[PATCH] arm64: probes: Fix incorrect bl/blr address and register usage

From: Jeremy Linton

Date: Thu Sep 18 2025 - 13:54:28 EST


The pt_regs registers are 64-bit on arm64, and should be u64 when
manipulated. Correct this so that we aren't truncating the address
during br/blr sequences.

Fixes: efb07ac534e2 ("arm64: probes: Add GCS support to bl/blr/ret")
Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
---
arch/arm64/kernel/probes/simulate-insn.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/probes/simulate-insn.c b/arch/arm64/kernel/probes/simulate-insn.c
index 97ed4db75417..89fbeb32107e 100644
--- a/arch/arm64/kernel/probes/simulate-insn.c
+++ b/arch/arm64/kernel/probes/simulate-insn.c
@@ -145,7 +145,7 @@ void __kprobes
simulate_br_blr(u32 opcode, long addr, struct pt_regs *regs)
{
int xn = (opcode >> 5) & 0x1f;
- int b_target = get_x_reg(regs, xn);
+ u64 b_target = get_x_reg(regs, xn);

if (((opcode >> 21) & 0x3) == 1)
if (update_lr(regs, addr + 4))
@@ -160,7 +160,7 @@ simulate_ret(u32 opcode, long addr, struct pt_regs *regs)
u64 ret_addr;
int err = 0;
int xn = (opcode >> 5) & 0x1f;
- unsigned long r_target = get_x_reg(regs, xn);
+ u64 r_target = get_x_reg(regs, xn);

if (user_mode(regs) && task_gcs_el0_enabled(current)) {
ret_addr = pop_user_gcs(&err);
--
2.50.1