Updates to gitignore, Makefile, README, STATS. Cleaned up t/ for `-…

…ansi -Wall -pedantic`. Added `_end` & friends segment pointers, and tests for `_end` & a basic implementation of `sys_brk`, `sbrk` and `brk` as a test (malloc should be a snap to write now)
lpsantil · Oct 9, 2015 · eaf696a · eaf696a
1 parent 7e5dead
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Showing 16 changed files with 386 additions and 111 deletions.
diff --git a/.gitignore b/.gitignore
@@ -32,3 +32,5 @@
 *.pid
 *.tmp
 *.footprint
+*.log
+*.d
diff --git a/Makefile b/Makefile
@@ -25,9 +25,10 @@ endif
 ######################################################################
 
 # Comment next line if you want System Default/GNU BFD LD instead
-LD = gold
-CFLAGS ?= -Os -nostdlib -fomit-frame-pointer
-LDFLAGS ?= -s -nostdlib
+#LD = gold
+CFLAGS ?= -Os -Wall -ansi -pedantic -nostdlib -fomit-frame-pointer -fno-stack-protector -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-unroll-loops -fmerge-all-constants -fno-ident -mfpmath=387 -mfancy-math-387 -ffunction-sections -fdata-sections -Wl,--gc-sections
+LDFLAGS ?= -s -nostdlib -z norelro --hash-style=sysv --build-id=none --gc-sections
+#LDFLAGS ?= -g -nostdlib
 #LDFLAGS ?= -s -nostdlib -Wl,--gc-sections
 
 DDIR = docs
@@ -59,6 +60,8 @@ TMPCI = $(shell cat tmp.ci.pid)
 TMPCT = $(shell cat tmp.ct.pid)
 TMPCD = $(shell cat tmp.cd.pid)
 
+CILOG ?= tmp.ci.log
+
 # DEPS
 DEPS =
 LIBDEP =
@@ -118,7 +121,7 @@ runtest: $(TEXE)
 	for T in $^ ; do $(TAP) $$T ; done
 
 start_ci:
-	watch time -p make clean all & echo $$! > tmp.ci.pid
+	( watch time -p make clean all ) &> $(CILOG) & echo $$! > tmp.ci.pid
 
 stop_ci:
 	kill -9 $(TMPCI)

diff --git a/README.md b/README.md
@@ -2,15 +2,16 @@
 A minimal C runtime for Linux on i386 &amp; x86_64
 
 ## Features
-* Implemented in just 195 SLOC of C code.
+* Implemented in just 202 SLOC of C code.
 * Just 9 lines of GCC inline ASM for i386, or,
 * Just 6 lines GCC inline ASM for x86_64
-* Small runtime providing just `argc`, `argv`, `envp`, `__environ`, `errno`, `_exit`, and `syscall0/1/2/3/4/5/6`
-* Uses [gold][19] (Google LD, part of GNU Binutils) instead of GNU ld to save 100-200 bytes at static link time
-* Hello World in just 1140 bytes (i386) or 1328 bytes (x86_64)
+* Small runtime providing just `argc`, `argv`, `envp`, `__environ`, `errno`, `_exit`, `_end`, `_edata`, `_etext`, `__executable_start` and `syscall0/1/2/3/4/5/6`
+* An example implementation of `sys_brk`, `brk`, and `sbrk`
+* Can be used with [gold][19] (Google LD, part of GNU Binutils)
+* Hello World in just 608 bytes (i386) or 792 bytes (x86_64)
 * Small binary sizes vs. other libc's
 
-See STATS.md to see how rt0 fares.
+See [STATS.md][20] to see how rt0 fares.
 See the [musl libc comparison][0] to see how other libc's fare.
 
 ## Building
@@ -21,15 +22,17 @@ Try:
 * `make runtest`
 * `make DESTDIR=/usr/local install`, or simply, `make install`
 * You can also do `make uninstall`
+* It is highly recommended that you build using `WITH_FAST_SYSCALL=1`, e.g., `make WITH_FAST_SYSCALL=1`
 
 ## Usage
 * Include `rt0/rt0.h` for `__environ`, `_exit`
 * Include `rt0/syscall.h` for `SYS_*`, `syscall0/1/2/3/4/5/6`
 * Define `main` as `int main( int, char**, char** )`
-* Compile your code with `-nostdlib`, e.g., `cc -c prog.c -nostdlib -o prog.o`
+* Compile your code with at least `-nostdlib`, e.g., `cc -c prog.c -nostdlib -o prog.o`
 * On Linux, link with librt0, e.g., `cc prog.o -nostdlib -lrt0 -o prog`
 * On FreeBSD, link with librt0 using, `cc prog.o -Wl,-u_start -nostdlib -lrt0 -o prog`
-* To enable GNU ld, type `make LD=ld`
+* To enable Google ld, type `make LD=gold`
+* To enable GNU ld, type `make LD=ld` (default)
 * To enable a slightly faster version of the syscalls, type `make WITH_FAST_SYSCALL=1`
 * To enable `-fdata-sections -ffunction-sections`, type `make WITH_SECTIONS=1`
 * To enable a debug build, type `make WITH_DEBUG=1`
@@ -43,6 +46,10 @@ Try:
 * [System V ABI/Calling Convention][6]
 * [Linux syscall interface][7]
 * [gold - Google ld][19]
+* [brk(2) man page][21]
+* [malloc implementation@Stack Overflow][22]
+* [A Quick Tutorial on Implementing and Debugging Malloc, Free, Calloc, and Realloc][23]
+* [Tips of malloc & free][24]
 
 ## Other small libc's and runtimes
 * [musl libc][8]
@@ -77,3 +84,8 @@ Try:
 [17]: http://www.fefe.de/djb/
 [18]: https://gist.github.com/lunixbochs/462ee21c3353c56b910f
 [19]: http://en.wikipedia.org/wiki/Gold_%28linker%29
+[20]: https://github.com/lpsantil/rt0/blob/master/STATS.md
+[21]: http://linux.die.net/man/2/brk
+[22]: http://stackoverflow.com/questions/5422061/malloc-implementation
+[23]: http://danluu.com/malloc-tutorial/
+[24]: http://elinux.org/images/b/b5/Elc2013_Kobayashi.pdf
diff --git a/STATS.md b/STATS.md
@@ -1,23 +1,46 @@
 # rt0 library & binary sizes
 
-| Binary      | Arch   | Size | Purpose                  | Compile Args                          |
--------------:|:-------|-----:|:-------------------------|:--------------------------------------|
-| librt0.a    | i386   | 3502 | Startup code+syscall     | -Os -nostdlib -fomit-frame-pointer    |
-| librt0.a    | x86_64 | 4798 | Startup code+syscall     | -Os -nostdlib -fomit-frame-pointer    |
-| t/hello.exe | i386   | 1140 | Hello World\n            | -Os -s -nostdlib -fomit-frame-pointer |
-| t/hello.exe | x86_64 | 1328 | Hello World\n            | -Os -s -nostdlib -fomit-frame-pointer |
-| hello.exe   | i386   | 5532 | Hello World\n with glibc | -Os -s -fomit-frame-pointer           |
-| hello.exe   | x86_64 | 6240 | Hello World\n with glibc | -Os -s -fomit-frame-pointer           |
-| t/null.exe  | i386   | 1044 | Empty main               | -Os -s -nostdlib -fomit-frame-pointer |
-| t/null.exe  | x86_64 | 1272 | Empty main               | -Os -s -nostdlib -fomit-frame-pointer |
-| null.exe    | i386   | 5528 | Empty main               | -Os -s -fomit-frame-pointer           |
-| null.exe    | x86_64 | 6232 | Empty main               | -Os -s -fomit-frame-pointer           |
-| ...         | ...    | ...  | ...                      | With `__RT0_WITH_FASTER_SYSCALL__`    |
-| librt0.a    | i386   | 4168 | Startup code+syscall     | -Os -nostdlib -fomit-frame-pointer    |
-| librt0.a    | x86_64 | 5660 | Startup code+syscall     | -Os -nostdlib -fomit-frame-pointer    |
-| t/hello.exe | i386   | 1440 | Hello World\n            | -Os -s -nostdlib -fomit-frame-pointer |
-| t/hello.exe | x86_64 | 1600 | Hello World\n            | -Os -s -nostdlib -fomit-frame-pointer |
-| t/null.exe  | i386   | 1368 | Empty main               | -Os -s -nostdlib -fomit-frame-pointer |
-| t/null.exe  | x86_64 | 1560 | Empty main               | -Os -s -nostdlib -fomit-frame-pointer |
+| Binary      | Arch   | Size | Purpose                            |
+-------------:|:-------|-----:|:-----------------------------------|
+| librt0.a    | i386   | 2810 | Startup code+syscall               |
+| librt0.a    | x86_64 | 3974 | Startup code+syscall               |
+| t/hello.exe | i386   | 624  | Hello World\n                      |
+| t/hello.exe | x86_64 | 824  | Hello World\n                      |
+| hello.exe   | i386   | 2988 | Hello World\n with glibc           |
+| hello.exe   | x86_64 | 4200 | Hello World\n with glibc           |
+| t/null.exe  | i386   | 560  | Empty main                         |
+| t/null.exe  | x86_64 | 768  | Empty main                         |
+| null.exe    | i386   | 2888 | Empty main with glibc              |
+| null.exe    | x86_64 | 2988 | Empty main with glibc              |
+| ...         | ...    | ...  | With `__RT0_WITH_FASTER_SYSCALL__` |
+| librt0.a    | i386   | 3980 | Startup code+syscall               |
+| librt0.a    | x86_64 | 5604 | Startup code+syscall               |
+| t/hello.exe | i386   | 608  | Hello World\n                      |
+| t/hello.exe | x86_64 | 792  | Hello World\n                      |
+| t/null.exe  | i386   | 552  | Empty main                         |
+| t/null.exe  | x86_64 | 752  | Empty main                         |
 
-Compiler: GCC 4.8.2, gold linker 1.11 (binutils 2.24) OS: Ubuntu 14.04.2, Source: Author
+Compiler: GCC 4.8.4, gold linker 1.11, ld/binutils 2.24, OS: Ubuntu 14.04.3, Source: Author
+Compile Flags: `-Os -nostdlib -fomit-frame-pointer -fno-stack-protector -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-unroll-loops -fmerge-all-constants -fno-ident -mfpmath=387 -mfancy-math-387 -ffunction-sections -fdata-sections Wl,--gc-sections`
+Link Flags: `-s -nostdlib -z norelro --hash-style=sysv --build-id=none --gc-sections`
+
+`HelloWorld` & `null` compiled with flags above but without `-nostdlib`.
+
+`HelloWorld.glibc.c`
+```
+#include <unistd.h>
+
+int main( int argc, char** argv, char** envp )
+{
+   int ret = write( 1, "Hello World!\n", 13 );
+   return( 0 );
+}
+```
+
+`null.glibc.c`
+```
+int main( int argc, char** argv, char** envp )
+{
+   return( 0 );
+}
+```
diff --git a/include/rt0/rt0.h b/include/rt0/rt0.h
@@ -8,6 +8,7 @@
 
 extern char **__environ; /* pointer to array of char * strings that define the current environment variables */
 extern int errno;
+extern char _end, _edata, _etext, __executable_start;
 
 void _exit( int r ) __attribute__((noreturn));
 /*

diff --git a/lib/.gitignore b/lib/.gitignore
@@ -0,0 +1,34 @@
+# Object files
+*.o
+*.ko
+*.obj
+*.elf
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+
+# Temporary files
+*.pid
+*.tmp
+*.footprint
diff --git a/t/_end.c b/t/_end.c
@@ -0,0 +1,73 @@
+#include <rt0/syscall.h>
+
+int write( int f, const char* d, int l )
+{
+   int ret = syscall3( SYS_write, f, ( long )( d ), l );
+
+   return( ret );
+}
+
+int str_len( const char *string )
+{
+   int length = 0;
+   while( *string ) { string++; length++; }
+   return length;
+}
+
+void print( const char* string )
+{
+   write( 1, string, str_len( string ) );
+}
+
+void printLongHex( long i )
+{
+   char* nums = "0123456789ABCDEF";
+   long d = 1,
+        r;
+
+   if( i < 0 )
+   {
+      print( "-" );
+
+      printLongHex( -i );
+
+      return;
+   }
+
+   d = i / 16;
+   r = i % 16;
+
+   if( d != 0 )
+   {
+     printLongHex( d );
+   }
+
+   write( 1, &( nums[ r ] ), 1 );
+}
+
+int main( int argc, char **argv, char **envp )
+{
+   long addr;
+
+   addr = ( long )( &__executable_start );
+   print( "Address of __executable_start: " );
+   printLongHex( addr );
+   print( "\n" );
+
+   addr = ( long )( &_etext );
+   print( "Address of _etext: " );
+   printLongHex( addr );
+   print( "\n" );
+
+   addr = ( long )( &_edata );
+   print( "Address of _edata: " );
+   printLongHex( addr );
+   print( "\n" );
+
+   addr = ( long )( &_end );
+   print( "Address of _end: " );
+   printLongHex( addr );
+   print( "\n" );
+
+   return( 0 );
+}
diff --git a/t/argc.c b/t/argc.c
@@ -1,5 +1,19 @@
 #include <rt0/syscall.h>
 
+int write( int f, const char* d, int l )
+{
+   int ret = syscall3( SYS_write, f, ( long )( d ), l );
+
+   return( ret );
+}
+
+int str_len( const char *string )
+{
+   int length = 0;
+   while( *string ) { string++; length++; }
+   return length;
+}
+
 void print( const char* string )
 {
    write( 1, string, str_len( string ) );
@@ -39,17 +53,3 @@ int main( int argc, char** argv, char** envp )
 
    return( 0 );
 }
-
-int write( int f, char* d, int l )
-{
-   int ret = syscall3( SYS_write, f, ( long )( d ), l );
-
-   return( ret );
-}
-
-int str_len( const char *string )
-{
-   int length = 0;
-   while( *string ) { string++; length++; }
-   return length;
-}
diff --git a/t/argv.c b/t/argv.c
@@ -1,5 +1,19 @@
 #include <rt0/syscall.h>
 
+int write( int f, const char* d, int l )
+{
+   int ret = syscall3( SYS_write, f, ( long )( d ), l );
+
+   return( ret );
+}
+
+int str_len( const char *string )
+{
+   int length = 0;
+   while( *string ) { string++; length++; }
+   return length;
+}
+
 void print( const char* string )
 {
    write( 1, string, str_len( string ) );
@@ -19,17 +33,3 @@ int main( int argc, char** argv, char** envp )
 
    return( 0 );
 }
-
-int write( int f, char* d, int l )
-{
-   int ret = syscall3( SYS_write, f, ( long )( d ), l );
-
-   return( ret );
-}
-
-int str_len( const char *string )
-{
-   int length = 0;
-   while( *string ) { string++; length++; }
-   return length;
-}
diff --git a/t/envp.c b/t/envp.c
@@ -1,5 +1,19 @@
 #include <rt0/syscall.h>
 
+int write( int f, const char* d, int l )
+{
+   int ret = syscall3( SYS_write, f, ( long )( d ), l );
+
+   return( ret );
+}
+
+int str_len( const char *string )
+{
+   int length = 0;
+   while( *string ) { string++; length++; }
+   return length;
+}
+
 void println( const char* string )
 {
    write( 1, string, str_len( string ) );
@@ -20,17 +34,3 @@ int main( int argc, char** argv, char** envp )
 
    return( 0 );
 }
-
-int write( int f, char* d, int l )
-{
-   int ret = syscall3( SYS_write, f, ( long )( d ), l );
-
-   return( ret );
-}
-
-int str_len( const char *string )
-{
-   int length = 0;
-   while( *string ) { string++; length++; }
-   return length;
-}