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| author | Robert Morris <rtm@csail.mit.edu> | 2019-07-24 10:39:05 -0400 |
|---|---|---|
| committer | Robert Morris <rtm@csail.mit.edu> | 2019-07-24 10:39:05 -0400 |
| commit | b4f89bb5290cff5926e5a735487b024f8314e028 (patch) | |
| tree | 5af3d92b47d18552a12343cf91fafacb48f43c01 | |
| parent | 8f6865d1f1b945aae1a7989798571de5382cf930 (diff) | |
| download | xv6-labs-b4f89bb5290cff5926e5a735487b024f8314e028.tar.gz xv6-labs-b4f89bb5290cff5926e5a735487b024f8314e028.tar.bz2 xv6-labs-b4f89bb5290cff5926e5a735487b024f8314e028.zip | |
ping-pong exercise
| -rw-r--r-- | kernel/trampoline.S | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/kernel/trampoline.S b/kernel/trampoline.S index f067627..d4066c9 100644 --- a/kernel/trampoline.S +++ b/kernel/trampoline.S @@ -2,8 +2,8 @@ # code to switch between user and kernel space. # # this code is mapped at the same virtual address - # in user and kernel space so that it can switch - # page tables. + # in user and kernel space so that it continues + # to work when it switches page tables. # # kernel.ld causes trampout to be aligned # to a page boundary. @@ -18,7 +18,7 @@ trampout: # a0: p->tf in user page table # a1: new value for satp, for user page table - # switch to user page table. + # switch to the user page table. sfence.vma zero, zero csrw satp, a1 @@ -59,11 +59,11 @@ trampout: ld t5, 272(a0) ld t6, 280(a0) - # restore user a0, and save p->tf + # restore user a0, and save p->tf in sscratch csrrw a0, sscratch, a0 # return to user mode and user pc. - # caller has set up sstatus and sepc. + # usertrapret() set up sstatus and sepc. sret .align 4 |