Move .BSS zeroing into early assembly, avoid using section attribute

fwsGonzo · Jul 1, 2019 · 0064e3d · 0064e3d
1 parent abd2555
commit 0064e3d
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Showing 4 changed files with 14 additions and 15 deletions.
diff --git a/src/crt/c_abi.c b/src/crt/c_abi.c
@@ -34,33 +34,26 @@ static void* multiboot_free_begin(intptr_t mb_addr)
 void __init_stdlib(uint32_t mb_magic, uint32_t mb_addr)
 {
 	assert(mb_magic == 0x2badb002);
-	// 1. initialize BSS area
-	extern char _BSS_START_;
-	extern char _BSS_END_;
 
-	for (char* bss = &_BSS_START_; bss < &_BSS_END_; bss++) {
-		*bss = 0;
-	}
-
-	// 2. enable printf facilities
+	// 1. enable printf facilities
 	init_printf(NULL, __serial_putchr);
 
-	// 3. find end of multiboot areas
+	// 2. find end of multiboot areas
 	void* free_begin = multiboot_free_begin(mb_addr);
 	assert(free_begin >= (void*) &_end);
 
-	// 4. initialize heap (malloc, etc.)
+	// 3. initialize heap (malloc, etc.)
 	extern void __init_heap(void*);
 	__init_heap(free_begin);
 
 #ifdef EH_ENABLED
-	/// 5. initialize exceptions before we run constructors
+	/// 4. initialize exceptions before we run constructors
     extern char __eh_frame_start[];
     extern void __register_frame(void*);
   	__register_frame(&__eh_frame_start);
 #endif
 
-	// 6. call global C/C++ constructors
+	// 5. call global C/C++ constructors
 	extern void(*__init_array_start [])();
 	extern void(*__init_array_end [])();
 	int count = __init_array_end - __init_array_start;

diff --git a/src/hw/serial1.c b/src/hw/serial1.c
@@ -1,7 +1,7 @@
 #include <stdint.h>
 
 static const uint16_t port = 0x3F8; // Serial port 1
-static char initialized __attribute__((section(".data"))) = 0;
+static char initialized = 0;
 
 static inline uint8_t inb(int port)
 {

diff --git a/src/kernel/kernel_start.c b/src/kernel/kernel_start.c
@@ -21,7 +21,6 @@ static void __init_paging()
 void kernel_start(uint32_t eax, uint32_t ebx)
 {
 	kprintf("kernel_start(eax: %x, ebx: %x)\n", eax, ebx);
-	assert(eax == 0x2badb002);
 
 	extern void __init_stdlib(uint32_t, uint32_t);
 	__init_stdlib(eax, ebx);

diff --git a/src/kernel/start.asm b/src/kernel/start.asm
@@ -68,7 +68,14 @@ rock_bottom:
     rdtsc
     mov DWORD [0x1014], eax
 
-    ;; eax, ebx still on stack
+	;; zero .bss (used to be in the C portion, but easier to do here)
+	extern _BSS_START_
+	extern _BSS_END_
+	mov ecx, _BSS_END_
+	sub ecx, _BSS_START_
+	mov eax, 0
+	rep stosb
+
     ;; for 32-bit kernels just call kernel_start here
     call begin_enter_longmode
     add esp, 8