Re: [PATCH v15 05/27] riscv: usercfi state for task and save/restore of CSR_SSP on trap entry/exit

[Ah, I missed v13 and v14, feel free to Cc me on next versions.]

2025-05-02T16:30:36-07:00, Deepak Gupta debug@rivosinc.com:

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S @@ -91,6 +91,32 @@ +.macro save_userssp tmp, status

• ALTERNATIVE("nops(4)",

• __stringify(				\
  

• andi \tmp, \status, SR_SPP;		\
  

• bnez \tmp, skip_ssp_save;		\
  

• csrrw \tmp, CSR_SSP, x0;		\
  

• REG_S \tmp, TASK_TI_USER_SSP(tp);	\
  

• skip_ssp_save:),
  

• 0,
  

• RISCV_ISA_EXT_ZICFISS,
  

• CONFIG_RISCV_USER_CFI)
  

+.endm

+.macro restore_userssp tmp

• ALTERNATIVE("nops(2)",

• __stringify(				\
  

• REG_L \tmp, TASK_TI_USER_SSP(tp);	\
  

• csrw CSR_SSP, \tmp),
  

• 0,
  

• RISCV_ISA_EXT_ZICFISS,
  

• CONFIG_RISCV_USER_CFI)
  

+.endm

Do we need to emit the nops when CONFIG_RISCV_USER_CFI isn't selected?

(Why not put #ifdef CONFIG_RISCV_USER_CFI around the ALTERNATIVES?)

Thanks.