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CTSRD-CHERI / clang

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casts from pointers to capabilities broken #184

Closed brooksdavis closed 6 years ago

brooksdavis commented 6 years ago

When I compile the following previously working code with 23a11c89beddc2fddf8048eba4814d45b4c8c348 applied I get warning which is an error in CheriBSD.

struct malloc_type;

void    *kmalloc(unsigned long size, struct malloc_type *type, int flags);

void * __capability
malloc_c(unsigned long size, struct malloc_type *type, int flags)
{
        return ((__cheri_tocap void * __capability)kmalloc(size, type, flags));
}
$clang -target cheri-unknown-freebsd -march=mips4 -mabi=64 -mcpu=mips4 -cheri=128 -c -o /dev/null foo.c            
foo.c:8:25: warning: cast from provenance-free integer type to pointer type will
      give pointer that can not be dereferenced. [-Wcheri-capability-misuse]    
        return ((__cheri_tocap void * __capability)kmalloc(size, type, flags)); 
                               ^        
foo.c:8:25: note: insert cast to intptr_t to silence this warning               
1 warning generated.