diff options
| author | Deepak Gupta <debug@rivosinc.com> | 2026-01-25 21:09:55 -0700 |
|---|---|---|
| committer | Paul Walmsley <pjw@kernel.org> | 2026-01-29 02:38:40 -0700 |
| commit | 41213bf2ae6c936f51a79986b37f95da9ecbb970 (patch) | |
| tree | c0a3e34c70940969493e139928372ed9ed704802 /arch/riscv/kernel | |
| parent | c9b859c4d8f56c014b3d5fbd1bcfb916c34955a1 (diff) | |
riscv: enable kernel access to shadow stack memory via the FWFT SBI call
The kernel has to perform shadow stack operations on the user shadow stack.
During signal delivery and sigreturn, the shadow stack token must be
created and validated respectively. Thus shadow stack access for the kernel
must be enabled.
In the future, when kernel shadow stacks are enabled, they must be
enabled as early as possible for better coverage and to prevent any
imbalance between the regular stack and the shadow stack. After
'relocate_enable_mmu' has completed, this is the earliest that it can
be enabled.
Reviewed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Tested-by: Andreas Korb <andreas.korb@aisec.fraunhofer.de> # QEMU, custom CVA6
Tested-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>
Link: https://patch.msgid.link/20251112-v5_user_cfi_series-v23-22-b55691eacf4f@rivosinc.com
[pjw@kernel.org: updated to apply; cleaned up commit message]
Signed-off-by: Paul Walmsley <pjw@kernel.org>
Diffstat (limited to 'arch/riscv/kernel')
| -rw-r--r-- | arch/riscv/kernel/asm-offsets.c | 6 | ||||
| -rw-r--r-- | arch/riscv/kernel/head.S | 27 |
2 files changed, 33 insertions, 0 deletions
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c index 8a2b2656cb2f..af827448a609 100644 --- a/arch/riscv/kernel/asm-offsets.c +++ b/arch/riscv/kernel/asm-offsets.c @@ -533,4 +533,10 @@ void asm_offsets(void) DEFINE(FREGS_A6, offsetof(struct __arch_ftrace_regs, a6)); DEFINE(FREGS_A7, offsetof(struct __arch_ftrace_regs, a7)); #endif +#ifdef CONFIG_RISCV_SBI + 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); +#endif } diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index bdf3352acf4c..9c99c5ad6fe8 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -15,6 +15,7 @@ #include <asm/image.h> #include <asm/scs.h> #include <asm/xip_fixup.h> +#include <asm/usercfi.h> #include "efi-header.S" __HEAD @@ -170,6 +171,19 @@ secondary_start_sbi: call relocate_enable_mmu #endif call .Lsetup_trap_vector +#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_USER_CFI) + 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 + beqz a0, 1f + la a1, riscv_nousercfi + li a0, CMDLINE_DISABLE_RISCV_USERCFI_BCFI + REG_S a0, (a1) +1: +#endif scs_load_current call smp_callin #endif /* CONFIG_SMP */ @@ -330,6 +344,19 @@ SYM_CODE_START(_start_kernel) la tp, init_task la sp, init_thread_union + THREAD_SIZE addi sp, sp, -PT_SIZE_ON_STACK +#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_USER_CFI) + 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 + beqz a0, 1f + la a1, riscv_nousercfi + li a0, CMDLINE_DISABLE_RISCV_USERCFI_BCFI + REG_S a0, (a1) +1: +#endif scs_load_current #ifdef CONFIG_KASAN |