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tcg-mips: Constrain the code_gen_buffer to be within one 256mb segment

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This assures us use of J for exit_tb and goto_tb, and JAL for calling
into the generated bswap helpers.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Richard Henderson 2014-04-24 09:16:07 -07:00
parent 479eb12108
commit 483c76e140
1 changed files with 85 additions and 5 deletions
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90
translate-all.c
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@ -513,14 +513,47 @@ static inline size_t size_code_gen_buffer(size_t tb_size)
return tb_size;
}
#ifdef __mips__
/* In order to use J and JAL within the code_gen_buffer, we require
that the buffer not cross a 256MB boundary. */
static inline bool cross_256mb(void *addr, size_t size)
{
return ((uintptr_t)addr ^ ((uintptr_t)addr + size)) & 0xf0000000;
}
/* We weren't able to allocate a buffer without crossing that boundary,
so make do with the larger portion of the buffer that doesn't cross.
Returns the new base of the buffer, and adjusts code_gen_buffer_size. */
static inline void *split_cross_256mb(void *buf1, size_t size1)
{
void *buf2 = (void *)(((uintptr_t)buf1 + size1) & 0xf0000000);
size_t size2 = buf1 + size1 - buf2;
size1 = buf2 - buf1;
if (size1 < size2) {
size1 = size2;
buf1 = buf2;
}
tcg_ctx.code_gen_buffer_size = size1;
return buf1;
}
#endif
#ifdef USE_STATIC_CODE_GEN_BUFFER
static uint8_t static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
__attribute__((aligned(CODE_GEN_ALIGN)));
static inline void *alloc_code_gen_buffer(void)
{
map_exec(static_code_gen_buffer, tcg_ctx.code_gen_buffer_size);
return static_code_gen_buffer;
void *buf = static_code_gen_buffer;
#ifdef __mips__
if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
buf = split_cross_256mb(buf, tcg_ctx.code_gen_buffer_size);
}
#endif
map_exec(buf, tcg_ctx.code_gen_buffer_size);
return buf;
}
#elif defined(USE_MMAP)
static inline void *alloc_code_gen_buffer(void)
@ -562,16 +595,63 @@ static inline void *alloc_code_gen_buffer(void)
buf = mmap((void *)start, tcg_ctx.code_gen_buffer_size,
PROT_WRITE | PROT_READ | PROT_EXEC, flags, -1, 0);
return buf == MAP_FAILED ? NULL : buf;
if (buf == MAP_FAILED) {
return NULL;
}
#ifdef __mips__
if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
/* Try again, with the original still mapped, to avoid re-aquiring
that 256mb crossing. This time don't specify an address. */
size_t size2, size1 = tcg_ctx.code_gen_buffer_size;
void *buf2 = mmap(NULL, size1, PROT_WRITE | PROT_READ | PROT_EXEC,
flags, -1, 0);
if (buf2 != MAP_FAILED) {
if (!cross_256mb(buf2, size1)) {
/* Success! Use the new buffer. */
munmap(buf, size1);
return buf2;
}
/* Failure. Work with what we had. */
munmap(buf2, size1);
}
/* Split the original buffer. Free the smaller half. */
buf2 = split_cross_256mb(buf, size1);
size2 = tcg_ctx.code_gen_buffer_size;
munmap(buf + (buf == buf2 ? size2 : 0), size1 - size2);
return buf2;
}
#endif
return buf;
}
#else
static inline void *alloc_code_gen_buffer(void)
{
void *buf = g_malloc(tcg_ctx.code_gen_buffer_size);
if (buf) {
map_exec(buf, tcg_ctx.code_gen_buffer_size);
if (buf == NULL) {
return NULL;
}
#ifdef __mips__
if (cross_256mb(buf, tcg_ctx.code_gen_buffer_size)) {
void *buf2 = g_malloc(tcg_ctx.code_gen_buffer_size);
if (buf2 != NULL && !cross_256mb(buf2, size1)) {
/* Success! Use the new buffer. */
free(buf);
buf = buf2;
} else {
/* Failure. Work with what we had. Since this is malloc
and not mmap, we can't free the other half. */
free(buf2);
buf = split_cross_256mb(buf, tcg_ctx.code_gen_buffer_size);
}
}
#endif
map_exec(buf, tcg_ctx.code_gen_buffer_size);
return buf;
}
#endif /* USE_STATIC_CODE_GEN_BUFFER, USE_MMAP */