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[i386] Add data32 prefixes to all lgdt/lidt instructions

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With a 16-bit operand, lgdt/lidt will load only a 24-bit base address,
ignoring the high-order bits.  This meant that we could fail to fully
restore the GDT across a call into gPXE, if the GDT happened to be
located above the 16MB mark.

Not all of our lgdt/lidt instructions require a data32 prefix (for
example, reloading the real-mode IDT can never require a 32-bit base
address), but by adding them everywhere we will hopefully not forget
the necessary ones in future.
This commit is contained in:
Michael Brown
2008-11-06 23:08:10 +00:00
parent aa95744915
commit 29e6f9835e
2 changed files with 7 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
src/arch/i386/prefix/libprefix.S
View File

@@ -341,7 +341,7 @@ pm_call:
/* Switch CPU to protected mode and load up segment registers */ /* Switch CPU to protected mode and load up segment registers */
pushl %eax pushl %eax
cli cli
lgdt PM_CALL_VAR(gdt)(%bp) data32 lgdt PM_CALL_VAR(gdt)(%bp)
movl %cr0, %eax movl %cr0, %eax
orb $CR0_PE, %al orb $CR0_PE, %al
movl %eax, %cr0 movl %eax, %cr0
@@ -377,7 +377,7 @@ pm_call:
popw %es popw %es
popw %fs popw %fs
popw %gs popw %gs
lgdt PM_CALL_VAR(pm_saved_gdt)(%bp) data32 lgdt PM_CALL_VAR(pm_saved_gdt)(%bp)
popfl popfl
movw %bp, %sp movw %bp, %sp
popw %bp popw %bp

6
src/arch/i386/transitions/librm.S
View File

@@ -316,7 +316,7 @@ p2r_jump_target:
movl %edx, %esp movl %edx, %esp
/* Reset IDTR to the real-mode defaults */ /* Reset IDTR to the real-mode defaults */
lidt rm_idtr data32 lidt rm_idtr
/* Return to real-mode address */ /* Return to real-mode address */
data32 ret data32 ret
@@ -424,8 +424,8 @@ prot_call:
1: 1:
/* Reload GDT and IDT, restore registers and flags and return */ /* Reload GDT and IDT, restore registers and flags and return */
movw %sp, %bp movw %sp, %bp
lgdt (%bp) data32 lgdt (%bp)
lidt 8(%bp) data32 lidt 8(%bp)
addw $20, %sp /* also skip %cs and %ss */ addw $20, %sp /* also skip %cs and %ss */
popw %ds popw %ds
popw %es popw %es