s390/kprobes: replace kretprobe with rethook

That's an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
Replace kretprobe with rethook on x86") to s390.

Replaces the kretprobe code with rethook on s390. With this patch,
kretprobe on s390 uses the rethook instead of kretprobe specific
trampoline code.

Tested-by: Ilya Leoshkevich <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/s390/kernel/rethook.c b/arch/s390/kernel/rethook.c
new file mode 100644
index 000000000000..f2b6237bc35d
--- /dev/null
+++ b/arch/s390/kernel/rethook.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/rethook.h>
+#include <linux/kprobes.h>
+
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+	rh->ret_addr = regs->gprs[14];
+	rh->frame = regs->gprs[15];
+
+	/* Replace the return addr with trampoline addr */
+	regs->gprs[14] = (unsigned long)&arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
+
+void arch_rethook_fixup_return(struct pt_regs *regs,
+			       unsigned long correct_ret_addr)
+{
+	/* Replace fake return address with real one. */
+	regs->gprs[14] = correct_ret_addr;
+}
+NOKPROBE_SYMBOL(arch_rethook_fixup_return);
+
+/*
+ * Called from arch_rethook_trampoline
+ */
+unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+	return rethook_trampoline_handler(regs, regs->gprs[15]);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+/* assembler function that handles the rethook must not be probed itself */
+NOKPROBE_SYMBOL(arch_rethook_trampoline);