[PATCH 0/7] Fixes for liblockdep

[PATCH 0/7] Fixes for liblockdep

[Ben Hutchings]

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Here are a number of fixes for liblockdep.  The first three need to
go into 4.7 and 4.6-stable; the second should probably go to all
stable branches.

Ben.

Ben Hutchings (7):
  liblockdep: Fix undefined symbol prandom_u32
  liblockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing
    lock_chain::depth
  liblockdep: Define the ARRAY_SIZE() macro
  liblockdep: Enable -Wall by default
  liblockdep: Fix 'unused value' warnings
  liblockdep: Fix 'set but not used' warnings
  liblockdep: Fix 'defined but not used' warning for init_utsname()

 tools/lib/lockdep/Makefile                     |  1 +
 tools/lib/lockdep/common.c                     |  6 ++++++
 tools/lib/lockdep/lockdep.c                    | 10 ++++++++++
 tools/lib/lockdep/uinclude/linux/debug_locks.h |  2 +-
 tools/lib/lockdep/uinclude/linux/irqflags.h    |  8 ++++----
 tools/lib/lockdep/uinclude/linux/kernel.h      | 14 +++++++++++---
 tools/lib/lockdep/uinclude/linux/lockdep.h     | 18 ++++++------------
 7 files changed, 39 insertions(+), 20 deletions(-)


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[PATCH 1/7] liblockdep: Fix undefined symbol prandom_u32

[Ben Hutchings]

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__lock_pin_lock() now calls prandom_u32() which is not defined in
liblockdep.  __lock_pin_lock() and its caller lock_pin_lock() are dead
code in liblockdep, but we still need to provide a definition of
prandom_u32() in case lazy binding is disabled.

Fixes: e7904a28f533 ("locking/lockdep, sched/core: Implement a better ...")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/lib/lockdep/common.c b/tools/lib/lockdep/common.c
index d1c89cc06f5f..405c17667c4d 100644
--- a/tools/lib/lockdep/common.c
+++ b/tools/lib/lockdep/common.c
@@ -1,5 +1,6 @@
 #include <stddef.h>
 #include <stdbool.h>
+#include <stdlib.h>
 #include <linux/compiler.h>
 #include <linux/lockdep.h>
 #include <unistd.h>
@@ -10,6 +11,11 @@ static __thread struct task_struct current_obj;
 /* lockdep wants these */
 bool debug_locks = true;
 bool debug_locks_silent;
+u32 prandom_u32(void)
+{
+	/* Used only by lock_pin_lock() which is dead code */
+	abort();
+}
 
 __attribute__((destructor)) static void liblockdep_exit(void)
 {


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Re: [PATCH 1/7] liblockdep: Fix undefined symbol prandom_u32

[Sasha Levin]

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On 06/14/2016 04:47 PM, Ben Hutchings wrote:
> __lock_pin_lock() now calls prandom_u32() which is not defined in
> liblockdep.  __lock_pin_lock() and its caller lock_pin_lock() are dead
> code in liblockdep, but we still need to provide a definition of
> prandom_u32() in case lazy binding is disabled.
> 
> Fixes: e7904a28f533 ("locking/lockdep, sched/core: Implement a better ...")
> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
>  tools/lib/lockdep/common.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/tools/lib/lockdep/common.c b/tools/lib/lockdep/common.c
> index d1c89cc06f5f..405c17667c4d 100644
> --- a/tools/lib/lockdep/common.c
> +++ b/tools/lib/lockdep/common.c
> @@ -1,5 +1,6 @@
>  #include <stddef.h>
>  #include <stdbool.h>
> +#include <stdlib.h>
>  #include <linux/compiler.h>
>  #include <linux/lockdep.h>
>  #include <unistd.h>
> @@ -10,6 +11,11 @@ static __thread struct task_struct current_obj;
>  /* lockdep wants these */
>  bool debug_locks = true;
>  bool debug_locks_silent;
> +u32 prandom_u32(void)
> +{
> +	/* Used only by lock_pin_lock() which is dead code */
> +	abort();
> +}

I had to place this bit in lockdep.c rather than common.c, since lockdep.c
is the one building kernel/lockdep.c.


Thanks,
Sasha



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[PATCH 2/7] liblockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain::depth

[Ben Hutchings]

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liblockdep has been broken since commit 75dd602a5198 ("lockdep: Fix
lock_chain::base size"), as that adds a check that MAX_LOCK_DEPTH is
within the range of lock_chain::depth and in liblockdep it is much
too large.

That should have resulted in a compiler error, but didn't because:

- the check uses ARRAY_SIZE(), which isn't yet defined in liblockdep
  so is assumed to be an (undeclared) function
- putting a function call inside a BUILD_BUG_ON() expression quietly
  turns it into some nonsense involving a variable-length array

It did produce a compiler warning, but I didn't notice because
liblockdep already produces too many warnings if -Wall is enabled
(which I'll fix shortly).

Even before that commit, which reduced lock_chain::depth from 8 bits
to 6, MAX_LOCK_DEPTH was too large.

Cc: <stable@vger.kernel.org> # for versions before 4.6, use a value of 255
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/uinclude/linux/lockdep.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/lockdep/uinclude/linux/lockdep.h b/tools/lib/lockdep/uinclude/linux/lockdep.h
index c808c7d02d21..d30214221920 100644
--- a/tools/lib/lockdep/uinclude/linux/lockdep.h
+++ b/tools/lib/lockdep/uinclude/linux/lockdep.h
@@ -8,7 +8,7 @@
 #include <linux/utsname.h>
 #include <linux/compiler.h>
 
-#define MAX_LOCK_DEPTH 2000UL
+#define MAX_LOCK_DEPTH 63UL
 
 #define asmlinkage
 #define __visible


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Re: [PATCH 2/7] liblockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain::depth

[Peter Zijlstra]

On Tue, Jun 14, 2016 at 09:47:53PM +0100, Ben Hutchings wrote:

> Even before that commit, which reduced lock_chain::depth from 8 bits
> to 6, MAX_LOCK_DEPTH was too large.

> -#define MAX_LOCK_DEPTH 2000UL
> +#define MAX_LOCK_DEPTH 63UL

So per that commit; there still is a 4 byte hole we could fill. So if a
bigger number is desired here, there is room to make that happen.

Good to see those assertions did their job, albeit somewhat belated.

[PATCH 3/7] liblockdep: Define the ARRAY_SIZE() macro

[Ben Hutchings]

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lockdep.c now uses ARRAY_SIZE().

Fixes: 75dd602a5198 ("lockdep: Fix lock_chain::base size")
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/uinclude/linux/kernel.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/lib/lockdep/uinclude/linux/kernel.h b/tools/lib/lockdep/uinclude/linux/kernel.h
index 276c7a8b2ed1..da87bd9ad2c1 100644
--- a/tools/lib/lockdep/uinclude/linux/kernel.h
+++ b/tools/lib/lockdep/uinclude/linux/kernel.h
@@ -7,6 +7,8 @@
 #include <linux/hardirq.h>
 #include <linux/kern_levels.h>
 
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
 #ifndef container_of
 #define container_of(ptr, type, member) ({			\
 	const typeof(((type *)0)->member) * __mptr = (ptr);	\


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[PATCH 4/7] liblockdep: Enable -Wall by default

[Ben Hutchings]

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Regressions in liblockdep may be missed because it doesn't enable
warnings.

Adding -Wall immediately introduces a lot of warnings, but those will
be fixed by the following commits.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/lockdep/Makefile b/tools/lib/lockdep/Makefile
index 1d57af56814b..710a0edfe1b1 100644
--- a/tools/lib/lockdep/Makefile
+++ b/tools/lib/lockdep/Makefile
@@ -79,6 +79,7 @@ INCLUDES = -I. -I./uinclude -I./include -I../../include $(CONFIG_INCLUDES)
 # Set compile option CFLAGS if not set elsewhere
 CFLAGS ?= -g -DCONFIG_LOCKDEP -DCONFIG_STACKTRACE -DCONFIG_PROVE_LOCKING -DBITS_PER_LONG=__WORDSIZE -DLIBLOCKDEP_VERSION='"$(LIBLOCKDEP_VERSION)"' -rdynamic -O0 -g
 CFLAGS += -fPIC
+CFLAGS += -Wall
 
 override CFLAGS += $(CONFIG_FLAGS) $(INCLUDES) $(PLUGIN_DIR_SQ)
 


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[PATCH 5/7] liblockdep: Fix 'unused value' warnings

[Ben Hutchings]

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liblockdep defines various macros that may expand to an expression
with no effect, while the in-kernel definition does have an effect.
This results in warnings from gcc when -Wunused-value is enabled, and
is is enabled by -Wall.  Fix this by introducing trivial functions,
as function return values are generally allowed to be ignored.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/uinclude/linux/debug_locks.h |  2 +-
 tools/lib/lockdep/uinclude/linux/kernel.h      | 12 +++++++++---
 tools/lib/lockdep/uinclude/linux/lockdep.h     |  6 +++++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/lib/lockdep/uinclude/linux/debug_locks.h b/tools/lib/lockdep/uinclude/linux/debug_locks.h
index f38eb64df794..1d4fbec5c649 100644
--- a/tools/lib/lockdep/uinclude/linux/debug_locks.h
+++ b/tools/lib/lockdep/uinclude/linux/debug_locks.h
@@ -4,7 +4,7 @@
 #include <stddef.h>
 #include <linux/compiler.h>
 
-#define DEBUG_LOCKS_WARN_ON(x) (x)
+#define DEBUG_LOCKS_WARN_ON(x) WARN_ON(x)
 
 extern bool debug_locks;
 extern bool debug_locks_silent;
diff --git a/tools/lib/lockdep/uinclude/linux/kernel.h b/tools/lib/lockdep/uinclude/linux/kernel.h
index da87bd9ad2c1..021cff4f4e3d 100644
--- a/tools/lib/lockdep/uinclude/linux/kernel.h
+++ b/tools/lib/lockdep/uinclude/linux/kernel.h
@@ -22,10 +22,16 @@
 	_max1 > _max2 ? _max1 : _max2; })
 
 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
-#define WARN_ON(x) (x)
-#define WARN_ON_ONCE(x) (x)
+
+static inline int lockdep_warn(int condition)
+{
+	return condition;
+}
+#define WARN_ON(x) lockdep_warn(x)
+#define WARN_ON_ONCE(x) WARN_ON(x)
+#define WARN(x, y...) WARN_ON(x)
+
 #define likely(x) (x)
-#define WARN(x, y...) (x)
 #define uninitialized_var(x) x
 #define __init
 #define noinline
diff --git a/tools/lib/lockdep/uinclude/linux/lockdep.h b/tools/lib/lockdep/uinclude/linux/lockdep.h
index d30214221920..d1079034a14d 100644
--- a/tools/lib/lockdep/uinclude/linux/lockdep.h
+++ b/tools/lib/lockdep/uinclude/linux/lockdep.h
@@ -29,7 +29,11 @@ extern struct task_struct *__curr(void);
 
 #define current (__curr())
 
-#define debug_locks_off() 1
+static inline int debug_locks_off(void)
+{
+	return 1;
+}
+
 #define task_pid_nr(tsk) ((tsk)->pid)
 
 #define KSYM_NAME_LEN 128


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[PATCH 6/7] liblockdep: Fix 'set but not used' warnings

[Ben Hutchings]

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liblockdep defines trivial macros for working with interrupt flags, as
interrupts are never disabled in userland.  This results in warnings
from gcc when -Wunused-but-set-variable is enabled, and it is enabled
by -Wall.  Fix this by evaluating the flags parameter and casting it to
void.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/uinclude/linux/irqflags.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/lib/lockdep/uinclude/linux/irqflags.h b/tools/lib/lockdep/uinclude/linux/irqflags.h
index 6cc296f0fad0..df77669cfe1c 100644
--- a/tools/lib/lockdep/uinclude/linux/irqflags.h
+++ b/tools/lib/lockdep/uinclude/linux/irqflags.h
@@ -17,19 +17,19 @@
 #define raw_local_irq_disable() do { } while (0)
 #define raw_local_irq_enable() do { } while (0)
 #define raw_local_irq_save(flags) ((flags) = 0)
-#define raw_local_irq_restore(flags) do { } while (0)
+#define raw_local_irq_restore(flags) ((void)(flags))
 #define raw_local_save_flags(flags) ((flags) = 0)
-#define raw_irqs_disabled_flags(flags) do { } while (0)
+#define raw_irqs_disabled_flags(flags) ((void)(flags))
 #define raw_irqs_disabled() 0
 #define raw_safe_halt()
 
 #define local_irq_enable() do { } while (0)
 #define local_irq_disable() do { } while (0)
 #define local_irq_save(flags) ((flags) = 0)
-#define local_irq_restore(flags) do { } while (0)
+#define local_irq_restore(flags) ((void)(flags))
 #define local_save_flags(flags)	((flags) = 0)
 #define irqs_disabled() (1)
-#define irqs_disabled_flags(flags) (0)
+#define irqs_disabled_flags(flags) ((void)(flags), 0)
 #define safe_halt() do { } while (0)
 
 #define trace_lock_release(x, y)


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[PATCH 7/7] liblockdep: Fix 'defined but not used' warning for init_utsname()

[Ben Hutchings]

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We define init_utsname() as static but not inline, resulting
in a warning for every source file that includes lockdep.h but
doesn't call it.

Since it is only used by lockdep.c, define it in there.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/lib/lockdep/lockdep.c                | 10 ++++++++++
 tools/lib/lockdep/uinclude/linux/lockdep.h | 10 ----------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/tools/lib/lockdep/lockdep.c b/tools/lib/lockdep/lockdep.c
index a0a2e3a266af..513140ea8a58 100644
--- a/tools/lib/lockdep/lockdep.c
+++ b/tools/lib/lockdep/lockdep.c
@@ -5,4 +5,14 @@
 #define hlist_add_head_rcu		hlist_add_head
 #define hlist_del_rcu			hlist_del
 
+static struct new_utsname *init_utsname(void)
+{
+	static struct new_utsname n = (struct new_utsname) {
+		.release = "liblockdep",
+		.version = LIBLOCKDEP_VERSION,
+	};
+
+	return &n;
+}
+
 #include "../../../kernel/locking/lockdep.c"
diff --git a/tools/lib/lockdep/uinclude/linux/lockdep.h b/tools/lib/lockdep/uinclude/linux/lockdep.h
index d1079034a14d..c157242e0417 100644
--- a/tools/lib/lockdep/uinclude/linux/lockdep.h
+++ b/tools/lib/lockdep/uinclude/linux/lockdep.h
@@ -44,16 +44,6 @@ static inline int debug_locks_off(void)
 #define atomic_t unsigned long
 #define atomic_inc(x) ((*(x))++)
 
-static struct new_utsname *init_utsname(void)
-{
-	static struct new_utsname n = (struct new_utsname) {
-		.release = "liblockdep",
-		.version = LIBLOCKDEP_VERSION,
-	};
-
-	return &n;
-}
-
 #define print_tainted() ""
 #define static_obj(x) 1
 

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Re: [PATCH 0/7] Fixes for liblockdep

[Sasha Levin]

On 06/14/2016 04:44 PM, Ben Hutchings wrote:
> Here are a number of fixes for liblockdep.  The first three need to
> go into 4.7 and 4.6-stable; the second should probably go to all
> stable branches.

Thanks Ben! I've added it all to the queue and will send it along.


Thanks,
Sasha