From ec0810b91aba837f684ed15f0b8abfb03299f661 Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Fri, 14 Jul 2017 16:19:58 +0200
Subject: some linkage tweaking, the kernel is not linked against libssp (which
 is using linux/glibc), we provide our own SSP guards leading to kernel_panic
 (for now). per default build the kernel with ld (as we need precise control
 how we link it) the libc tests are per default linked with the same compiler
 as provided with $(CC) using #include_next of gcc/clang to include the real
 stdint.h header file in stdint.h stub

---
 doc/LINKS.TODO           |  3 +++
 src/Makefile             |  1 +
 src/kernel/kernel.c      | 18 ++++++++++++++++++
 src/kernel/kernel.h      | 11 +++++++++++
 src/libc/stdint.h        |  4 ++++
 tests/libc/Makefile      |  4 ++--
 tests/libc/kernel_stub.c |  7 +++++++
 tests/libc/kernel_stub.h |  9 +++++++++
 8 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/doc/LINKS.TODO b/doc/LINKS.TODO
index 89f7ce8..968ff6d 100644
--- a/doc/LINKS.TODO
+++ b/doc/LINKS.TODO
@@ -102,3 +102,6 @@ https://stackoverflow.com/questions/26143123/how-do-i-ensure-the-entry-function-
 
 Linux:
 https://blog.packagecloud.io/eng/2016/04/05/the-definitive-guide-to-linux-system-calls/
+
+Security:
+http://wiki.osdev.org/Stack_Smashing_Protector
diff --git a/src/Makefile b/src/Makefile
index b4ceff1..3c2849e 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -3,6 +3,7 @@ DEFINES = -DOS_ABAOS
 INCLUDES = -I. -Ilibc -Ihardware -Idrivers -Idrivers/hdi -Idrivers/hdi/ps2 -Idrivers/video -Ikernel -Igui
 CFLAGS := -std=c99 -m32 -march=i486 -ffreestanding -O0 -g -Werror $(INCLUDES) $(DEFINES)
 LD := ld
+LDFLAGS := -lgcc
 NASMFLAGS := -f elf32
 NASM := nasm
 OBJCOPY := objcopy
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index a472cde..be5da7c 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -419,4 +419,22 @@ static void print_memory_status( global_context_t *global_context )
 	
 }
 
+uintptr_t __stack_chk_guard = STACK_CHK_GUARD;
 
+__attribute__( ( noreturn ) )
+void __stack_chk_fail_local( void )
+{
+	kernel_panic( "Stack smashing detected!" );
+
+	// make gcc happy on noreturn does return
+	for( ;; );
+}
+
+__attribute__( ( noreturn ) )
+void __stack_chk_fail( void )
+{
+	kernel_panic( "Stack smashing detected!" );
+
+	// make gcc happy on noreturn does return
+	for( ;; );
+}
diff --git a/src/kernel/kernel.h b/src/kernel/kernel.h
index dc23fd6..87733c8 100644
--- a/src/kernel/kernel.h
+++ b/src/kernel/kernel.h
@@ -1,10 +1,21 @@
 #ifndef KERNEL_H
 #define KERNEL_H
 
+#include "stdint.h"
 #include "stdio.h"
 
 void kernel_main( void );
 void kernel_panic( const char *format, ... );
 void kernel_halt( void );
 
+#define STACK_CHK_GUARD 0xe2dee396
+
+extern uintptr_t __stack_chk_guard;
+
+__attribute__( ( noreturn ) )
+void __stack_chk_fail_local( void );
+
+__attribute__( ( noreturn ) )
+void __stack_chk_fail( void );
+
 #endif // KERNEL_H
diff --git a/src/libc/stdint.h b/src/libc/stdint.h
index e0f35b6..23dc370 100644
--- a/src/libc/stdint.h
+++ b/src/libc/stdint.h
@@ -10,6 +10,10 @@ typedef unsigned short uint16_t;
 typedef signed short int16_t;
 typedef unsigned char uint8_t;
 typedef signed char int8_t;
+typedef uint32_t uintptr_t;
+#else
+// gcc and clang provide a stdint.h
+#include_next <stdint.h>
 #endif
 
 #endif // STDINT_H
diff --git a/tests/libc/Makefile b/tests/libc/Makefile
index d9d2927..2d89940 100644
--- a/tests/libc/Makefile
+++ b/tests/libc/Makefile
@@ -2,8 +2,8 @@ CC := gcc
 DEFINES = -DOS_LINUX
 INCLUDES = -I. -I../../src/libc -I../../src/kernel -I/home/abaumann/cross-compilers/include
 CFLAGS := -std=c99 -m32 -ffreestanding -O0 -g -Wall -Werror $(INCLUDES) $(DEFINES)
-LD := ld
-LDFLAGS := 
+LD := $(CC)
+LDFLAGS :=
 NASMFLAGS := -f elf32
 NASM := nasm
 
diff --git a/tests/libc/kernel_stub.c b/tests/libc/kernel_stub.c
index 610c3d3..cacab34 100644
--- a/tests/libc/kernel_stub.c
+++ b/tests/libc/kernel_stub.c
@@ -22,3 +22,10 @@ void kernel_panic( const char *format, ... )
 	exit( 255 );
 }
 
+uintptr_t __stack_chk_guard = STACK_CHK_GUARD;
+
+__attribute__( ( noreturn ) )
+void __stack_chk_fail_local( void )
+{
+	abort( );
+}
diff --git a/tests/libc/kernel_stub.h b/tests/libc/kernel_stub.h
index 467ad20..65047f9 100644
--- a/tests/libc/kernel_stub.h
+++ b/tests/libc/kernel_stub.h
@@ -24,4 +24,13 @@ long syscall1( long n, long a1 );
 long syscall2( long n, long a1, long a2 );
 long syscall3( long n, long a1, long a2, long a3 );
 
+// SSP stub, we don't want to link against libssp
+
+#include <stdint.h>
+#include <stdlib.h>
+ 
+#define STACK_CHK_GUARD 0xe2dee396
+ 
+extern uintptr_t __stack_chk_guard;
+
 #endif
-- 
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