[PATCH v16 07/27] riscv mm: manufacture shadow stack pte

Deepak Gupta
2025-05-23T05:31:40Z

This patch implements creating shadow stack pte (on riscv). Creating
shadow stack PTE on riscv means that clearing RWX and then setting W=1.

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
arch/riscv/include/asm/pgtable.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index dba257cc4e2d..f21c888f59eb 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -433,6 +433,11 @@ static inline pte_t pte_mkwrite_novma(pte_t pte)
return __pte(pte_val(pte) | _PAGE_WRITE);
}

+static inline pte_t pte_mkwrite_shstk(pte_t pte)
+{
+ return __pte((pte_val(pte) & ~(_PAGE_LEAF)) | _PAGE_WRITE);
+}
+
/* static inline pte_t pte_mkexec(pte_t pte) */

static inline pte_t pte_mkdirty(pte_t pte)
@@ -778,6 +783,11 @@ static inline pmd_t pmd_mkwrite_novma(pmd_t pmd)
return pte_pmd(pte_mkwrite_novma(pmd_pte(pmd)));
}

+static inline pmd_t pmd_mkwrite_shstk(pmd_t pte)
+{
+ return __pmd((pmd_val(pte) & ~(_PAGE_LEAF)) | _PAGE_WRITE);
+}
+
static inline pmd_t pmd_wrprotect(pmd_t pmd)
{
return pte_pmd(pte_wrprotect(pmd_pte(pmd)));

--
2.43.0