From: Rick Edgecombe <rick.p.edgecombe@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>,
Weijiang Yang <weijiang.yang@intel.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
John Allen <john.allen@amd.com>,
kcc@google.com, eranian@google.com, rppt@kernel.org,
jamorris@linux.microsoft.com, dethoma@microsoft.com,
akpm@linux-foundation.org, Andrew.Cooper3@citrix.com,
christina.schimpe@intel.com, david@redhat.com,
debug@rivosinc.com, szabolcs.nagy@arm.com
Cc: rick.p.edgecombe@intel.com, Yu-cheng Yu <yu-cheng.yu@intel.com>
Subject: [PATCH v8 16/40] x86/mm: Start actually marking _PAGE_SAVED_DIRTY
Date: Sat, 18 Mar 2023 17:15:11 -0700 [thread overview]
Message-ID: <20230319001535.23210-17-rick.p.edgecombe@intel.com> (raw)
In-Reply-To: <20230319001535.23210-1-rick.p.edgecombe@intel.com>
The recently introduced _PAGE_SAVED_DIRTY should be used instead of the
HW Dirty bit whenever a PTE is Write=0, in order to not inadvertently
create shadow stack PTEs. Update pte_mk*() helpers to do this, and apply
the same changes to pmd and pud.
For pte_modify() this is a bit trickier. It takes a "raw" pgprot_t which
was not necessarily created with any of the existing PTE bit helpers.
That means that it can return a pte_t with Write=0,Dirty=1, a shadow
stack PTE, when it did not intend to create one.
Modify it to also move _PAGE_DIRTY to _PAGE_SAVED_DIRTY. To avoid
creating Write=0,Dirty=1 PTEs, pte_modify() needs to avoid:
1. Marking Write=0 PTEs Dirty=1
2. Marking Dirty=1 PTEs Write=0
The first case cannot happen as the existing behavior of pte_modify() is to
filter out any Dirty bit passed in newprot. Handle the second case by
shifting _PAGE_DIRTY=1 to _PAGE_SAVED_DIRTY=1 if the PTE was write
protected by the pte_modify() call. Apply the same changes to
pmd_modify().
Co-developed-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Kees Cook <keescook@chromium.org>
---
v6:
- Rename _PAGE_COW to _PAGE_SAVED_DIRTY (David Hildenbrand)
- Open code _PAGE_SAVED_DIRTY part in pte_modify() (Boris)
- Change the logic so the open coded part is not too ugly
- Merge pte_modify() patch with this one because of the above
v4:
- Break part patch for better bisectability
---
arch/x86/include/asm/pgtable.h | 168 ++++++++++++++++++++++++++++-----
1 file changed, 145 insertions(+), 23 deletions(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 349fcab0405a..05dfdbdf96b4 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -124,9 +124,17 @@ 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;
+ return pte_flags(pte) & _PAGE_DIRTY_BITS;
+}
+
+static inline bool pte_shstk(pte_t pte)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK))
+ return false;
+
+ return (pte_flags(pte) & (_PAGE_RW | _PAGE_DIRTY)) == _PAGE_DIRTY;
}
static inline int pte_young(pte_t pte)
@@ -134,9 +142,18 @@ 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;
+ return pmd_flags(pmd) & _PAGE_DIRTY_BITS;
+}
+
+static inline bool pmd_shstk(pmd_t pmd)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK))
+ return false;
+
+ return (pmd_flags(pmd) & (_PAGE_RW | _PAGE_DIRTY | _PAGE_PSE)) ==
+ (_PAGE_DIRTY | _PAGE_PSE);
}
#define pmd_young pmd_young
@@ -145,9 +162,9 @@ 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;
+ return pud_flags(pud) & _PAGE_DIRTY_BITS;
}
static inline int pud_young(pud_t pud)
@@ -157,13 +174,21 @@ static inline int pud_young(pud_t pud)
static inline int pte_write(pte_t pte)
{
- return pte_flags(pte) & _PAGE_RW;
+ /*
+ * Shadow stack pages are logically writable, but do not have
+ * _PAGE_RW. Check for them separately from _PAGE_RW itself.
+ */
+ 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;
+ /*
+ * Shadow stack pages are logically writable, but do not have
+ * _PAGE_RW. Check for them separately from _PAGE_RW itself.
+ */
+ return (pmd_flags(pmd) & _PAGE_RW) || pmd_shstk(pmd);
}
#define pud_write pud_write
@@ -342,7 +367,16 @@ static inline pte_t pte_clear_saveddirty(pte_t pte)
static inline pte_t pte_wrprotect(pte_t pte)
{
- return pte_clear_flags(pte, _PAGE_RW);
+ pte = pte_clear_flags(pte, _PAGE_RW);
+
+ /*
+ * Blindly clearing _PAGE_RW might accidentally create
+ * a shadow stack PTE (Write=0,Dirty=1). Move the hardware
+ * dirty value to the software bit.
+ */
+ if (pte_dirty(pte))
+ pte = pte_mksaveddirty(pte);
+ return pte;
}
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
@@ -380,7 +414,7 @@ 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);
+ return pte_clear_flags(pte, _PAGE_DIRTY_BITS);
}
static inline pte_t pte_mkold(pte_t pte)
@@ -395,7 +429,19 @@ static inline pte_t pte_mkexec(pte_t pte)
static inline pte_t pte_mkdirty(pte_t pte)
{
- return pte_set_flags(pte, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+ pteval_t dirty = _PAGE_DIRTY;
+
+ /* Avoid creating Dirty=1,Write=0 PTEs */
+ if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && !pte_write(pte))
+ dirty = _PAGE_SAVED_DIRTY;
+
+ return pte_set_flags(pte, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_mkwrite_shstk(pte_t pte)
+{
+ /* pte_clear_saveddirty() also sets Dirty=1 */
+ return pte_clear_saveddirty(pte);
}
static inline pte_t pte_mkyoung(pte_t pte)
@@ -412,7 +458,12 @@ struct vm_area_struct;
static inline pte_t pte_mkwrite(pte_t pte, struct vm_area_struct *vma)
{
- return pte_mkwrite_kernel(pte);
+ pte = pte_mkwrite_kernel(pte);
+
+ if (pte_dirty(pte))
+ pte = pte_clear_saveddirty(pte);
+
+ return pte;
}
static inline pte_t pte_mkhuge(pte_t pte)
@@ -481,7 +532,15 @@ static inline pmd_t pmd_clear_saveddirty(pmd_t pmd)
static inline pmd_t pmd_wrprotect(pmd_t pmd)
{
- return pmd_clear_flags(pmd, _PAGE_RW);
+ pmd = pmd_clear_flags(pmd, _PAGE_RW);
+ /*
+ * 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 (pmd_dirty(pmd))
+ pmd = pmd_mksaveddirty(pmd);
+ return pmd;
}
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
@@ -508,12 +567,23 @@ 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);
+ return pmd_clear_flags(pmd, _PAGE_DIRTY_BITS);
}
static inline pmd_t pmd_mkdirty(pmd_t pmd)
{
- return pmd_set_flags(pmd, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+ pmdval_t dirty = _PAGE_DIRTY;
+
+ /* Avoid creating (HW)Dirty=1, Write=0 PMDs */
+ if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && !pmd_write(pmd))
+ dirty = _PAGE_SAVED_DIRTY;
+
+ return pmd_set_flags(pmd, dirty | _PAGE_SOFT_DIRTY);
+}
+
+static inline pmd_t pmd_mkwrite_shstk(pmd_t pmd)
+{
+ return pmd_clear_saveddirty(pmd);
}
static inline pmd_t pmd_mkdevmap(pmd_t pmd)
@@ -533,7 +603,12 @@ static inline pmd_t pmd_mkyoung(pmd_t pmd)
static inline pmd_t pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
{
- return pmd_set_flags(pmd, _PAGE_RW);
+ pmd = pmd_set_flags(pmd, _PAGE_RW);
+
+ if (pmd_dirty(pmd))
+ pmd = pmd_clear_saveddirty(pmd);
+
+ return pmd;
}
static inline pud_t pud_set_flags(pud_t pud, pudval_t set)
@@ -577,17 +652,32 @@ 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);
+ return pud_clear_flags(pud, _PAGE_DIRTY_BITS);
}
static inline pud_t pud_wrprotect(pud_t pud)
{
- return pud_clear_flags(pud, _PAGE_RW);
+ pud = pud_clear_flags(pud, _PAGE_RW);
+
+ /*
+ * 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 (pud_dirty(pud))
+ pud = pud_mksaveddirty(pud);
+ return pud;
}
static inline pud_t pud_mkdirty(pud_t pud)
{
- return pud_set_flags(pud, _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
+ pudval_t dirty = _PAGE_DIRTY;
+
+ /* Avoid creating (HW)Dirty=1, Write=0 PUDs */
+ if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && !pud_write(pud))
+ dirty = _PAGE_SAVED_DIRTY;
+
+ return pud_set_flags(pud, dirty | _PAGE_SOFT_DIRTY);
}
static inline pud_t pud_mkdevmap(pud_t pud)
@@ -607,7 +697,11 @@ static inline pud_t pud_mkyoung(pud_t pud)
static inline pud_t pud_mkwrite(pud_t pud)
{
- return pud_set_flags(pud, _PAGE_RW);
+ pud = pud_set_flags(pud, _PAGE_RW);
+
+ if (pud_dirty(pud))
+ pud = pud_clear_saveddirty(pud);
+ return pud;
}
#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
@@ -724,6 +818,8 @@ static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask);
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
pteval_t val = pte_val(pte), oldval = val;
+ bool wr_protected;
+ pte_t pte_result;
/*
* Chop off the NX bit (if present), and add the NX portion of
@@ -732,17 +828,43 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
val &= _PAGE_CHG_MASK;
val |= check_pgprot(newprot) & ~_PAGE_CHG_MASK;
val = flip_protnone_guard(oldval, val, PTE_PFN_MASK);
- return __pte(val);
+
+ pte_result = __pte(val);
+
+ /*
+ * Do the saveddirty fixup if the PTE was just write protected and
+ * it's dirty.
+ */
+ wr_protected = (oldval & _PAGE_RW) && !(val & _PAGE_RW);
+ if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && wr_protected &&
+ (val & _PAGE_DIRTY))
+ pte_result = pte_mksaveddirty(pte_result);
+
+ return pte_result;
}
static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
{
pmdval_t val = pmd_val(pmd), oldval = val;
+ bool wr_protected;
+ pmd_t pmd_result;
- val &= _HPAGE_CHG_MASK;
+ val &= (_HPAGE_CHG_MASK & ~_PAGE_DIRTY);
val |= check_pgprot(newprot) & ~_HPAGE_CHG_MASK;
val = flip_protnone_guard(oldval, val, PHYSICAL_PMD_PAGE_MASK);
- return __pmd(val);
+
+ pmd_result = __pmd(val);
+
+ /*
+ * Do the saveddirty fixup if the PMD was just write protected and
+ * it's dirty.
+ */
+ wr_protected = (oldval & _PAGE_RW) && !(val & _PAGE_RW);
+ if (cpu_feature_enabled(X86_FEATURE_USER_SHSTK) && wr_protected &&
+ (val & _PAGE_DIRTY))
+ pmd_result = pmd_mksaveddirty(pmd_result);
+
+ return pmd_result;
}
/*
--
2.17.1
next prev parent reply other threads:[~2023-03-19 0:16 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-19 0:14 [PATCH v8 00/40] Shadow stacks for userspace Rick Edgecombe
2023-03-19 0:14 ` [PATCH v8 01/40] Documentation/x86: Add CET shadow stack description Rick Edgecombe
2023-03-19 0:14 ` [PATCH v8 02/40] x86/shstk: Add Kconfig option for shadow stack Rick Edgecombe
2023-03-19 0:14 ` [PATCH v8 03/40] x86/cpufeatures: Add CPU feature flags for shadow stacks Rick Edgecombe
2023-03-19 0:14 ` [PATCH v8 04/40] x86/cpufeatures: Enable CET CR4 bit for shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 05/40] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 06/40] x86/fpu: Add helper for modifying xstate Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 07/40] x86/traps: Move control protection handler to separate file Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 08/40] x86/shstk: Add user control-protection fault handler Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 09/40] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 10/40] x86/mm: Move pmd_write(), pud_write() up in the file Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 11/40] mm: Introduce pte_mkwrite_kernel() Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 12/40] s390/mm: Introduce pmd_mkwrite_kernel() Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 13/40] mm: Make pte_mkwrite() take a VMA Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 14/40] x86/mm: Introduce _PAGE_SAVED_DIRTY Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 15/40] x86/mm: Update ptep/pmdp_set_wrprotect() for _PAGE_SAVED_DIRTY Rick Edgecombe
2023-03-19 0:15 ` Rick Edgecombe [this message]
2023-03-19 0:15 ` [PATCH v8 17/40] mm: Move VM_UFFD_MINOR_BIT from 37 to 38 Rick Edgecombe
2023-03-20 10:55 ` David Hildenbrand
2023-03-19 0:15 ` [PATCH v8 18/40] mm: Introduce VM_SHADOW_STACK for shadow stack memory Rick Edgecombe
2023-03-20 10:55 ` David Hildenbrand
2023-03-19 0:15 ` [PATCH v8 19/40] x86/mm: Check shadow stack page fault errors Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 20/40] x86/mm: Teach pte_mkwrite() about stack memory Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 21/40] mm: Add guard pages around a shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 22/40] mm/mmap: Add shadow stack pages to memory accounting Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 23/40] mm: Re-introduce vm_flags to do_mmap() Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 24/40] mm: Don't allow write GUPs to shadow stack memory Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 25/40] x86/mm: Introduce MAP_ABOVE4G Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 26/40] mm: Warn on shadow stack memory in wrong vma Rick Edgecombe
2023-03-20 11:00 ` David Hildenbrand
2023-03-19 0:15 ` [PATCH v8 27/40] x86/mm: Warn if create Write=0,Dirty=1 with raw prot Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 28/40] x86: Introduce userspace API for shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 29/40] x86/shstk: Add user-mode shadow stack support Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 30/40] x86/shstk: Handle thread shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 31/40] x86/shstk: Introduce routines modifying shstk Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 32/40] x86/shstk: Handle signals for shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 33/40] x86/shstk: Introduce map_shadow_stack syscall Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 34/40] x86/shstk: Support WRSS for userspace Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 35/40] x86: Expose thread features in /proc/$PID/status Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 36/40] x86/shstk: Wire in shadow stack interface Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 37/40] selftests/x86: Add shadow stack test Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 38/40] x86: Add PTRACE interface for shadow stack Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 39/40] x86/shstk: Add ARCH_SHSTK_UNLOCK Rick Edgecombe
2023-03-19 0:15 ` [PATCH v8 40/40] x86/shstk: Add ARCH_SHSTK_STATUS Rick Edgecombe
2023-03-19 14:00 ` [PATCH v8 00/40] Shadow stacks for userspace Borislav Petkov
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