riscv/mm: teach pte_mkwrite to manufacture shadow stack PTEs

pte_mkwrite() creates PTEs with WRITE encodings for the underlying
architecture.  The underlying architecture can have two types of
writeable mappings: one that can be written using regular store
instructions, and another one that can only be written using
specialized store instructions (like shadow stack stores).
pte_mkwrite can select write PTE encoding based on VMA range (i.e.
VM_SHADOW_STACK)

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
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-v23-8-b55691eacf4f@rivosinc.com
[pjw@kernel.org: cleaned up patch description]
Signed-off-by: Paul Walmsley <pjw@kernel.org>

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 153a692a56406e8e5595b5ad5e1622e48c721e97..7f81eecac243c649391f95deb83f63d387d51e5b 100644 (file)
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -451,6 +451,10 @@ static inline pte_t pte_swp_clear_uffd_wp(pte_t pte)
 
 /* static inline pte_t pte_mkread(pte_t pte) */
 
+struct vm_area_struct;
+pte_t pte_mkwrite(pte_t pte, struct vm_area_struct *vma);
+#define pte_mkwrite pte_mkwrite
+
 static inline pte_t pte_mkwrite_novma(pte_t pte)
 {
        return __pte(pte_val(pte) | _PAGE_WRITE);
@@ -839,6 +843,9 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd)
        return pte_pmd(pte_mkyoung(pmd_pte(pmd)));
 }
 
+pmd_t pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
+#define pmd_mkwrite pmd_mkwrite
+
 static inline pmd_t pmd_mkwrite_novma(pmd_t pmd)
 {
        return pte_pmd(pte_mkwrite_novma(pmd_pte(pmd)));

diff --git a/arch/riscv/mm/pgtable.c b/arch/riscv/mm/pgtable.c
index 807c0a0de18275b1a33bcd41d7dce27ee7de0662..e0ab04d721cc1df965bd02c4e4533cc656ee3958 100644 (file)
--- a/arch/riscv/mm/pgtable.c
+++ b/arch/riscv/mm/pgtable.c
@@ -163,3 +163,19 @@ pud_t pudp_invalidate(struct vm_area_struct *vma, unsigned long address,
        return old;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+pte_t pte_mkwrite(pte_t pte, struct vm_area_struct *vma)
+{
+       if (vma->vm_flags & VM_SHADOW_STACK)
+               return pte_mkwrite_shstk(pte);
+
+       return pte_mkwrite_novma(pte);
+}
+
+pmd_t pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
+{
+       if (vma->vm_flags & VM_SHADOW_STACK)
+               return pmd_mkwrite_shstk(pmd);
+
+       return pmd_mkwrite_novma(pmd);
+}