1 files changed, 304 insertions, 91 deletions

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 8618faa82e6d..a650f5e11fc5 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -15,8 +15,134 @@
 #include <asm/debug-monitors.h>
 #include <asm/ftrace.h>
 #include <asm/insn.h>
+#include <asm/patching.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
+struct fregs_offset {
+	const char *name;
+	int offset;
+};
+
+#define FREGS_OFFSET(n, field)				\
+{							\
+	.name = n,					\
+	.offset = offsetof(struct ftrace_regs, field),	\
+}
+
+static const struct fregs_offset fregs_offsets[] = {
+	FREGS_OFFSET("x0", regs[0]),
+	FREGS_OFFSET("x1", regs[1]),
+	FREGS_OFFSET("x2", regs[2]),
+	FREGS_OFFSET("x3", regs[3]),
+	FREGS_OFFSET("x4", regs[4]),
+	FREGS_OFFSET("x5", regs[5]),
+	FREGS_OFFSET("x6", regs[6]),
+	FREGS_OFFSET("x7", regs[7]),
+	FREGS_OFFSET("x8", regs[8]),
+
+	FREGS_OFFSET("x29", fp),
+	FREGS_OFFSET("x30", lr),
+	FREGS_OFFSET("lr", lr),
+
+	FREGS_OFFSET("sp", sp),
+	FREGS_OFFSET("pc", pc),
+};
+
+int ftrace_regs_query_register_offset(const char *name)
+{
+	for (int i = 0; i < ARRAY_SIZE(fregs_offsets); i++) {
+		const struct fregs_offset *roff = &fregs_offsets[i];
+		if (!strcmp(roff->name, name))
+			return roff->offset;
+	}
+
+	return -EINVAL;
+}
+#endif
+
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+	/*
+	 * When using mcount, addr is the address of the mcount call
+	 * instruction, and no adjustment is necessary.
+	 */
+	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
+		return addr;
+
+	/*
+	 * When using patchable-function-entry without pre-function NOPS, addr
+	 * is the address of the first NOP after the function entry point.
+	 *
+	 * The compiler has either generated:
+	 *
+	 * addr+00:	func:	NOP		// To be patched to MOV X9, LR
+	 * addr+04:		NOP		// To be patched to BL <caller>
+	 *
+	 * Or:
+	 *
+	 * addr-04:		BTI	C
+	 * addr+00:	func:	NOP		// To be patched to MOV X9, LR
+	 * addr+04:		NOP		// To be patched to BL <caller>
+	 *
+	 * We must adjust addr to the address of the NOP which will be patched
+	 * to `BL <caller>`, which is at `addr + 4` bytes in either case.
+	 *
+	 */
+	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return addr + AARCH64_INSN_SIZE;
+
+	/*
+	 * When using patchable-function-entry with pre-function NOPs, addr is
+	 * the address of the first pre-function NOP.
+	 *
+	 * Starting from an 8-byte aligned base, the compiler has either
+	 * generated:
+	 *
+	 * addr+00:		NOP		// Literal (first 32 bits)
+	 * addr+04:		NOP		// Literal (last 32 bits)
+	 * addr+08:	func:	NOP		// To be patched to MOV X9, LR
+	 * addr+12:		NOP		// To be patched to BL <caller>
+	 *
+	 * Or:
+	 *
+	 * addr+00:		NOP		// Literal (first 32 bits)
+	 * addr+04:		NOP		// Literal (last 32 bits)
+	 * addr+08:	func:	BTI	C
+	 * addr+12:		NOP		// To be patched to MOV X9, LR
+	 * addr+16:		NOP		// To be patched to BL <caller>
+	 *
+	 * We must adjust addr to the address of the NOP which will be patched
+	 * to `BL <caller>`, which is at either addr+12 or addr+16 depending on
+	 * whether there is a BTI.
+	 */
+
+	if (!IS_ALIGNED(addr, sizeof(unsigned long))) {
+		WARN_RATELIMIT(1, "Misaligned patch-site %pS\n",
+			       (void *)(addr + 8));
+		return 0;
+	}
+
+	/* Skip the NOPs placed before the function entry point */
+	addr += 2 * AARCH64_INSN_SIZE;
+
+	/* Skip any BTI */
+	if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) {
+		u32 insn = le32_to_cpu(*(__le32 *)addr);
+
+		if (aarch64_insn_is_bti(insn)) {
+			addr += AARCH64_INSN_SIZE;
+		} else if (insn != aarch64_insn_gen_nop()) {
+			WARN_RATELIMIT(1, "unexpected insn in patch-site %pS: 0x%08x\n",
+				       (void *)addr, insn);
+		}
+	}
+
+	/* Skip the first NOP after function entry */
+	addr += AARCH64_INSN_SIZE;
+
+	return addr;
+}
 
-#ifdef CONFIG_DYNAMIC_FTRACE
 /*
  * Replace a single instruction, which may be a branch or NOP.
  * If @validate == true, a replaced instruction is checked against 'old'.
@@ -55,80 +181,181 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	unsigned long pc;
 	u32 new;
 
-	pc = (unsigned long)&ftrace_call;
+	/*
+	 * When using CALL_OPS, the function to call is associated with the
+	 * call site, and we don't have a global function pointer to update.
+	 */
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+		return 0;
+
+	pc = (unsigned long)ftrace_call;
 	new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func,
 					  AARCH64_INSN_BRANCH_LINK);
 
 	return ftrace_modify_code(pc, 0, new, false);
 }
 
-static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
+static struct plt_entry *get_ftrace_plt(struct module *mod)
 {
-#ifdef CONFIG_ARM64_MODULE_PLTS
+#ifdef CONFIG_MODULES
 	struct plt_entry *plt = mod->arch.ftrace_trampolines;
 
-	if (addr == FTRACE_ADDR)
-		return &plt[FTRACE_PLT_IDX];
-	if (addr == FTRACE_REGS_ADDR && IS_ENABLED(CONFIG_FTRACE_WITH_REGS))
-		return &plt[FTRACE_REGS_PLT_IDX];
-#endif
+	return &plt[FTRACE_PLT_IDX];
+#else
 	return NULL;
+#endif
+}
+
+static bool reachable_by_bl(unsigned long addr, unsigned long pc)
+{
+	long offset = (long)addr - (long)pc;
+
+	return offset >= -SZ_128M && offset < SZ_128M;
 }
 
 /*
- * Turn on the call to ftrace_caller() in instrumented function
+ * Find the address the callsite must branch to in order to reach '*addr'.
+ *
+ * Due to the limited range of 'BL' instructions, modules may be placed too far
+ * away to branch directly and must use a PLT.
+ *
+ * Returns true when '*addr' contains a reachable target address, or has been
+ * modified to contain a PLT address. Returns false otherwise.
  */
-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+static bool ftrace_find_callable_addr(struct dyn_ftrace *rec,
+				      struct module *mod,
+				      unsigned long *addr)
 {
 	unsigned long pc = rec->ip;
-	u32 old, new;
-	long offset = (long)pc - (long)addr;
+	struct plt_entry *plt;
 
-	if (offset < -SZ_128M || offset >= SZ_128M) {
-		struct module *mod;
-		struct plt_entry *plt;
+	/*
+	 * If a custom trampoline is unreachable, rely on the ftrace_caller
+	 * trampoline which knows how to indirectly reach that trampoline
+	 * through ops->direct_call.
+	 */
+	if (*addr != FTRACE_ADDR && !reachable_by_bl(*addr, pc))
+		*addr = FTRACE_ADDR;
 
-		if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
-			return -EINVAL;
+	/*
+	 * When the target is within range of the 'BL' instruction, use 'addr'
+	 * as-is and branch to that directly.
+	 */
+	if (reachable_by_bl(*addr, pc))
+		return true;
 
-		/*
-		 * On kernels that support module PLTs, the offset between the
-		 * branch instruction and its target may legally exceed the
-		 * range of an ordinary relative 'bl' opcode. In this case, we
-		 * need to branch via a trampoline in the module.
-		 *
-		 * NOTE: __module_text_address() must be called with preemption
-		 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
-		 * retains its validity throughout the remainder of this code.
-		 */
+	/*
+	 * When the target is outside of the range of a 'BL' instruction, we
+	 * must use a PLT to reach it. We can only place PLTs for modules, and
+	 * only when module PLT support is built-in.
+	 */
+	if (!IS_ENABLED(CONFIG_MODULES))
+		return false;
+
+	/*
+	 * 'mod' is only set at module load time, but if we end up
+	 * dealing with an out-of-range condition, we can assume it
+	 * is due to a module being loaded far away from the kernel.
+	 *
+	 * NOTE: __module_text_address() must be called with preemption
+	 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
+	 * retains its validity throughout the remainder of this code.
+	 */
+	if (!mod) {
 		preempt_disable();
 		mod = __module_text_address(pc);
 		preempt_enable();
+	}
 
-		if (WARN_ON(!mod))
-			return -EINVAL;
+	if (WARN_ON(!mod))
+		return false;
 
-		plt = get_ftrace_plt(mod, addr);
-		if (!plt) {
-			pr_err("ftrace: no module PLT for %ps\n", (void *)addr);
-			return -EINVAL;
-		}
+	plt = get_ftrace_plt(mod);
+	if (!plt) {
+		pr_err("ftrace: no module PLT for %ps\n", (void *)*addr);
+		return false;
+	}
+
+	*addr = (unsigned long)plt;
+	return true;
+}
 
-		addr = (unsigned long)plt;
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
+static const struct ftrace_ops *arm64_rec_get_ops(struct dyn_ftrace *rec)
+{
+	const struct ftrace_ops *ops = NULL;
+
+	if (rec->flags & FTRACE_FL_CALL_OPS_EN) {
+		ops = ftrace_find_unique_ops(rec);
+		WARN_ON_ONCE(!ops);
 	}
 
+	if (!ops)
+		ops = &ftrace_list_ops;
+
+	return ops;
+}
+
+static int ftrace_rec_set_ops(const struct dyn_ftrace *rec,
+			      const struct ftrace_ops *ops)
+{
+	unsigned long literal = ALIGN_DOWN(rec->ip - 12, 8);
+	return aarch64_insn_write_literal_u64((void *)literal,
+					      (unsigned long)ops);
+}
+
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, &ftrace_nop_ops);
+}
+
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec)
+{
+	return ftrace_rec_set_ops(rec, arm64_rec_get_ops(rec));
+}
+#else
+static int ftrace_rec_set_nop_ops(struct dyn_ftrace *rec) { return 0; }
+static int ftrace_rec_update_ops(struct dyn_ftrace *rec) { return 0; }
+#endif
+
+/*
+ * Turn on the call to ftrace_caller() in instrumented function
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long pc = rec->ip;
+	u32 old, new;
+	int ret;
+
+	ret = ftrace_rec_update_ops(rec);
+	if (ret)
+		return ret;
+
+	if (!ftrace_find_callable_addr(rec, NULL, &addr))
+		return -EINVAL;
+
 	old = aarch64_insn_gen_nop();
 	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
 
 	return ftrace_modify_code(pc, old, new, true);
 }
 
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS
 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
-			unsigned long addr)
+		       unsigned long addr)
 {
 	unsigned long pc = rec->ip;
 	u32 old, new;
+	int ret;
+
+	ret = ftrace_rec_set_ops(rec, arm64_rec_get_ops(rec));
+	if (ret)
+		return ret;
+
+	if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
+		return -EINVAL;
+	if (!ftrace_find_callable_addr(rec, NULL, &addr))
+		return -EINVAL;
 
 	old = aarch64_insn_gen_branch_imm(pc, old_addr,
 					  AARCH64_INSN_BRANCH_LINK);
@@ -136,7 +363,9 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 
 	return ftrace_modify_code(pc, old, new, true);
 }
+#endif
 
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
 /*
  * The compiler has inserted two NOPs before the regular function prologue.
  * All instrumented functions follow the AAPCS, so x0-x8 and x19-x30 are live,
@@ -152,7 +381,7 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
  * | NOP      | MOV X9, LR | MOV X9, LR |
  * | NOP      | NOP        | BL <entry> |
  *
- * The LR value will be recovered by ftrace_regs_entry, and restored into LR
+ * The LR value will be recovered by ftrace_caller, and restored into LR
  * before returning to the regular function prologue. When a function is not
  * being traced, the MOV is not harmful given x9 is not live per the AAPCS.
  *
@@ -163,6 +392,11 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
 {
 	unsigned long pc = rec->ip - AARCH64_INSN_SIZE;
 	u32 old, new;
+	int ret;
+
+	ret = ftrace_rec_set_nop_ops(rec);
+	if (ret)
+		return ret;
 
 	old = aarch64_insn_gen_nop();
 	new = aarch64_insn_gen_move_reg(AARCH64_INSN_REG_9,
@@ -179,54 +413,33 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
 	unsigned long pc = rec->ip;
-	bool validate = true;
 	u32 old = 0, new;
-	long offset = (long)pc - (long)addr;
-
-	if (offset < -SZ_128M || offset >= SZ_128M) {
-		u32 replaced;
+	int ret;
 
-		if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
-			return -EINVAL;
+	new = aarch64_insn_gen_nop();
 
-		/*
-		 * 'mod' is only set at module load time, but if we end up
-		 * dealing with an out-of-range condition, we can assume it
-		 * is due to a module being loaded far away from the kernel.
-		 */
-		if (!mod) {
-			preempt_disable();
-			mod = __module_text_address(pc);
-			preempt_enable();
-
-			if (WARN_ON(!mod))
-				return -EINVAL;
-		}
+	ret = ftrace_rec_set_nop_ops(rec);
+	if (ret)
+		return ret;
 
-		/*
-		 * The instruction we are about to patch may be a branch and
-		 * link instruction that was redirected via a PLT entry. In
-		 * this case, the normal validation will fail, but we can at
-		 * least check that we are dealing with a branch and link
-		 * instruction that points into the right module.
-		 */
-		if (aarch64_insn_read((void *)pc, &replaced))
-			return -EFAULT;
-
-		if (!aarch64_insn_is_bl(replaced) ||
-		    !within_module(pc + aarch64_get_branch_offset(replaced),
-				   mod))
-			return -EINVAL;
+	/*
+	 * When using mcount, callsites in modules may have been initalized to
+	 * call an arbitrary module PLT (which redirects to the _mcount stub)
+	 * rather than the ftrace PLT we'll use at runtime (which redirects to
+	 * the ftrace trampoline). We can ignore the old PLT when initializing
+	 * the callsite.
+	 *
+	 * Note: 'mod' is only set at module load time.
+	 */
+	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS) && mod)
+		return aarch64_insn_patch_text_nosync((void *)pc, new);
 
-		validate = false;
-	} else {
-		old = aarch64_insn_gen_branch_imm(pc, addr,
-						  AARCH64_INSN_BRANCH_LINK);
-	}
+	if (!ftrace_find_callable_addr(rec, mod, &addr))
+		return -EINVAL;
 
-	new = aarch64_insn_gen_nop();
+	old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
 
-	return ftrace_modify_code(pc, old, new, validate);
+	return ftrace_modify_code(pc, old, new, true);
 }
 
 void arch_ftrace_update_code(int command)
@@ -235,20 +448,12 @@ void arch_ftrace_update_code(int command)
 	ftrace_modify_all_code(command);
 }
 
-int __init ftrace_dyn_arch_init(void)
-{
-	return 0;
-}
-#endif /* CONFIG_DYNAMIC_FTRACE */
-
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 /*
  * function_graph tracer expects ftrace_return_to_handler() to be called
  * on the way back to parent. For this purpose, this function is called
  * in _mcount() or ftrace_caller() to replace return address (*parent) on
  * the call stack to return_to_handler.
- *
- * Note that @frame_pointer is used only for sanity check later.
  */
 void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 			   unsigned long frame_pointer)
@@ -266,11 +471,19 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 	 */
 	old = *parent;
 
-	if (!function_graph_enter(old, self_addr, frame_pointer, NULL))
+	if (!function_graph_enter(old, self_addr, frame_pointer,
+	    (void *)frame_pointer)) {
 		*parent = return_hooker;
+	}
 }
 
-#ifdef CONFIG_DYNAMIC_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	prepare_ftrace_return(ip, &fregs->lr, fregs->fp);
+}
+#else
 /*
  * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
  * depending on @enable.
@@ -300,5 +513,5 @@ int ftrace_disable_ftrace_graph_caller(void)
 {
 	return ftrace_modify_graph_caller(false);
 }
-#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */