probing intermittent sys_brk failures in wsl

Author: Sharpiro

.gitignore

@@ -23,3 +23,4 @@ a.out
 /readwin
 /windynamic_linux
 *.dll
+*.log

.vscode/launch.json

@@ -6,7 +6,7 @@
       "type": "cppdbg",
       "request": "launch",
       "program": "${workspaceFolder}/loader",
-      "args": ["./tinyfetch"],
+      "args": ["./string"],
       "stopAtEntry": false,
       "cwd": "${workspaceFolder}",
       "environment": [{ "name": "CFLAGS", "value": "-DVERBOSE" }],

Makefile

@@ -3,14 +3,15 @@ ifeq ($(CC),cc)
 endif
 
 OBJDUMP ?= objdump
+
 WARNINGS = \
 	-std=gnu2x \
 	-Wall -Wextra -Wpedantic -Wno-varargs \
 	-Wno-gnu-zero-variadic-macro-arguments \
-	-Wno-gnu-statement-expression-from-macro-expansion \
 	-Wconversion \
-    -Werror=return-type \
-    -Werror=incompatible-pointer-types \
+	-Werror=return-type \
+	-Werror=incompatible-pointer-types \
+	-Wno-gnu-empty-initializer \
 	-Wvla
 
 all: \

loader_test.sh

@@ -8,13 +8,13 @@ assert() {
     fi
 }
 
-# Unit Test
-$PRELOADER ./unit_test
-assert [ $? == 0 ]
+# # Unit Test
+# $PRELOADER ./unit_test
+# assert [ $? == 0 ]
 
-# Env Test
-assert [ "`$PRELOADER ./loader ./env | wc -c`" == "8" ]
-assert [ "`$PRELOADER ./loader ./env x`" == $'2\n./env\nx' ]
+# # Env Test
+# assert [ "`$PRELOADER ./loader ./env | wc -c`" == "8" ]
+# assert [ "`$PRELOADER ./loader ./env x`" == $'2\n./env\nx' ]
 
 # String Test
 expected=`cat <<EOF
@@ -36,24 +36,24 @@ EOF
 `
 assert [ "`$PRELOADER ./loader string silent`" == "$expected" ]
 
-# Dynamic Test
-expected=`cat <<EOF
-1st call
-2nd call
-16 + 16 = 32
-dynamic_var: 0
-dynamic_var: 42
-2nd shared lib length of 'how now brown cow': 17
-lib test_number_data: 12345
-lib test_number_data: 54321
-lib test_number_bss: 0
-lib test_number_bss: 54321
-lib get_test_number_data_internal_ref: 12345
-lib get_test_number_data_internal_ref: 54321
-malloc: ok
-add_many_result: 36
-EOF
-`
-assert [ "`$PRELOADER ./loader ./dynamic`" == "$expected" ]
+# # Dynamic Test
+# expected=`cat <<EOF
+# 1st call
+# 2nd call
+# 16 + 16 = 32
+# dynamic_var: 0
+# dynamic_var: 42
+# 2nd shared lib length of 'how now brown cow': 17
+# lib test_number_data: 12345
+# lib test_number_data: 54321
+# lib test_number_bss: 0
+# lib test_number_bss: 54321
+# lib get_test_number_data_internal_ref: 12345
+# lib get_test_number_data_internal_ref: 54321
+# malloc: ok
+# add_many_result: 36
+# EOF
+# `
+# assert [ "`$PRELOADER ./loader ./dynamic`" == "$expected" ]
 
 echo All tests passed

src/dlls/msvcrt.c

@@ -1,5 +1,6 @@
 #include "msvcrt.h"
 #include <stdarg.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 

src/loader/loader_lib.c

@@ -131,7 +131,7 @@ bool find_got_entry(
 bool read_to_string(const char *path, char **content, size_t size) {
     char *buffer = loader_malloc_arena(size);
     if (buffer == NULL) {
-        BAIL("malloc failed\n");
+        BAIL("loader_malloc_arena failed\n");
     }
 
     int32_t fd = tiny_c_open(path, O_RDONLY);
@@ -196,7 +196,7 @@ bool get_runtime_symbols(
             .size = curr_symbol->size,
         };
         if (!RuntimeSymbolList_add(runtime_symbols, runtime_symbol)) {
-            BAIL("malloc failed\n");
+            BAIL("RuntimeSymbolList_add failed\n");
         }
     }
 

src/loader/loader_main.c

@@ -278,7 +278,7 @@ static bool initialize_dynamic_data(
         sizeof(struct RuntimeObject) * inferior_dyn_data->shared_libraries_len
     );
     if (shared_libraries == NULL) {
-        BAIL("malloc failed\n");
+        BAIL("loader_malloc_arena failed\n");
     }
 
     size_t dynamic_lib_offset = LOADER_SHARED_LIB_START;
@@ -397,7 +397,7 @@ static bool initialize_dynamic_data(
         sizeof(struct RuntimeRelocation) * runtime_var_relocations_len
     );
     if (runtime_var_relocations == NULL) {
-        BAIL("malloc failed\n");
+        BAIL("loader_malloc_arena failed\n");
     }
 
     for (size_t i = 0; i < inferior_dyn_data->var_relocations_len; i++) {

src/loader/pe_tools.c

@@ -4,6 +4,7 @@
 #include "elf_tools.h"
 #include "loader_lib.h"
 #include "memory_map.h"
+#include <assert.h>
 #include <stdatomic.h>
 #include <stddef.h>
 #include <stdint.h>

src/programs/linux/string/string_main.c

@@ -19,6 +19,11 @@ extern int test_number_data;
 
 int get_test_number_data();
 
+// @todo:
+extern size_t tinyc_heap_start;
+extern size_t tinyc_heap_end;
+extern size_t tinyc_heap_index;
+
 int main(void) {
     tiny_c_printf("inline string\n");
 
@@ -32,7 +37,14 @@ int main(void) {
     tiny_c_printf("bss_int %d\n", bss_int);
     tiny_c_printf("bss_string %s\n", bss_string);
 
+    tiny_c_fprintf(STDERR, "tinyc_heap_start %x\n", tinyc_heap_start);
+    tiny_c_fprintf(STDERR, "tinyc_heap_end %x\n", tinyc_heap_end);
+    tiny_c_fprintf(STDERR, "tinyc_heap_index %x\n", tinyc_heap_index);
+    tiny_c_fprintf(STDERR, "mallocing...\n");
     char *malloc_string = tinyc_malloc_arena(0x1000);
+    tiny_c_fprintf(STDERR, "tinyc_heap_start %x\n", tinyc_heap_start);
+    tiny_c_fprintf(STDERR, "tinyc_heap_end %x\n", tinyc_heap_end);
+    tiny_c_fprintf(STDERR, "tinyc_heap_index %x\n", tinyc_heap_index);
     if (malloc_string == NULL) {
         tiny_c_fprintf(STDERR, "malloc failed\n");
         tiny_c_exit(-1);

src/tiny_c/tiny_c.c

@@ -6,6 +6,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
@@ -57,7 +58,7 @@ static void tiny_c_print(int32_t file_handle, const char *data) {
 static void tiny_c_newline(int32_t file_handle) {
     struct SysArgs args = (struct SysArgs){
         .param_one = (size_t)file_handle,
-        .param_two = (size_t)"\n",
+        .param_two = (size_t) "\n",
         .param_three = 1,
     };
     tiny_c_syscall(SYS_write, &args);
@@ -410,23 +411,39 @@ const char *tinyc_strerror(int32_t err_number) {
 
 // @todo: alignment
 void *tinyc_malloc_arena(size_t n) {
-    const size_t PAGE_SIZE = 0x1000;
-
-    if (tinyc_heap_start == 0) {
-        tinyc_heap_start = tinyc_sys_brk(0);
-        tinyc_heap_end = tinyc_heap_start;
-        tinyc_heap_index = tinyc_heap_start;
-    }
-    if (tinyc_heap_index + n > tinyc_heap_end) {
-        size_t extend_size = PAGE_SIZE * (n / PAGE_SIZE) + PAGE_SIZE;
-        tinyc_heap_end = tinyc_sys_brk(tinyc_heap_end + extend_size);
-        if (tinyc_heap_end <= tinyc_heap_start) {
-            return NULL;
-        }
+    // const size_t PAGE_SIZE = 0x1000;
+
+    // if (tinyc_heap_start == 0) {
+    size_t start = tinyc_sys_brk(0);
+    size_t end = start;
+    size_t index = start;
+    // tinyc_heap_start = tinyc_sys_brk(0);
+    // tinyc_heap_end = tinyc_heap_start;
+    // tinyc_heap_index = tinyc_heap_start;
+    // }
+    // if (tinyc_heap_index + n > tinyc_heap_end) {
+    // size_t extend_size = PAGE_SIZE * (n / PAGE_SIZE) + PAGE_SIZE;
+    // tinyc_heap_end = tinyc_sys_brk(tinyc_heap_end + extend_size);
+    // tinyc_heap_start = tinyc_sys_brk(0);
+    // tinyc_heap_end = tinyc_sys_brk(tinyc_heap_end + 0x2000);
+    // size_t temp_start = tinyc_sys_brk(0);
+    // size_t temp_end = tinyc_sys_brk(temp_start + 0x2000);
+    // if (temp_end <= temp_start) {
+    //     return NULL;
+    // }
+    end = tinyc_sys_brk(start + 0x2000);
+
+    tinyc_heap_start = start;
+    tinyc_heap_end = end;
+    tinyc_heap_index = index;
+
+    if (end <= start) {
+        return NULL;
     }
+    // }
 
-    void *address = (void *)tinyc_heap_index;
-    tinyc_heap_index += n;
+    void *address = (void *)index;
+    // tinyc_heap_index += n;
 
     return address;
 }