1 files changed, 360 insertions, 0 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 000000000..416b5a943
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Dynamic function tracer architecture backend.
+ *
+ * Copyright IBM Corp. 2009,2014
+ *
+ *   Author(s): 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/text-patching.h>
+#include <asm/cacheflush.h>
+#include <asm/ftrace.lds.h>
+#include <asm/nospec-branch.h>
+#include <asm/set_memory.h>
+#include "entry.h"
+#include "ftrace.h"
+
+/*
+ * To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
+ * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
+ * (since gcc 9 / clang 10) is used.
+ * In both cases 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
+ *
+ * The instruction will be patched by ftrace_make_call / ftrace_make_nop.
+ * 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.
+ */
+
+void *ftrace_func __read_mostly = ftrace_stub;
+struct ftrace_insn {
+	u16 opc;
+	s32 disp;
+} __packed;
+
+asm(
+	"	.align 16\n"
+	"ftrace_shared_hotpatch_trampoline_br:\n"
+	"	lmg	%r0,%r1,2(%r1)\n"
+	"	br	%r1\n"
+	"ftrace_shared_hotpatch_trampoline_br_end:\n"
+);
+
+#ifdef CONFIG_EXPOLINE
+asm(
+	"	.align 16\n"
+	"ftrace_shared_hotpatch_trampoline_exrl:\n"
+	"	lmg	%r0,%r1,2(%r1)\n"
+	"	exrl	%r0,0f\n"
+	"	j	.\n"
+	"0:	br	%r1\n"
+	"ftrace_shared_hotpatch_trampoline_exrl_end:\n"
+);
+#endif /* CONFIG_EXPOLINE */
+
+#ifdef CONFIG_MODULES
+static char *ftrace_plt;
+#endif /* CONFIG_MODULES */
+
+static const char *ftrace_shared_hotpatch_trampoline(const char **end)
+{
+	const char *tstart, *tend;
+
+	tstart = ftrace_shared_hotpatch_trampoline_br;
+	tend = ftrace_shared_hotpatch_trampoline_br_end;
+#ifdef CONFIG_EXPOLINE
+	if (!nospec_disable) {
+		tstart = ftrace_shared_hotpatch_trampoline_exrl;
+		tend = ftrace_shared_hotpatch_trampoline_exrl_end;
+	}
+#endif /* CONFIG_EXPOLINE */
+	if (end)
+		*end = tend;
+	return tstart;
+}
+
+bool ftrace_need_init_nop(void)
+{
+	return true;
+}
+
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+	static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline =
+		__ftrace_hotpatch_trampolines_start;
+	static const char orig[6] = { 0xc0, 0x04, 0x00, 0x00, 0x00, 0x00 };
+	static struct ftrace_hotpatch_trampoline *trampoline;
+	struct ftrace_hotpatch_trampoline **next_trampoline;
+	struct ftrace_hotpatch_trampoline *trampolines_end;
+	struct ftrace_hotpatch_trampoline tmp;
+	struct ftrace_insn *insn;
+	const char *shared;
+	s32 disp;
+
+	BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) !=
+		     SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE);
+
+	next_trampoline = &next_vmlinux_trampoline;
+	trampolines_end = __ftrace_hotpatch_trampolines_end;
+	shared = ftrace_shared_hotpatch_trampoline(NULL);
+#ifdef CONFIG_MODULES
+	if (mod) {
+		next_trampoline = &mod->arch.next_trampoline;
+		trampolines_end = mod->arch.trampolines_end;
+		shared = ftrace_plt;
+	}
+#endif
+
+	if (WARN_ON_ONCE(*next_trampoline >= trampolines_end))
+		return -ENOMEM;
+	trampoline = (*next_trampoline)++;
+
+	/* Check for the compiler-generated fentry nop (brcl 0, .). */
+	if (WARN_ON_ONCE(memcmp((const void *)rec->ip, &orig, sizeof(orig))))
+		return -EINVAL;
+
+	/* Generate the trampoline. */
+	tmp.brasl_opc = 0xc015; /* brasl %r1, shared */
+	tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2;
+	tmp.interceptor = FTRACE_ADDR;
+	tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn);
+	s390_kernel_write(trampoline, &tmp, sizeof(tmp));
+
+	/* Generate a jump to the trampoline. */
+	disp = ((char *)trampoline - (char *)rec->ip) / 2;
+	insn = (struct ftrace_insn *)rec->ip;
+	s390_kernel_write(&insn->disp, &disp, sizeof(disp));
+
+	return 0;
+}
+
+static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
+{
+	struct ftrace_hotpatch_trampoline *trampoline;
+	struct ftrace_insn insn;
+	s64 disp;
+	u16 opc;
+
+	if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn)))
+		return ERR_PTR(-EFAULT);
+	disp = (s64)insn.disp * 2;
+	trampoline = (void *)(rec->ip + disp);
+	if (get_kernel_nofault(opc, &trampoline->brasl_opc))
+		return ERR_PTR(-EFAULT);
+	if (opc != 0xc015)
+		return ERR_PTR(-EINVAL);
+	return trampoline;
+}
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+		       unsigned long addr)
+{
+	struct ftrace_hotpatch_trampoline *trampoline;
+	u64 old;
+
+	trampoline = ftrace_get_trampoline(rec);
+	if (IS_ERR(trampoline))
+		return PTR_ERR(trampoline);
+	if (get_kernel_nofault(old, &trampoline->interceptor))
+		return -EFAULT;
+	if (old != old_addr)
+		return -EINVAL;
+	s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
+	return 0;
+}
+
+static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
+{
+	u16 old;
+	u8 op;
+
+	if (get_kernel_nofault(old, addr))
+		return -EFAULT;
+	if (old != expected)
+		return -EINVAL;
+	/* set mask field to all ones or zeroes */
+	op = enable ? 0xf4 : 0x04;
+	s390_kernel_write((char *)addr + 1, &op, sizeof(op));
+	return 0;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+		    unsigned long addr)
+{
+	/* Expect brcl 0xf,... */
+	return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	struct ftrace_hotpatch_trampoline *trampoline;
+
+	trampoline = ftrace_get_trampoline(rec);
+	if (IS_ERR(trampoline))
+		return PTR_ERR(trampoline);
+	s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
+	/* Expect brcl 0x0,... */
+	return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	ftrace_func = func;
+	return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+	ftrace_modify_all_code(command);
+}
+
+void ftrace_arch_code_modify_post_process(void)
+{
+	/*
+	 * Flush any pre-fetched instructions on all
+	 * CPUs to make the new code visible.
+	 */
+	text_poke_sync_lock();
+}
+
+#ifdef CONFIG_MODULES
+
+static int __init ftrace_plt_init(void)
+{
+	const char *start, *end;
+
+	ftrace_plt = module_alloc(PAGE_SIZE);
+	if (!ftrace_plt)
+		panic("cannot allocate ftrace plt\n");
+
+	start = ftrace_shared_hotpatch_trampoline(&end);
+	memcpy(ftrace_plt, start, end - start);
+	set_memory_ro((unsigned long)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)
+{
+	int rc;
+
+	/* Expect brc 0xf,... */
+	rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
+	if (rc)
+		return rc;
+	text_poke_sync_lock();
+	return 0;
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	int rc;
+
+	/* Expect brc 0x0,... */
+	rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
+	if (rc)
+		return rc;
+	text_poke_sync_lock();
+	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 ftrace_regs *fregs)
+{
+	struct kprobe_ctlblk *kcb;
+	struct pt_regs *regs;
+	struct kprobe *p;
+	int bit;
+
+	bit = ftrace_test_recursion_trylock(ip, parent_ip);
+	if (bit < 0)
+		return;
+
+	regs = ftrace_get_regs(fregs);
+	p = get_kprobe((kprobe_opcode_t *)ip);
+	if (!regs || unlikely(!p) || kprobe_disabled(p))
+		goto out;
+
+	if (kprobe_running()) {
+		kprobes_inc_nmissed_count(p);
+		goto out;
+	}
+
+	__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);
+out:
+	ftrace_test_recursion_unlock(bit);
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	p->ainsn.insn = NULL;
+	return 0;
+}
+#endif