cstart: initialize .bss

The initialization of .bss is available only when the test is loaded by an ELF
loader, which is not the case when it is started directly by a
multiboot-compliant bootloader.

This patch explicitly clears .bss, except the stack which is already in use when
initializing .bss.

Signed-off-by: Junjie Mao <[email protected]>

Author: junjiemao1

lib/x86/setup.c

@@ -18,6 +18,7 @@
 #include "processor.h"
 #include "smp.h"
 
+extern char bss_start;
 extern char edata;
 
 struct mbi_bootinfo {
@@ -55,6 +56,8 @@ struct mbi_mem {
 void setup_env(char *env, int size);
 void setup_multiboot(struct mbi_bootinfo *bootinfo);
 void setup_libcflat(void);
+void bss_init(void);
+
 
 char *initrd;
 u32 initrd_size;
@@ -151,6 +154,11 @@ unsigned long setup_tss(u8 *stacktop)
 }
 #endif
 
+void bss_init(void)
+{
+	memset(&bss_start, 0, &edata - &bss_start);
+}
+
 void setup_multiboot(struct mbi_bootinfo *bi)
 {
 	struct mbi_module *mods;

x86/cstart64.S

@@ -5,7 +5,7 @@ ipi_vector = 0x20
 
 max_cpus = MAX_TEST_CPUS
 
-.bss
+.section stack
 
 	. = . + 4096 * max_cpus
 	.align 16
@@ -104,6 +104,7 @@ gdt32_end:
 
 .code64
 start64:
+	call bss_init
 	call load_idt
 	load_tss
 	call reset_apic

x86/flat.lds

@@ -14,6 +14,9 @@ SECTIONS
     . = ALIGN(16);
     .rodata : { *(.rodata) }
     . = ALIGN(16);
+    .stack : { *(stack) }
+    . = ALIGN(16);
+    bss_start = .;
     .bss : { *(.bss) }
     . = ALIGN(4K);
     edata = .;