core: make thread ID a short int

Changes thread_get_id() and thread_get_id_may_fail() to return 'short
int' instead of 'int'. That is, 16 bits instead of 32 on all supported
architectures which is more than enough since the largest thread ID
value is (CFG_NUM_THREADS - 1). Note, struct wait_queue_elem::handle
is already a short int.

trace_ext_get_thread_id() is not changed (still returns an int) because
it is part of the TA API and modifying it would needlessly introduce
incompatibilities.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Reviewed-by: Etienne Carriere <etienne.carriere@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>

7 files changed, 16 insertions, 14 deletions

diff --git a/core/arch/arm/include/kernel/thread.h b/core/arch/arm/include/kernel/thread.h
index 98abe26a..c0443e5c 100644
--- a/core/arch/arm/include/kernel/thread.h
+++ b/core/arch/arm/include/kernel/thread.h
@@ -42,7 +42,7 @@ struct thread_core_local {
 	uint64_t x[4];
 #endif
 	vaddr_t tmp_stack_va_end;
-	int curr_thread;
+	short int curr_thread;
 	uint32_t flags;
 	vaddr_t abt_stack_va_end;
 #ifdef CFG_TEE_CORE_DEBUG
@@ -299,12 +299,12 @@ void thread_clr_boot_thread(void);
 /*
  * Returns current thread id.
  */
-int thread_get_id(void);
+short int thread_get_id(void);
 
 /*
  * Returns current thread id, return -1 on failure.
  */
-int thread_get_id_may_fail(void);
+short int thread_get_id_may_fail(void);
 
 /* Returns Thread Specific Data (TSD) pointer. */
 struct thread_specific_data *thread_get_tsd(void);
diff --git a/core/arch/arm/kernel/mutex_lockdep.c b/core/arch/arm/kernel/mutex_lockdep.c
index 144e7b8e..2095c862 100644
--- a/core/arch/arm/kernel/mutex_lockdep.c
+++ b/core/arch/arm/kernel/mutex_lockdep.c
@@ -36,7 +36,7 @@ void mutex_lockdep_init(void)
 
 void mutex_lock_check(struct mutex *m)
 {
-	int thread = thread_get_id();
+	short int thread = thread_get_id();
 	uint32_t exceptions = 0;
 
 	exceptions = cpu_spin_lock_xsave(&graph_lock);
@@ -46,7 +46,7 @@ void mutex_lock_check(struct mutex *m)
 
 void mutex_trylock_check(struct mutex *m)
 {
-	int thread = thread_get_id();
+	short int thread = thread_get_id();
 	uint32_t exceptions = 0;
 
 	exceptions = cpu_spin_lock_xsave(&graph_lock);
@@ -56,7 +56,7 @@ void mutex_trylock_check(struct mutex *m)
 
 void mutex_unlock_check(struct mutex *m)
 {
-	int thread = thread_get_id();
+	short int thread = thread_get_id();
 	uint32_t exceptions = 0;
 
 	exceptions = cpu_spin_lock_xsave(&graph_lock);
diff --git a/core/arch/arm/kernel/thread.c b/core/arch/arm/kernel/thread.c
index 3d876aec..21a00ba3 100644
--- a/core/arch/arm/kernel/thread.c
+++ b/core/arch/arm/kernel/thread.c
@@ -834,23 +834,25 @@ bool thread_init_stack(uint32_t thread_id, vaddr_t sp)
 	return true;
 }
 
-int thread_get_id_may_fail(void)
+short int thread_get_id_may_fail(void)
 {
 	/*
 	 * thread_get_core_local() requires foreign interrupts to be disabled
 	 */
 	uint32_t exceptions = thread_mask_exceptions(THREAD_EXCP_FOREIGN_INTR);
 	struct thread_core_local *l = thread_get_core_local();
-	int ct = l->curr_thread;
+	short int ct = l->curr_thread;
 
 	thread_unmask_exceptions(exceptions);
 	return ct;
 }
 
-int thread_get_id(void)
+short int thread_get_id(void)
 {
-	int ct = thread_get_id_may_fail();
+	short int ct = thread_get_id_may_fail();
 
+	/* Thread ID has to fit in a short int */
+	COMPILE_TIME_ASSERT(CFG_NUM_THREADS <= SHRT_MAX);
 	assert(ct >= 0 && ct < CFG_NUM_THREADS);
 	return ct;
 }
diff --git a/core/arch/arm/kernel/thread_a64.S b/core/arch/arm/kernel/thread_a64.S
index d0df9bf8..74512089 100644
--- a/core/arch/arm/kernel/thread_a64.S
+++ b/core/arch/arm/kernel/thread_a64.S
@@ -16,7 +16,7 @@
 #include "thread_private.h"
 
 	.macro get_thread_ctx core_local, res, tmp0, tmp1
-		ldr	w\tmp0, [\core_local, \
+		ldrh	w\tmp0, [\core_local, \
 				#THREAD_CORE_LOCAL_CURR_THREAD]
 		ldr	x\res, =threads
 		mov	x\tmp1, #THREAD_CTX_SIZE
diff --git a/core/include/kernel/tee_ta_manager.h b/core/include/kernel/tee_ta_manager.h
index f8eb7c0f..eb87501b 100644
--- a/core/include/kernel/tee_ta_manager.h
+++ b/core/include/kernel/tee_ta_manager.h
@@ -105,7 +105,7 @@ struct tee_ta_session {
 	uint32_t ref_count;	/* reference counter */
 	struct condvar refc_cv;	/* CV used to wait for ref_count to be 0 */
 	struct condvar lock_cv;	/* CV used to wait for lock */
-	int lock_thread;	/* Id of thread holding the lock */
+	short int lock_thread;	/* Id of thread holding the lock */
 	bool unlink;		/* True if session is to be unlinked */
 #if defined(CFG_TA_GPROF_SUPPORT)
 	struct sample_buf *sbuf; /* Profiling data (PC sampling) */
diff --git a/core/kernel/tee_ta_manager.c b/core/kernel/tee_ta_manager.c
index 82bf2707..deb6754b 100644
--- a/core/kernel/tee_ta_manager.c
+++ b/core/kernel/tee_ta_manager.c
@@ -39,7 +39,7 @@ struct tee_ta_ctx_head tee_ctxes = TAILQ_HEAD_INITIALIZER(tee_ctxes);
 
 #ifndef CFG_CONCURRENT_SINGLE_INSTANCE_TA
 static struct condvar tee_ta_cv = CONDVAR_INITIALIZER;
-static int tee_ta_single_instance_thread = THREAD_ID_INVALID;
+static short int tee_ta_single_instance_thread = THREAD_ID_INVALID;
 static size_t tee_ta_single_instance_count;
 #endif
 
diff --git a/lib/libutils/ext/ftrace/ftrace.c b/lib/libutils/ext/ftrace/ftrace.c
index bf3d968e..dff56d13 100644
--- a/lib/libutils/ext/ftrace/ftrace.c
+++ b/lib/libutils/ext/ftrace/ftrace.c
@@ -32,7 +32,7 @@ static const char hex_str[] = "0123456789abcdef";
 static __noprof struct ftrace_buf *get_fbuf(void)
 {
 #if defined(__KERNEL__)
-	int ct = thread_get_id_may_fail();
+	short int ct = thread_get_id_may_fail();
 	struct tee_ta_session *s = NULL;
 	struct thread_specific_data *tsd = NULL;