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riscv/mm: teach pte_mkwrite to manufacture shadow stack PTEs

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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>
This commit is contained in:
Deepak Gupta 2026-01-25 21:09:53 -07:00 committed by Paul Walmsley
parent f56ffb8ada
commit c68c2ef9d6
2 changed files with 23 additions and 0 deletions
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7
arch/riscv/include/asm/pgtable.h
View File

@ -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)));

16
arch/riscv/mm/pgtable.c
View File

@ -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);
}