Commit c68c2ef9 authored by Deepak Gupta's avatar Deepak Gupta Committed by Paul Walmsley
Browse files

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: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: default avatarZong Li <zong.li@sifive.com>
Signed-off-by: default avatarDeepak Gupta <debug@rivosinc.com>
Tested-by: Andreas Korb <andreas.korb@aisec.fraunhofer.de> # QEMU, custom CVA6
Tested-by: default avatarValentin 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: default avatarPaul Walmsley <pjw@kernel.org>
parent f56ffb8a

arch/riscv/include/asm/pgtable.h

+7 −0
Original line number Diff line number Diff line
@@ -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)));

arch/riscv/mm/pgtable.c

+16 −0
Original line number Diff line number Diff line
@@ -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);

}