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[v9,07/26] riscv mm: manufacture shadow stack pte

Message ID 20250204-v5_user_cfi_series-v9-7-b37a49c5205c@rivosinc.com (mailing list archive)
State New
Headers show
Series riscv control-flow integrity for usermode | expand

Commit Message

Deepak Gupta Feb. 5, 2025, 1:21 a.m. UTC 
This patch implements creating shadow stack pte (on riscv). Creating
shadow stack PTE on riscv means that clearing RWX and then setting W=1.

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

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 8c528cd7347a..ede43185ffdf 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -421,6 +421,11 @@  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)
@@ -749,6 +754,11 @@  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)));