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cmd/internal/obj/mips: mark unsafe points

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For async preemption, we will be using REGTMP as a temporary
register in injected call on MIPS, which will clobber it. So any
code that uses REGTMP is not safe for async preemption.

In the assembler backend, we expand a Prog to multiple machine
instructions and use REGTMP as a temporary register if necessary.
These need to be marked unsafe. In fact, most of the
multi-instruction Progs use REGTMP, so we mark all of them,
except ones that are whitelisted.

Change-Id: Ic00ae5589683c2c9525abdaee076d884df6b0d1e
Reviewed-on: https://go-review.googlesource.com/c/go/+/203718
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This commit is contained in:
Cherry Zhang 2019-10-26 22:49:13 -04:00
parent 1b0b980904
commit 69dcdbd2ba
2 changed files with 62 additions and 20 deletions
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6
src/cmd/internal/obj/mips/obj0.go
View file

@ -339,6 +339,10 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
// Store link register before decrement SP, so if a signal comes
// during the execution of the function prologue, the traceback
// code will not see a half-updated stack frame.
// This sequence is not async preemptible, as if we open a frame
// at the current SP, it will clobber the saved LR.
q = c.ctxt.StartUnsafePoint(q, c.newprog)
q = obj.Appendp(q, newprog)
q.As = mov
q.Pos = p.Pos
@ -356,6 +360,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
q.To.Type = obj.TYPE_REG
q.To.Reg = REGSP
q.Spadj = +autosize
q = c.ctxt.EndUnsafePoint(q, c.newprog, -1)
}
if c.cursym.Func.Text.From.Sym.Wrapper() && c.cursym.Func.Text.Mark&LEAF == 0 {