Help Request - Fix Out of Bounds Subscript Warning in Raspberry Pi

[Pavel Pisa]

From 3a2957faeb744af08196f1fd3baac71f15d76c85 Mon Sep 17 00:00:00 2001
Message-Id: <3a2957faeb744af08196f1fd3baac71f15d76c85.1493113587.git.ppisa at pikron.com>
From: Pavel Pisa <ppisa at pikron.com>
Date: Tue, 25 Apr 2017 11:45:57 +0200
Subject: [PATCH] bsp/raspberrypi: GPIO silence warning and ensure that lock is
 always released.
To: rtems-devel at rtems.org

Signed-off-by: Pavel Pisa <ppisa at pikron.com>
---
 c/src/lib/libbsp/shared/gpio.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

Not tested or even compiled quick fix of warning and more serious real problem.
The waning seems to be GCC false positive. The first iteration
(i == 0) sets *bank_number for sure. But return with RTEMS_INVALID_ID can
happen without lock release.

diff --git a/c/src/lib/libbsp/shared/gpio.c b/c/src/lib/libbsp/shared/gpio.c
index 9ceeb407..bf0e415 100644
--- a/c/src/lib/libbsp/shared/gpio.c
+++ b/c/src/lib/libbsp/shared/gpio.c
@@ -303,6 +303,7 @@ static rtems_status_code get_pin_bitmask(
   uint32_t pin_number;
   uint32_t bank;
   uint8_t i;
+  int locked_bank = -1;
 
   if ( pin_count < 1 ) {
     return RTEMS_UNSATISFIED;
@@ -314,18 +315,23 @@ static rtems_status_code get_pin_bitmask(
     pin_number = pins[i];
 
     if ( pin_number < 0 || pin_number >= BSP_GPIO_PIN_COUNT ) {
+      if (locked_bank >= 0)
+        RELEASE_LOCK(gpio_bank_state[locked_bank].lock);
+
       return RTEMS_INVALID_ID;
     }
 
     bank = BANK_NUMBER(pin_number);
 
-    if ( i == 0 ) {
+    if ( locked_bank < 0 ) {
       *bank_number = bank;
+      locked_bank = bank;
 
-      ACQUIRE_LOCK(gpio_bank_state[bank].lock);
+      ACQUIRE_LOCK(gpio_bank_state[locked_bank].lock);
     }
-    else if ( bank != *bank_number ) {
-      RELEASE_LOCK(gpio_bank_state[*bank_number].lock);
+    else if ( bank != locked_bank ) {
+      if (locked_bank >= 0)
+        RELEASE_LOCK(gpio_bank_state[locked_bank].lock);
 
       return RTEMS_UNSATISFIED;
     }
@@ -334,7 +340,7 @@ static rtems_status_code get_pin_bitmask(
         gpio_pin_state[pin_number].pin_function != function ||
         gpio_pin_state[pin_number].on_group
     ) {
-      RELEASE_LOCK(gpio_bank_state[bank].lock);
+      RELEASE_LOCK(gpio_bank_state[locked_bank].lock);
 
       return RTEMS_NOT_CONFIGURED;
     }
@@ -342,7 +348,7 @@ static rtems_status_code get_pin_bitmask(
     *bitmask |= (1 << PIN_NUMBER(pin_number));
   }
 
-  RELEASE_LOCK(gpio_bank_state[bank].lock);
+  RELEASE_LOCK(gpio_bank_state[locked_bank].lock);
 
   return RTEMS_SUCCESSFUL;
 }
-- 
1.9.1