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Fixed bug 4683 - SDL_atomic infinite recursion on armv6/armv5 w/ thumb 

The real problem is that SDL_atomic.c was built in thumb mode instead of ARM mode, which is required to use the mcr instruction on ARM platforms. Added a compiler error to catch this case so we don't generate code that does infinite recursion.

I also added a potentially better way to handle things on Linux ARM platforms, based on comments in the Chromium headers, which we can try out after 2.0.10 ships.
This commit is contained in:
Sam Lantinga 2019-06-30 23:26:16 -07:00
parent 797d2c5957
commit cc47810d36
2 changed files with 21 additions and 0 deletions
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17
include/SDL_atomic.h
View File

@ -162,6 +162,22 @@ extern DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void);
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory")
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory")
#elif defined(__GNUC__) && defined(__arm__) #elif defined(__GNUC__) && defined(__arm__)
#if 0 /* defined(__LINUX__) || defined(__ANDROID__) */
/* Information from:
https://chromium.googlesource.com/chromium/chromium/+/trunk/base/atomicops_internals_arm_gcc.h#19
The Linux kernel provides a helper function which provides the right code for a memory barrier,
hard-coded at address 0xffff0fa0
*/
typedef void (*SDL_KernelMemoryBarrierFunc)();
#define SDL_MemoryBarrierRelease() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)()
#define SDL_MemoryBarrierAcquire() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)()
#elif 0 /* defined(__QNXNTO__) */
#include <sys/cpuinline.h>
#define SDL_MemoryBarrierRelease() __cpu_membarrier()
#define SDL_MemoryBarrierAcquire() __cpu_membarrier()
#else
#if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7S__) || defined(__ARM_ARCH_8A__) #if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7S__) || defined(__ARM_ARCH_8A__)
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory") #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory")
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory") #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory")
@ -177,6 +193,7 @@ extern DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void);
#else #else
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("" : : : "memory") #define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("" : : : "memory")
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("" : : : "memory") #define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("" : : : "memory")
#endif /* __LINUX__ || __ANDROID__ */
#endif /* __GNUC__ && __arm__ */ #endif /* __GNUC__ && __arm__ */
#else #else
#if (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120)) #if (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120))

4
src/atomic/SDL_atomic.c
View File

@ -289,6 +289,10 @@ SDL_AtomicGetPtr(void **a)
#endif #endif
} }
#ifdef __thumb__
#error This file should be built in arm mode so the mcr instruction is available for memory barriers
#endif
void void
SDL_MemoryBarrierReleaseFunction(void) SDL_MemoryBarrierReleaseFunction(void)
{ {