Re: [PATCH v3 11/29] riscv mm: manufacture shadow stack pte

[Alexandre Ghiti]

On 04/04/2024 01:34, Deepak Gupta wrote:

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 <de...@rivosinc.com>
---
  arch/riscv/include/asm/pgtable.h | 12 ++++++++++++
  1 file changed, 12 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 4d5983bc6766..6362407f1e83 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -408,6 +408,12 @@ 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)

+{
+       /* shadow stack on risc-v is XWR = 010. Clear everything and only set 
_PAGE_WRITE */

Nit: Not sure the comment is necessary

+       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)

@@ -693,6 +699,12 @@ 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)

+{
+       /* shadow stack on risc-v is XWR = 010. Clear everything and only set 
_PAGE_WRITE */
+       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)));

Otherwise:

Reviewed-by: Alexandre Ghiti <alexgh...@rivosinc.com>

Thanks,

Alex