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| author | Freya Murphy <freya@freyacat.org> | 2025-03-31 12:41:04 -0400 |
|---|---|---|
| committer | Freya Murphy <freya@freyacat.org> | 2025-03-31 12:41:04 -0400 |
| commit | 4dc44e8fce222a21f5eb8b86ecb226855c34999b (patch) | |
| tree | 83e42cbd2cfde437a35216e9c1ee58c0af995e94 /kernel/startup.S | |
| parent | track changes (diff) | |
| download | comus-4dc44e8fce222a21f5eb8b86ecb226855c34999b.tar.gz comus-4dc44e8fce222a21f5eb8b86ecb226855c34999b.tar.bz2 comus-4dc44e8fce222a21f5eb8b86ecb226855c34999b.zip | |
track upstream
Diffstat (limited to 'kernel/startup.S')
| -rw-r--r-- | kernel/startup.S | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/kernel/startup.S b/kernel/startup.S index 73a081e..94b93b0 100644 --- a/kernel/startup.S +++ b/kernel/startup.S @@ -33,18 +33,18 @@ /* ** A symbol for locating the beginning of the code. */ - .globl begtext - .text -begtext: + + .globl begtext + .globl _start +_start = V2PNC(begtext) /* ** The entry point. When we get here, we have just entered protected ** mode, so all the segment registers are incorrect except for CS. */ - .globl _start +begtext: -_start: cli /* seems to be reset on entry to p. mode */ movb $NMI_ENABLE, %al /* re-enable NMIs (bootstrap */ outb $CMOS_ADDR /* turned them off) */ @@ -110,10 +110,18 @@ clearbss: # set the initial frame pointer xorl %ebp, %ebp + # now, jump and switch into using high addresses + # we use an indirect jump here because the assembler + # would ordinarily generate a PC-relative target + # address for the jump, which would not have the + # desired effect + movl $onward, %eax + jmp *%eax + +onward: + /* -** Call the system initialization routine, and switch to -** executing at high addresses. We use an indirect jump -** here to avoid getting a PC-relative 'jmp' instruction. +** Call the system initialization routine. ** ** Alternate idea: push the address of isr_restore ** and just do an indirect jump? |