From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by sourceware.org (Postfix) with ESMTP id 9573B396E86B for ; Wed, 2 Dec 2020 21:33:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 9573B396E86B Received: from [192.168.254.32] (unknown [47.187.219.45]) by linux.microsoft.com (Postfix) with ESMTPSA id CD3FE20B717A; Wed, 2 Dec 2020 13:33:55 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com CD3FE20B717A Subject: Re: [RFC PATCH v1 1/4] Static Trampolines To: Anthony Green Cc: libffi-discuss , fw@deneb.enyo.de References: <20201124193206.10289-1-madvenka@linux.microsoft.com> <20201124193206.10289-2-madvenka@linux.microsoft.com> From: "Madhavan T. Venkataraman" Message-ID: Date: Wed, 2 Dec 2020 15:33:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-26.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, ENV_AND_HDR_SPF_MATCH, GIT_PATCH_0, KAM_ASCII_DIVIDERS, NICE_REPLY_A, SPF_HELO_PASS, SPF_PASS, TXREP, USER_IN_DEF_DKIM_WL, USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libffi-discuss@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libffi-discuss mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Dec 2020 21:34:02 -0000 Thanks, Anthony. Madhavan On 12/2/20 12:14 PM, Anthony Green wrote: > Thanks, Madhavan.  It seems that the travis-ci testing is stalled -- perhaps because they just changed their policies around free usage.  I've reached out to them for help.   It's possible we could move some of the load to GitHub Actions, but as far as I know, travis-ci is the only platform with s390 (and perhaps other) support. > > AG > > > On Wed, Dec 2, 2020 at 11:49 AM Madhavan T. Venkataraman > wrote: > > > > On 11/24/20 1:49 PM, Anthony Green wrote: > > Thank you for your submission, Madhavan.  This will be interesting reading! > > > > In the meantime, it would be helpful if you submitted this as a PR on GitHub.  This will trigger CI testing for over 20 different systems so we can have an initial look at any build/test problems. > > > > Just submitted the PR: > > https://github.com/libffi/libffi/pull/603 > > Thanks. > > Madhavan > > > AG > > > > On Tue, Nov 24, 2020 at 2:32 PM madvenka--- via Libffi-discuss >> wrote: > > > >     From: "Madhavan T. Venkataraman" >> > > > >     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 be required 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 > >               (when the trampoline was invoked) > > > >     Thus the ABI handlers will have a couple of lines of code at the very > >     beginning to do this so that all ABIs will work. > > > >     NOTE: > >             The documentation for this feature will contain information on: > > > >             - the name of the scratch register for each architecture > > > >             - the stack offsets at which the closure and the scratch register > >               will be copied > > > >     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, there will be a data mapping that contains > >     a parameter table, one parameter block for each trampoline. The parameter > >     table will contain: > > > >             - a pointer to the closure > >             - a pointer to the ABI handler > > > >     The 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 > > > >     Trampoline API > >     ============== > > > >     There is a lot of dynamic code out there. They all have the same security > >     issue. Dynamic code can be re-written into static code provided the data > >     required by the static code can be passed to it just like we pass the > >     closure pointer to an ABI handler. > > > >     So, the same trampoline functions used by libffi internally need to be > >     made available to the rest of the world in the form of an API. The > >     following API has been defined in this solution: > > > >     int ffi_tramp_is_supported(void); > > > >             To support static trampolines, code needs to be added to each > >             architecture. Also, the feature itself can be enabled via a > >             configuration option. So, this function tells us if the feature > >             is supported and enabled in the current libffi or not. > > > >     void *ffi_tramp_alloc (int flags); > > > >             Allocate a trampoline. Currently, flags are zero. An opaque > >             trampoline structure pointer is returned. > > > >             Internally, libffi manages trampoline tables and individual > >             trampolines in each table. > > > >     int ffi_tramp_set_parms (void *tramp, void *target, void *data); > > > >             Initialize the parameters of a trampoline. That is, the target code > >             that the trampoline should jump to and the data that needs to be > >             passed to the target code. > > > >     void *ffi_tramp_get_addr (void *tramp); > > > >             Return the address of the trampoline to invoke the trampoline with. > >             The trampoline can be invoked in one of two ways: > > > >                     - Simply branch to the trampoline address > >                     - Treat the trampoline address as a function pointer and > >                       call it. > > > >             Which method is used depends on the target code. > > > >     void ffi_tramp_free (void *tramp); > > > >             Free a trampoline. > > > >     Configuration > >     ============= > > > >     A new configuration option, --enable-static-tramp has been added to enable > >     the use of static trampolines. > > > >     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 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, the static trampoline API 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. > > > >     Signed-off-by: Madhavan T. Venkataraman >> > >     --- > >      Makefile.am                                 |   3 +- > >      configure.ac                                 |   7 + > >      include/ffi.h.in                             |  13 +- > >      include/ffi_common.h                        |   4 + > >      libffi.map.in                                |  11 + > >      src/closures.c                              |  54 +- > >      src/tramp.c                                 | 563 ++++++++++++++++++++ > >      testsuite/libffi.closures/closure_loc_fn0.c |   3 + > >      8 files changed, 654 insertions(+), 4 deletions(-) > >      create mode 100644 src/tramp.c > > > >     diff --git a/Makefile.am b/Makefile.am > >     index 7654bf5..1b18198 100644 > >     --- a/Makefile.am > >     +++ b/Makefile.am > >     @@ -38,7 +38,8 @@ toolexeclib_LTLIBRARIES = libffi.la > >      noinst_LTLIBRARIES = libffi_convenience.la > > > >      libffi_la_SOURCES = src/prep_cif.c src/types.c \ > >     -               src/raw_api.c src/java_raw_api.c src/closures.c > >     +               src/raw_api.c src/java_raw_api.c src/closures.c \ > >     +               src/tramp.c > > > >      if FFI_DEBUG > >      libffi_la_SOURCES += src/debug.c > >     diff --git a/configure.ac b/configure.ac > >     index 790274e..898ede6 100644 > >     --- a/configure.ac > >     +++ b/configure.ac > >     @@ -360,6 +360,13 @@ AC_ARG_ENABLE(raw-api, > >          AC_DEFINE(FFI_NO_RAW_API, 1, [Define this if you do not want support for the raw API.]) > >        fi) > > > >     +AC_ARG_ENABLE(static-tramp, > >     +[  --enable-static-tramp        use statically defined trampolines], > >     +  if test "$enable_static_tramp" = "yes"; then > >     +    AC_DEFINE(FFI_EXEC_STATIC_TRAMP, 1, > >     +      [Define this if you want to use statically defined trampolines.]) > >     +  fi) > >     + > >      AC_ARG_ENABLE(purify-safety, > >      [  --enable-purify-safety  purify-safe mode], > >        if test "$enable_purify_safety" = "yes"; then > >     diff --git a/include/ffi.h.in b/include/ffi.h.in > >     index 38885b0..c6a21d9 100644 > >     --- a/include/ffi.h.in > >     +++ b/include/ffi.h.in > >     @@ -310,7 +310,10 @@ typedef struct { > >        void *trampoline_table; > >        void *trampoline_table_entry; > >      #else > >     -  char tramp[FFI_TRAMPOLINE_SIZE]; > >     +  union { > >     +    char tramp[FFI_TRAMPOLINE_SIZE]; > >     +    void *ftramp; > >     +  }; > >      #endif > >        ffi_cif   *cif; > >        void     (*fun)(ffi_cif*,void*,void**,void*); > >     @@ -457,6 +460,14 @@ FFI_API void ffi_call_go (ffi_cif *cif, void (*fn)(void), void *rvalue, > > > >      #endif /* FFI_GO_CLOSURES */ > > > >     +/* ---- Static Trampoline Definitions -------------------------------------- */ > >     + > >     +FFI_API int ffi_tramp_is_supported(void); > >     +FFI_API void *ffi_tramp_alloc (int flags); > >     +FFI_API int ffi_tramp_set_parms (void *tramp, void *data, void *code); > >     +FFI_API void *ffi_tramp_get_addr (void *tramp); > >     +FFI_API void ffi_tramp_free (void *tramp); > >     + > >      /* ---- Public interface definition -------------------------------------- */ > > > >      FFI_API > >     diff --git a/include/ffi_common.h b/include/ffi_common.h > >     index 76b9dd6..8743126 100644 > >     --- a/include/ffi_common.h > >     +++ b/include/ffi_common.h > >     @@ -103,6 +103,10 @@ ffi_status ffi_prep_cif_core(ffi_cif *cif, > >         some targets.  */ > >      void *ffi_data_to_code_pointer (void *data) FFI_HIDDEN; > > > >     +/* The arch code calls this to set the code and data parameters for a > >     +   closure's static trampoline, if any. */ > >     +int ffi_closure_tramp_set_parms (void *closure, void *code); > >     + > >      /* Extended cif, used in callback from assembly routine */ > >      typedef struct > >      { > >     diff --git a/libffi.map.in b/libffi.map.in > >     index de8778a..049c73e 100644 > >     --- a/libffi.map.in > >     +++ b/libffi.map.in > >     @@ -74,3 +74,14 @@ LIBFFI_GO_CLOSURE_8.0 { > >             ffi_prep_go_closure; > >      } LIBFFI_CLOSURE_8.0; > >      #endif > >     + > >     +#if FFI_EXEC_STATIC_TRAMP > >     +LIBFFI_STATIC_TRAMP_8.0 { > >     +  global: > >     +       ffi_tramp_is_supported; > >     +       ffi_tramp_alloc; > >     +       ffi_tramp_set_parms; > >     +       ffi_tramp_get_addr; > >     +       ffi_tramp_free; > >     +} LIBFFI_BASE_8.0; > >     +#endif > >     diff --git a/src/closures.c b/src/closures.c > >     index 4fe6158..cf1d3de 100644 > >     --- a/src/closures.c > >     +++ b/src/closures.c > >     @@ -109,6 +109,12 @@ ffi_closure_free (void *ptr) > >        munmap(dataseg, rounded_size); > >        munmap(codeseg, rounded_size); > >      } > >     + > >     +int > >     +ffi_closure_tramp_set_parms (void *ptr, void *code) > >     +{ > >     +  return 0; > >     +} > >      #else /* !NetBSD with PROT_MPROTECT */ > > > >      #if !FFI_MMAP_EXEC_WRIT && !FFI_EXEC_TRAMPOLINE_TABLE > >     @@ -843,6 +849,12 @@ dlmmap (void *start, size_t length, int prot, > >               && flags == (MAP_PRIVATE | MAP_ANONYMOUS) > >               && fd == -1 && offset == 0); > > > >     +  if (execfd == -1 && ffi_tramp_is_supported ()) > >     +    { > >     +      ptr = mmap (start, length, prot & ~PROT_EXEC, flags, fd, offset); > >     +      return ptr; > >     +    } > >     + > >        if (execfd == -1 && is_emutramp_enabled ()) > >          { > >            ptr = mmap (start, length, prot & ~PROT_EXEC, flags, fd, offset); > >     @@ -922,7 +934,7 @@ segment_holding_code (mstate m, char* addr) > >      void * > >      ffi_closure_alloc (size_t size, void **code) > >      { > >     -  void *ptr; > >     +  void *ptr, *ftramp; > > > >        if (!code) > >          return NULL; > >     @@ -934,6 +946,17 @@ ffi_closure_alloc (size_t size, void **code) > >            msegmentptr seg = segment_holding (gm, ptr); > > > >            *code = add_segment_exec_offset (ptr, seg); > >     +      if (!ffi_tramp_is_supported ()) > >     +        return ptr; > >     + > >     +      ftramp = ffi_tramp_alloc (0); > >     +      if (ftramp == NULL) > >     +      { > >     +        dlfree (FFI_RESTORE_PTR (ptr)); > >     +        return NULL; > >     +      } > >     +      *code = ffi_tramp_get_addr (ftramp); > >     +      ((ffi_closure *) ptr)->ftramp = ftramp; > >          } > > > >        return ptr; > >     @@ -943,12 +966,17 @@ void * > >      ffi_data_to_code_pointer (void *data) > >      { > >        msegmentptr seg = segment_holding (gm, data); > >     + > >        /* We expect closures to be allocated with ffi_closure_alloc(), in > >           which case seg will be non-NULL.  However, some users take on the > >           burden of managing this memory themselves, in which case this > >           we'll just return data. */ > >        if (seg) > >     -    return add_segment_exec_offset (data, seg); > >     +    { > >     +      if (!ffi_tramp_is_supported ()) > >     +        return add_segment_exec_offset (data, seg); > >     +      return ffi_tramp_get_addr (((ffi_closure *) data)->ftramp); > >     +    } > >        else > >          return data; > >      } > >     @@ -966,10 +994,26 @@ ffi_closure_free (void *ptr) > >        if (seg) > >          ptr = sub_segment_exec_offset (ptr, seg); > >      #endif > >     +  if (ffi_tramp_is_supported ()) > >     +    ffi_tramp_free (((ffi_closure *) ptr)->ftramp); > > > >        dlfree (FFI_RESTORE_PTR (ptr)); > >      } > > > >     +int > >     +ffi_closure_tramp_set_parms (void *ptr, void *code) > >     +{ > >     +  void *ftramp; > >     + > >     +  msegmentptr seg = segment_holding (gm, ptr); > >     +  if (!seg || !ffi_tramp_is_supported()) > >     +    return 0; > >     + > >     +  ftramp = ((ffi_closure *) ptr)->ftramp; > >     +  ffi_tramp_set_parms (ftramp, code, ptr); > >     +  return 1; > >     +} > >     + > >      # else /* ! FFI_MMAP_EXEC_WRIT */ > > > >      /* On many systems, memory returned by malloc is writable and > >     @@ -998,6 +1042,12 @@ ffi_data_to_code_pointer (void *data) > >        return data; > >      } > > > >     +int > >     +ffi_closure_tramp_set_parms (void *ptr, void *code) > >     +{ > >     +  return 0; > >     +} > >     + > >      # endif /* ! FFI_MMAP_EXEC_WRIT */ > >      #endif /* FFI_CLOSURES */ > > > >     diff --git a/src/tramp.c b/src/tramp.c > >     new file mode 100644 > >     index 0000000..3170152 > >     --- /dev/null > >     +++ b/src/tramp.c > >     @@ -0,0 +1,563 @@ > >     +/* ----------------------------------------------------------------------- > >     +   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 > >     +#include > >     +#include > >     +#include > >     +#include > >     +#include > >     +#include > >     +#include > >     +#include > >     +#include > >     + > >     +#if defined(FFI_EXEC_STATIC_TRAMP) > >     + > >     +#if !defined(__linux__) > >     +#error "FFI_EXEC_STATIC_TRAMP is currently only supported on Linux" > >     +#endif > >     + > >     +#if !defined _GNU_SOURCE > >     +#define _GNU_SOURCE 1 > >     +#endif > >     + > >     +/* > >     + * 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 --------------------*/ > >     + > >     +static pthread_mutex_t tramp_lock = PTHREAD_MUTEX_INITIALIZER; > >     + > >     +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; > >     +}; > >     + > >     +/* > >     + * Trampoline globals. > >     + * > >     + * fd > >     + *     File descriptor of binary file that contains the trampoline code table. > >     + * offset > >     + *     Offset of the trampoline code table in that file. > >     + * 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. > >     + * tables > >     + *     List of trampoline tables that contain free trampolines. > >     + * ntables > >     + *     Number of trampoline tables that contain free trampolines. > >     + */ > >     +struct tramp_global > >     +{ > >     +  int fd; > >     +  off_t offset; > >     +  size_t map_size; > >     +  size_t size; > >     +  int ntramp; > >     +  struct tramp_table *tables; > >     +  int ntables; > >     +}; > >     + > >     +static struct tramp_global gtramp = { -1 }; > >     + > >     +/* ------------------------ Trampoline Initialization ----------------------*/ > >     + > >     +static int ffi_tramp_get_fd_offset (void *tramp_text, off_t *offset); > >     + > >     +/* > >     + * Initialize the static trampoline feature. > >     + */ > >     +static int > >     +ffi_tramp_init (void) > >     +{ > >     +  if (ffi_tramp_arch == NULL) > >     +    return 0; > >     + > >     +  if (gtramp.fd == -1) > >     +    { > >     +      void *tramp_text; > >     + > >     +      gtramp.tables = NULL; > >     +      gtramp.ntables = 0; > >     + > >     +      /* > >     +       * Get trampoline code table information from the architecture. > >     +       */ > >     +      tramp_text = ffi_tramp_arch (>ramp.size, >ramp.map_size); > >     +      gtramp.ntramp = gtramp.map_size / gtramp.size; > >     + > >     +      /* > >     +       * Get the binary file that contains the trampoline code table and also > >     +       * the offset of the table within the file. These are used to mmap() > >     +       * the trampoline code table. > >     +       */ > >     +      gtramp.fd = ffi_tramp_get_fd_offset (tramp_text, >ramp.offset); > >     +    } > >     +  return gtramp.fd != -1; > >     +} > >     + > >     +/* > >     + * From the address of the trampoline code table in the text segment, find the > >     + * binary file and offset of the trampoline code table from /proc//maps. > >     + */ > >     +static int > >     +ffi_tramp_get_fd_offset (void *tramp_text, off_t *offset) > >     +{ > >     +  FILE *fp; > >     +  char file[PATH_MAX], line[PATH_MAX+100], perm[10], dev[10]; > >     +  unsigned long start, end, inode; > >     +  uintptr_t addr = (uintptr_t) tramp_text; > >     +  int nfields, found; > >     + > >     +  snprintf (file, PATH_MAX, "/proc/%d/maps", getpid()); > >     +  fp = fopen (file, "r"); > >     +  if (fp == NULL) > >     +    return -1; > >     + > >     +  found = 0; > >     +  while (feof (fp) == 0) { > >     +    if (fgets (line, sizeof (line), fp) == 0) > >     +      break; > >     + > >     +    nfields = sscanf (line, "%lx-%lx %s %lx %s %ld %s", > >     +      &start, &end, perm, offset, dev, &inode, file); > >     +    if (nfields != 7) > >     +      continue; > >     + > >     +    if (addr >= start && addr < end) { > >     +      *offset += (addr - start); > >     +      found = 1; > >     +      break; > >     +    } > >     +  } > >     +  fclose (fp); > >     + > >     +  if (!found) > >     +    return -1; > >     + > >     +  return open (file, O_RDONLY); > >     +} > >     + > >     +/* ---------------------- Trampoline Table functions ---------------------- */ > >     + > >     +static int tramp_table_map (char **code_table, char **parm_table); > >     +static void tramp_add (struct tramp *tramp); > >     + > >     +/* > >     + * Allocate and initialize a trampoline table. > >     + */ > >     +static int > >     +tramp_table_alloc (void) > >     +{ > >     +  char *code_table, *parm_table; > >     +  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 (gtramp.ntables > 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) * gtramp.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 (&code_table, &parm_table)) > >     +    goto free_tramp_array; > >     + > >     +  /* > >     +   * Initialize the trampoline table. > >     +   */ > >     +  table->code_table = code_table; > >     +  table->parm_table = parm_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 = gtramp.size; > >     +  code = code_table; > >     +  parm = parm_table; > >     +  for (i = 0; i < gtramp.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; > >     +    } > >     +  return 1; > >     + > >     +free_tramp_array: > >     +  free (tramp_array); > >     +free_table: > >     +  free (table); > >     +  return 0; > >     +} > >     + > >     +/* > >     + * 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. > >     + */ > >     +static int > >     +tramp_table_map (char **code_table, char **parm_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, gtramp.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. > >     +   */ > >     +  *code_table = mmap (addr, gtramp.map_size, PROT_READ | PROT_EXEC, > >     +    MAP_PRIVATE | MAP_FIXED, gtramp.fd, gtramp.offset); > >     +  if (*code_table == MAP_FAILED) > >     +    { > >     +      (void) munmap (addr, gtramp.map_size * 2); > >     +      return 0; > >     +    } > >     +  *parm_table = *code_table + gtramp.map_size; > >     +  return 1; > >     +} > >     + > >     +/* > >     + * Free a trampoline table. > >     + */ > >     +static void > >     +tramp_table_free (struct tramp_table *table) > >     +{ > >     +  (void) munmap (table->code_table, gtramp.map_size); > >     +  (void) munmap (table->parm_table, gtramp.map_size); > >     +  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 = gtramp.tables; > >     +  table->prev = NULL; > >     +  if (gtramp.tables != NULL) > >     +    gtramp.tables->prev = table; > >     +  gtramp.tables = table; > >     +  gtramp.ntables++; > >     +} > >     + > >     +/* > >     + * Delete a trampoline table from the global table list. > >     + */ > >     +static void > >     +tramp_table_del (struct tramp_table *table) > >     +{ > >     +  gtramp.ntables--; > >     +  if (table->prev != NULL) > >     +    table->prev->next = table->next; > >     +  if (table->next != NULL) > >     +    table->next->prev = table->prev; > >     +  if (gtramp.tables == table) > >     +    gtramp.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 == gtramp.ntramp && gtramp.ntables > 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; > >     + > >     +  pthread_mutex_lock (&tramp_lock); > >     +  ret = ffi_tramp_init (); > >     +  pthread_mutex_unlock (&tramp_lock); > >     +  return ret; > >     +} > >     + > >     +/* > >     + * Allocate a trampoline and return its opaque address. > >     + */ > >     +void * > >     +ffi_tramp_alloc (int flags) > >     +{ > >     +  struct tramp *tramp; > >     + > >     +  pthread_mutex_lock (&tramp_lock); > >     + > >     +  if (!ffi_tramp_init () || flags != 0) > >     +    { > >     +      pthread_mutex_unlock (&tramp_lock); > >     +      return NULL; > >     +    } > >     + > >     +  if (!tramp_table_alloc ()) > >     +    { > >     +      pthread_mutex_unlock (&tramp_lock); > >     +      return NULL; > >     +    } > >     + > >     +  tramp = gtramp.tables->free; > >     +  tramp_del (tramp); > >     + > >     +  pthread_mutex_unlock (&tramp_lock); > >     + > >     +  return tramp; > >     +} > >     + > >     +/* > >     + * Set the parameters for a trampoline. > >     + */ > >     +void > >     +ffi_tramp_set_parms (void *arg, void *target, void *data) > >     +{ > >     +  struct tramp *tramp = arg; > >     + > >     +  pthread_mutex_lock (&tramp_lock); > >     +  tramp->parm->target = target; > >     +  tramp->parm->data = data; > >     +  pthread_mutex_unlock (&tramp_lock); > >     +} > >     + > >     +/* > >     + * Get the invocation address of a trampoline. > >     + */ > >     +void * > >     +ffi_tramp_get_addr (void *arg) > >     +{ > >     +  struct tramp *tramp = arg; > >     +  void *addr; > >     + > >     +  pthread_mutex_lock (&tramp_lock); > >     +  addr = tramp->code; > >     +  pthread_mutex_unlock (&tramp_lock); > >     + > >     +  return addr; > >     +} > >     + > >     +/* > >     + * Free a trampoline. > >     + */ > >     +void > >     +ffi_tramp_free (void *arg) > >     +{ > >     +  struct tramp *tramp = arg; > >     + > >     +  pthread_mutex_lock (&tramp_lock); > >     +  tramp_add (tramp); > >     +  pthread_mutex_unlock (&tramp_lock); > >     +} > >     + > >     +/* ------------------------------------------------------------------------- */ > >     + > >     +#else /* !FFI_EXEC_STATIC_TRAMP */ > >     + > >     +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 */ > >     diff --git a/testsuite/libffi.closures/closure_loc_fn0.c b/testsuite/libffi.closures/closure_loc_fn0.c > >     index b3afa0b..ad488ac 100644 > >     --- a/testsuite/libffi.closures/closure_loc_fn0.c > >     +++ b/testsuite/libffi.closures/closure_loc_fn0.c > >     @@ -83,7 +83,10 @@ int main (void) > >        CHECK(ffi_prep_closure_loc(pcl, &cif, closure_loc_test_fn0, > >                              (void *) 3 /* userdata */, codeloc) == FFI_OK); > > > >     +#ifndef FFI_EXEC_STATIC_TRAMP > >     +  /* With static trampolines, the codeloc does not point to closure */ > >        CHECK(memcmp(pcl, codeloc, sizeof(*pcl)) == 0); > >     +#endif > > > >        res = (*((closure_loc_test_type0)codeloc)) > >          (1LL, 2, 3LL, 4, 127, 429LL, 7, 8, 9.5, 10, 11, 12, 13, > >     -- > >     2.25.1 > > >