Linux-arch Archive on lore.kernel.org
 help / color / Atom feed
From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: 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>,
	Borislav Petkov <bp@alien8.de>,
	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>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v14 08/26] x86/mm: Introduce _PAGE_COW
Date: Fri,  9 Oct 2020 11:32:12 -0700
Message-ID: <20201009183230.26717-9-yu-cheng.yu@intel.com> (raw)
In-Reply-To: <20201009183230.26717-1-yu-cheng.yu@intel.com>

There is essentially no room left in the x86 hardware PTEs on some OSes
(not Linux).  That left the hardware architects looking for a way to
represent a new memory type (shadow stack) within the existing bits.
They chose to repurpose a lightly-used state: Write=0,Dirty=1.

The reason it's lightly used is that Dirty=1 is normally set by hardware
and cannot normally be set by hardware on a Write=0 PTE.  Software must
normally be involved to create one of these PTEs, so software can simply
opt to not create them.

But that leaves us with a Linux problem: we need to ensure we never create
Write=0,Dirty=1 PTEs.  In places where we do create them, we need to find
an alternative way to represent them _without_ using the same hardware bit
combination.  Thus, enter _PAGE_COW.  This results in the following:

(a) A modified, copy-on-write (COW) page: (R/O + _PAGE_COW)
(b) A R/O page that has been COW'ed: (R/O + _PAGE_COW)
    The user page is in a R/O VMA, and get_user_pages() needs a writable
    copy.  The page fault handler creates a copy of the page and sets
    the new copy's PTE as R/O and _PAGE_COW.
(c) A shadow stack PTE: (R/O + _PAGE_DIRTY_HW)
(d) A shared shadow stack PTE: (R/O + _PAGE_COW)
    When a shadow stack page is being shared among processes (this happens
    at fork()), its PTE is cleared of _PAGE_DIRTY_HW, so the next shadow
    stack access causes a fault, and the page is duplicated and
    _PAGE_DIRTY_HW is set again.  This is the COW equivalent for shadow
    stack pages, even though it's copy-on-access rather than copy-on-write.
(e) A page where the processor observed a Write=1 PTE, started a write, set
    Dirty=1, but then observed a Write=0 PTE.  That's possible today, but
    will not happen on processors that support shadow stack.

Use _PAGE_COW in pte_wrprotect() and _PAGE_DIRTY_HW in pte_mkwrite().
Apply the same changes to pmd and pud.

When this patch is applied, there are six free bits left in the 64-bit PTE.
There are no more free bits in the 32-bit PTE (except for PAE) and shadow
stack is not implemented for the 32-bit kernel.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

v10:
- Change _PAGE_BIT_DIRTY_SW to _PAGE_BIT_COW, as it is used for copy-on-
  write PTEs.
- Update pte_write() and treat shadow stack as writable.
- Change *_mkdirty_shstk() to *_mkwrite_shstk() as these make shadow stack
  pages writable.
- Use bit test & shift to move _PAGE_BIT_DIRTY_HW to _PAGE_BIT_COW.
- Change static_cpu_has() to cpu_feature_enabled().
- Revise commit log.

v9:
- Remove pte_move_flags() etc. and put the logic directly in
  pte_wrprotect()/pte_mkwrite() etc.
- Change compile-time conditionals to run-time checks.
- Split out pte_modify()/pmd_modify() to a new patch.
- Update comments.
---
 arch/x86/include/asm/pgtable.h       | 120 ++++++++++++++++++++++++---
 arch/x86/include/asm/pgtable_types.h |  41 ++++++++-
 2 files changed, 150 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 86b7acd221c1..ac4ed814be96 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -122,9 +122,9 @@ extern pmdval_t early_pmd_flags;
  * The following only work if pte_present() is true.
  * Undefined behaviour if not..
  */
-static inline int pte_dirty(pte_t pte)
+static inline bool pte_dirty(pte_t pte)
 {
-	return pte_flags(pte) & _PAGE_DIRTY_HW;
+	return pte_flags(pte) & _PAGE_DIRTY_BITS;
 }
 
 
@@ -161,9 +161,9 @@ static inline int pte_young(pte_t pte)
 	return pte_flags(pte) & _PAGE_ACCESSED;
 }
 
-static inline int pmd_dirty(pmd_t pmd)
+static inline bool pmd_dirty(pmd_t pmd)
 {
-	return pmd_flags(pmd) & _PAGE_DIRTY_HW;
+	return pmd_flags(pmd) & _PAGE_DIRTY_BITS;
 }
 
 static inline int pmd_young(pmd_t pmd)
@@ -171,9 +171,9 @@ static inline int pmd_young(pmd_t pmd)
 	return pmd_flags(pmd) & _PAGE_ACCESSED;
 }
 
-static inline int pud_dirty(pud_t pud)
+static inline bool pud_dirty(pud_t pud)
 {
-	return pud_flags(pud) & _PAGE_DIRTY_HW;
+	return pud_flags(pud) & _PAGE_DIRTY_BITS;
 }
 
 static inline int pud_young(pud_t pud)
@@ -183,6 +183,12 @@ static inline int pud_young(pud_t pud)
 
 static inline int pte_write(pte_t pte)
 {
+	/*
+	 * If _PAGE_DIRTY_HW is set, the PTE must either have
+	 * _PAGE_RW or be a shadow stack PTE, which is logically writable.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pte_flags(pte) & (_PAGE_RW | _PAGE_DIRTY_HW);
 	return pte_flags(pte) & _PAGE_RW;
 }
 
@@ -334,7 +340,7 @@ static inline pte_t pte_clear_uffd_wp(pte_t pte)
 
 static inline pte_t pte_mkclean(pte_t pte)
 {
-	return pte_clear_flags(pte, _PAGE_DIRTY_HW);
+	return pte_clear_flags(pte, _PAGE_DIRTY_BITS);
 }
 
 static inline pte_t pte_mkold(pte_t pte)
@@ -344,6 +350,17 @@ static inline pte_t pte_mkold(pte_t pte)
 
 static inline pte_t pte_wrprotect(pte_t pte)
 {
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PTE (RW=0,Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		pte.pte |= (pte.pte & _PAGE_DIRTY_HW) >>
+			   _PAGE_BIT_DIRTY_HW << _PAGE_BIT_COW;
+		pte = pte_clear_flags(pte, _PAGE_DIRTY_HW);
+	}
+
 	return pte_clear_flags(pte, _PAGE_RW);
 }
 
@@ -354,6 +371,18 @@ static inline pte_t pte_mkexec(pte_t pte)
 
 static inline pte_t pte_mkdirty(pte_t pte)
 {
+	pteval_t dirty = _PAGE_DIRTY_HW;
+
+	/* Avoid creating (HW)Dirty=1,Write=0 PTEs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !pte_write(pte))
+		dirty = _PAGE_COW;
+
+	return pte_set_flags(pte, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_mkwrite_shstk(pte_t pte)
+{
+	pte = pte_clear_flags(pte, _PAGE_COW);
 	return pte_set_flags(pte, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY);
 }
 
@@ -364,6 +393,13 @@ static inline pte_t pte_mkyoung(pte_t pte)
 
 static inline pte_t pte_mkwrite(pte_t pte)
 {
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		if (pte_flags(pte) & _PAGE_COW) {
+			pte = pte_clear_flags(pte, _PAGE_COW);
+			pte = pte_set_flags(pte, _PAGE_DIRTY_HW);
+		}
+	}
+
 	return pte_set_flags(pte, _PAGE_RW);
 }
 
@@ -435,16 +471,41 @@ static inline pmd_t pmd_mkold(pmd_t pmd)
 
 static inline pmd_t pmd_mkclean(pmd_t pmd)
 {
-	return pmd_clear_flags(pmd, _PAGE_DIRTY_HW);
+	return pmd_clear_flags(pmd, _PAGE_DIRTY_BITS);
 }
 
 static inline pmd_t pmd_wrprotect(pmd_t pmd)
 {
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PMD (RW=0,Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		pmdval_t v = native_pmd_val(pmd);
+
+		v |= (v & _PAGE_DIRTY_HW) >> _PAGE_BIT_DIRTY_HW <<
+		     _PAGE_BIT_COW;
+		pmd = pmd_clear_flags(__pmd(v), _PAGE_DIRTY_HW);
+	}
+
 	return pmd_clear_flags(pmd, _PAGE_RW);
 }
 
 static inline pmd_t pmd_mkdirty(pmd_t pmd)
 {
+	pmdval_t dirty = _PAGE_DIRTY_HW;
+
+	/* Avoid creating (HW)Dirty=1,Write=0 PMDs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pmd_flags(pmd) & _PAGE_RW))
+		dirty = _PAGE_COW;
+
+	return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pmd_t pmd_mkwrite_shstk(pmd_t pmd)
+{
+	pmd = pmd_clear_flags(pmd, _PAGE_COW);
 	return pmd_set_flags(pmd, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY);
 }
 
@@ -465,6 +526,13 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd)
 
 static inline pmd_t pmd_mkwrite(pmd_t pmd)
 {
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		if (pmd_flags(pmd) & _PAGE_COW) {
+			pmd = pmd_clear_flags(pmd, _PAGE_COW);
+			pmd = pmd_set_flags(pmd, _PAGE_DIRTY_HW);
+		}
+	}
+
 	return pmd_set_flags(pmd, _PAGE_RW);
 }
 
@@ -489,17 +557,36 @@ static inline pud_t pud_mkold(pud_t pud)
 
 static inline pud_t pud_mkclean(pud_t pud)
 {
-	return pud_clear_flags(pud, _PAGE_DIRTY_HW);
+	return pud_clear_flags(pud, _PAGE_DIRTY_BITS);
 }
 
 static inline pud_t pud_wrprotect(pud_t pud)
 {
+	/*
+	 * Blindly clearing _PAGE_RW might accidentally create
+	 * a shadow stack PUD (RW=0,Dirty=1).  Move the hardware
+	 * dirty value to the software bit.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		pudval_t v = native_pud_val(pud);
+
+		v |= (v & _PAGE_DIRTY_HW) >> _PAGE_BIT_DIRTY_HW <<
+		     _PAGE_BIT_COW;
+		pud = pud_clear_flags(__pud(v), _PAGE_DIRTY_HW);
+	}
+
 	return pud_clear_flags(pud, _PAGE_RW);
 }
 
 static inline pud_t pud_mkdirty(pud_t pud)
 {
-	return pud_set_flags(pud, _PAGE_DIRTY_HW | _PAGE_SOFT_DIRTY);
+	pudval_t dirty = _PAGE_DIRTY_HW;
+
+	/* Avoid creating (HW)Dirty=1,Write=0 PUDs */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK) && !(pud_flags(pud) & _PAGE_RW))
+		dirty = _PAGE_COW;
+
+	return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY);
 }
 
 static inline pud_t pud_mkdevmap(pud_t pud)
@@ -519,6 +606,13 @@ static inline pud_t pud_mkyoung(pud_t pud)
 
 static inline pud_t pud_mkwrite(pud_t pud)
 {
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK)) {
+		if (pud_flags(pud) & _PAGE_COW) {
+			pud = pud_clear_flags(pud, _PAGE_COW);
+			pud = pud_set_flags(pud, _PAGE_DIRTY_HW);
+		}
+	}
+
 	return pud_set_flags(pud, _PAGE_RW);
 }
 
@@ -1132,6 +1226,12 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 #define pmd_write pmd_write
 static inline int pmd_write(pmd_t pmd)
 {
+	/*
+	 * If _PAGE_DIRTY_HW is set, then the PMD must either have
+	 * _PAGE_RW or be a shadow stack PMD, which is logically writable.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_SHSTK))
+		return pmd_flags(pmd) & (_PAGE_RW | _PAGE_DIRTY_HW);
 	return pmd_flags(pmd) & _PAGE_RW;
 }
 
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 5f31f1c407b9..75362df8b226 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -23,7 +23,8 @@
 #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 */
@@ -36,6 +37,16 @@
 #define _PAGE_BIT_SOFT_DIRTY	_PAGE_BIT_SOFTW3 /* software dirty tracking */
 #define _PAGE_BIT_DEVMAP	_PAGE_BIT_SOFTW4
 
+/*
+ * This bit indicates a copy-on-write page, and is different from
+ * _PAGE_BIT_SOFT_DIRTY, which tracks which pages a task writes to.
+ */
+#ifdef CONFIG_X86_64
+#define _PAGE_BIT_COW		_PAGE_BIT_SOFTW5 /* copy-on-write */
+#else
+#define _PAGE_BIT_COW		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 +128,34 @@
 #define _PAGE_DEVMAP	(_AT(pteval_t, 0))
 #endif
 
+/*
+ * _PAGE_COW is used to separate R/O and copy-on-write PTEs created by
+ * software from the shadow stack PTE setting required by the hardware:
+ * (a) A modified, copy-on-write (COW) page: (R/O + _PAGE_COW)
+ * (b) A R/O page that has been COW'ed: (R/O +_PAGE_COW)
+ *     The user page is in a R/O VMA, and get_user_pages() needs a
+ *     writable copy.  The page fault handler creates a copy of the page
+ *     and sets the new copy's PTE as R/O and _PAGE_COW.
+ * (c) A shadow stack PTE: (R/O + _PAGE_DIRTY_HW)
+ * (d) A shared (copy-on-access) shadow stack PTE: (R/O + _PAGE_COW)
+ *     When a shadow stack page is being shared among processes (this
+ *     happens at fork()), its PTE is cleared of _PAGE_DIRTY_HW, so the
+ *     next shadow stack access causes a fault, and the page is duplicated
+ *     and _PAGE_DIRTY_HW is set again.  This is the COW equivalent for
+ *     shadow stack pages, even though it's copy-on-access rather than
+ *     copy-on-write.
+ * (e) A page where the processor observed a Write=1 PTE, started a write,
+ *     set Dirty=1, but then observed a Write=0 PTE.  That's possible
+ *     today, but will not happen on processors that support shadow stack.
+ */
+#ifdef CONFIG_X86_SHADOW_STACK_USER
+#define _PAGE_COW	(_AT(pteval_t, 1) << _PAGE_BIT_COW)
+#else
+#define _PAGE_COW	(_AT(pteval_t, 0))
+#endif
+
+#define _PAGE_DIRTY_BITS (_PAGE_DIRTY_HW | _PAGE_COW)
+
 #define _PAGE_PROTNONE	(_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
 
 /*
-- 
2.21.0


  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09 18:32 [PATCH v14 00/26] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 01/26] Documentation/x86: Add CET description Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 03/26] x86/fpu/xstate: Introduce CET MSR XSAVES supervisor states Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 04/26] x86/cet: Add control-protection fault handler Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 05/26] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 06/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 07/26] x86/mm: Remove _PAGE_DIRTY_HW from kernel RO pages Yu-cheng Yu
2020-10-09 18:32 ` Yu-cheng Yu [this message]
2020-10-09 18:32 ` [PATCH v14 09/26] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 10/26] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY_HW to _PAGE_COW Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 12/26] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 13/26] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 14/26] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 15/26] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 16/26] mm: Add guard pages around a shadow stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 17/26] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 18/26] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2020-10-09 18:32 ` [PATCH v14 19/26] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2020-10-09 18:45 ` [PATCH v14 00/26] Control-flow Enforcement: Shadow Stack Yu, Yu-cheng
2020-10-12 15:38 Yu-cheng Yu
2020-10-12 15:38 ` [PATCH v14 08/26] x86/mm: Introduce _PAGE_COW Yu-cheng Yu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201009183230.26717-9-yu-cheng.yu@intel.com \
    --to=yu-cheng.yu@intel.com \
    --cc=Dave.Martin@arm.com \
    --cc=arnd@arndb.de \
    --cc=bp@alien8.de \
    --cc=bsingharora@gmail.com \
    --cc=corbet@lwn.net \
    --cc=dave.hansen@linux.intel.com \
    --cc=esyr@redhat.com \
    --cc=fweimer@redhat.com \
    --cc=gorcunov@gmail.com \
    --cc=hjl.tools@gmail.com \
    --cc=hpa@zytor.com \
    --cc=jannh@google.com \
    --cc=keescook@chromium.org \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-doc@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=luto@kernel.org \
    --cc=mike.kravetz@oracle.com \
    --cc=mingo@redhat.com \
    --cc=nadav.amit@gmail.com \
    --cc=oleg@redhat.com \
    --cc=pavel@ucw.cz \
    --cc=pengfei.xu@intel.com \
    --cc=peterz@infradead.org \
    --cc=ravi.v.shankar@intel.com \
    --cc=rdunlap@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=vedvyas.shanbhogue@intel.com \
    --cc=weijiang.yang@intel.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-arch Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arch/0 linux-arch/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arch linux-arch/ https://lore.kernel.org/linux-arch \
		linux-arch@vger.kernel.org
	public-inbox-index linux-arch

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-arch


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git