tramp.c

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Author : Madhavan T. Venkataraman
Date : 2021-03-05 10:07:30
Hash : 9ba55921
Message : Static tramp v5 (#624) * Static Trampolines Closure Trampoline Security Issue ================================= Currently, the trampoline code used in libffi is not statically defined in a source file (except for MACH). The trampoline is either pre-defined machine code in a data buffer. Or, it is generated at runtime. In order to execute a trampoline, it needs to be placed in a page with executable permissions. Executable data pages are attack surfaces for attackers who may try to inject their own code into the page and contrive to have it executed. The security settings in a system may prevent various tricks used in user land to write code into a page and to have it executed somehow. On such systems, libffi trampolines would not be able to run. Static Trampoline ================= To solve this problem, the trampoline code needs to be defined statically in a source file, compiled and placed in the text segment so it can be mapped and executed naturally without any tricks. However, the trampoline needs to be able to access the closure pointer at runtime. PC-relative data referencing ============================ The solution implemented in this patch set uses PC-relative data references. The trampoline is mapped in a code page. Adjacent to the code page, a data page is mapped that contains the parameters of the trampoline: - the closure pointer - pointer to the ABI handler to jump to The trampoline code uses an offset relative to its current PC to access its data. Some architectures support PC-relative data references in the ISA itself. E.g., X64 supports RIP-relative references. For others, the PC has to somehow be loaded into a general purpose register to do PC-relative data referencing. To do this, we need to define a get_pc() kind of function and call it to load the PC in a desired register. There are two cases: 1. The call instruction pushes the return address on the stack. In this case, get_pc() will extract the return address from the stack and load it in the desired register and return. 2. The call instruction stores the return address in a designated register. In this case, get_pc() will copy the return address to the desired register and return. Either way, the PC next to the call instruction is obtained. Scratch register ================ In order to do its job, the trampoline code would need to use a scratch register. Depending on the ABI, there may not be a register available for scratch. This problem needs to be solved so that all ABIs will work. The trampoline will save two values on the stack: - the closure pointer - the original value of the scratch register This is what the stack will look like: sp before trampoline ------> -------------------- | closure pointer | -------------------- | scratch register | sp after trampoline -------> -------------------- The ABI handler can do the following as needed by the ABI: - the closure pointer can be loaded in a desired register - the scratch register can be restored to its original value - the stack pointer can be restored to its original value (the value when the trampoline was invoked) To do this, I have defined prolog code for each ABI handler. The legacy trampoline jumps to the ABI handler directly. But the static trampoline defined in this patch jumps tp the prolog code which performs the above actions before jumping to the ABI handler. Trampoline Table ================ In order to reduce the trampoline memory footprint, the trampoline code would be defined as a code array in the text segment. This array would be mapped into the address space of the caller. The mapping would, therefore, contain a trampoline table. Adjacent to the trampoline table mapping, there will be a data mapping that contains a parameter table, one parameter block for each trampoline. The parameter block will contain: - a pointer to the closure - a pointer to the ABI handler The static trampoline code would finally look like this: - Make space on the stack for the closure and the scratch register by moving the stack pointer down - Store the original value of the scratch register on the stack - Using PC-relative reference, get the closure pointer - Store the closure pointer on the stack - Using PC-relative reference, get the ABI handler pointer - Jump to the ABI handler Mapping size ============ The size of the code mapping that contains the trampoline table needs to be determined on a per architecture basis. If a particular architecture supports multiple base page sizes, then the largest supported base page size needs to be chosen. E.g., we choose 16K for ARM64. Trampoline allocation and free ============================== Static trampolines are allocated in ffi_closure_alloc() and freed in ffi_closure_free(). Normally, applications use these functions. But there are some cases out there where the user of libffi allocates and manages its own closure memory. In such cases, static trampolines cannot be used. These will fall back to using legacy trampolines. The user has to make sure that the memory is executable. ffi_closure structure ===================== I did not want to make any changes to the size of the closure structure for this feature to guarantee compatibility. But the opaque static trampoline handle needs to be stored in the closure. I have defined it as follows: - char tramp[FFI_TRAMPOLINE_SIZE]; + union { + char tramp[FFI_TRAMPOLINE_SIZE]; + void *ftramp; + }; If static trampolines are used, then tramp[] is not needed to store a dynamic trampoline. That space can be reused to store the handle. Hence, the union. Architecture Support ==================== Support has been added for x64, i386, aarch64 and arm. Support for other architectures can be added very easily in the future. OS Support ========== Support has been added for Linux. Support for other OSes can be added very easily. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> * x86: Support for Static Trampolines - Define the arch-specific initialization function ffi_tramp_arch () that returns trampoline size information to common code. - Define the trampoline code mapping and data mapping sizes. - Define the trampoline code table statically. Define two tables, actually, one with CET and one without. - Introduce a tiny prolog for each ABI handling function. The ABI handlers addressed are: - ffi_closure_unix64 - ffi_closure_unix64_sse - ffi_closure_win64 The prolog functions are called: - ffi_closure_unix64_alt - ffi_closure_unix64_sse_alt - ffi_closure_win64_alt The legacy trampoline jumps to the ABI handler. The static trampoline jumps to the prolog function. The prolog function uses the information provided by the static trampoline, sets things up for the ABI handler and then jumps to the ABI handler. - Call ffi_tramp_set_parms () in ffi_prep_closure_loc () to initialize static trampoline parameters. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> * i386: Support for Static Trampolines - Define the arch-specific initialization function ffi_tramp_arch () that returns trampoline size information to common code. - Define the trampoline code table statically. Define two tables, actually, one with CET and one without. - Define the trampoline code table statically. - Introduce a tiny prolog for each ABI handling function. The ABI handlers addressed are: - ffi_closure_i386 - ffi_closure_STDCALL - ffi_closure_REGISTER The prolog functions are called: - ffi_closure_i386_alt - ffi_closure_STDCALL_alt - ffi_closure_REGISTER_alt The legacy trampoline jumps to the ABI handler. The static trampoline jumps to the prolog function. The prolog function uses the information provided by the static trampoline, sets things up for the ABI handler and then jumps to the ABI handler. - Call ffi_tramp_set_parms () in ffi_prep_closure_loc () to initialize static trampoline parameters. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> * arm64: Support for Static Trampolines - Define the arch-specific initialization function ffi_tramp_arch () that returns trampoline size information to common code. - Define the trampoline code mapping and data mapping sizes. - Define the trampoline code table statically. - Introduce a tiny prolog for each ABI handling function. The ABI handlers addressed are: - ffi_closure_SYSV - ffi_closure_SYSV_V The prolog functions are called: - ffi_closure_SYSV_alt - ffi_closure_SYSV_V_alt The legacy trampoline jumps to the ABI handler. The static trampoline jumps to the prolog function. The prolog function uses the information provided by the static trampoline, sets things up for the ABI handler and then jumps to the ABI handler. - Call ffi_tramp_set_parms () in ffi_prep_closure_loc () to initialize static trampoline parameters. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> * arm: Support for Static Trampolines - Define the arch-specific initialization function ffi_tramp_arch () that returns trampoline size information to common code. - Define the trampoline code mapping and data mapping sizes. - Define the trampoline code table statically. - Introduce a tiny prolog for each ABI handling function. The ABI handlers addressed are: - ffi_closure_SYSV - ffi_closure_VFP The prolog functions are called: - ffi_closure_SYSV_alt - ffi_closure_VFP_alt The legacy trampoline jumps to the ABI handler. The static trampoline jumps to the prolog function. The prolog function uses the information provided by the static trampoline, sets things up for the ABI handler and then jumps to the ABI handler. - Call ffi_tramp_set_parms () in ffi_prep_closure_loc () to initialize static trampoline parameters. Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>

src/tramp.c

/* -----------------------------------------------------------------------
   tramp.c - Copyright (c) 2020 Madhavan T. Venkataraman

   API and support functions for managing statically defined closure
   trampolines.

   Permission is hereby granted, free of charge, to any person obtaining
   a copy of this software and associated documentation files (the
   ``Software''), to deal in the Software without restriction, including
   without limitation the rights to use, copy, modify, merge, publish,
   distribute, sublicense, and/or sell copies of the Software, and to
   permit persons to whom the Software is furnished to do so, subject to
   the following conditions:

   The above copyright notice and this permission notice shall be included
   in all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
   NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   DEALINGS IN THE SOFTWARE.
   ----------------------------------------------------------------------- */

#include <fficonfig.h>

#ifdef FFI_EXEC_STATIC_TRAMP

/* -------------------------- Headers and Definitions ---------------------*/
/*
 * Add support for other OSes later. For now, it is just Linux.
 */

#if defined __linux__
#ifdef __linux__
#define _GNU_SOURCE 1
#endif
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <fcntl.h>
#include <pthread.h>
#include <sys/mman.h>
#include <tramp.h>
#ifdef __linux__
#include <linux/limits.h>
#include <linux/types.h>
#endif
#endif /* __linux__ */

/*
 * Each architecture defines static code for a trampoline code table. The
 * trampoline code table is mapped into the address space of a process.
 *
 * The following architecture specific function returns:
 *
 *	- the address of the trampoline code table in the text segment
 *	- the size of each trampoline in the trampoline code table
 *	- the size of the mapping for the whole trampoline code table
 */
void __attribute__((weak)) *ffi_tramp_arch (size_t *tramp_size,
  size_t *map_size);

/* ------------------------- Trampoline Data Structures --------------------*/

struct tramp;

/*
 * Trampoline table. Manages one trampoline code table and one trampoline
 * parameter table.
 *
 * prev, next	Links in the global trampoline table list.
 * code_table	Trampoline code table mapping.
 * parm_table	Trampoline parameter table mapping.
 * array	Array of trampolines malloced.
 * free		List of free trampolines.
 * nfree	Number of free trampolines.
 */
struct tramp_table
{
  struct tramp_table *prev;
  struct tramp_table *next;
  void *code_table;
  void *parm_table;
  struct tramp *array;
  struct tramp *free;
  int nfree;
};

/*
 * Parameters for each trampoline.
 *
 * data
 *	Data for the target code that the trampoline jumps to.
 * target
 *	Target code that the trampoline jumps to.
 */
struct tramp_parm
{
  void *data;
  void *target;
};

/*
 * Trampoline structure for each trampoline.
 *
 * prev, next	Links in the trampoline free list of a trampoline table.
 * table	Trampoline table to which this trampoline belongs.
 * code		Address of this trampoline in the code table mapping.
 * parm		Address of this trampoline's parameters in the parameter
 *		table mapping.
 */
struct tramp
{
  struct tramp *prev;
  struct tramp *next;
  struct tramp_table *table;
  void *code;
  struct tramp_parm *parm;
};

enum tramp_globals_status {
	TRAMP_GLOBALS_UNINITIALIZED = 0,
	TRAMP_GLOBALS_PASSED,
	TRAMP_GLOBALS_FAILED,
};

/*
 * Trampoline globals.
 *
 * fd
 *	File descriptor of binary file that contains the trampoline code table.
 * offset
 *	Offset of the trampoline code table in that file.
 * text
 *	Address of the trampoline code table in the text segment.
 * map_size
 *	Size of the trampoline code table mapping.
 * size
 *	Size of one trampoline in the trampoline code table.
 * ntramp
 *	Total number of trampolines in the trampoline code table.
 * free_tables
 *	List of trampoline tables that contain free trampolines.
 * nfree_tables
 *	Number of trampoline tables that contain free trampolines.
 * status
 *	Initialization status.
 */
struct tramp_globals
{
  int fd;
  off_t offset;
  void *text;
  size_t map_size;
  size_t size;
  int ntramp;
  struct tramp_table *free_tables;
  int nfree_tables;
  enum tramp_globals_status status;
};

static struct tramp_globals tramp_globals;

/* --------------------- Trampoline File Initialization --------------------*/

/*
 * The trampoline file is the file used to map the trampoline code table into
 * the address space of a process. There are two ways to get this file:
 *
 * - From the OS. E.g., on Linux, /proc/<pid>/maps lists all the memory
 *   mappings for <pid>. For file-backed mappings, maps supplies the file name
 *   and the file offset. Using this, we can locate the mapping that maps
 *   libffi and get the path to the libffi binary. And, we can compute the
 *   offset of the trampoline code table within that binary.
 *
 * - Else, if we can create a temporary file, we can write the trampoline code
 *   table from the text segment into the temporary file.
 *
 * The first method is the preferred one. If the OS security subsystem
 * disallows mapping unsigned files with PROT_EXEC, then the second method
 * will fail.
 *
 * If an OS allows the trampoline code table in the text segment to be
 * directly remapped (e.g., MACH vm_remap ()), then we don't need the
 * trampoline file.
 */
static int tramp_table_alloc (void);

#if defined __linux__

static int
ffi_tramp_get_libffi (void)
{
  FILE *fp;
  char file[PATH_MAX], line[PATH_MAX+100], perm[10], dev[10];
  unsigned long start, end, offset, inode;
  uintptr_t addr = (uintptr_t) tramp_globals.text;
  int nfields, found;

  snprintf (file, PATH_MAX, "/proc/%d/maps", getpid());
  fp = fopen (file, "r");
  if (fp == NULL)
    return 0;

  found = 0;
  while (feof (fp) == 0) {
    if (fgets (line, sizeof (line), fp) == 0)
      break;

    nfields = sscanf (line, "%lx-%lx %9s %lx %9s %ld %s",
      &start, &end, perm, &offset, dev, &inode, file);
    if (nfields != 7)
      continue;

    if (addr >= start && addr < end) {
      tramp_globals.offset = offset + (addr - start);
      found = 1;
      break;
    }
  }
  fclose (fp);

  if (!found)
    return 0;

  tramp_globals.fd = open (file, O_RDONLY);
  if (tramp_globals.fd == -1)
    return 0;

  /*
   * Allocate a trampoline table just to make sure that the trampoline code
   * table can be mapped.
   */
  if (!tramp_table_alloc ())
    {
      close (tramp_globals.fd);
      tramp_globals.fd = -1;
      return 0;
    }
  return 1;
}

#endif /* __linux__ */

#if defined __linux__

#if defined HAVE_MKSTEMP

static int
ffi_tramp_get_temp_file (void)
{
  char template[12] = "/tmp/XXXXXX";
  ssize_t count;

  tramp_globals.offset = 0;
  tramp_globals.fd = mkstemp (template);
  if (tramp_globals.fd == -1)
    return 0;

  unlink (template);
  /*
   * Write the trampoline code table into the temporary file and allocate a
   * trampoline table to make sure that the temporary file can be mapped.
   */
  count = write(tramp_globals.fd, tramp_globals.text, tramp_globals.map_size);
  if (count == tramp_globals.map_size && tramp_table_alloc ())
    return 1;

  close (tramp_globals.fd);
  tramp_globals.fd = -1;
  return 0;
}

#else /* !defined HAVE_MKSTEMP */

/*
 * TODO:
 * src/closures.c contains code for finding temp file that has EXEC
 * permissions. May be, some of that code can be shared with static
 * trampolines.
 */
static int
ffi_tramp_get_temp_file (void)
{
  tramp_globals.offset = 0;
  tramp_globals.fd = -1;
  return 0;
}

#endif /* defined HAVE_MKSTEMP */

#endif /* __linux__ */

/* ------------------------ OS-specific Initialization ----------------------*/

#if defined __linux__

static int
ffi_tramp_init_os (void)
{
  if (ffi_tramp_get_libffi ())
    return 1;
  return ffi_tramp_get_temp_file ();
}

#endif /* __linux__ */

/* --------------------------- OS-specific Locking -------------------------*/

#if defined __linux__

static pthread_mutex_t tramp_globals_mutex = PTHREAD_MUTEX_INITIALIZER;

static void
ffi_tramp_lock(void)
{
  pthread_mutex_lock (&tramp_globals_mutex);
}

static void
ffi_tramp_unlock()
{
  pthread_mutex_unlock (&tramp_globals_mutex);
}

#endif /* __linux__ */

/* ------------------------ OS-specific Memory Mapping ----------------------*/

/*
 * Create a trampoline code table mapping and a trampoline parameter table
 * mapping. The two mappings must be adjacent to each other for PC-relative
 * access.
 *
 * For each trampoline in the code table, there is a corresponding parameter
 * block in the parameter table. The size of the parameter block is the same
 * as the size of the trampoline. This means that the parameter block is at
 * a fixed offset from its trampoline making it easy for a trampoline to find
 * its parameters using PC-relative access.
 *
 * The parameter block will contain a struct tramp_parm. This means that
 * sizeof (struct tramp_parm) cannot exceed the size of a parameter block.
 */

#if defined __linux__

static int
tramp_table_map (struct tramp_table *table)
{
  char *addr;

  /*
   * Create an anonymous mapping twice the map size. The top half will be used
   * for the code table. The bottom half will be used for the parameter table.
   */
  addr = mmap (NULL, tramp_globals.map_size * 2, PROT_READ | PROT_WRITE,
    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  if (addr == MAP_FAILED)
    return 0;

  /*
   * Replace the top half of the anonymous mapping with the code table mapping.
   */
  table->code_table = mmap (addr, tramp_globals.map_size, PROT_READ | PROT_EXEC,
    MAP_PRIVATE | MAP_FIXED, tramp_globals.fd, tramp_globals.offset);
  if (table->code_table == MAP_FAILED)
    {
      (void) munmap (addr, tramp_globals.map_size * 2);
      return 0;
    }
  table->parm_table = table->code_table + tramp_globals.map_size;
  return 1;
}

static void
tramp_table_unmap (struct tramp_table *table)
{
  (void) munmap (table->code_table, tramp_globals.map_size);
  (void) munmap (table->parm_table, tramp_globals.map_size);
}

#endif /* __linux__ */

/* ------------------------ Trampoline Initialization ----------------------*/

/*
 * Initialize the static trampoline feature.
 */
static int
ffi_tramp_init (void)
{
  if (tramp_globals.status == TRAMP_GLOBALS_PASSED)
    return 1;

  if (tramp_globals.status == TRAMP_GLOBALS_FAILED)
    return 0;

  if (ffi_tramp_arch == NULL)
    {
      tramp_globals.status = TRAMP_GLOBALS_FAILED;
      return 0;
    }

  tramp_globals.free_tables = NULL;
  tramp_globals.nfree_tables = 0;

  /*
   * Get trampoline code table information from the architecture.
   */
  tramp_globals.text = ffi_tramp_arch (&tramp_globals.size,
    &tramp_globals.map_size);
  tramp_globals.ntramp = tramp_globals.map_size / tramp_globals.size;

  if (sysconf (_SC_PAGESIZE) > tramp_globals.map_size)
    return 0;

  if (ffi_tramp_init_os ())
    {
      tramp_globals.status = TRAMP_GLOBALS_PASSED;
      return 1;
    }

  tramp_globals.status = TRAMP_GLOBALS_FAILED;
  return 0;
}

/* ---------------------- Trampoline Table functions ---------------------- */

/* This code assumes that malloc () is available on all OSes. */

static void tramp_add (struct tramp *tramp);

/*
 * Allocate and initialize a trampoline table.
 */
static int
tramp_table_alloc (void)
{
  struct tramp_table *table;
  struct tramp *tramp_array, *tramp;
  size_t size;
  char *code, *parm;
  int i;

  /*
   * If we already have tables with free trampolines, there is no need to
   * allocate a new table.
   */
  if (tramp_globals.nfree_tables > 0)
    return 1;

  /*
   * Allocate a new trampoline table structure.
   */
  table = malloc (sizeof (*table));
  if (table == NULL)
    return 0;

  /*
   * Allocate new trampoline structures.
   */
  tramp_array = malloc (sizeof (*tramp) * tramp_globals.ntramp);
  if (tramp_array == NULL)
    goto free_table;

  /*
   * Map a code table and a parameter table into the caller's address space.
   */
  if (!tramp_table_map (table))
    {
      /*
       * Failed to map the code and parameter tables.
       */
      goto free_tramp_array;
    }

  /*
   * Initialize the trampoline table.
   */
  table->array = tramp_array;
  table->free = NULL;
  table->nfree = 0;

  /*
   * Populate the trampoline table free list. This will also add the trampoline
   * table to the global list of trampoline tables.
   */
  size = tramp_globals.size;
  code = table->code_table;
  parm = table->parm_table;
  for (i = 0; i < tramp_globals.ntramp; i++)
    {
      tramp = &tramp_array[i];
      tramp->table = table;
      tramp->code = code;
      tramp->parm = (struct tramp_parm *) parm;
      tramp_add (tramp);

      code += size;
      parm += size;
    }
  /* Success */
  return 1;

/* Failure */
free_tramp_array:
  free (tramp_array);
free_table:
  free (table);
  return 0;
}

/*
 * Free a trampoline table.
 */
static void
tramp_table_free (struct tramp_table *table)
{
  tramp_table_unmap (table);
  free (table->array);
  free (table);
}

/*
 * Add a new trampoline table to the global table list.
 */
static void
tramp_table_add (struct tramp_table *table)
{
  table->next = tramp_globals.free_tables;
  table->prev = NULL;
  if (tramp_globals.free_tables != NULL)
    tramp_globals.free_tables->prev = table;
  tramp_globals.free_tables = table;
  tramp_globals.nfree_tables++;
}

/*
 * Delete a trampoline table from the global table list.
 */
static void
tramp_table_del (struct tramp_table *table)
{
  tramp_globals.nfree_tables--;
  if (table->prev != NULL)
    table->prev->next = table->next;
  if (table->next != NULL)
    table->next->prev = table->prev;
  if (tramp_globals.free_tables == table)
    tramp_globals.free_tables = table->next;
}

/* ------------------------- Trampoline functions ------------------------- */

/*
 * Add a trampoline to its trampoline table.
 */
static void
tramp_add (struct tramp *tramp)
{
  struct tramp_table *table = tramp->table;

  tramp->next = table->free;
  tramp->prev = NULL;
  if (table->free != NULL)
    table->free->prev = tramp;
  table->free = tramp;
  table->nfree++;

  if (table->nfree == 1)
    tramp_table_add (table);

  /*
   * We don't want to keep too many free trampoline tables lying around.
   */
  if (table->nfree == tramp_globals.ntramp &&
    tramp_globals.nfree_tables > 1)
    {
      tramp_table_del (table);
      tramp_table_free (table);
    }
}

/*
 * Remove a trampoline from its trampoline table.
 */
static void
tramp_del (struct tramp *tramp)
{
  struct tramp_table *table = tramp->table;

  table->nfree--;
  if (tramp->prev != NULL)
    tramp->prev->next = tramp->next;
  if (tramp->next != NULL)
    tramp->next->prev = tramp->prev;
  if (table->free == tramp)
    table->free = tramp->next;

  if (table->nfree == 0)
    tramp_table_del (table);
}

/* ------------------------ Trampoline API functions ------------------------ */

int
ffi_tramp_is_supported(void)
{
  int ret;

  ffi_tramp_lock();
  ret = ffi_tramp_init ();
  ffi_tramp_unlock();
  return ret;
}

/*
 * Allocate a trampoline and return its opaque address.
 */
void *
ffi_tramp_alloc (int flags)
{
  struct tramp *tramp;

  ffi_tramp_lock();

  if (!ffi_tramp_init () || flags != 0)
    {
      ffi_tramp_unlock();
      return NULL;
    }

  if (!tramp_table_alloc ())
    {
      ffi_tramp_unlock();
      return NULL;
    }

  tramp = tramp_globals.free_tables->free;
  tramp_del (tramp);

  ffi_tramp_unlock();

  return tramp;
}

/*
 * Set the parameters for a trampoline.
 */
void
ffi_tramp_set_parms (void *arg, void *target, void *data)
{
  struct tramp *tramp = arg;

  ffi_tramp_lock();
  tramp->parm->target = target;
  tramp->parm->data = data;
  ffi_tramp_unlock();
}

/*
 * Get the invocation address of a trampoline.
 */
void *
ffi_tramp_get_addr (void *arg)
{
  struct tramp *tramp = arg;
  void *addr;

  ffi_tramp_lock();
  addr = tramp->code;
  ffi_tramp_unlock();

  return addr;
}

/*
 * Free a trampoline.
 */
void
ffi_tramp_free (void *arg)
{
  struct tramp *tramp = arg;

  ffi_tramp_lock();
  tramp_add (tramp);
  ffi_tramp_unlock();
}

/* ------------------------------------------------------------------------- */

#else /* !FFI_EXEC_STATIC_TRAMP */

#include <stddef.h>

int
ffi_tramp_is_supported(void)
{
  return 0;
}

void *
ffi_tramp_alloc (int flags)
{
  return NULL;
}

void
ffi_tramp_set_parms (void *arg, void *target, void *data)
{
}

void *
ffi_tramp_get_addr (void *arg)
{
  return NULL;
}

void
ffi_tramp_free (void *arg)
{
}

#endif /* FFI_EXEC_STATIC_TRAMP */

kc3-lang/libffi/src/tramp.c

Commit

kc3-lang/libffi /src/tramp.c