Skip to content

Commit

Permalink
exec: Split up and tidy code_gen_buffer
Browse files Browse the repository at this point in the history 
It now consists of:

A macro definition of MAX_CODE_GEN_BUFFER_SIZE with host-specific values,

A function size_code_gen_buffer that applies most of the reasoning for
choosing a buffer size,

Three variations of a function alloc_code_gen_buffer that contain all
of the logic for allocating executable memory via a given allocation
mechanism.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
  • Loading branch information
@rth7680 @blueswirl
rth7680 authored and blueswirl committed Oct 20, 2012
1 parent 5f072e1 commit f1bc0bc
Showing 1 changed file with 103 additions and 92 deletions.
195 changes: 103 additions & 92 deletions exec.c
View file
Expand Up @@ -103,9 +103,9 @@ spinlock_t tb_lock = SPIN_LOCK_UNLOCKED;

uint8_t code_gen_prologue[1024] code_gen_section;
static uint8_t *code_gen_buffer;
static unsigned long code_gen_buffer_size;
static size_t code_gen_buffer_size;
/* threshold to flush the translated code buffer */
static unsigned long code_gen_buffer_max_size;
static size_t code_gen_buffer_max_size;
static uint8_t *code_gen_ptr;

#if !defined(CONFIG_USER_ONLY)
Expand Down Expand Up @@ -497,110 +497,121 @@ bool memory_region_is_unassigned(MemoryRegion *mr)
#define mmap_unlock() do { } while(0)
#endif

#define DEFAULT_CODE_GEN_BUFFER_SIZE (32 * 1024 * 1024)

#if defined(CONFIG_USER_ONLY)
/* Currently it is not recommended to allocate big chunks of data in
user mode. It will change when a dedicated libc will be used */
user mode. It will change when a dedicated libc will be used. */
/* ??? 64-bit hosts ought to have no problem mmaping data outside the
region in which the guest needs to run. Revisit this. */
#define USE_STATIC_CODE_GEN_BUFFER
#endif

#ifdef USE_STATIC_CODE_GEN_BUFFER
static uint8_t static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
__attribute__((aligned (CODE_GEN_ALIGN)));
/* ??? Should configure for this, not list operating systems here. */
#if (defined(__linux__) \
|| defined(__FreeBSD__) || defined(__FreeBSD_kernel__) \
|| defined(__DragonFly__) || defined(__OpenBSD__) \
|| defined(__NetBSD__))
# define USE_MMAP
#endif

static void code_gen_alloc(unsigned long tb_size)
/* Maximum size of the code gen buffer we'd like to use. Unless otherwise
indicated, this is constrained by the range of direct branches on the
host cpu, as used by the TCG implementation of goto_tb. */
#if defined(__x86_64__)
# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024)
#elif defined(__sparc__)
# define MAX_CODE_GEN_BUFFER_SIZE (2ul * 1024 * 1024 * 1024)
#elif defined(__arm__)
# define MAX_CODE_GEN_BUFFER_SIZE (16u * 1024 * 1024)
#elif defined(__s390x__)
/* We have a +- 4GB range on the branches; leave some slop. */
# define MAX_CODE_GEN_BUFFER_SIZE (3ul * 1024 * 1024 * 1024)
#else
# define MAX_CODE_GEN_BUFFER_SIZE ((size_t)-1)
#endif

#define DEFAULT_CODE_GEN_BUFFER_SIZE (32u * 1024 * 1024)

static inline size_t size_code_gen_buffer(size_t tb_size)
{
/* Size the buffer. */
if (tb_size == 0) {
#ifdef USE_STATIC_CODE_GEN_BUFFER
code_gen_buffer = static_code_gen_buffer;
code_gen_buffer_size = DEFAULT_CODE_GEN_BUFFER_SIZE;
map_exec(code_gen_buffer, code_gen_buffer_size);
#else
code_gen_buffer_size = tb_size;
if (code_gen_buffer_size == 0) {
#if defined(CONFIG_USER_ONLY)
code_gen_buffer_size = DEFAULT_CODE_GEN_BUFFER_SIZE;
tb_size = DEFAULT_CODE_GEN_BUFFER_SIZE;
#else
/* XXX: needs adjustments */
code_gen_buffer_size = (unsigned long)(ram_size / 4);
/* ??? Needs adjustments. */
/* ??? If we relax the requirement that CONFIG_USER_ONLY use the
static buffer, we could size this on RESERVED_VA, on the text
segment size of the executable, or continue to use the default. */
tb_size = (unsigned long)(ram_size / 4);
#endif
}
if (code_gen_buffer_size < MIN_CODE_GEN_BUFFER_SIZE)
code_gen_buffer_size = MIN_CODE_GEN_BUFFER_SIZE;
/* The code gen buffer location may have constraints depending on
the host cpu and OS */
#if defined(__linux__)
{
int flags;
void *start = NULL;

flags = MAP_PRIVATE | MAP_ANONYMOUS;
#if defined(__x86_64__)
flags |= MAP_32BIT;
/* Cannot map more than that */
if (code_gen_buffer_size > (800 * 1024 * 1024))
code_gen_buffer_size = (800 * 1024 * 1024);
#elif defined(__sparc__) && HOST_LONG_BITS == 64
// Map the buffer below 2G, so we can use direct calls and branches
start = (void *) 0x40000000UL;
if (code_gen_buffer_size > (512 * 1024 * 1024))
code_gen_buffer_size = (512 * 1024 * 1024);
#elif defined(__arm__)
/* Keep the buffer no bigger than 16MB to branch between blocks */
if (code_gen_buffer_size > 16 * 1024 * 1024)
code_gen_buffer_size = 16 * 1024 * 1024;
#elif defined(__s390x__)
/* Map the buffer so that we can use direct calls and branches. */
/* We have a +- 4GB range on the branches; leave some slop. */
if (code_gen_buffer_size > (3ul * 1024 * 1024 * 1024)) {
code_gen_buffer_size = 3ul * 1024 * 1024 * 1024;
}
start = (void *)0x90000000UL;
#endif
code_gen_buffer = mmap(start, code_gen_buffer_size,
PROT_WRITE | PROT_READ | PROT_EXEC,
flags, -1, 0);
if (code_gen_buffer == MAP_FAILED) {
fprintf(stderr, "Could not allocate dynamic translator buffer\n");
exit(1);
}
if (tb_size < MIN_CODE_GEN_BUFFER_SIZE) {
tb_size = MIN_CODE_GEN_BUFFER_SIZE;
}
#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) \
|| defined(__DragonFly__) || defined(__OpenBSD__) \
|| defined(__NetBSD__)
{
int flags;
void *addr = NULL;
flags = MAP_PRIVATE | MAP_ANONYMOUS;
#if defined(__x86_64__)
/* FreeBSD doesn't have MAP_32BIT, use MAP_FIXED and assume
* 0x40000000 is free */
flags |= MAP_FIXED;
addr = (void *)0x40000000;
/* Cannot map more than that */
if (code_gen_buffer_size > (800 * 1024 * 1024))
code_gen_buffer_size = (800 * 1024 * 1024);
#elif defined(__sparc__) && HOST_LONG_BITS == 64
// Map the buffer below 2G, so we can use direct calls and branches
addr = (void *) 0x40000000UL;
if (code_gen_buffer_size > (512 * 1024 * 1024)) {
code_gen_buffer_size = (512 * 1024 * 1024);
}
#endif
code_gen_buffer = mmap(addr, code_gen_buffer_size,
PROT_WRITE | PROT_READ | PROT_EXEC,
flags, -1, 0);
if (code_gen_buffer == MAP_FAILED) {
fprintf(stderr, "Could not allocate dynamic translator buffer\n");
exit(1);
}
if (tb_size > MAX_CODE_GEN_BUFFER_SIZE) {
tb_size = MAX_CODE_GEN_BUFFER_SIZE;
}
code_gen_buffer_size = tb_size;
return tb_size;
}

#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, code_gen_buffer_size);
return static_code_gen_buffer;
}
#elif defined(USE_MMAP)
static inline void *alloc_code_gen_buffer(void)
{
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
uintptr_t start = 0;
void *buf;

/* Constrain the position of the buffer based on the host cpu.
Note that these addresses are chosen in concert with the
addresses assigned in the relevant linker script file. */
# if defined(__x86_64__) && defined(MAP_32BIT)
/* Force the memory down into low memory with the executable.
Leave the choice of exact location with the kernel. */
flags |= MAP_32BIT;
/* Cannot expect to map more than 800MB in low memory. */
if (code_gen_buffer_size > 800u * 1024 * 1024) {
code_gen_buffer_size = 800u * 1024 * 1024;
}
# elif defined(__sparc__)
start = 0x40000000ul;
# elif defined(__s390x__)
start = 0x90000000ul;
# endif

buf = mmap((void *)start, code_gen_buffer_size,
PROT_WRITE | PROT_READ | PROT_EXEC, flags, -1, 0);
return buf == MAP_FAILED ? NULL : buf;
}
#else
code_gen_buffer = g_malloc(code_gen_buffer_size);
map_exec(code_gen_buffer, code_gen_buffer_size);
#endif
#endif /* !USE_STATIC_CODE_GEN_BUFFER */
static inline void *alloc_code_gen_buffer(void)
{
void *buf = g_malloc(code_gen_buffer_size);
if (buf) {
map_exec(buf, code_gen_buffer_size);
}
return buf;
}
#endif /* USE_STATIC_CODE_GEN_BUFFER, USE_MMAP */

static inline void code_gen_alloc(size_t tb_size)
{
code_gen_buffer_size = size_code_gen_buffer(tb_size);
code_gen_buffer = alloc_code_gen_buffer();
if (code_gen_buffer == NULL) {
fprintf(stderr, "Could not allocate dynamic translator buffer\n");
exit(1);
}

map_exec(code_gen_prologue, sizeof(code_gen_prologue));
code_gen_buffer_max_size = code_gen_buffer_size -
(TCG_MAX_OP_SIZE * OPC_BUF_SIZE);
Expand Down Expand Up @@ -4188,7 +4199,7 @@ void dump_exec_info(FILE *f, fprintf_function cpu_fprintf)
}
/* XXX: avoid using doubles ? */
cpu_fprintf(f, "Translation buffer state:\n");
cpu_fprintf(f, "gen code size %td/%ld\n",
cpu_fprintf(f, "gen code size %td/%zd\n",
code_gen_ptr - code_gen_buffer, code_gen_buffer_max_size);
cpu_fprintf(f, "TB count %d/%d\n",
nb_tbs, code_gen_max_blocks);
Expand Down

0 comments on commit f1bc0bc

Please sign in to comment.