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| author | Kevin O'Connor <kevin@koconnor.net> | 2008-03-31 21:56:04 -0400 |
|---|---|---|
| committer | Kevin O'Connor <kevin@koconnor.net> | 2008-03-31 21:56:04 -0400 |
| commit | 18f368edc5141b55efd11d9ca82e7e6ff5914a14 (patch) | |
| tree | c1f095d128649fe85d29e92fe2e8eea7736c99d9 | |
| parent | 67c2cf387f1d89d8a03308834c8d681733243ea6 (diff) | |
| download | seabios-18f368edc5141b55efd11d9ca82e7e6ff5914a14.tar.gz | |
Don't clobber %esp highbits on C code entry.
Theoretically, %esp high bits could be set - the C code will use %esp
(not %sp), so these bits need to be zeroed. However, they can't
be clobbered, so the entry code needs to save/restore it.
Also improve some comments in romlayout.S
| -rw-r--r-- | src/romlayout.S | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/src/romlayout.S b/src/romlayout.S index d11741e2..c5f48eb6 100644 --- a/src/romlayout.S +++ b/src/romlayout.S @@ -35,15 +35,18 @@ bios16c_end: // those registers that are call clobbered by the C compiler. .macro ENTRY cfunc cld - pushl %eax + pushl %eax // Save registers clobbered by C code pushl %ecx pushl %edx pushw %es pushw %ds - movw %ss, %ax + movw %ss, %ax // Move %ss to %ds movw %ax, %ds + pushl %esp // Backup %esp, then clear high bits + movzwl %sp, %esp calll \cfunc - popw %ds + popl %esp // Restore %esp (including high bits) + popw %ds // Restore registers saved above popw %es popl %edx popl %ecx @@ -56,7 +59,7 @@ bios16c_end: // restored from the structure. .macro ENTRY_ARG cfunc cld - pushl %eax + pushl %eax // Save registers (matches struct bregs) pushl %ecx pushl %edx pushl %ebx @@ -64,12 +67,14 @@ bios16c_end: pushl %edi pushw %es pushw %ds - movw %ss, %ax + movw %ss, %ax // Move %ss to %ds movw %ax, %ds + movl %esp, %ebx // Backup %esp, then zero high bits movzwl %sp, %esp - movl %esp, %eax + movl %esp, %eax // First arg is pointer to struct bregs calll \cfunc - popw %ds + movl %ebx, %esp // Restore %esp (including high bits) + popw %ds // Restore registers (from struct bregs) popw %es popl %edi popl %esi @@ -191,6 +196,8 @@ __call16_from32: movw %ax, %ss // Assume stack is in segment 0 popl %eax + + // Set __call16 return address to be transition32 pushl $transition32 // Fall through to __call16 @@ -248,7 +255,8 @@ __call16: retl - // APM trampolines + +// APM trampolines .globl apm16protected_entry apm16protected_entry: pushfw // save flags @@ -357,7 +365,6 @@ rombios32_gdt: IRQ_ENTRY 76 IRQ_ENTRY 1c IRQ_ENTRY 70 - IRQ_ENTRY 74 .org 0xe3fe jmp entry_13 @@ -378,6 +385,7 @@ rombios32_gdt: .org 0xe739 IRQ_ENTRY_ARG 14 + IRQ_ENTRY 74 IRQ_ENTRY 75 // int 18/19 are special - they reset the stack and do not return. |