Re: [PATCH v21 08/26] x86/mm: Introduce _PAGE_COW

From: Borislav Petkov <bp@alien8.de>
To: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>,
	Pengfei Xu <pengfei.xu@intel.com>,
	Haitao Huang <haitao.huang@intel.com>
Subject: Re: [PATCH v21 08/26] x86/mm: Introduce _PAGE_COW
Date: Wed, 3 Mar 2021 18:26:52 +0100	[thread overview]
Message-ID: <20210303172652.GF22305@zn.tnic> (raw)
In-Reply-To: <167f58a3-20ef-7210-1d66-cf25f4a9bbef@intel.com>

On Tue, Mar 02, 2021 at 03:46:31PM -0800, Yu, Yu-cheng wrote:
> There is a problem of doing that: pmd_write() is defined after this
> function.  Maybe we can declare it first, or leave this as-is?

Or a third option: you lift those two functions in a prepatch and then
in this patch use them directly.

Combined diff ontop:

---

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1a6c0784af0a..b7e4d031ce22 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -209,6 +209,18 @@ static inline int pte_write(pte_t pte)
 	return (pte_flags(pte) & _PAGE_RW) || pte_shstk(pte);
 }
 
+#define pmd_write pmd_write
+static inline int pmd_write(pmd_t pmd)
+{
+	return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
+}
+
+#define pud_write pud_write
+static inline int pud_write(pud_t pud)
+{
+	return pud_flags(pud) & _PAGE_RW;
+}
+
 static inline int pte_huge(pte_t pte)
 {
 	return pte_flags(pte) & _PAGE_PSE;
@@ -540,7 +552,7 @@ static inline pmd_t pmd_mkdirty(pmd_t pmd)
 	pmdval_t dirty = _PAGE_DIRTY;
 
 	/* Avoid creating (HW)Dirty=1, Write=0 PMDs */
-	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pmd_flags(pmd) & _PAGE_RW))
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pmd_write(pmd))
 		dirty = _PAGE_COW;
 
 	return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY);
@@ -636,7 +648,7 @@ static inline pud_t pud_mkdirty(pud_t pud)
 	pudval_t dirty = _PAGE_DIRTY;
 
 	/* Avoid creating (HW)Dirty=1, Write=0 PUDs */
-	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pud_flags(pud) & _PAGE_RW))
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pud_write(pud))
 		dirty = _PAGE_COW;
 
 	return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY);
@@ -1273,12 +1285,6 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 				  unsigned long address, pmd_t *pmdp);
 
 
-#define pmd_write pmd_write
-static inline int pmd_write(pmd_t pmd)
-{
-	return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
-}
-
 #define __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
 static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, unsigned long addr,
 				       pmd_t *pmdp)
@@ -1300,12 +1306,6 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 	clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp);
 }
 
-#define pud_write pud_write
-static inline int pud_write(pud_t pud)
-{
-	return pud_flags(pud) & _PAGE_RW;
-}
-
 #ifndef pmdp_establish
 #define pmdp_establish pmdp_establish
 static inline pmd_t pmdp_establish(struct vm_area_struct *vma,

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

