From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org
Cc: peterz@infradead.org, linux-kernel@vger.kernel.org,
rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com,
jbaron@akamai.com, torvalds@linux-foundation.org,
tglx@linutronix.de, mingo@kernel.org, namit@vmware.com,
hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org,
jpoimboe@redhat.com, pbonzini@redhat.com,
mathieu.desnoyers@efficios.com, linux@rasmusvillemoes.dk
Subject: [PATCH v6 14/17] static_call: Handle tail-calls
Date: Fri, 10 Jul 2020 15:38:45 +0200 [thread overview]
Message-ID: <20200710134336.977578032@infradead.org> (raw)
In-Reply-To: 20200710133831.943894387@infradead.org
GCC can turn our static_call(name)(args...) into a tail call, in which
case we get a JMP.d32 into the trampoline (which then does a further
tail-call).
Teach objtool to recognise and mark these in .static_call_sites and
adjust the code patching to deal with this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/static_call.c | 21 ++++++++++++++++++---
include/linux/static_call.h | 4 ++--
include/linux/static_call_types.h | 7 +++++++
kernel/static_call.c | 21 +++++++++++++--------
tools/include/linux/static_call_types.h | 7 +++++++
tools/objtool/check.c | 18 +++++++++++++-----
6 files changed, 60 insertions(+), 18 deletions(-)
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -41,15 +41,30 @@ static void __static_call_transform(void
text_poke_bp(insn, code, size, NULL);
}
-void arch_static_call_transform(void *site, void *tramp, void *func)
+static inline enum insn_type __sc_insn(bool null, bool tail)
+{
+ /*
+ * Encode the following table without branches:
+ *
+ * tail null insn
+ * -----+-------+------
+ * 0 | 0 | CALL
+ * 0 | 1 | NOP
+ * 1 | 0 | JMP
+ * 1 | 1 | RET
+ */
+ return 2*tail + null;
+}
+
+void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
{
mutex_lock(&text_mutex);
if (tramp)
- __static_call_transform(tramp, func ? JMP : RET, func);
+ __static_call_transform(tramp, __sc_insn(!func, true), func);
if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site)
- __static_call_transform(site, func ? CALL : NOP, func);
+ __static_call_transform(site, __sc_insn(!func, tail), func);
mutex_unlock(&text_mutex);
}
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -103,7 +103,7 @@
/*
* Either @site or @tramp can be NULL.
*/
-extern void arch_static_call_transform(void *site, void *tramp, void *func);
+extern void arch_static_call_transform(void *site, void *tramp, void *func, bool tail);
#define STATIC_CALL_TRAMP_ADDR(name) &STATIC_CALL_TRAMP(name)
@@ -206,7 +206,7 @@ void __static_call_update(struct static_
{
cpus_read_lock();
WRITE_ONCE(key->func, func);
- arch_static_call_transform(NULL, tramp, func);
+ arch_static_call_transform(NULL, tramp, func, false);
cpus_read_unlock();
}
--- a/include/linux/static_call_types.h
+++ b/include/linux/static_call_types.h
@@ -17,6 +17,13 @@
#define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name))
/*
+ * Flags in the low bits of static_call_site::key.
+ */
+#define STATIC_CALL_SITE_TAIL 1UL /* tail call */
+#define STATIC_CALL_SITE_INIT 2UL /* init section */
+#define STATIC_CALL_SITE_FLAGS 3UL
+
+/*
* The static call site table needs to be created by external tooling (objtool
* or a compiler plugin).
*/
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -15,8 +15,6 @@ extern struct static_call_site __start_s
static bool static_call_initialized;
-#define STATIC_CALL_INIT 1UL
-
/* mutex to protect key modules/sites */
static DEFINE_MUTEX(static_call_mutex);
@@ -39,18 +37,23 @@ static inline void *static_call_addr(str
static inline struct static_call_key *static_call_key(const struct static_call_site *site)
{
return (struct static_call_key *)
- (((long)site->key + (long)&site->key) & ~STATIC_CALL_INIT);
+ (((long)site->key + (long)&site->key) & ~STATIC_CALL_SITE_FLAGS);
}
/* These assume the key is word-aligned. */
static inline bool static_call_is_init(struct static_call_site *site)
{
- return ((long)site->key + (long)&site->key) & STATIC_CALL_INIT;
+ return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_INIT;
+}
+
+static inline bool static_call_is_tail(struct static_call_site *site)
+{
+ return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_TAIL;
}
static inline void static_call_set_init(struct static_call_site *site)
{
- site->key = ((long)static_call_key(site) | STATIC_CALL_INIT) -
+ site->key = ((long)static_call_key(site) | STATIC_CALL_SITE_INIT) -
(long)&site->key;
}
@@ -104,7 +107,7 @@ void __static_call_update(struct static_
key->func = func;
- arch_static_call_transform(NULL, tramp, func);
+ arch_static_call_transform(NULL, tramp, func, false);
/*
* If uninitialized, we'll not update the callsites, but they still
@@ -154,7 +157,8 @@ void __static_call_update(struct static_
continue;
}
- arch_static_call_transform(site_addr, NULL, func);
+ arch_static_call_transform(site_addr, NULL, func,
+ static_call_is_tail(site));
}
}
@@ -198,7 +202,8 @@ static int __static_call_init(struct mod
key->mods = site_mod;
}
- arch_static_call_transform(site_addr, NULL, key->func);
+ arch_static_call_transform(site_addr, NULL, key->func,
+ static_call_is_tail(site));
}
return 0;
--- a/tools/include/linux/static_call_types.h
+++ b/tools/include/linux/static_call_types.h
@@ -17,6 +17,13 @@
#define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name))
/*
+ * Flags in the low bits of static_call_site::key.
+ */
+#define STATIC_CALL_SITE_TAIL 1UL /* tail call */
+#define STATIC_CALL_SITE_INIT 2UL /* init section */
+#define STATIC_CALL_SITE_FLAGS 3UL
+
+/*
* The static call site table needs to be created by external tooling (objtool
* or a compiler plugin).
*/
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -511,7 +511,7 @@ static int create_static_call_sections(s
}
memset(reloc, 0, sizeof(*reloc));
reloc->sym = key_sym;
- reloc->addend = 0;
+ reloc->addend = is_sibling_call(insn) ? STATIC_CALL_SITE_TAIL : 0;
reloc->type = R_X86_64_PC32;
reloc->offset = idx * sizeof(struct static_call_site) + 4;
reloc->sec = reloc_sec;
@@ -720,6 +720,10 @@ static int add_jump_destinations(struct
} else {
/* external sibling call */
insn->call_dest = reloc->sym;
+ if (insn->call_dest->static_call_tramp) {
+ list_add_tail(&insn->static_call_node,
+ &file->static_call_list);
+ }
continue;
}
@@ -771,6 +775,10 @@ static int add_jump_destinations(struct
/* internal sibling call */
insn->call_dest = insn->jump_dest->func;
+ if (insn->call_dest->static_call_tramp) {
+ list_add_tail(&insn->static_call_node,
+ &file->static_call_list);
+ }
}
}
}
@@ -1639,6 +1647,10 @@ static int decode_sections(struct objtoo
if (ret)
return ret;
+ ret = read_static_call_tramps(file);
+ if (ret)
+ return ret;
+
ret = add_jump_destinations(file);
if (ret)
return ret;
@@ -1671,10 +1683,6 @@ static int decode_sections(struct objtoo
if (ret)
return ret;
- ret = read_static_call_tramps(file);
- if (ret)
- return ret;
-
return 0;
}
next prev parent reply other threads:[~2020-07-10 13:44 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 13:38 [PATCH v6 00/17] Add static_call Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 01/17] notifier: Fix broken error handling pattern Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 02/17] module: Fix up module_notifier return values Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 03/17] module: Properly propagate MODULE_STATE_COMING failure Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 04/17] jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 05/17] compiler.h: Make __ADDRESSABLE() symbol truly unique Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 06/17] static_call: Add basic static call infrastructure Peter Zijlstra
2020-07-10 21:56 ` Steven Rostedt
2020-07-10 13:38 ` [PATCH v6 07/17] static_call: Add inline " Peter Zijlstra
2020-07-10 21:57 ` Steven Rostedt
2020-07-10 13:38 ` [PATCH v6 08/17] static_call: Avoid kprobes on inline static_call()s Peter Zijlstra
2020-07-10 22:00 ` Steven Rostedt
2020-07-11 10:30 ` Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 09/17] x86/static_call: Add out-of-line static call implementation Peter Zijlstra
2020-07-10 22:13 ` Steven Rostedt
2020-07-11 10:11 ` Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 10/17] x86/static_call: Add inline static call implementation for x86-64 Peter Zijlstra
2020-07-10 22:31 ` Steven Rostedt
2020-07-11 9:56 ` Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 11/17] static_call: Simple self-test Peter Zijlstra
2020-07-10 22:42 ` Steven Rostedt
2020-07-11 10:27 ` Peter Zijlstra
2020-07-13 20:26 ` Steven Rostedt
2020-07-10 13:38 ` [PATCH v6 12/17] x86/alternatives: Teach text_poke_bp() to emulate RET Peter Zijlstra
2020-07-10 22:44 ` Steven Rostedt
2020-07-10 13:38 ` [PATCH v6 13/17] static_call: Add static_call_cond() Peter Zijlstra
2020-07-10 23:08 ` Steven Rostedt
2020-07-11 5:09 ` Peter Zijlstra
2020-07-11 10:49 ` Peter Zijlstra
2020-07-13 20:32 ` Steven Rostedt
2020-07-14 9:53 ` Peter Zijlstra
2020-07-10 13:38 ` Peter Zijlstra [this message]
2020-07-11 0:23 ` [PATCH v6 14/17] static_call: Handle tail-calls Steven Rostedt
2020-07-11 5:06 ` Peter Zijlstra
2020-07-11 5:08 ` Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 15/17] static_call: Allow early init Peter Zijlstra
2020-07-11 1:14 ` Steven Rostedt
2020-07-11 5:08 ` Peter Zijlstra
2020-07-13 20:24 ` Steven Rostedt
2020-07-14 9:51 ` Peter Zijlstra
2020-07-14 14:16 ` Steven Rostedt
2020-07-14 15:54 ` Peter Zijlstra
2020-07-14 16:07 ` Steven Rostedt
2020-07-14 18:31 ` Peter Zijlstra
2020-07-14 19:38 ` Steven Rostedt
2020-07-10 13:38 ` [PATCH v6 16/17] tracepoint: Optimize using static_call() Peter Zijlstra
2020-07-10 13:38 ` [PATCH v6 17/17] x86/perf, static_call: Optimize x86_pmu methods Peter Zijlstra
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