Re: [Xen-devel] [PATCH 13/34] xen/arm: gic: Introduce GIC_SGI_MAX

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 26/03/14 09:03, Ian Campbell wrote:
 > Does ASSERT(sgi < GIC_SGI_MAX) not compiler without warnings?

I reworked this patch (see below):

commit a07ef8994c10ae45c0fa42040e802006f7a510c6
Author: Julien Grall <julien.grall@xxxxxxxxxx>
Date:   Wed Mar 19 20:51:51 2014 +0000

    xen/arm: gic: Introduce GIC_SGI_MAX
    
    All the functions that send an SGI takes an enum. Therefore checking 
everytime
    if the value is in the range is not correct.
    
    Introduce GIC_SGI_MAX to check the enum will never reach more than 16 
values and
    use it to check if the developper will use a wrong SGI by mistake.
    
    This is fix the compilation with Clang 3.5:
    
    gic.c:515:15: error: comparison of constant 16 with expression of type 
'enum gic_sgi' is always true 
[-Werror,-Wtautological-constant-out-of-range-compare]
       ASSERT(sgi < 16); /* There are only 16 SGIs */
              ~~~ ^ ~~
    xen/xen/include/xen/lib.h:43:26: note: expanded from macro 'ASSERT'
        do { if ( unlikely(!(p)) ) assert_failed(#p); } while (0)
                             ^
    xen/xen/include/xen/compiler.h:11:41: note: expanded from macro 'unlikely'
     #define unlikely(x)   __builtin_expect((x),0)
    
    Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
    Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
    Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
    Cc: Tim Deegan <tim@xxxxxxx>
    
    ---
        Changes in v2:
            - Replace ASSERT(sgi != GIC_SGI_MAX) by ASSERT(sgi < GIC_SGI_MAX)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index b03f2c2..2b9cdc5 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -473,7 +473,8 @@ void send_SGI_mask(const cpumask_t *cpumask, enum gic_sgi 
sgi)
     unsigned int mask = 0;
     cpumask_t online_mask;
 
-    ASSERT(sgi < 16); /* There are only 16 SGIs */
+    BUILD_BUG_ON(GIC_SGI_MAX >= 16);
+    ASSERT(sgi < GIC_SGI_MAX);
 
     cpumask_and(&online_mask, cpumask, &cpu_online_map);
     mask = gic_cpu_mask(&online_mask);
@@ -493,7 +494,7 @@ void send_SGI_one(unsigned int cpu, enum gic_sgi sgi)
 
 void send_SGI_self(enum gic_sgi sgi)
 {
-    ASSERT(sgi < 16); /* There are only 16 SGIs */
+    ASSERT(sgi < GIC_SGI_MAX);
 
     dsb(sy);
 
@@ -503,7 +504,7 @@ void send_SGI_self(enum gic_sgi sgi)
 
 void send_SGI_allbutself(enum gic_sgi sgi)
 {
-   ASSERT(sgi < 16); /* There are only 16 SGIs */
+   ASSERT(sgi < GIC_SGI_MAX);
 
    dsb(sy);
 
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 76586ab..a4e513f 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -198,6 +198,8 @@ enum gic_sgi {
     GIC_SGI_EVENT_CHECK = 0,
     GIC_SGI_DUMP_STATE  = 1,
     GIC_SGI_CALL_FUNCTION = 2,
+    /* GIC_SGI_MAX must be the last type of the enum */
+    GIC_SGI_MAX,
 };
 extern void send_SGI_mask(const cpumask_t *cpumask, enum gic_sgi sgi);
 extern void send_SGI_one(unsigned int cpu, enum gic_sgi sgi);

-- 
Julien Grall

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