When transitioning to 32bit via call32() track the stack segment register and support restoring it on call16() requests. This permits call16() to work properly.
Signed-off-by: Kevin O'Connor kevin@koconnor.net --- src/romlayout.S | 16 +++++++++++++++- src/stacks.c | 20 ++++++++++++++------ 2 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/src/romlayout.S b/src/romlayout.S index 8415c9f..9de91a2 100644 --- a/src/romlayout.S +++ b/src/romlayout.S @@ -146,9 +146,23 @@ __call16big:
// Make call. .code16gcc -1: popl %ecx +1: movl $_zonelow_seg, %edx // Adjust %ds, %ss, and %esp + movl %edx, %ds + movzwl StackSeg, %edx + movl %edx, %ecx + shll $4, %ecx + movl %edx, %ss + subl %ecx, %esp + movl %edx, %ds + + popl %ecx // Call function popl %edx calll *%ecx + + movl %ss, %edx // Readjust %esp + shll $4, %edx + addl %edx, %esp + // Return via transition32 movl $(2f + BUILD_BIOS_ADDR), %edx jmp transition32 diff --git a/src/stacks.c b/src/stacks.c index 563ce1c..78ad65c 100644 --- a/src/stacks.c +++ b/src/stacks.c @@ -13,6 +13,8 @@ #include "stacks.h" // struct mutex_s #include "util.h" // useRTC
+#define MAIN_STACK_MAX (1024*1024) +
/**************************************************************** * Extra 16bit stack @@ -107,6 +109,8 @@ static inline void lgdt(struct descloc_s *desc) { asm("lgdtl %0" : : "m"(*desc) : "memory"); }
+u16 StackSeg VARLOW; + // Call a 32bit SeaBIOS function from a 16bit SeaBIOS function. u32 VISIBLE16 call32(void *func, u32 eax, u32 errret) @@ -127,6 +131,8 @@ call32(void *func, u32 eax, u32 errret) struct descloc_s gdt; sgdt(&gdt);
+ u16 oldstackseg = GET_LOW(StackSeg); + SET_LOW(StackSeg, GET_SEG(SS)); u32 bkup_ss, bkup_esp; asm volatile( // Backup ss/esp / set esp to flat stack location @@ -153,6 +159,8 @@ call32(void *func, u32 eax, u32 errret) : "r" (func) : "ecx", "edx", "cc", "memory");
+ SET_LOW(StackSeg, oldstackseg); + // Restore gdt and fs/gs lgdt(&gdt); SET_SEG(FS, fs); @@ -169,7 +177,7 @@ static inline u32 call16(u32 eax, u32 edx, void *func) { ASSERT32FLAT(); - if (getesp() > BUILD_STACK_ADDR) + if (getesp() > MAIN_STACK_MAX) panic("call16 with invalid stack\n"); extern u32 __call16(u32 eax, u32 edx, void *func); return __call16(eax, edx, func - BUILD_BIOS_ADDR); @@ -179,7 +187,7 @@ static inline u32 call16big(u32 eax, u32 edx, void *func) { ASSERT32FLAT(); - if (getesp() > BUILD_STACK_ADDR) + if (getesp() > MAIN_STACK_MAX) panic("call16big with invalid stack\n"); extern u32 __call16big(u32 eax, u32 edx, void *func); return __call16big(eax, edx, func - BUILD_BIOS_ADDR); @@ -214,14 +222,14 @@ farcall16(struct bregs *callregs) return; } extern void _cfunc16__farcall16(void); - call16((u32)callregs, 0, _cfunc16__farcall16); + call16((u32)callregs - StackSeg * 16, StackSeg, _cfunc16__farcall16); }
inline void farcall16big(struct bregs *callregs) { extern void _cfunc16__farcall16(void); - call16big((u32)callregs, 0, _cfunc16__farcall16); + call16big((u32)callregs - StackSeg * 16, StackSeg, _cfunc16__farcall16); }
// Invoke a 16bit software interrupt. @@ -265,7 +273,7 @@ struct thread_info * getCurThread(void) { u32 esp = getesp(); - if (esp <= BUILD_STACK_ADDR) + if (esp <= MAIN_STACK_MAX) return &MainThread; return (void*)ALIGN_DOWN(esp, THREADSTACKSIZE); } @@ -477,7 +485,7 @@ int wait_preempt(void) { if (MODESEGMENT || !CONFIG_THREAD_OPTIONROMS || !CanPreempt - || getesp() < 1024*1024) + || getesp() < MAIN_STACK_MAX) return 0; while (CanPreempt) yield();
-
Kevin O'Connor