On Mon, Mar 10, 2025 at 11:44 PM Deepak Gupta <debug@xxxxxxxxxxxx> wrote: > > Kernel will have to perform shadow stack operations on user shadow stack. > Like during signal delivery and sigreturn, shadow stack token must be > created and validated respectively. Thus shadow stack access for kernel > must be enabled. > > In future when kernel shadow stacks are enabled for linux kernel, it must > be enabled as early as possible for better coverage and prevent imbalance > between regular stack and shadow stack. After `relocate_enable_mmu` has > been done, this is as early as possible it can enabled. > > Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx> > --- > arch/riscv/kernel/asm-offsets.c | 4 ++++ > arch/riscv/kernel/head.S | 12 ++++++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c > index 0c188aaf3925..21f99d5757b6 100644 > --- a/arch/riscv/kernel/asm-offsets.c > +++ b/arch/riscv/kernel/asm-offsets.c > @@ -515,4 +515,8 @@ void asm_offsets(void) > DEFINE(FREGS_A6, offsetof(struct __arch_ftrace_regs, a6)); > DEFINE(FREGS_A7, offsetof(struct __arch_ftrace_regs, a7)); > #endif > + DEFINE(SBI_EXT_FWFT, SBI_EXT_FWFT); > + DEFINE(SBI_EXT_FWFT_SET, SBI_EXT_FWFT_SET); > + DEFINE(SBI_FWFT_SHADOW_STACK, SBI_FWFT_SHADOW_STACK); > + DEFINE(SBI_FWFT_SET_FLAG_LOCK, SBI_FWFT_SET_FLAG_LOCK); > } > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S > index 356d5397b2a2..6244408ca917 100644 > --- a/arch/riscv/kernel/head.S > +++ b/arch/riscv/kernel/head.S > @@ -164,6 +164,12 @@ secondary_start_sbi: > call relocate_enable_mmu > #endif > call .Lsetup_trap_vector > + li a7, SBI_EXT_FWFT > + li a6, SBI_EXT_FWFT_SET > + li a0, SBI_FWFT_SHADOW_STACK > + li a1, 1 /* enable supervisor to access shadow stack access */ > + li a2, SBI_FWFT_SET_FLAG_LOCK > + ecall > scs_load_current > call smp_callin > #endif /* CONFIG_SMP */ > @@ -320,6 +326,12 @@ SYM_CODE_START(_start_kernel) > la tp, init_task > la sp, init_thread_union + THREAD_SIZE > addi sp, sp, -PT_SIZE_ON_STACK > + li a7, SBI_EXT_FWFT > + li a6, SBI_EXT_FWFT_SET > + li a0, SBI_FWFT_SHADOW_STACK > + li a1, 1 /* enable supervisor to access shadow stack access */ > + li a2, SBI_FWFT_SET_FLAG_LOCK > + ecall > scs_load_current > > #ifdef CONFIG_KASAN > LGTM. Reviewed-by: Zong Li <zong.li@xxxxxxxxxx> > -- > 2.34.1 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-riscv
