Add fcontext support for DEC Alpha (SysV/ELF)

CMakeLists.txt

@@ -50,7 +50,7 @@ unset(_default_abi)
 
 ## Arch-and-model
 
-set(_all_archs arm arm64 e2k loongarch64 mips32 mips64 ppc32 ppc64 riscv64 s390x i386 x86_64 combined)
+set(_all_archs alpha arm arm64 e2k loongarch64 mips32 mips64 ppc32 ppc64 riscv64 s390x i386 x86_64 combined)
 
 # Try at start to auto determine arch from CMake.
 if(CMAKE_SYSTEM_PROCESSOR IN_LIST _all_archs)
@@ -80,7 +80,7 @@ else()
   endif()
 endif()
 
-set(BOOST_CONTEXT_ARCHITECTURE "${_default_arch}" CACHE STRING "Boost.Context architecture (arm, arm64, e2k, loongarch64, mips32, mips64, ppc32, ppc64, riscv64, s390x, i386, x86_64, combined)")
+set(BOOST_CONTEXT_ARCHITECTURE "${_default_arch}" CACHE STRING "Boost.Context architecture (alpha, arm, arm64, e2k, loongarch64, mips32, mips64, ppc32, ppc64, riscv64, s390x, i386, x86_64, combined)")
 set_property(CACHE BOOST_CONTEXT_ARCHITECTURE PROPERTY STRINGS ${_all_archs})
 
 unset(_all_archs)

build/Jamfile.v2

@@ -528,6 +528,30 @@ alias asm_sources
      <toolset>gcc
    ;
 
+# ALPHA
+# ALPHA/SYSV/ELF
+alias asm_sources
+   : asm/make_alpha_sysv_elf_gas.S
+     asm/jump_alpha_sysv_elf_gas.S
+     asm/ontop_alpha_sysv_elf_gas.S
+   : <abi>sysv
+     <address-model>64
+     <architecture>alpha
+     <binary-format>elf
+     <toolset>gcc
+   ;
+
+alias asm_sources
+   : asm/make_alpha_sysv_elf_gas.S
+     asm/jump_alpha_sysv_elf_gas.S
+     asm/ontop_alpha_sysv_elf_gas.S
+   : <abi>sysv
+     <address-model>64
+     <architecture>alpha
+     <binary-format>elf
+     <toolset>clang
+   ;
+
 # S390X
 # S390X/SYSV/ELF
 alias asm_sources

doc/architectures.qbk

@@ -12,6 +12,7 @@ architectures:
 
 [table Supported architectures (<ABI|binary format>)
     [[Architecture]  [LINUX (UNIX)]   [Windows]  [MacOS X]      [iOS]]
+    [[alpha]         [SYSV|ELF]       [-]        [-]            [-]]
     [[arm (aarch32)] [AAPCS|ELF]      [AAPCS|PE] [-]            [AAPCS|MACH-O]]
     [[arm (aarch64)] [AAPCS|ELF]      [-]        [AAPCS|MACH-O] [AAPCS|MACH-O]]
     [[i386]          [SYSV|ELF]       [MS|PE]    [SYSV|MACH-O]  [-]]

src/asm/jump_alpha_sysv_elf_gas.S

@@ -0,0 +1,143 @@
+/*
+   Distributed under the Boost Software License, Version 1.0.
+      (See accompanying file LICENSE_1_0.txt or copy at
+          http://www.boost.org/LICENSE_1_0.txt)
+*/
+/*********************************************************
+ *                                                       *
+ *  ---------------------------------------------------  *
+ *  |    0    |    1    |    2    |    3    |    4    |  *
+ *  ---------------------------------------------------  *
+ *  |   0x0   |   0x8   |   0x10  |   0x18  |   0x20  |  *
+ *  ---------------------------------------------------  *
+ *  |   $f2   |   $f3   |   $f4   |   $f5   |   $f6   |  *
+ *  ---------------------------------------------------  *
+ *  |    5    |    6    |    7    |    8    |    9    |  *
+ *  ---------------------------------------------------  *
+ *  |   0x28  |   0x30  |   0x38  |   0x40  |   0x48  |  *
+ *  ---------------------------------------------------  *
+ *  |   $f7   |   $f8   |   $f9   |    $9   |   $10   |  *
+ *  ---------------------------------------------------  *
+ *  |    10   |    11   |    12   |    13   |    14   |  *
+ *  ---------------------------------------------------  *
+ *  |   0x50  |   0x58  |   0x60  |   0x68  |   0x70  |  *
+ *  ---------------------------------------------------  *
+ *  |   $11   |   $12   |   $13   |   $14   |   $15   |  *
+ *  ---------------------------------------------------  *
+ *  |    15   |    16   |    17   |    18   |    19   |  *
+ *  ---------------------------------------------------  *
+ *  |   0x78  |   0x80  |   0x88  |   0x90  |   0x98  |  *
+ *  ---------------------------------------------------  *
+ *  |   $29   |   $26   |    PC   |  hidden |   pad   |  *
+ *  |   (gp)  |   (ra)  |         |   ptr   |         |  *
+ *  ---------------------------------------------------  *
+ *                                                       *
+ ********************************************************/
+
+/* The Alpha calling standard returns a 16 byte struct such as transfer_t
+   via a hidden pointer in $16, shifting the declared arguments to $17 and
+   $18.  That pointer belongs to the frame that made the call, so it has to
+   travel with the context: each context records the pointer its own
+   suspending call was given, and whoever resumes it stores through it. */
+
+.file "jump_alpha_sysv_elf_gas.S"
+.text
+.align 4
+.globl jump_fcontext
+.hidden jump_fcontext
+.type jump_fcontext, @function
+.ent jump_fcontext
+jump_fcontext:
+    .frame $30, 0, $26, 0
+    .prologue 0
+
+    # reserve space for context-data on the current stack
+    lda   $30, -0xa0($30)
+
+    # save callee-saved floating point registers $f2 - $f9
+    stt   $f2,  0x00($30)
+    stt   $f3,  0x08($30)
+    stt   $f4,  0x10($30)
+    stt   $f5,  0x18($30)
+    stt   $f6,  0x20($30)
+    stt   $f7,  0x28($30)
+    stt   $f8,  0x30($30)
+    stt   $f9,  0x38($30)
+
+    # save callee-saved integer registers $9 - $15
+    stq   $9,   0x40($30)
+    stq   $10,  0x48($30)
+    stq   $11,  0x50($30)
+    stq   $12,  0x58($30)
+    stq   $13,  0x60($30)
+    stq   $14,  0x68($30)
+    stq   $15,  0x70($30)
+
+    # save gp and return address
+    stq   $29,  0x78($30)
+    stq   $26,  0x80($30)
+
+    # save the return address as the resumption PC
+    stq   $26,  0x88($30)
+
+    # save the hidden transfer_t pointer this call was given
+    stq   $16,  0x90($30)
+
+    # $1 = fcontext_t of the context we are suspending
+    bis   $31, $30, $1
+
+    # switch to the stack of the context we are resuming
+    bis   $31, $17, $30
+
+    # restore callee-saved floating point registers $f2 - $f9
+    ldt   $f2,  0x00($30)
+    ldt   $f3,  0x08($30)
+    ldt   $f4,  0x10($30)
+    ldt   $f5,  0x18($30)
+    ldt   $f6,  0x20($30)
+    ldt   $f7,  0x28($30)
+    ldt   $f8,  0x30($30)
+    ldt   $f9,  0x38($30)
+
+    # restore callee-saved integer registers $9 - $15
+    ldq   $9,   0x40($30)
+    ldq   $10,  0x48($30)
+    ldq   $11,  0x50($30)
+    ldq   $12,  0x58($30)
+    ldq   $13,  0x60($30)
+    ldq   $14,  0x68($30)
+    ldq   $15,  0x70($30)
+
+    # restore gp and return address
+    ldq   $29,  0x78($30)
+    ldq   $26,  0x80($30)
+
+    # load the resumption PC into $27; it doubles as the procedure value
+    # for a context-function entered for the first time, which computes
+    # its own gp from it
+    ldq   $27,  0x88($30)
+
+    # load the hidden transfer_t pointer of the resumed context
+    ldq   $2,   0x90($30)
+
+    # release the context-data
+    lda   $30, 0xa0($30)
+
+    # return transfer_t{ $1, $18 } through the hidden pointer
+    stq   $1,  0x00($2)
+    stq   $18, 0x08($2)
+    bis   $31, $2, $0
+
+    # and pass it by value, for a context entered via make_fcontext
+    bis   $31, $1,  $16
+    bis   $31, $18, $17
+
+    # the ret hint pops the return prediction stack entry pushed by the
+    # bsr that called us; the resumption PC is where that call appears to
+    # return.  A jmp hint would orphan one entry per switch.
+    ret   $31, ($27), 0
+.end jump_fcontext
+.size jump_fcontext, .-jump_fcontext
+
+/* Mark that we don't need executable stack. */
+.section .note.GNU-stack,"",@progbits

src/asm/make_alpha_sysv_elf_gas.S

@@ -0,0 +1,118 @@
+/*
+   Distributed under the Boost Software License, Version 1.0.
+      (See accompanying file LICENSE_1_0.txt or copy at
+          http://www.boost.org/LICENSE_1_0.txt)
+*/
+/*********************************************************
+ *                                                       *
+ *  ---------------------------------------------------  *
+ *  |    0    |    1    |    2    |    3    |    4    |  *
+ *  ---------------------------------------------------  *
+ *  |   0x0   |   0x8   |   0x10  |   0x18  |   0x20  |  *
+ *  ---------------------------------------------------  *
+ *  |   $f2   |   $f3   |   $f4   |   $f5   |   $f6   |  *
+ *  ---------------------------------------------------  *
+ *  |    5    |    6    |    7    |    8    |    9    |  *
+ *  ---------------------------------------------------  *
+ *  |   0x28  |   0x30  |   0x38  |   0x40  |   0x48  |  *
+ *  ---------------------------------------------------  *
+ *  |   $f7   |   $f8   |   $f9   |    $9   |   $10   |  *
+ *  ---------------------------------------------------  *
+ *  |    10   |    11   |    12   |    13   |    14   |  *
+ *  ---------------------------------------------------  *
+ *  |   0x50  |   0x58  |   0x60  |   0x68  |   0x70  |  *
+ *  ---------------------------------------------------  *
+ *  |   $11   |   $12   |   $13   |   $14   |   $15   |  *
+ *  ---------------------------------------------------  *
+ *  |    15   |    16   |    17   |    18   |    19   |  *
+ *  ---------------------------------------------------  *
+ *  |   0x78  |   0x80  |   0x88  |   0x90  |   0x98  |  *
+ *  ---------------------------------------------------  *
+ *  |   $29   |   $26   |    PC   |  hidden |   pad   |  *
+ *  |   (gp)  |   (ra)  |         |   ptr   |         |  *
+ *  ---------------------------------------------------  *
+ *  |    20   |    21   |         |         |         |  *
+ *  ---------------------------------------------------  *
+ *  |   0xa0  |   0xa8  |         |         |         |  *
+ *  ---------------------------------------------------  *
+ *  |                transfer_t scratch               |  *
+ *  ---------------------------------------------------  *
+ *                                                       *
+ ********************************************************/
+
+.file "make_alpha_sysv_elf_gas.S"
+.text
+.align 4
+.globl make_fcontext
+.hidden make_fcontext
+.type make_fcontext, @function
+.ent make_fcontext
+make_fcontext:
+    .frame $30, 0, $26, 0
+    ldgp  $29, 0($27)
+    .prologue 1
+
+    # $16: top address of the context-stack
+    # $17: size of the context-stack
+    # $18: address of the context-function
+
+    # shift the address in $16 down to a 16 byte boundary
+    bic   $16, 0xF, $0
+
+    # reserve space for the context-data and for the transfer_t that
+    # jump_fcontext writes through the hidden pointer when it enters the
+    # context-function
+    lda   $0, -0xc0($0)
+
+    # the context-function is the resumption PC
+    stq   $18, 0x88($0)
+
+    # jump_fcontext restores gp before entering the context-function; the
+    # context-function computes its own, but leave a valid value here
+    stq   $29, 0x78($0)
+
+    # point the hidden pointer at the scratch transfer_t
+    lda   $1, 0xa0($0)
+    stq   $1, 0x90($0)
+
+    # start the context with cleared callee-saved registers
+    stt   $f31, 0x00($0)
+    stt   $f31, 0x08($0)
+    stt   $f31, 0x10($0)
+    stt   $f31, 0x18($0)
+    stt   $f31, 0x20($0)
+    stt   $f31, 0x28($0)
+    stt   $f31, 0x30($0)
+    stt   $f31, 0x38($0)
+    stq   $31,  0x40($0)
+    stq   $31,  0x48($0)
+    stq   $31,  0x50($0)
+    stq   $31,  0x58($0)
+    stq   $31,  0x60($0)
+    stq   $31,  0x68($0)
+    stq   $31,  0x70($0)
+
+    # save the address of finish as the return address of the
+    # context-function; it is entered after the context-function returns
+    ldq   $1, finish($29)    !literal
+    stq   $1, 0x80($0)
+
+    # return the pointer to the context-data in $0
+    ret   $31, ($26), 1
+
+finish:
+    # the context-function returned; gp is not live here, so recompute it
+    br    $29, 1f
+1:  ldgp  $29, 0($29)
+
+    # exit code is zero
+    bis   $31, $31, $16
+
+    # exit application
+    ldq   $27, _exit($29)    !literal
+    jsr   $26, ($27), _exit
+.end make_fcontext
+.size make_fcontext, .-make_fcontext
+
+/* Mark that we don't need executable stack. */
+.section .note.GNU-stack,"",@progbits