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cmd/internal/obj: save link register in leaf function with non-empty frame on PPC64, ARM64, S390X
The runtime traceback code assumes non-empty frame has link link register saved on LR architectures. Make sure it is so in the assember. Also make sure that LR is stored before update SP, so the traceback code will not see a half-updated stack frame if a signal comes during the execution of function prologue. Fixes #17381. Change-Id: I668b04501999b7f9b080275a2d1f8a57029cbbb3 Reviewed-on: https://go-review.googlesource.com/31760 Reviewed-by: Michael Munday <munday@ca.ibm.com>
This commit is contained in:
Cherry Zhang
parent
cf73bbfa25
commit
698bfa17a8
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@ -750,38 +750,54 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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if ctxt.Autosize == 0 {
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break
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}
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aoffset = 0
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}
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// Frame is non-empty. Make sure to save link register, even if
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// it is a leaf function, so that traceback works.
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q = p
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if ctxt.Autosize > aoffset {
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q = ctxt.NewProg()
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q.As = ASUB
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// Frame size is too large for a MOVD.W instruction.
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// Store link register before decrementing SP, so if a signal comes
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// during the execution of the function prologue, the traceback
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// code will not see a half-updated stack frame.
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q = obj.Appendp(ctxt, q)
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q.Lineno = p.Lineno
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q.As = ASUB
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q.From.Type = obj.TYPE_CONST
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q.From.Offset = int64(ctxt.Autosize) - int64(aoffset)
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q.From.Offset = int64(ctxt.Autosize)
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q.Reg = REGSP
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q.To.Type = obj.TYPE_REG
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q.To.Reg = REGSP
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q.Spadj = int32(q.From.Offset)
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q.Link = p.Link
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p.Link = q
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if cursym.Text.Mark&LEAF != 0 {
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break
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}
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}
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q.To.Reg = REGTMP
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q1 = ctxt.NewProg()
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q1.As = AMOVD
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q1.Lineno = p.Lineno
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q1.From.Type = obj.TYPE_REG
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q1.From.Reg = REGLINK
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q1.To.Type = obj.TYPE_MEM
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q1.Scond = C_XPRE
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q1.To.Offset = int64(-aoffset)
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q1.To.Reg = REGSP
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q1.Link = q.Link
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q1.Spadj = aoffset
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q.Link = q1
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q = obj.Appendp(ctxt, q)
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q.Lineno = p.Lineno
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q.As = AMOVD
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REGLINK
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q.To.Type = obj.TYPE_MEM
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q.To.Reg = REGTMP
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q1 = obj.Appendp(ctxt, q)
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q1.Lineno = p.Lineno
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q1.As = AMOVD
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q1.From.Type = obj.TYPE_REG
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q1.From.Reg = REGTMP
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q1.To.Type = obj.TYPE_REG
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q1.To.Reg = REGSP
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q1.Spadj = ctxt.Autosize
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} else {
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// small frame, update SP and save LR in a single MOVD.W instruction
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q1 = obj.Appendp(ctxt, q)
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q1.As = AMOVD
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q1.Lineno = p.Lineno
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q1.From.Type = obj.TYPE_REG
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q1.From.Reg = REGLINK
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q1.To.Type = obj.TYPE_MEM
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q1.Scond = C_XPRE
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q1.To.Offset = int64(-aoffset)
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q1.To.Reg = REGSP
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q1.Spadj = aoffset
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}
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if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
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// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
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@ -445,16 +445,12 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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}
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autosize := int32(0)
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var aoffset int
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var mov obj.As
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var p1 *obj.Prog
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var p2 *obj.Prog
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for p := cursym.Text; p != nil; p = p.Link {
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o := p.As
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switch o {
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case obj.ATEXT:
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mov = AMOVD
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aoffset = 0
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autosize = int32(textstksiz)
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if p.Mark&LEAF != 0 && autosize == 0 {
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@ -520,11 +516,49 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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}
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if autosize != 0 {
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/* use MOVDU to adjust R1 when saving R31, if autosize is small */
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// Make sure to save link register for non-empty frame, even if
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// it is a leaf function, so that traceback works.
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if cursym.Text.Mark&LEAF == 0 && autosize >= -BIG && autosize <= BIG {
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mov = AMOVDU
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aoffset = int(-autosize)
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// Use MOVDU to adjust R1 when saving R31, if autosize is small.
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_LR
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q.To.Type = obj.TYPE_REG
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q.To.Reg = REGTMP
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q = obj.Appendp(ctxt, q)
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q.As = AMOVDU
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REGTMP
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q.To.Type = obj.TYPE_MEM
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q.To.Offset = int64(-autosize)
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q.To.Reg = REGSP
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q.Spadj = int32(autosize)
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} else {
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// Frame size is too large for a MOVDU instruction.
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// Store link register before decrementing SP, so if a signal comes
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// during the execution of the function prologue, the traceback
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// code will not see a half-updated stack frame.
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_LR
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q.To.Type = obj.TYPE_REG
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q.To.Reg = REG_R29 // REGTMP may be used to synthesize large offset in the next instruction
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_R29
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q.To.Type = obj.TYPE_MEM
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q.To.Offset = int64(-autosize)
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q.To.Reg = REGSP
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q = obj.Appendp(ctxt, q)
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q.As = AADD
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q.Lineno = p.Lineno
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@ -546,26 +580,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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break
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}
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_LR
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q.To.Type = obj.TYPE_REG
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q.To.Reg = REGTMP
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q = obj.Appendp(ctxt, q)
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q.As = mov
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q.Lineno = p.Lineno
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REGTMP
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q.To.Type = obj.TYPE_MEM
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q.To.Offset = int64(aoffset)
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q.To.Reg = REGSP
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if q.As == AMOVDU {
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q.Spadj = int32(-aoffset)
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}
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if ctxt.Flag_shared {
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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@ -408,8 +408,21 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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}
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if autosize != 0 {
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// Make sure to save link register for non-empty frame, even if
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// it is a leaf function, so that traceback works.
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// Store link register before decrementing SP, so if a signal comes
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// during the execution of the function prologue, the traceback
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// code will not see a half-updated stack frame.
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q = obj.Appendp(ctxt, p)
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q.As = AMOVD
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_LR
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q.To.Type = obj.TYPE_MEM
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q.To.Reg = REGSP
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q.To.Offset = int64(-autosize)
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.From.Type = obj.TYPE_ADDR
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q.From.Offset = int64(-autosize)
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q.From.Reg = REGSP // not actually needed - REGSP is assumed if no reg is provided
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@ -428,14 +441,6 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
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break
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}
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q = obj.Appendp(ctxt, q)
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q.As = AMOVD
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q.From.Type = obj.TYPE_REG
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q.From.Reg = REG_LR
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q.To.Type = obj.TYPE_MEM
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q.To.Reg = REGSP
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q.To.Offset = 0
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if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
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// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
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//
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54
test/fixedbugs/issue17381.go
Normal file
54
test/fixedbugs/issue17381.go
Normal file
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@ -0,0 +1,54 @@
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// run
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// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// issue 17381: make sure leave function with non-empty frame
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// saves link register, so that traceback will work.
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package main
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import (
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"runtime"
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"unsafe"
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)
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func main() {
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defer func() {
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if recover() == nil {
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panic("did not panic")
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}
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pcs := make([]uintptr, 20)
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n := runtime.Callers(1, pcs)
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for _, pc := range pcs[:n] {
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if runtime.FuncForPC(pc).Name() == "main.main" {
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return
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}
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}
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panic("cannot find main.main in backtrace")
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}()
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prep()
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f() // should panic
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}
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func funcPC(f interface{}) uintptr {
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var ptr uintptr
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return **(**uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&f)) + unsafe.Sizeof(ptr)))
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}
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//go:noinline
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func f() {
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var t [1]int // non-empty frame
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*(*int)(nil) = t[0]
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}
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var p = funcPC(runtime.GC) + 8
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//go:noinline
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func prep() {
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// put some garbage on stack
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var x = [20]uintptr{p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p, p}
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_ = x
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}
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