{
+	if (unlikely(ftrace_graph_is_dead()))
+		goto out;
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		goto out;
+	ip -= MCOUNT_INSN_SIZE;
+	if (!function_graph_enter(ra, ip, 0, (void *) sp))
+		ra = (unsigned long) return_to_handler;
+out:
+	return ra;
+}
+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 */
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+		struct ftrace_ops *ops, struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb;
+	struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
+
+	if (unlikely(!p) || kprobe_disabled(p))
+		return;
+
+	if (kprobe_running()) {
+		kprobes_inc_nmissed_count(p);
+		return;
+	}
+
+	__this_cpu_write(current_kprobe, p);
+
+	kcb = get_kprobe_ctlblk();
+	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+	instruction_pointer_set(regs, ip);
+
+	if (!p->pre_handler || !p->pre_handler(p, regs)) {
+
+		instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
+
+		if (unlikely(p->post_handler)) {
+			kcb->kprobe_status = KPROBE_HIT_SSDONE;
+			p->post_handler(p, regs, 0);
+		}
+	}
+	__this_cpu_write(current_kprobe, NULL);
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	p->ainsn.insn = NULL;
+	return 0;
+}
+#endif