From patchwork series 421684

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=421684

arch/powerpc/Kconfig

@@ -269,6 +269,7 @@ config PPC
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
 	select HAVE_PERF_USER_STACK_DUMP
+	select HAVE_RETHOOK			if KPROBES
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE
 	select HAVE_RSEQ

arch/powerpc/kernel/Makefile

@@ -139,6 +139,7 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o
 obj-$(CONFIG_OPTPROBES)		+= optprobes.o optprobes_head.o
 obj-$(CONFIG_KPROBES_ON_FTRACE)	+= kprobes-ftrace.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o
+obj-$(CONFIG_RETHOOK)           += rethook.o
 obj-$(CONFIG_PPC_UDBG_16550)	+= legacy_serial.o udbg_16550.o
 obj-$(CONFIG_SWIOTLB)		+= dma-swiotlb.o
 obj-$(CONFIG_ARCH_HAS_DMA_SET_MASK) += dma-mask.o

arch/powerpc/kernel/kprobes.c

@@ -228,16 +228,6 @@ static nokprobe_inline void set_current_kprobe(struct kprobe *p, struct pt_regs
 	kcb->kprobe_saved_msr = regs->msr;
 }
 
-void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)
-{
-	ri->ret_addr = (kprobe_opcode_t *)regs->link;
-	ri->fp = NULL;
-
-	/* Replace the return addr with trampoline addr */
-	regs->link = (unsigned long)__kretprobe_trampoline;
-}
-NOKPROBE_SYMBOL(arch_prepare_kretprobe);
-
 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 {
 	int ret;
@@ -394,49 +384,6 @@ int kprobe_handler(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(kprobe_handler);
 
-/*
- * Function return probe trampoline:
- * 	- init_kprobes() establishes a probepoint here
- * 	- When the probed function returns, this probe
- * 		causes the handlers to fire
- */
-asm(".global __kretprobe_trampoline\n"
-	".type __kretprobe_trampoline, @function\n"
-	"__kretprobe_trampoline:\n"
-	"nop\n"
-	"blr\n"
-	".size __kretprobe_trampoline, .-__kretprobe_trampoline\n");
-
-/*
- * Called when the probe at kretprobe trampoline is hit
- */
-static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
-{
-	unsigned long orig_ret_address;
-
-	orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
-	/*
-	 * We get here through one of two paths:
-	 * 1. by taking a trap -> kprobe_handler() -> here
-	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
-	 *
-	 * When going back through (1), we need regs->nip to be setup properly
-	 * as it is used to determine the return address from the trap.
-	 * For (2), since nip is not honoured with optprobes, we instead setup
-	 * the link register properly so that the subsequent 'blr' in
-	 * __kretprobe_trampoline jumps back to the right instruction.
-	 *
-	 * For nip, we should set the address to the previous instruction since
-	 * we end up emulating it in kprobe_handler(), which increments the nip
-	 * again.
-	 */
-	regs_set_return_ip(regs, orig_ret_address - 4);
-	regs->link = orig_ret_address;
-
-	return 0;
-}
-NOKPROBE_SYMBOL(trampoline_probe_handler);
-
 /*
  * Called after single-stepping.  p->addr is the address of the
  * instruction whose first byte has been replaced by the "breakpoint"
@@ -539,19 +486,9 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 }
 NOKPROBE_SYMBOL(kprobe_fault_handler);
 
-static struct kprobe trampoline_p = {
-	.addr = (kprobe_opcode_t *) &__kretprobe_trampoline,
-	.pre_handler = trampoline_probe_handler
-};
-
-int __init arch_init_kprobes(void)
-{
-	return register_kprobe(&trampoline_p);
-}
-
 int arch_trampoline_kprobe(struct kprobe *p)
 {
-	if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
+	if (p->addr == (kprobe_opcode_t *)&arch_rethook_trampoline)
 		return 1;
 
 	return 0;

arch/powerpc/kernel/optprobes.c

@@ -56,7 +56,7 @@ static unsigned long can_optimize(struct kprobe *p)
 	 * has a 'nop' instruction, which can be emulated.
 	 * So further checks can be skipped.
 	 */
-	if (p->addr == (kprobe_opcode_t *)&__kretprobe_trampoline)
+	if (p->addr == (kprobe_opcode_t *)&arch_rethook_trampoline)
 		return addr + sizeof(kprobe_opcode_t);
 
 	/*

arch/powerpc/kernel/rethook.c

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PowerPC implementation of rethook. This depends on kprobes.
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+
+/*
+ * Function return trampoline:
+ *     - init_kprobes() establishes a probepoint here
+ *     - When the probed function returns, this probe
+ *         causes the handlers to fire
+ */
+asm(".global arch_rethook_trampoline\n"
+	".type arch_rethook_trampoline, @function\n"
+	"arch_rethook_trampoline:\n"
+	"nop\n"
+	"blr\n"
+	".size arch_rethook_trampoline, .-arch_rethook_trampoline\n");
+
+/*
+ * Called when the probe at kretprobe trampoline is hit
+ */
+static int trampoline_rethook_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	return !rethook_trampoline_handler(regs, regs->gpr[1]);
+}
+NOKPROBE_SYMBOL(trampoline_rethook_handler);
+
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+	rh->ret_addr = regs->link;
+	rh->frame = regs->gpr[1];
+
+	/* Replace the return addr with trampoline addr */
+	regs->link = (unsigned long)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
+
+/* This is called from rethook_trampoline_handler(). */
+void arch_rethook_fixup_return(struct pt_regs *regs, unsigned long orig_ret_address)
+{
+	/*
+	 * We get here through one of two paths:
+	 * 1. by taking a trap -> kprobe_handler() -> here
+	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
+	 *
+	 * When going back through (1), we need regs->nip to be setup properly
+	 * as it is used to determine the return address from the trap.
+	 * For (2), since nip is not honoured with optprobes, we instead setup
+	 * the link register properly so that the subsequent 'blr' in
+	 * arch_rethook_trampoline jumps back to the right instruction.
+	 *
+	 * For nip, we should set the address to the previous instruction since
+	 * we end up emulating it in kprobe_handler(), which increments the nip
+	 * again.
+	 */
+	regs_set_return_ip(regs, orig_ret_address - 4);
+	regs->link = orig_ret_address;
+}
+NOKPROBE_SYMBOL(arch_rethook_fixup_return);
+
+static struct kprobe trampoline_p = {
+	.addr = (kprobe_opcode_t *) &arch_rethook_trampoline,
+	.pre_handler = trampoline_rethook_handler
+};
+
+/* rethook initializer */
+int __init arch_init_kprobes(void)
+{
+	return register_kprobe(&trampoline_p);
+}

arch/powerpc/kernel/stacktrace.c

@@ -21,6 +21,7 @@
 #include <asm/processor.h>
 #include <linux/ftrace.h>
 #include <asm/kprobes.h>
+#include <linux/rethook.h>
 
 #include <asm/paca.h>
 
@@ -133,12 +134,13 @@ int __no_sanitize_address arch_stack_walk_reliable(stack_trace_consume_fn consum
 		 * arch-dependent code, they are generic.
 		 */
 		ip = ftrace_graph_ret_addr(task, &graph_idx, ip, stack);
-#ifdef CONFIG_KPROBES
+
 		/*
 		 * Mark stacktraces with kretprobed functions on them
 		 * as unreliable.
 		 */
-		if (ip == (unsigned long)__kretprobe_trampoline)
+#ifdef CONFIG_RETHOOK
+		if (ip == (unsigned long)arch_rethook_trampoline)
 			return -EINVAL;
 #endif