1 files changed, 206 insertions, 16 deletions

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 2d8f595d9196..0a464d328467 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -18,8 +18,11 @@
 #include <trace/syscall.h>
 #include <asm/asm-offsets.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)
@@ -41,7 +44,130 @@
  */
 
 void *ftrace_func __read_mostly = ftrace_stub;
-unsigned long ftrace_plt;
+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_ex:\n"
+	"	lmg	%r0,%r1,2(%r1)\n"
+	"	ex	%r0," __stringify(__LC_BR_R1) "(%r0)\n"
+	"	j	.\n"
+	"ftrace_shared_hotpatch_trampoline_ex_end:\n"
+);
+
+asm(
+	"	.align 16\n"
+	"ftrace_shared_hotpatch_trampoline_exrl:\n"
+	"	lmg	%r0,%r1,2(%r1)\n"
+	"	.insn	ril,0xc60000000000,%r0,0f\n" /* exrl */
+	"	j	.\n"
+	"0:	br	%r1\n"
+	"ftrace_shared_hotpatch_trampoline_exrl_end:\n"
+);
+#endif /* CONFIG_EXPOLINE */
+
+#ifdef CONFIG_MODULES
+static char *ftrace_plt;
+
+asm(
+	"	.data\n"
+	"ftrace_plt_template:\n"
+	"	basr	%r1,%r0\n"
+	"	lg	%r1,0f-.(%r1)\n"
+	"	br	%r1\n"
+	"0:	.quad	ftrace_caller\n"
+	"ftrace_plt_template_end:\n"
+	"	.previous\n"
+);
+#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_ex;
+		tend = ftrace_shared_hotpatch_trampoline_ex_end;
+		if (test_facility(35)) { /* exrl */
+			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 ftrace_shared_hotpatch_trampoline(NULL);
+}
+
+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;
+}
 
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 		       unsigned long addr)
@@ -49,11 +175,45 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	return 0;
 }
 
+static void ftrace_generate_nop_insn(struct ftrace_insn *insn)
+{
+	/* brcl 0,0 */
+	insn->opc = 0xc004;
+	insn->disp = 0;
+}
+
+static void ftrace_generate_call_insn(struct ftrace_insn *insn,
+				      unsigned long ip)
+{
+	unsigned long target;
+
+	/* brasl r0,ftrace_caller */
+	target = FTRACE_ADDR;
+#ifdef CONFIG_MODULES
+	if (is_module_addr((void *)ip))
+		target = (unsigned long)ftrace_plt;
+#endif /* CONFIG_MODULES */
+	insn->opc = 0xc005;
+	insn->disp = (target - ip) / 2;
+}
+
+static void brcl_disable(void *brcl)
+{
+	u8 op = 0x04; /* set mask field to zero */
+
+	s390_kernel_write((char *)brcl + 1, &op, sizeof(op));
+}
+
 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
 	struct ftrace_insn orig, new, old;
 
+	if (ftrace_shared_hotpatch_trampoline(NULL)) {
+		brcl_disable((void *)rec->ip);
+		return 0;
+	}
+
 	if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
 		return -EFAULT;
 	/* Replace ftrace call with a nop. */
@@ -67,10 +227,22 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 	return 0;
 }
 
+static void brcl_enable(void *brcl)
+{
+	u8 op = 0xf4; /* set mask field to all ones */
+
+	s390_kernel_write((char *)brcl + 1, &op, sizeof(op));
+}
+
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
 	struct ftrace_insn orig, new, old;
 
+	if (ftrace_shared_hotpatch_trampoline(NULL)) {
+		brcl_enable((void *)rec->ip);
+		return 0;
+	}
+
 	if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
 		return -EFAULT;
 	/* Replace nop with an ftrace call. */
@@ -95,22 +267,44 @@ int __init ftrace_dyn_arch_init(void)
 	return 0;
 }
 
+void arch_ftrace_update_code(int command)
+{
+	if (ftrace_shared_hotpatch_trampoline(NULL))
+		ftrace_modify_all_code(command);
+	else
+		ftrace_run_stop_machine(command);
+}
+
+static void __ftrace_sync(void *dummy)
+{
+}
+
+int ftrace_arch_code_modify_post_process(void)
+{
+	if (ftrace_shared_hotpatch_trampoline(NULL)) {
+		/* Send SIGP to the other CPUs, so they see the new code. */
+		smp_call_function(__ftrace_sync, NULL, 1);
+	}
+	return 0;
+}
+
 #ifdef CONFIG_MODULES
 
 static int __init ftrace_plt_init(void)
 {
-	unsigned int *ip;
+	const char *start, *end;
 
-	ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
+	ftrace_plt = 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);
+
+	start = ftrace_shared_hotpatch_trampoline(&end);
+	if (!start) {
+		start = ftrace_plt_template;
+		end = ftrace_plt_template_end;
+	}
+	memcpy(ftrace_plt, start, end - start);
+	set_memory_ro((unsigned long)ftrace_plt, 1);
 	return 0;
 }
 device_initcall(ftrace_plt_init);
@@ -147,17 +341,13 @@ NOKPROBE_SYMBOL(prepare_ftrace_return);
  */
 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));
+	brcl_disable(__va(ftrace_graph_caller));
 	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));
+	brcl_enable(__va(ftrace_graph_caller));
 	return 0;
 }