From: Chenghao Duan duanchenghao@kylinos.cn

commit 45cb47c628dfbd1994c619f3eac271a780602826 upstream.

Refactor the register restoration sequence in the ftrace_common_return function to clearly distinguish between the logic of normal returns and direct call returns in function tracing scenarios. The logic is as follows:

1. In the case of a normal return, the execution flow returns to the traced function, and ftrace must ensure that the register data is consistent with the state when the function was entered.

ra = parent return address; t0 = traced function return address.

2. In the case of a direct call return, the execution flow jumps to the custom trampoline function, and ftrace must ensure that the register data is consistent with the state when ftrace was entered.

ra = traced function return address; t0 = parent return address.

Cc: stable@vger.kernel.org Fixes: 9cdc3b6a299c ("LoongArch: ftrace: Add direct call support") Signed-off-by: Chenghao Duan duanchenghao@kylinos.cn Signed-off-by: Huacai Chen chenhuacai@loongson.cn --- arch/loongarch/kernel/mcount_dyn.S | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S index 482aa553aa2d..5fb3a6e5e5c6 100644 --- a/arch/loongarch/kernel/mcount_dyn.S +++ b/arch/loongarch/kernel/mcount_dyn.S @@ -93,7 +93,6 @@ SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) * at the callsite, so there is no need to restore the T series regs. */ ftrace_common_return: - PTR_L ra, sp, PT_R1 PTR_L a0, sp, PT_R4 PTR_L a1, sp, PT_R5 PTR_L a2, sp, PT_R6 @@ -103,12 +102,17 @@ ftrace_common_return: PTR_L a6, sp, PT_R10 PTR_L a7, sp, PT_R11 PTR_L fp, sp, PT_R22 - PTR_L t0, sp, PT_ERA PTR_L t1, sp, PT_R13 - PTR_ADDI sp, sp, PT_SIZE bnez t1, .Ldirect + + PTR_L ra, sp, PT_R1 + PTR_L t0, sp, PT_ERA + PTR_ADDI sp, sp, PT_SIZE jr t0 .Ldirect: + PTR_L t0, sp, PT_R1 + PTR_L ra, sp, PT_ERA + PTR_ADDI sp, sp, PT_SIZE jr t1 SYM_CODE_END(ftrace_common)

@@ -155,6 +159,8 @@ SYM_CODE_END(return_to_handler)

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS SYM_CODE_START(ftrace_stub_direct_tramp) - jr t0 + move t1, ra + move ra, t0 + jr t1 SYM_CODE_END(ftrace_stub_direct_tramp) #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */