Hi Radim, On 06/05/2025 12:10, Radim Krčmář wrote:
[Ah, I missed v13 and v14, feel free to Cc me on next versions.] 2025-05-02T16:30:36-07:00, Deepak Gupta <debug@xxxxxxxxxxxx>: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) +.endmDo 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?)
The alternatives are used to create a generic kernel that contains the code for a large number of extensions and only enable it at runtime depending on the platform capabilities. This way distros can ship a single kernel that works on all platforms.
Thanks for your reviews on this series, Alex
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