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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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
src/cmd/internal/obj/mips/asm0.go
View File

@ -72,15 +72,20 @@ type Optab struct {
flag uint8
}
const (
// Optab.flag
NOTUSETMP = 1 << iota // p expands to multiple instructions, but does NOT use REGTMP
)
var optab = []Optab{
{obj.ATEXT, C_LEXT, C_NONE, C_TEXTSIZE, 0, 0, 0, sys.MIPS64, 0},
{obj.ATEXT, C_ADDR, C_NONE, C_TEXTSIZE, 0, 0, 0, 0, 0},
{AMOVW, C_REG, C_NONE, C_REG, 1, 4, 0, 0, 0},
{AMOVV, C_REG, C_NONE, C_REG, 1, 4, 0, sys.MIPS64, 0},
{AMOVB, C_REG, C_NONE, C_REG, 12, 8, 0, 0, 0},
{AMOVB, C_REG, C_NONE, C_REG, 12, 8, 0, 0, NOTUSETMP},
{AMOVBU, C_REG, C_NONE, C_REG, 13, 4, 0, 0, 0},
{AMOVWU, C_REG, C_NONE, C_REG, 14, 8, 0, sys.MIPS64, 0},
{AMOVWU, C_REG, C_NONE, C_REG, 14, 8, 0, sys.MIPS64, NOTUSETMP},
{ASUB, C_REG, C_REG, C_REG, 2, 4, 0, 0, 0},
{ASUBV, C_REG, C_REG, C_REG, 2, 4, 0, sys.MIPS64, 0},
@ -182,11 +187,11 @@ var optab = []Optab{
{AMOVB, C_REG, C_NONE, C_ADDR, 50, 12, 0, sys.MIPS64, 0},
{AMOVBU, C_REG, C_NONE, C_ADDR, 50, 8, 0, sys.MIPS, 0},
{AMOVBU, C_REG, C_NONE, C_ADDR, 50, 12, 0, sys.MIPS64, 0},
{AMOVW, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, 0},
{AMOVWU, C_REG, C_NONE, C_TLS, 53, 8, 0, sys.MIPS64, 0},
{AMOVV, C_REG, C_NONE, C_TLS, 53, 8, 0, sys.MIPS64, 0},
{AMOVB, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, 0},
{AMOVBU, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, 0},
{AMOVW, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, NOTUSETMP},
{AMOVWU, C_REG, C_NONE, C_TLS, 53, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVV, C_REG, C_NONE, C_TLS, 53, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVB, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, NOTUSETMP},
{AMOVBU, C_REG, C_NONE, C_TLS, 53, 8, 0, 0, NOTUSETMP},
{AMOVW, C_LEXT, C_NONE, C_REG, 36, 12, REGSB, sys.MIPS64, 0},
{AMOVWU, C_LEXT, C_NONE, C_REG, 36, 12, REGSB, sys.MIPS64, 0},
@ -211,19 +216,19 @@ var optab = []Optab{
{AMOVB, C_ADDR, C_NONE, C_REG, 51, 12, 0, sys.MIPS64, 0},
{AMOVBU, C_ADDR, C_NONE, C_REG, 51, 8, 0, sys.MIPS, 0},
{AMOVBU, C_ADDR, C_NONE, C_REG, 51, 12, 0, sys.MIPS64, 0},
{AMOVW, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, 0},
{AMOVWU, C_TLS, C_NONE, C_REG, 54, 8, 0, sys.MIPS64, 0},
{AMOVV, C_TLS, C_NONE, C_REG, 54, 8, 0, sys.MIPS64, 0},
{AMOVB, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, 0},
{AMOVBU, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, 0},
{AMOVW, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, NOTUSETMP},
{AMOVWU, C_TLS, C_NONE, C_REG, 54, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVV, C_TLS, C_NONE, C_REG, 54, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVB, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, NOTUSETMP},
{AMOVBU, C_TLS, C_NONE, C_REG, 54, 8, 0, 0, NOTUSETMP},
{AMOVW, C_SECON, C_NONE, C_REG, 3, 4, REGSB, sys.MIPS64, 0},
{AMOVV, C_SECON, C_NONE, C_REG, 3, 4, REGSB, sys.MIPS64, 0},
{AMOVW, C_SACON, C_NONE, C_REG, 3, 4, REGSP, 0, 0},
{AMOVV, C_SACON, C_NONE, C_REG, 3, 4, REGSP, sys.MIPS64, 0},
{AMOVW, C_LECON, C_NONE, C_REG, 52, 8, REGSB, sys.MIPS, 0},
{AMOVW, C_LECON, C_NONE, C_REG, 52, 12, REGSB, sys.MIPS64, 0},
{AMOVV, C_LECON, C_NONE, C_REG, 52, 12, REGSB, sys.MIPS64, 0},
{AMOVW, C_LECON, C_NONE, C_REG, 52, 8, REGSB, sys.MIPS, NOTUSETMP},
{AMOVW, C_LECON, C_NONE, C_REG, 52, 12, REGSB, sys.MIPS64, NOTUSETMP},
{AMOVV, C_LECON, C_NONE, C_REG, 52, 12, REGSB, sys.MIPS64, NOTUSETMP},
{AMOVW, C_LACON, C_NONE, C_REG, 26, 12, REGSP, 0, 0},
{AMOVV, C_LACON, C_NONE, C_REG, 26, 12, REGSP, sys.MIPS64, 0},
@ -231,13 +236,13 @@ var optab = []Optab{
{AMOVV, C_ADDCON, C_NONE, C_REG, 3, 4, REGZERO, sys.MIPS64, 0},
{AMOVW, C_ANDCON, C_NONE, C_REG, 3, 4, REGZERO, 0, 0},
{AMOVV, C_ANDCON, C_NONE, C_REG, 3, 4, REGZERO, sys.MIPS64, 0},
{AMOVW, C_STCON, C_NONE, C_REG, 55, 8, 0, 0, 0},
{AMOVV, C_STCON, C_NONE, C_REG, 55, 8, 0, sys.MIPS64, 0},
{AMOVW, C_STCON, C_NONE, C_REG, 55, 8, 0, 0, NOTUSETMP},
{AMOVV, C_STCON, C_NONE, C_REG, 55, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVW, C_UCON, C_NONE, C_REG, 24, 4, 0, 0, 0},
{AMOVV, C_UCON, C_NONE, C_REG, 24, 4, 0, sys.MIPS64, 0},
{AMOVW, C_LCON, C_NONE, C_REG, 19, 8, 0, 0, 0},
{AMOVV, C_LCON, C_NONE, C_REG, 19, 8, 0, sys.MIPS64, 0},
{AMOVW, C_LCON, C_NONE, C_REG, 19, 8, 0, 0, NOTUSETMP},
{AMOVV, C_LCON, C_NONE, C_REG, 19, 8, 0, sys.MIPS64, NOTUSETMP},
{AMOVW, C_HI, C_NONE, C_REG, 20, 4, 0, 0, 0},
{AMOVV, C_HI, C_NONE, C_REG, 20, 4, 0, sys.MIPS64, 0},
@ -292,7 +297,7 @@ var optab = []Optab{
{ABEQ, C_REG, C_REG, C_SBRA, 6, 4, 0, 0, 0},
{ABEQ, C_REG, C_NONE, C_SBRA, 6, 4, 0, 0, 0},
{ABLEZ, C_REG, C_NONE, C_SBRA, 6, 4, 0, 0, 0},
{ABFPT, C_NONE, C_NONE, C_SBRA, 6, 8, 0, 0, 0},
{ABFPT, C_NONE, C_NONE, C_SBRA, 6, 8, 0, 0, NOTUSETMP},
{AJMP, C_NONE, C_NONE, C_LBRA, 11, 4, 0, 0, 0},
{AJAL, C_NONE, C_NONE, C_LBRA, 11, 4, 0, 0, 0},
@ -506,6 +511,23 @@ func span0(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
bp = bp[4:]
}
}
// Mark nonpreemptible instruction sequences.
// We use REGTMP as a scratch register during call injection,
// so instruction sequences that use REGTMP are unsafe to
// preempt asynchronously.
obj.MarkUnsafePoints(c.ctxt, c.cursym.Func.Text, c.newprog, c.isUnsafePoint)
}
// Return whether p is an unsafe point.
func (c *ctxt0) isUnsafePoint(p *obj.Prog) bool {
if p.From.Reg == REGTMP || p.To.Reg == REGTMP || p.Reg == REGTMP {
return true
}
// Most of the multi-instruction sequence uses REGTMP, except
// ones marked safe.
o := c.oplook(p)
return o.size > 4 && o.flag&NOTUSETMP == 0
}
func isint32(v int64) bool {
@ -1253,6 +1275,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
}
case 12: /* movbs r,r */
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
v := 16
if p.As == AMOVB {
v = 24
@ -1268,6 +1292,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
}
case 14: /* movwu r,r */
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
o1 = OP_SRR(c.opirr(-ASLLV), uint32(0), uint32(p.From.Reg), uint32(p.To.Reg))
o2 = OP_SRR(c.opirr(-ASRLV), uint32(0), uint32(p.To.Reg), uint32(p.To.Reg))
@ -1309,6 +1335,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
rel.Type = objabi.R_CALLIND
case 19: /* mov $lcon,r ==> lu+or */
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
v := c.regoff(&p.From)
o1 = OP_IRR(c.opirr(ALUI), uint32(v>>16), uint32(REGZERO), uint32(p.To.Reg))
o2 = OP_IRR(c.opirr(AOR), uint32(v), uint32(p.To.Reg), uint32(p.To.Reg))
@ -1539,6 +1567,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
}
case 52: /* mov $lext, r ==> lu + add REGSB, r + add */
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
o1 = OP_IRR(c.opirr(ALUI), uint32(0), uint32(REGZERO), uint32(p.To.Reg))
rel := obj.Addrel(c.cursym)
rel.Off = int32(c.pc)
@ -1563,6 +1593,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
case 53: /* mov r, tlsvar ==> rdhwr + sw o(r3) */
// clobbers R3 !
// load thread pointer with RDHWR, R3 is used for fast kernel emulation on Linux
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
o1 = (037<<26 + 073) | (29 << 11) | (3 << 16) // rdhwr $29, r3
o2 = OP_IRR(c.opirr(p.As), uint32(0), uint32(REG_R3), uint32(p.From.Reg))
rel := obj.Addrel(c.cursym)
@ -1574,6 +1606,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
case 54: /* mov tlsvar, r ==> rdhwr + lw o(r3) */
// clobbers R3 !
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
o1 = (037<<26 + 073) | (29 << 11) | (3 << 16) // rdhwr $29, r3
o2 = OP_IRR(c.opirr(-p.As), uint32(0), uint32(REG_R3), uint32(p.To.Reg))
rel := obj.Addrel(c.cursym)
@ -1585,6 +1619,8 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
case 55: /* mov $tlsvar, r ==> rdhwr + add */
// clobbers R3 !
// NOTE: this case does not use REGTMP. If it ever does,
// remove the NOTUSETMP flag in optab.
o1 = (037<<26 + 073) | (29 << 11) | (3 << 16) // rdhwr $29, r3
o2 = OP_IRR(c.opirr(add), uint32(0), uint32(REG_R3), uint32(p.To.Reg))
rel := obj.Addrel(c.cursym)

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 {