The Tor Browser: media/libvpx/vpx_ports/x86_abi_support.asm@ac0c01689b40 (annotated)

media/libvpx/vpx_ports/x86_abi_support.asm@ac0c01689b40 (annotated)

media/libvpx/vpx_ports/x86_abi_support.asm

Thu, 15 Jan 2015 15:59:08 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:59:08 +0100
branch: TOR_BUG_9701
changeset 10: ac0c01689b40
permissions: -rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 ;
 ;  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 ;
 ;  Use of this source code is governed by a BSD-style license
 ;  that can be found in the LICENSE file in the root of the source
 ;  tree. An additional intellectual property rights grant can be found
 ;  in the file PATENTS.  All contributing project authors may
 ;  be found in the AUTHORS file in the root of the source tree.
 ;
 %include "vpx_config.asm"
 ; 32/64 bit compatibility macros
 ;
 ; In general, we make the source use 64 bit syntax, then twiddle with it using
 ; the preprocessor to get the 32 bit syntax on 32 bit platforms.
 ;
 %ifidn __OUTPUT_FORMAT__,elf32
 %define ABI_IS_32BIT 1
 %elifidn __OUTPUT_FORMAT__,macho32
 %define ABI_IS_32BIT 1
 %elifidn __OUTPUT_FORMAT__,win32
 %define ABI_IS_32BIT 1
 %elifidn __OUTPUT_FORMAT__,aout
 %define ABI_IS_32BIT 1
 %else
 %define ABI_IS_32BIT 0
 %endif
 %if ABI_IS_32BIT
 %define rax eax
 %define rbx ebx
 %define rcx ecx
 %define rdx edx
 %define rsi esi
 %define rdi edi
 %define rsp esp
 %define rbp ebp
 %define movsxd mov
 %macro movq 2
   %ifidn %1,eax
     movd %1,%2
   %elifidn %2,eax
     movd %1,%2
   %elifidn %1,ebx
     movd %1,%2
   %elifidn %2,ebx
     movd %1,%2
   %elifidn %1,ecx
     movd %1,%2
   %elifidn %2,ecx
     movd %1,%2
   %elifidn %1,edx
     movd %1,%2
   %elifidn %2,edx
     movd %1,%2
   %elifidn %1,esi
     movd %1,%2
   %elifidn %2,esi
     movd %1,%2
   %elifidn %1,edi
     movd %1,%2
   %elifidn %2,edi
     movd %1,%2
   %elifidn %1,esp
     movd %1,%2
   %elifidn %2,esp
     movd %1,%2
   %elifidn %1,ebp
     movd %1,%2
   %elifidn %2,ebp
     movd %1,%2
   %else
     movq %1,%2
   %endif
 %endmacro
 %endif
 ; LIBVPX_YASM_WIN64
 ; Set LIBVPX_YASM_WIN64 if output is Windows 64bit so the code will work if x64
 ; or win64 is defined on the Yasm command line.
 %ifidn __OUTPUT_FORMAT__,win64
 %define LIBVPX_YASM_WIN64 1
 %elifidn __OUTPUT_FORMAT__,x64
 %define LIBVPX_YASM_WIN64 1
 %else
 %define LIBVPX_YASM_WIN64 0
 %endif
 ; sym()
 ; Return the proper symbol name for the target ABI.
 ;
 ; Certain ABIs, notably MS COFF and Darwin MACH-O, require that symbols
 ; with C linkage be prefixed with an underscore.
 ;
 %ifidn   __OUTPUT_FORMAT__,elf32
 %define sym(x) x
 %elifidn __OUTPUT_FORMAT__,elf64
 %define sym(x) x
 %elifidn __OUTPUT_FORMAT__,elfx32
 %define sym(x) x
 %elif LIBVPX_YASM_WIN64
 %define sym(x) x
 %else
 %define sym(x) _ %+ x
 %endif
 ;  PRIVATE
 ;  Macro for the attribute to hide a global symbol for the target ABI.
 ;  This is only active if CHROMIUM is defined.
 ;
 ;  Chromium doesn't like exported global symbols due to symbol clashing with
 ;  plugins among other things.
 ;
 ;  Requires Chromium's patched copy of yasm:
 ;    http://src.chromium.org/viewvc/chrome?view=rev&revision=73761
 ;    http://www.tortall.net/projects/yasm/ticket/236
 ;
 %ifdef CHROMIUM
   %ifidn   __OUTPUT_FORMAT__,elf32
     %define PRIVATE :hidden
   %elifidn __OUTPUT_FORMAT__,elf64
     %define PRIVATE :hidden
   %elifidn __OUTPUT_FORMAT__,elfx32
     %define PRIVATE :hidden
   %elif LIBVPX_YASM_WIN64
     %define PRIVATE
   %else
     %define PRIVATE :private_extern
   %endif
 %else
   %define PRIVATE
 %endif
 ; arg()
 ; Return the address specification of the given argument
 ;
 %if ABI_IS_32BIT
   %define arg(x) [ebp+8+4*x]
 %else
   ; 64 bit ABI passes arguments in registers. This is a workaround to get up
   ; and running quickly. Relies on SHADOW_ARGS_TO_STACK
   %if LIBVPX_YASM_WIN64
     %define arg(x) [rbp+16+8*x]
   %else
     %define arg(x) [rbp-8-8*x]
   %endif
 %endif
 ; REG_SZ_BYTES, REG_SZ_BITS
 ; Size of a register
 %if ABI_IS_32BIT
 %define REG_SZ_BYTES 4
 %define REG_SZ_BITS  32
 %else
 %define REG_SZ_BYTES 8
 %define REG_SZ_BITS  64
 %endif
 ; ALIGN_STACK <alignment> <register>
 ; This macro aligns the stack to the given alignment (in bytes). The stack
 ; is left such that the previous value of the stack pointer is the first
 ; argument on the stack (ie, the inverse of this macro is 'pop rsp.')
 ; This macro uses one temporary register, which is not preserved, and thus
 ; must be specified as an argument.
 %macro ALIGN_STACK 2
     mov         %2, rsp
     and         rsp, -%1
     lea         rsp, [rsp - (%1 - REG_SZ_BYTES)]
     push        %2
 %endmacro
 ;
 ; The Microsoft assembler tries to impose a certain amount of type safety in
 ; its register usage. YASM doesn't recognize these directives, so we just
 ; %define them away to maintain as much compatibility as possible with the
 ; original inline assembler we're porting from.
 ;
 %idefine PTR
 %idefine XMMWORD
 %idefine MMWORD
 ; PIC macros
 ;
 %if ABI_IS_32BIT
   %if CONFIG_PIC=1
   %ifidn __OUTPUT_FORMAT__,elf32
     %define GET_GOT_SAVE_ARG 1
     %define WRT_PLT wrt ..plt
     %macro GET_GOT 1
       extern _GLOBAL_OFFSET_TABLE_
       push %1
       call %%get_got
       %%sub_offset:
       jmp %%exitGG
       %%get_got:
       mov %1, [esp]
       add %1, _GLOBAL_OFFSET_TABLE_ + $$ - %%sub_offset wrt ..gotpc
       ret
       %%exitGG:
       %undef GLOBAL
       %define GLOBAL(x) x + %1 wrt ..gotoff
       %undef RESTORE_GOT
       %define RESTORE_GOT pop %1
     %endmacro
   %elifidn __OUTPUT_FORMAT__,macho32
     %define GET_GOT_SAVE_ARG 1
     %macro GET_GOT 1
       push %1
       call %%get_got
       %%get_got:
       pop  %1
       %undef GLOBAL
       %define GLOBAL(x) x + %1 - %%get_got
       %undef RESTORE_GOT
       %define RESTORE_GOT pop %1
     %endmacro
   %endif
   %endif
   %ifdef CHROMIUM
     %ifidn __OUTPUT_FORMAT__,macho32
       %define HIDDEN_DATA(x) x:private_extern
     %else
       %define HIDDEN_DATA(x) x
     %endif
   %else
     %define HIDDEN_DATA(x) x
   %endif
 %else
   %macro GET_GOT 1
   %endmacro
   %define GLOBAL(x) rel x
   %ifidn __OUTPUT_FORMAT__,elf64
     %define WRT_PLT wrt ..plt
     %define HIDDEN_DATA(x) x:data hidden
   %elifidn __OUTPUT_FORMAT__,elfx32
     %define WRT_PLT wrt ..plt
     %define HIDDEN_DATA(x) x:data hidden
   %elifidn __OUTPUT_FORMAT__,macho64
     %ifdef CHROMIUM
       %define HIDDEN_DATA(x) x:private_extern
     %else
       %define HIDDEN_DATA(x) x
     %endif
   %else
     %define HIDDEN_DATA(x) x
   %endif
 %endif
 %ifnmacro GET_GOT
     %macro GET_GOT 1
     %endmacro
     %define GLOBAL(x) x
 %endif
 %ifndef RESTORE_GOT
 %define RESTORE_GOT
 %endif
 %ifndef WRT_PLT
 %define WRT_PLT
 %endif
 %if ABI_IS_32BIT
   %macro SHADOW_ARGS_TO_STACK 1
   %endm
   %define UNSHADOW_ARGS
 %else
 %if LIBVPX_YASM_WIN64
   %macro SHADOW_ARGS_TO_STACK 1 ; argc
     %if %1 > 0
         mov arg(0),rcx
     %endif
     %if %1 > 1
         mov arg(1),rdx
     %endif
     %if %1 > 2
         mov arg(2),r8
     %endif
     %if %1 > 3
         mov arg(3),r9
     %endif
   %endm
 %else
   %macro SHADOW_ARGS_TO_STACK 1 ; argc
     %if %1 > 0
         push rdi
     %endif
     %if %1 > 1
         push rsi
     %endif
     %if %1 > 2
         push rdx
     %endif
     %if %1 > 3
         push rcx
     %endif
     %if %1 > 4
         push r8
     %endif
     %if %1 > 5
         push r9
     %endif
     %if %1 > 6
       %assign i %1-6
       %assign off 16
       %rep i
         mov rax,[rbp+off]
         push rax
         %assign off off+8
       %endrep
     %endif
   %endm
 %endif
   %define UNSHADOW_ARGS mov rsp, rbp
 %endif
 ; Win64 ABI requires that XMM6:XMM15 are callee saved
 ; SAVE_XMM n, [u]
 ; store registers 6-n on the stack
 ; if u is specified, use unaligned movs.
 ; Win64 ABI requires 16 byte stack alignment, but then pushes an 8 byte return
 ; value. Typically we follow this up with 'push rbp' - re-aligning the stack -
 ; but in some cases this is not done and unaligned movs must be used.
 %if LIBVPX_YASM_WIN64
 %macro SAVE_XMM 1-2 a
   %if %1 < 6
     %error Only xmm registers 6-15 must be preserved
   %else
     %assign last_xmm %1
     %define movxmm movdq %+ %2
     %assign xmm_stack_space ((last_xmm - 5) * 16)
     sub rsp, xmm_stack_space
     %assign i 6
     %rep (last_xmm - 5)
       movxmm [rsp + ((i - 6) * 16)], xmm %+ i
       %assign i i+1
     %endrep
   %endif
 %endmacro
 %macro RESTORE_XMM 0
   %ifndef last_xmm
     %error RESTORE_XMM must be paired with SAVE_XMM n
   %else
     %assign i last_xmm
     %rep (last_xmm - 5)
       movxmm xmm %+ i, [rsp +((i - 6) * 16)]
       %assign i i-1
     %endrep
     add rsp, xmm_stack_space
     ; there are a couple functions which return from multiple places.
     ; otherwise, we could uncomment these:
     ; %undef last_xmm
     ; %undef xmm_stack_space
     ; %undef movxmm
   %endif
 %endmacro
 %else
 %macro SAVE_XMM 1-2
 %endmacro
 %macro RESTORE_XMM 0
 %endmacro
 %endif
 ; Name of the rodata section
 ;
 ; .rodata seems to be an elf-ism, as it doesn't work on OSX.
 ;
 %ifidn __OUTPUT_FORMAT__,macho64
 %define SECTION_RODATA section .text
 %elifidn __OUTPUT_FORMAT__,macho32
 %macro SECTION_RODATA 0
 section .text
 %endmacro
 %elifidn __OUTPUT_FORMAT__,aout
 %define SECTION_RODATA section .data
 %else
 %define SECTION_RODATA section .rodata
 %endif
 ; Tell GNU ld that we don't require an executable stack.
 %ifidn __OUTPUT_FORMAT__,elf32
 section .note.GNU-stack noalloc noexec nowrite progbits
 section .text
 %elifidn __OUTPUT_FORMAT__,elf64
 section .note.GNU-stack noalloc noexec nowrite progbits
 section .text
 %elifidn __OUTPUT_FORMAT__,elfx32
 section .note.GNU-stack noalloc noexec nowrite progbits
 section .text
 %endif

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media/libvpx/vpx_ports/x86_abi_support.asm@ac0c01689b40 (annotated)

media/libvpx/vpx_ports/x86_abi_support.asm