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Add syntax highlighting to code blocks
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@ -85,7 +85,7 @@ For example, consider this
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[patch](http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=54a20552e1eae07aa240fa370a0293e006b5faed).
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which has the following hunk:
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```
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```diff
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@@ -3270,6 +3277,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
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[SVM_EXIT_EXCP_BASE + PF_VECTOR] = pf_interception,
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[SVM_EXIT_EXCP_BASE + NM_VECTOR] = nm_interception,
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@ -103,7 +103,7 @@ AC_VECTOR]`. That change is incompatible with kpatch.
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Looking at the source file, we can see that this function pointer is only
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accessed by a single function, `handle_exit()`:
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```
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```c
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if (exit_code >= ARRAY_SIZE(svm_exit_handlers)
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|| !svm_exit_handlers[exit_code]) {
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WARN_ONCE(1, "svm: unexpected exit reason 0x%x\n", exit_code);
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@ -117,7 +117,7 @@ accessed by a single function, `handle_exit()`:
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So an easy solution here is to just change the code to manually check for the
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new case before looking in the data structure:
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```
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```diff
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@@ -3580,6 +3580,9 @@ static int handle_exit(struct kvm_vcpu *vcpu)
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return 1;
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}
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@ -149,7 +149,7 @@ but to do so through kpatch-build, `kpatch-macros.h` defines the following:
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A pre-patch callback routine has the following signature:
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```
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```c
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static int callback(patch_object *obj) { }
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KPATCH_PRE_PATCH_CALLBACK(callback);
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```
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@ -161,7 +161,7 @@ section below.
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Post-patch, pre-unpatch, and post-unpatch callback routines all share the
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following signature:
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```
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```c
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static void callback(patch_object *obj) { }
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KPATCH_POST_PATCH_CALLBACK(callback); /* or */
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KPATCH_PRE_UNPATCH_CALLBACK(callback); /* or */
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@ -201,7 +201,7 @@ Example: a kpatch fix for CVE-2016-5389 could utilize the
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`KPATCH_PRE_PATCH_CALLBACK` and `KPATCH_POST_UNPATCH_CALLBACK` macros to modify
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variable `sysctl_tcp_challenge_ack_limit` in-place:
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```
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```diff
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+#include "kpatch-macros.h"
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+
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+static bool kpatch_write = false;
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@ -250,7 +250,7 @@ provide unique ID enumerations per kpatch as needed.
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`klp_shadow_alloc()` returns a pointer to the shadow variable, so we can
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dereference and make assignments as usual. In this patch chunk, the shadow
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`newpid` is allocated then assigned to a rolling `ctr` counter value:
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```
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```patch
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diff --git a/kernel/fork.c b/kernel/fork.c
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index 9bff3b28c357..18374fd35bd9 100644
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--- a/kernel/fork.c
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@ -285,7 +285,7 @@ modifies `task_context_switch_counts()` to fetch the shadow variable
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associated with the current `struct task_struct *p` object and a
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`KPATCH_SHADOW_NEWPID ID`. As in the previous patch chunk, the shadow
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variable pointer may be accessed as an ordinary pointer type:
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```
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```patch
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diff --git a/fs/proc/array.c b/fs/proc/array.c
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index 39684c79e8e2..fe0259d057a3 100644
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--- a/fs/proc/array.c
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@ -315,7 +315,7 @@ index 39684c79e8e2..fe0259d057a3 100644
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A shadow variable is freed by calling `klp_shadow_free()` and providing
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the object / enum ID combination. Once freed, the shadow variable is no
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longer safe to access:
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```
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```patch
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diff --git a/kernel/exit.c b/kernel/exit.c
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index 148a7842928d..44b6fe61e912 100644
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--- a/kernel/exit.c
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@ -369,7 +369,7 @@ also required to allocate/free a shadow variable with enum ID
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`KPATCH_SHADOW_REQS_ACTIVE_V2` whenever a new `struct kioctx` is
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created/released. No values are ever assigned to the shadow variable.)
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```
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```patch
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diff --git a/fs/aio.c b/fs/aio.c
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index ebd06fd0de89..6a33b73c9107 100644
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--- a/fs/aio.c
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@ -387,7 +387,7 @@ index ebd06fd0de89..6a33b73c9107 100644
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Shadow variable existence can be verified before applying the *new* data
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semantic of the associated object:
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```
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```diff
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@@ -678,6 +681,8 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
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put_rq:
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/* everything turned out well, dispose of the aiocb. */
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@ -401,7 +401,7 @@ semantic of the associated object:
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Likewise, shadow variable non-existence can be tested to continue applying the
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*old* data semantic:
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```
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```diff
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@@ -310,7 +312,8 @@ static void free_ioctx(struct kioctx *ctx)
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avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
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@ -430,7 +430,7 @@ critical sections throughout `net/mac80211/sta_info.c`.
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When allocating a new `struct sta_info`, allocate a corresponding shadow
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variable large enough to hold a `spinlock_t` instance, then initialize the
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spinlock:
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```
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```patch
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diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
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index decd30c1e290..758533dda4d8 100644
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--- a/net/mac80211/sta_info.c
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@ -468,7 +468,7 @@ index decd30c1e290..758533dda4d8 100644
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Patched code can reference the shadow variable associated with a given `struct
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sta_info` to determine and apply the correct locking semantic for that
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instance:
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```
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```patch
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diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
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index 97a02d3f7d87..0edb0ed8dc60 100644
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--- a/net/mac80211/tx.c
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@ -599,7 +599,7 @@ redirect existing functions, so "removed" functions will continue to exist in
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kernel address space as effectively dead code.
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That means this patch (source code removal of `cmdline_proc_show`):
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```
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```patch
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diff -Nupr src.orig/fs/proc/cmdline.c src/fs/proc/cmdline.c
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--- src.orig/fs/proc/cmdline.c 2016-11-30 19:39:49.317737234 +0000
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+++ src/fs/proc/cmdline.c 2016-11-30 19:39:52.696737234 +0000
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@ -628,7 +628,7 @@ diff -Nupr src.orig/fs/proc/cmdline.c src/fs/proc/cmdline.c
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```
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will generate an equivalent kpatch module to this patch (dead
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`cmdline_proc_show` left in source):
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```
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```patch
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diff -Nupr src.orig/fs/proc/cmdline.c src/fs/proc/cmdline.c
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--- src.orig/fs/proc/cmdline.c 2016-11-30 19:39:49.317737234 +0000
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+++ src/fs/proc/cmdline.c 2016-11-30 19:39:52.696737234 +0000
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@ -680,7 +680,7 @@ logic which doesn't store the static variable in the `.data..read_mostly`
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section.
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For example, a `pr_warn_once()` can be replaced with:
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```
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```c
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static bool print_once;
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...
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if (!print_once) {
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@ -695,7 +695,7 @@ inline implies notrace
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The linux kernel defines its own version of "inline" in
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include/linux/compiler_types.h which includes "notrace" as well:
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```
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```c
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#if !defined(CONFIG_OPTIMIZE_INLINING)
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#define inline inline __attribute__((__always_inline__)) __gnu_inline \
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__inline_maybe_unused notrace
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@ -710,7 +710,7 @@ to kpatch-build errors like the following:
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1. `__tcp_mtu_to_mss()` is marked as inline:
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```
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```c
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net/ipv4/tcp_output.c:
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/* Calculate MSS not accounting any TCP options. */
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@ -722,7 +722,7 @@ static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
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function-section. Then kpatch-build notices that it doesn't have an
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fentry/mcount call:
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```
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```console
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% kpatch-build ...
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tcp_output.o: function __tcp_mtu_to_mss has no fentry/mcount call, unable to patch
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@ -730,7 +730,7 @@ tcp_output.o: function __tcp_mtu_to_mss has no fentry/mcount call, unable to pat
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3. a peek at the generated code:
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```
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```c
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Disassembly of section .text.__tcp_mtu_to_mss:
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0000000000000000 <__tcp_mtu_to_mss>:
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@ -764,7 +764,7 @@ compiled default.
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The current workaround is to remove the jump label by explictly checking
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the static key:
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```
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```c
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DEFINE_STATIC_KEY_TRUE(true_key);
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DEFINE_STATIC_KEY_FALSE(false_key);
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