On Thu, 2023-03-02 at 13:48 +0100, Borislav Petkov wrote: > On Mon, Feb 27, 2023 at 02:29:30PM -0800, Rick Edgecombe wrote: > > diff --git a/arch/x86/include/asm/pgtable_types.h > > b/arch/x86/include/asm/pgtable_types.h > > index 0646ad00178b..56b374d1bffb 100644 > > --- a/arch/x86/include/asm/pgtable_types.h > > +++ b/arch/x86/include/asm/pgtable_types.h > > @@ -21,7 +21,8 @@ > > #define _PAGE_BIT_SOFTW2 10 /* " */ > > #define _PAGE_BIT_SOFTW3 11 /* " */ > > #define _PAGE_BIT_PAT_LARGE 12 /* On 2MB or 1GB pages */ > > -#define _PAGE_BIT_SOFTW4 58 /* available for programmer > > */ > > +#define _PAGE_BIT_SOFTW4 57 /* available for programmer > > */ > > +#define _PAGE_BIT_SOFTW5 58 /* available for programmer > > */ > > #define _PAGE_BIT_PKEY_BIT0 59 /* Protection Keys, bit 1/4 > > */ > > #define _PAGE_BIT_PKEY_BIT1 60 /* Protection Keys, bit 2/4 > > */ > > #define _PAGE_BIT_PKEY_BIT2 61 /* Protection Keys, bit 3/4 > > */ > > @@ -34,6 +35,15 @@ > > #define _PAGE_BIT_SOFT_DIRTY _PAGE_BIT_SOFTW3 /* software dirty > > tracking */ > > #define _PAGE_BIT_DEVMAP _PAGE_BIT_SOFTW4 > > > > +/* > > + * Indicates a Saved Dirty bit page. > > + */ > > +#ifdef CONFIG_X86_USER_SHADOW_STACK > > +#define _PAGE_BIT_SAVED_DIRTY _PAGE_BIT_SOFTW5 /* > > Saved Dirty bit */ > > +#else > > +#define _PAGE_BIT_SAVED_DIRTY 0 > > +#endif > > + > > /* If _PAGE_BIT_PRESENT is clear, we use these: */ > > /* - if the user mapped it with PROT_NONE; pte_present gives true > > */ > > #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL > > @@ -117,6 +127,25 @@ > > #define _PAGE_SOFTW4 (_AT(pteval_t, 0)) > > #endif > > > > +/* > > + * The hardware requires shadow stack to be Write=0,Dirty=1. > > However, > > + * there are valid cases where the kernel might create read-only > > PTEs that > > + * are dirty (e.g., fork(), mprotect(), uffd-wp(), soft-dirty > > tracking). In > > + * this case, the _PAGE_SAVED_DIRTY bit is used instead of the HW- > > dirty bit, > > + * to avoid creating a wrong "shadow stack" PTEs. Such PTEs have > > + * (Write=0,SavedDirty=1,Dirty=0) set. > > + * > > + * Note that on processors without shadow stack support, the > > .git/rebase-apply/patch:154: trailing whitespace. > * Note that on processors without shadow stack support, the > warning: 1 line adds whitespace errors. > > Hm, apparently git checks for that too - not only trailing empty > lines. Weird. And oops on the space. Just wondering how checkpatch missed this. It didn't, just was in a pile of false positives on that patch and I didn't notice it in there.
