Messages in this thread Patch in this message | | | From | Deepak Gupta <> | Subject | [RFC PATCH 08/12] riscv: dynamic (zicfiss) shadow call stack support | Date | Mon, 8 Apr 2024 23:10:39 -0700 |
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Adding support for dynamic shadow call stack on riscv. zicfiss ISA extn. enables protection for shadow stack against stray writes. This patch enables scs_* macros to use zicfiss shadow stack pointer (CSR_SSP) instead of relying on `gp`.
Since zicfiss based shadow stack needs to have correct encoding set in PTE init shadow stack can't be established too early. It has to be setup after `setup_vm` is called. Thus `scs_load_init_stack` is noped out if CONFIG_DYNAMIC_SCS is selected.
Adds `arch_scs_store` that can be used in generic scs magic store routine.
Signed-off-by: Deepak Gupta <debug@rivosinc.com> --- arch/riscv/include/asm/asm.h | 2 +- arch/riscv/include/asm/scs.h | 47 +++++++++++++++++++++++++++++------- arch/riscv/kernel/entry.S | 14 +++++------ arch/riscv/kernel/head.S | 4 +-- 4 files changed, 48 insertions(+), 19 deletions(-)
diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h index 776354895b81..0304978ea4e4 100644 --- a/arch/riscv/include/asm/asm.h +++ b/arch/riscv/include/asm/asm.h @@ -109,7 +109,7 @@ REG_L \dst, 0(\dst) .endm -#ifdef CONFIG_SHADOW_CALL_STACK +#if defined(CONFIG_SHADOW_CALL_STACK) && !defined(CONFIG_DYNAMIC_SCS) /* gp is used as the shadow call stack pointer instead */ .macro load_global_pointer .endm diff --git a/arch/riscv/include/asm/scs.h b/arch/riscv/include/asm/scs.h index 0e45db78b24b..14ef539922c2 100644 --- a/arch/riscv/include/asm/scs.h +++ b/arch/riscv/include/asm/scs.h @@ -9,46 +9,75 @@ /* Load init_shadow_call_stack to gp. */ .macro scs_load_init_stack +#ifndef CONFIG_DYNAMIC_SCS la gp, init_shadow_call_stack XIP_FIXUP_OFFSET gp +#endif .endm /* Load the per-CPU IRQ shadow call stack to gp. */ -.macro scs_load_irq_stack tmp +.macro scs_load_irq_stack tmp tmp1 +#ifdef CONFIG_DYNAMIC_SCS + load_per_cpu \tmp1, irq_shadow_call_stack_ptr, \tmp + li \tmp, 4096 + add \tmp, \tmp, \tmp1 + csrw CSR_SSP, \tmp +#else load_per_cpu gp, irq_shadow_call_stack_ptr, \tmp +#endif .endm /* Load task_scs_sp(current) to gp. */ -.macro scs_load_current +.macro scs_load_current tmp +#ifdef CONFIG_DYNAMIC_SCS + REG_L \tmp, TASK_TI_SCS_SP(tp) + csrw CSR_SSP, \tmp +#else REG_L gp, TASK_TI_SCS_SP(tp) +#endif .endm /* Load task_scs_sp(current) to gp, but only if tp has changed. */ -.macro scs_load_current_if_task_changed prev +.macro scs_load_current_if_task_changed prev tmp beq \prev, tp, _skip_scs - scs_load_current + scs_load_current \tmp _skip_scs: .endm /* Save gp to task_scs_sp(current). */ -.macro scs_save_current +.macro scs_save_current tmp +#ifdef CONFIG_DYNAMIC_SCS + csrr \tmp, CSR_SSP + REG_S \tmp, TASK_TI_SCS_SP(tp) +#else REG_S gp, TASK_TI_SCS_SP(tp) +#endif .endm #else /* CONFIG_SHADOW_CALL_STACK */ .macro scs_load_init_stack .endm -.macro scs_load_irq_stack tmp +.macro scs_load_irq_stack tmp tmp1 .endm -.macro scs_load_current +.macro scs_load_current tmp .endm -.macro scs_load_current_if_task_changed prev +.macro scs_load_current_if_task_changed prev tmp .endm -.macro scs_save_current +.macro scs_save_current tmp .endm #endif /* CONFIG_SHADOW_CALL_STACK */ #endif /* __ASSEMBLY__ */ +#ifdef CONFIG_DYNAMIC_SCS +#define arch_scs_store(ss_addr, magic_val) \ + asm volatile ("ssamoswap.d %0, %2, %1" \ + : "=r" (magic_val), "+A" (*ss_addr) \ + : "r" (magic_val) \ + : "memory") +#else +#define arch_scs_store(ss_addr, magic_val) +#endif + #endif /* _ASM_SCS_H */ diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index a35050a3e0ea..0262b46ab064 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -81,7 +81,7 @@ SYM_CODE_START(handle_exception) load_global_pointer /* Load the kernel shadow call stack pointer if coming from userspace */ - scs_load_current_if_task_changed s5 + scs_load_current_if_task_changed s5 t0 #ifdef CONFIG_RISCV_ISA_V_PREEMPTIVE move a0, sp @@ -135,7 +135,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception) REG_S s0, TASK_TI_KERNEL_SP(tp) /* Save the kernel shadow call stack pointer */ - scs_save_current + scs_save_current t0 /* * Save TP into the scratch register , so we can find the kernel data @@ -252,8 +252,8 @@ SYM_FUNC_START(call_on_irq_stack) addi s0, sp, STACKFRAME_SIZE_ON_STACK /* Switch to the per-CPU shadow call stack */ - scs_save_current - scs_load_irq_stack t0 + scs_save_current t0 + scs_load_irq_stack t0 t1 /* Switch to the per-CPU IRQ stack and call the handler */ load_per_cpu t0, irq_stack_ptr, t1 @@ -263,7 +263,7 @@ SYM_FUNC_START(call_on_irq_stack) jalr a1 /* Switch back to the thread shadow call stack */ - scs_load_current + scs_load_current t0 /* Switch back to the thread stack and restore ra and s0 */ addi sp, s0, -STACKFRAME_SIZE_ON_STACK @@ -305,7 +305,7 @@ SYM_FUNC_START(__switch_to) REG_S s10, TASK_THREAD_S10_RA(a3) REG_S s11, TASK_THREAD_S11_RA(a3) /* Save the kernel shadow call stack pointer */ - scs_save_current + scs_save_current t0 /* Restore context from next->thread */ REG_L ra, TASK_THREAD_RA_RA(a4) REG_L sp, TASK_THREAD_SP_RA(a4) @@ -324,7 +324,7 @@ SYM_FUNC_START(__switch_to) /* The offset of thread_info in task_struct is zero. */ move tp, a1 /* Switch to the next shadow call stack */ - scs_load_current + scs_load_current t0 ret SYM_FUNC_END(__switch_to) diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index 6c311517c3b5..bc248c137c90 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -164,7 +164,7 @@ secondary_start_sbi: call relocate_enable_mmu #endif call .Lsetup_trap_vector - scs_load_current + scs_load_current t0 lui t2, 0x1 tail smp_callin #endif /* CONFIG_SMP */ @@ -313,7 +313,7 @@ SYM_CODE_START(_start_kernel) la tp, init_task la sp, init_thread_union + THREAD_SIZE addi sp, sp, -PT_SIZE_ON_STACK - scs_load_current + scs_load_current t0 #ifdef CONFIG_KASAN call kasan_early_init -- 2.43.2
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