lib,smp,setup: rewrite write_sp() as macro

The write_sp() may not be inlined (esp. when compiled with -O0) and then it is called to. After stack swap, the function cannot return. Thus, this should be a macro to make things stay away from stack. To further simplify things during AP initialization, allocate new stack frames from BSP and use the new pointer value directly in AP's WRITE_SP. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
KernelTestFramework · Feb 9, 2021 · c5ddf18 · c5ddf18
1 parent 2516a58
commit c5ddf18
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Showing 3 changed files with 10 additions and 7 deletions.
diff --git a/common/setup.c b/common/setup.c
@@ -212,7 +212,7 @@ void __noreturn __text_init kernel_start(uint32_t multiboot_magic,
     /* Setup final pagetables */
     init_pagetables();
     write_cr3(cr3.paddr);
-    write_sp(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));
+    WRITE_SP(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));
     if (opt_debug)
         dump_pagetables();
 

diff --git a/include/lib.h b/include/lib.h
@@ -277,9 +277,10 @@ static inline unsigned long read_cr8(void) {
     return cr8;
 }
 
-static inline void write_sp(void *sp) {
-    asm volatile("mov %0, %%" STR(_ASM_SP)::"r"(sp) : "memory");
-}
+#define WRITE_SP(sp)                                                                     \
+    do {                                                                                 \
+        asm volatile("mov %0, %%" STR(_ASM_SP)::"r"((sp)) : "memory");                   \
+    } while (0)
 
 static inline void lgdt(const gdt_ptr_t *gdt_ptr) {
     asm volatile("lgdt %0" ::"m"(*gdt_ptr));

diff --git a/smp/smp.c b/smp/smp.c
@@ -42,12 +42,13 @@ extern void ap_start(void);
 
 static unsigned nr_cpus;
 
-static unsigned ap_cpuid;
-static bool ap_callin;
+static __data_init unsigned ap_cpuid;
+static __data_init bool ap_callin;
+static __data_init void *ap_new_sp;
 cr3_t __data_init ap_cr3;
 
 void __noreturn __naked ap_startup(void) {
-    write_sp(get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL));
+    WRITE_SP(ap_new_sp);
 
     init_traps(ap_cpuid);
     init_apic(ap_cpuid, apic_get_mode());
@@ -69,6 +70,7 @@ static __text_init void boot_cpu(percpu_t *percpu) {
     if (percpu->bsp)
         return;
 
+    ap_new_sp = get_free_pages_top(PAGE_ORDER_2M, GFP_KERNEL);
     ap_cpuid = percpu->cpu_id;
     ap_callin = false;
     smp_wmb();