From: Jeremy Linton <jeremy.linton@arm.com>
Date: Mon, 25 Aug 2025 03:34:15 +0000 (-0500)
Subject: arm64: probes: Break ret out from bl/blr
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=47687aa4d9c91a9d9b1dbae40c242cd291030bd9;p=users%2Fhch%2Fmisc.git

arm64: probes: Break ret out from bl/blr

Prepare for GCS by breaking RET out into its own function, where
it makes more sense to encapsulate the new behavior independent
from the branch instructions.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---

diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
index 6438bf62e753..4137cc5ef031 100644
--- a/arch/arm64/kernel/probes/decode-insn.c
+++ b/arch/arm64/kernel/probes/decode-insn.c
@@ -108,9 +108,10 @@ arm_probe_decode_insn(u32 insn, struct arch_probe_insn *api)
 	    aarch64_insn_is_bl(insn)) {
 		api->handler = simulate_b_bl;
 	} else if (aarch64_insn_is_br(insn) ||
-	    aarch64_insn_is_blr(insn) ||
-	    aarch64_insn_is_ret(insn)) {
-		api->handler = simulate_br_blr_ret;
+		aarch64_insn_is_blr(insn)) {
+		api->handler = simulate_br_blr;
+	} else if (aarch64_insn_is_ret(insn)) {
+		api->handler = simulate_ret;
 	} else {
 		/*
 		 * Instruction cannot be stepped out-of-line and we don't
diff --git a/arch/arm64/kernel/probes/simulate-insn.c b/arch/arm64/kernel/probes/simulate-insn.c
index 4c6d2d712fbd..09a0b36122d0 100644
--- a/arch/arm64/kernel/probes/simulate-insn.c
+++ b/arch/arm64/kernel/probes/simulate-insn.c
@@ -126,7 +126,7 @@ simulate_b_cond(u32 opcode, long addr, struct pt_regs *regs)
 }
 
 void __kprobes
-simulate_br_blr_ret(u32 opcode, long addr, struct pt_regs *regs)
+simulate_br_blr(u32 opcode, long addr, struct pt_regs *regs)
 {
 	int xn = (opcode >> 5) & 0x1f;
 
@@ -138,6 +138,14 @@ simulate_br_blr_ret(u32 opcode, long addr, struct pt_regs *regs)
 		set_x_reg(regs, 30, addr + 4);
 }
 
+void __kprobes
+simulate_ret(u32 opcode, long addr, struct pt_regs *regs)
+{
+	int xn = (opcode >> 5) & 0x1f;
+
+	instruction_pointer_set(regs, get_x_reg(regs, xn));
+}
+
 void __kprobes
 simulate_cbz_cbnz(u32 opcode, long addr, struct pt_regs *regs)
 {
diff --git a/arch/arm64/kernel/probes/simulate-insn.h b/arch/arm64/kernel/probes/simulate-insn.h
index efb2803ec943..9e772a292d56 100644
--- a/arch/arm64/kernel/probes/simulate-insn.h
+++ b/arch/arm64/kernel/probes/simulate-insn.h
@@ -11,7 +11,8 @@
 void simulate_adr_adrp(u32 opcode, long addr, struct pt_regs *regs);
 void simulate_b_bl(u32 opcode, long addr, struct pt_regs *regs);
 void simulate_b_cond(u32 opcode, long addr, struct pt_regs *regs);
-void simulate_br_blr_ret(u32 opcode, long addr, struct pt_regs *regs);
+void simulate_br_blr(u32 opcode, long addr, struct pt_regs *regs);
+void simulate_ret(u32 opcode, long addr, struct pt_regs *regs);
 void simulate_cbz_cbnz(u32 opcode, long addr, struct pt_regs *regs);
 void simulate_tbz_tbnz(u32 opcode, long addr, struct pt_regs *regs);
 void simulate_ldr_literal(u32 opcode, long addr, struct pt_regs *regs);