ab0db651af
The x86-64 doesn't just add two levels to page tables to support 64 bit addresses, but is a different processor. For example, calling conventions, system calls, and segmentation are different from 32-bit x86. Segmentation is basically gone, but gs/fs in combination with MSRs can be used to hold a per-core pointer. In general, x86-64 is more straightforward than 32-bit x86. The port uses code from sv6 and the xv6 "rsc-amd64" branch. A summary of the changes is as follows: - Booting: switch to grub instead of xv6's bootloader (pass -kernel to qemu), because xv6's boot loader doesn't understand 64bit ELF files. And, we don't care anymore about booting. - Makefile: use -m64 instead of -m32 flag for gcc, delete boot loader, xv6.img, bochs, and memfs. For now dont' use -O2, since usertests with -O2 is bigger than MAXFILE! - Update gdb.tmpl to be for i386 or x86-64 - Console/printf: use stdarg.h and treat 64-bit addresses different from ints (32-bit) - Update elfhdr to be 64 bit - entry.S/entryother.S: add code to switch to 64-bit mode: build a simple page table in 32-bit mode before switching to 64-bit mode, share code for entering boot processor and APs, and tweak boot gdt. The boot gdt is the gdt that the kernel proper also uses. (In 64-bit mode, the gdt/segmentation and task state mostly disappear.) - exec.c: fix passing argv (64-bit now instead of 32-bit). - initcode.c: use syscall instead of int. - kernel.ld: load kernel very high, in top terabyte. 64 bits is a lot of address space! - proc.c: initial return is through new syscall path instead of trapret. - proc.h: update struct cpu to have some scratch space since syscall saves less state than int, update struct context to reflect x86-64 calling conventions. - swtch: simplify for x86-64 calling conventions. - syscall: add fetcharg to handle x86-64 calling convetions (6 arguments are passed through registers), and fetchaddr to read a 64-bit value from user space. - sysfile: update to handle pointers from user space (e.g., sys_exec), which are 64 bits. - trap.c: no special trap vector for sys calls, because x86-64 has a different plan for system calls. - trapasm: one plan for syscalls and one plan for traps (interrupt and exceptions). On x86-64, the kernel is responsible for switching user/kernel stacks. To do, xv6 keeps some scratch space in the cpu structure, and uses MSR GS_KERN_BASE to point to the core's cpu structure (using swapgs). - types.h: add uint64, and change pde_t to uint64 - usertests: exit() when fork fails, which helped in tracking down one of the bugs in the switch from 32-bit to 64-bit - vectors: update to make them 64 bits - vm.c: use bootgdt in kernel too, program MSRs for syscalls and core-local state (for swapgs), walk 4 levels in walkpgdir, add DEVSPACETOP, use task segment to set kernel stack for interrupts (but simpler than in 32-bit mode), add an extra argument to freevm (size of user part of address space) to avoid checking all entries till KERNBASE (there are MANY TB before the top 1TB). - x86: update trapframe to have 64-bit entries, which is what the processor pushes on syscalls and traps. simplify lgdt and lidt, using struct desctr, which needs the gcc directives packed and aligned. TODO: - use int32 instead of int? - simplify curproc(). xv6 has per-cpu state again, but this time it must have it. - avoid repetition in walkpgdir - fix validateint() in usertests.c - fix bugs (e.g., observed one a case of entering kernel with invalid gs or proc
136 lines
2.1 KiB
ArmAsm
136 lines
2.1 KiB
ArmAsm
#include "param.h"
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#include "x86.h"
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#include "mmu.h"
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# vectors.S sends all traps here.
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.globl alltraps
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alltraps:
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# Build trap frame.
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push %r15
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push %r14
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push %r13
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push %r12
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push %r11
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push %r10
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push %r9
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push %r8
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push %rdi
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push %rsi
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push %rbp
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push %rdx
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push %rcx
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push %rbx
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push %rax
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cmpw $KCSEG, 32(%rsp) # compare to saved cs
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jz 1f
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swapgs
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1:mov %rsp, %rdi # frame in arg1
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call trap
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# Return falls through to trapret...
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.globl trapret
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trapret:
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cli
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cmpw $KCSEG, 32(%rsp) # compare to saved cs
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jz 1f
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swapgs
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1:pop %rax
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pop %rbx
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pop %rcx
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pop %rdx
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pop %rbp
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pop %rsi
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pop %rdi
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pop %r8
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pop %r9
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pop %r10
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pop %r11
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pop %r12
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pop %r13
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pop %r14
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pop %r15
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add $16, %rsp # discard trapnum and errorcode
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iretq
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#PAGEBREAK!
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# syscall_entry jumps here after syscall instruction
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.globl sysentry
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sysentry: # Build trap frame.
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// load kernel stack address
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swapgs
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movq %rax, %gs:0 // save %rax in syscallno of cpu entry
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movq %rsp, %gs:8 // user sp
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movq %gs:16, %rax // proc entry
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movq %ss:0(%rax), %rax // load kstack from proc
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addq $(KSTACKSIZE), %rax
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movq %rax, %rsp
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movq %gs:0, %rax // restore rax
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// push usp
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push $0
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push %gs:8
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// safe eflags and eip
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push %r11
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push $UCSEG
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push %rcx
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// push errno and trapno to make stack look like a trap
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push $0
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push $64
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// push values on kernel stack
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push %r15
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push %r14
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push %r13
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push %r12
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push %r11
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push %r10
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push %r9
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push %r8
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push %rdi
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push %rsi
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push %rbp
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push %rdx
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push %rcx
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push %rbx
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push %rax
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mov %rsp, %rdi # frame in arg1
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call trap
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#PAGEBREAK!
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# Return falls through to trapret...
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.globl sysexit
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sysexit:
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# to make sure we don't get any interrupts on the user stack while in
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# supervisor mode. insufficient? (see vunerability reports for sysret)
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cli
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pop %rax
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pop %rbx
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pop %rcx
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pop %rdx
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pop %rbp
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pop %rsi
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pop %rdi
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pop %r8
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pop %r9
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pop %r10
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pop %r11
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pop %r12
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pop %r13
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pop %r14
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pop %r15
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add $(5*8), %rsp # discard trapnum, errorcode, rip, cs and rflags
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mov (%rsp),%rsp # switch to the user stack
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swapgs
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sysretq
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