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| author | Michael Brown | 2012-07-10 23:08:38 +0200 |
|---|---|---|
| committer | Michael Brown | 2015-04-21 01:39:31 +0200 |
| commit | 0bbb2484c7e5c8e94ff6bbc74ef6dab6769a68d6 (patch) | |
| tree | 9c1f8ccdecaf83ecf8770e47acaed9f48d4f7788 | |
| parent | [pxe] Switch back to real mode on exit (diff) | |
| download | memtest86-0bbb2484c7e5c8e94ff6bbc74ef6dab6769a68d6.tar.gz memtest86-0bbb2484c7e5c8e94ff6bbc74ef6dab6769a68d6.tar.xz memtest86-0bbb2484c7e5c8e94ff6bbc74ef6dab6769a68d6.zip | |
[pxe] Exit back to the PXE stack instead of rebooting
Signed-off-by: Michael Brown <mcb30@ipxe.org>
| -rw-r--r-- | defs.h | 3 | ||||
| -rw-r--r-- | exit.S | 31 | ||||
| -rw-r--r-- | head.S | 6 | ||||
| -rw-r--r-- | pxe.S | 12 |
4 files changed, 52 insertions, 0 deletions
@@ -24,3 +24,6 @@ #define KERNEL_DS 0x18 /* 32 bit segment adrs for data */ #define REAL_CS 0x20 /* 16 bit segment adrs for code */ #define REAL_DS 0x28 /* 16 bit segment adrs for data */ + +/* Magic marker to determine if exit stack is intact */ +#define EXIT_MAGIC ( 'E' + ( 'X' << 8 ) + ( 'I' << 16 ) + ( 'T' << 24 ) ) @@ -12,6 +12,15 @@ exit: /* Exit status to %eax */ movl 4(%esp), %eax + /* Calculate real-mode exit %ss:esp in %dx:%edi */ + xorw %dx, %dx + xorl %edi, %edi + movl exit_esp, %ebp + cmpl $EXIT_MAGIC, 0(%ebp) + jne 1f + movl 8(%ebp), %edi + movw 6(%ebp), %dx +1: /* Load IDT and GDT and switch to 16-bit code segment */ cli lidt idt_descr @@ -45,6 +54,24 @@ exit: /* Reenable interrupts */ sti + /* If we have a real-mode exit stack, restore registers + * (except exit status) and return + */ + testl %edi, %edi + jz reset + movw %dx, %ss + movl %edi, %esp + movw %sp, %bp + movl %eax, 36(%bp) + popw %ds + popw %es + popw %fs + popw %gs + popal + popfl + lret + +reset: /* Perform a warm reset */ movw $0x1234, %ax movw %ax, 0x472 @@ -79,3 +106,7 @@ gdt_descr: idt_descr: .word 0xffff .long 0 + +.globl exit_esp +exit_esp: + .long 0 @@ -35,6 +35,12 @@ startup_32: 0: popl %ebx addl $_GLOBAL_OFFSET_TABLE_+[.-0b], %ebx + /* Store the exit stack address */ + cmpl $0, exit_esp@GOTOFF(%ebx) + jnz 0f + movl %esp, exit_esp@GOTOFF(%ebx) +0: + /* Pick the appropriate boot_stack address */ leal boot_stack_top@GOTOFF(%ebx), %esp @@ -23,6 +23,18 @@ _main: ljmp $BOOTSEG, $pxe_start pxe_start: + /* Preserve registers, %ss:%esp, and magic marker on PXE stack */ + pushfl + pushal + pushw %gs + pushw %fs + pushw %es + pushw %ds + pushl %esp + pushw %ss + pushw %ax /* Padding */ + pushl $EXIT_MAGIC + /* Store PXENV+ entry point */ movl %es:PXENV_ENTRY(%bx), %eax movl %eax, %cs:pxenv_vector |