diff options
| -rw-r--r-- | subx/012elf.cc | 2 | ||||
| -rw-r--r-- | subx/036global_variables.cc | 1 | ||||
| -rw-r--r-- | subx/037heap.cc | 29 | ||||
| -rw-r--r-- | subx/038---literal_strings.cc | 7 | ||||
| -rw-r--r-- | subx/066allocate.subx | 152 | ||||
| -rwxr-xr-x | subx/apps/crenshaw2-1 | bin | 7865 -> 8333 bytes | |||
| -rwxr-xr-x | subx/apps/crenshaw2-1b | bin | 8424 -> 8892 bytes | |||
| -rwxr-xr-x | subx/apps/factorial | bin | 6760 -> 7228 bytes | |||
| -rwxr-xr-x | subx/apps/hex | bin | 11372 -> 11840 bytes |
9 files changed, 183 insertions, 8 deletions
diff --git a/subx/012elf.cc b/subx/012elf.cc index 4d1ae19d..21019d18 100644 --- a/subx/012elf.cc +++ b/subx/012elf.cc @@ -133,7 +133,7 @@ void load_segment_from_program_header(uint8_t* elf_contents, int segment_index, // data/heap: 0x0a000000 -> 0x0affffff // stack: 0x0b000ffc -> 0x0b000000 (downward) const int CODE_SEGMENT = 0x09000000; -const int DATA_SEGMENT = 0x0a000000; +const int DATA_SEGMENT = 0x0a000000; // keep sync'd with `Heap.limit` in allocate.subx const int STACK_SEGMENT = 0x0b000000; const int AFTER_STACK = 0x0c000000; const int ARGV_DATA_SEGMENT = 0x0c000000; diff --git a/subx/036global_variables.cc b/subx/036global_variables.cc index 5c707bd3..c314a4f7 100644 --- a/subx/036global_variables.cc +++ b/subx/036global_variables.cc @@ -19,6 +19,7 @@ Transform.push_back(rewrite_global_variables); :(code) void rewrite_global_variables(program& p) { trace(99, "transform") << "-- rewrite global variables" << end(); + // Begin rewrite_global_variables map<string, uint32_t> address; compute_addresses_for_global_variables(p, address); if (trace_contains_errors()) return; diff --git a/subx/037heap.cc b/subx/037heap.cc new file mode 100644 index 00000000..315fd0d5 --- /dev/null +++ b/subx/037heap.cc @@ -0,0 +1,29 @@ +//: Support for dynamic allocation. +//: +//: Just provide a special label marking the first unused address in the data +//: segment. Then we'll write SubX helpers to make use of it. + +:(before "Begin rewrite_global_variables") +insert_heap_global_variable(p); +:(code) +void insert_heap_global_variable(program& p) { + if (SIZE(p.segments) < 2) + return; // no data segment defined + // Start-of-heap: + p.segments.at(1).lines.push_back(label("Start-of-heap")); +} + +line label(string s) { + line result; + result.words.push_back(word()); + result.words.back().data = (s+":"); + return result; +} + +line imm32(const string& s) { + line result; + result.words.push_back(word()); + result.words.back().data = s; + result.words.back().metadata.push_back("imm32"); + return result; +} diff --git a/subx/038---literal_strings.cc b/subx/038---literal_strings.cc index a899f725..7077a685 100644 --- a/subx/038---literal_strings.cc +++ b/subx/038---literal_strings.cc @@ -67,13 +67,6 @@ void add_global_to_data_segment(const string& name, const word& value, segment& } } -line label(string s) { - line result; - result.words.push_back(word()); - result.words.back().data = (s+":"); - return result; -} - //: Within strings, whitespace is significant. So we need to redo our instruction //: parsing. diff --git a/subx/066allocate.subx b/subx/066allocate.subx new file mode 100644 index 00000000..9194d9b8 --- /dev/null +++ b/subx/066allocate.subx @@ -0,0 +1,152 @@ +# Helper to dynamically allocate memory on the heap. +# +# We'd like to be able to write tests for functions that allocate memory, +# making assertions on the precise addresses used. To achieve this we'll pass +# in an *allocation descriptor* to allocate from. +# +# Allocation descriptors are also useful outside of tests. Assembly and machine +# code are of necessity unsafe languages, and one of the most insidious kinds +# of bugs unsafe languages expose us to are dangling pointers to memory that +# has been freed and potentially even reused for something totally different. +# To reduce the odds of such "use after free" errors, SubX programs tend to not +# reclaim and reuse dynamically allocated memory. (Running out of memory is far +# easier to debug.) Long-running programs that want to reuse memory are mostly +# on their own to be careful. However, they do get one bit of help: they can +# carve out chunks of memory and then allocate from them manually using this +# very same 'allocate' helper. They just need a new allocation descriptor for +# their book-keeping. + +== data + +# The 'global' allocation descriptor. Pass this into 'allocate' to claim a +# hitherto unused bit of memory. +Heap: + Start-of-heap/imm32 # curr + 00 00 00 0b # limit = 0x0b000000; keep sync'd with DATA_SEGMENT + SEGMENT_ALIGNMENT + +== code +# instruction effective address register displacement immediate +# . op subop mod rm32 base index scale r32 +# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes + +# main: + e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'. + # syscall(exit, Num-test-failures) + 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX + b8/copy-to-EAX 1/imm32/exit + cd/syscall 0x80/imm8 + +# Claim the next 'n' bytes of memory starting at ad->curr and update ad->curr. +# If there isn't enough memory before ad->limit, return 0 and leave 'ad' unmodified. +allocate: # ad : (address allocation-descriptor), n : int -> address-or-null/EAX + # . prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # . save registers + 51/push-ECX + 52/push-EDX + # ECX = ad + 8b/copy 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 1/r32/ECX 8/disp8 . # copy *(EBP+8) to ECX + # save ad->curr + 8b/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/EAX . . # copy *ECX to EAX + # check if there's enough space + # . EDX = ad->curr + n + 89/copy 3/mod/direct 2/rm32/EDX . . . 0/r32/EAX . . # copy EAX to EDX + 03/add 1/mod/*+disp8 4/rm32/sib 5/base/EBP 4/index/none . 2/r32/EDX 0xc/disp8 . # add *(EBP+12) to EDX + 3b/compare 1/mod/*+disp8 1/rm32/ECX . . . 2/r32/EDX 4/disp8 . # compare EDX with *(ECX+4) + 7c/jump-if-lesser $allocate:commit/disp8 + # return null if not + b8/copy-to-EAX 0/imm32 + eb/jump $allocate:end/disp8 +$allocate:commit: + # update ad->curr + 89/copy 0/mod/indirect 1/rm32/ECX . . . 2/r32/EDX . . # copy EDX to *ECX +$allocate:end: + # . restore registers + 5a/pop-to-EDX + 59/pop-to-ECX + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +test-allocate-success: + # . prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # var ad/ECX : (address allocation-descriptor) = {11, 15} + 68/push 0xf/imm32/limit + 68/push 0xb/imm32/curr + 89/copy 3/mod/direct 1/rm32/ECX . . . 4/r32/ESP . . # copy ESP to ECX + # EAX = allocate(ad, 3) + # . . push args + 68/push 3/imm32 + 51/push-ECX + # . . call + e8/call allocate/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 11, msg) + # . . push args + 68/push "F - test-allocate-success: returns current pointer of address descriptor"/imm32 + 68/push 0xb/imm32 + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # check-ints-equal(ad->curr, 14, msg) + # . . push args + 68/push "F - test-allocate-success: updates address descriptor"/imm32 + 68/push 0xe/imm32 + ff 6/subop/push 0/mod/indirect 1/rm32/ECX . . . . . . # push *ECX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +test-allocate-failure: + # . prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + # var ad/ECX : (address allocation-descriptor) = {11, 15} + 68/push 0xf/imm32/limit + 68/push 0xb/imm32/curr + 89/copy 3/mod/direct 1/rm32/ECX . . . 4/r32/ESP . . # copy ESP to ECX + # EAX = allocate(ad, 6) + # . . push args + 68/push 6/imm32 + 51/push-ECX + # . . call + e8/call allocate/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP + # check-ints-equal(EAX, 0, msg) + # . . push args + 68/push "F - test-allocate-failure: returns null"/imm32 + 68/push 0/imm32 + 50/push-EAX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # no change to ad->curr + # . check-ints-equal(ad->curr, 11) + # . . push args + 68/push "F - test-allocate-failure: updates address descriptor"/imm32 + 68/push 0xb/imm32 + ff 6/subop/push 0/mod/indirect 1/rm32/ECX . . . . . . # push *ECX + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +# . . vim:nowrap:textwidth=0 diff --git a/subx/apps/crenshaw2-1 b/subx/apps/crenshaw2-1 index 383f1b16..1f3b5436 100755 --- a/subx/apps/crenshaw2-1 +++ b/subx/apps/crenshaw2-1 Binary files differdiff --git a/subx/apps/crenshaw2-1b b/subx/apps/crenshaw2-1b index 4989d59e..08395a6b 100755 --- a/subx/apps/crenshaw2-1b +++ b/subx/apps/crenshaw2-1b Binary files differdiff --git a/subx/apps/factorial b/subx/apps/factorial index d4575e16..3bd1c65b 100755 --- a/subx/apps/factorial +++ b/subx/apps/factorial Binary files differdiff --git a/subx/apps/hex b/subx/apps/hex index d9bd1872..9287faa7 100755 --- a/subx/apps/hex +++ b/subx/apps/hex Binary files differ |