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cmd/asm: improve detector for incorrect R15 usage when dynamic linking
Fixes #58632 Change-Id: Idb19af2ac693ea5920da57c1808f1bc02702929d Reviewed-on: https://go-review.googlesource.com/c/go/+/476295 Reviewed-by: Cherry Mui <cherryyz@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Keith Randall <khr@google.com> Run-TryBot: Keith Randall <khr@golang.org>
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Keith Randall
Keith Randall
parent
70308d1375
commit
455168d113
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@ -72,3 +72,100 @@ one:
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TEXT ·a13(SB), 0, $0-0
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MULXQ runtime·writeBarrier(SB), AX, CX
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RET
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// Various special cases in the use-R15-after-global-access-when-dynlinking check.
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// See issue 58632.
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TEXT ·a14(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MULXQ R15, AX, BX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a15(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MULXQ AX, R15, BX
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ADDQ $1, R15
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RET
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TEXT ·a16(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MULXQ AX, BX, R15
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ADDQ $1, R15
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RET
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TEXT ·a17(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MOVQ (R15), AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a18(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MOVQ (CX)(R15*1), AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a19(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MOVQ AX, (R15) // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a20(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MOVQ AX, (CX)(R15*1) // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a21(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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MOVBLSX AX, R15
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ADDQ $1, R15
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RET
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TEXT ·a22(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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PMOVMSKB X0, R15
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ADDQ $1, R15
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RET
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TEXT ·a23(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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LEAQ (AX)(CX*1), R15
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RET
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TEXT ·a24(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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LEAQ (R15)(AX*1), AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a25(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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LEAQ (AX)(R15*1), AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a26(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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IMUL3Q $33, AX, R15
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ADDQ $1, R15
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RET
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TEXT ·a27(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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IMUL3Q $33, R15, AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a28(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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PEXTRD $0, X0, R15
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ADDQ $1, R15
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RET
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TEXT ·a29(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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VPEXTRD $0, X0, R15
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ADDQ $1, R15
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RET
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TEXT ·a30(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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BSFQ R15, AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a31(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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BSFQ AX, R15
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ADDQ $1, R15
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RET
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TEXT ·a32(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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POPCNTL R15, AX // ERROR "when dynamic linking, R15 is clobbered by a global variable access and is used here"
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RET
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TEXT ·a33(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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POPCNTL AX, R15
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ADDQ $1, R15
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RET
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TEXT ·a34(SB), 0, $0-0
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CMPL runtime·writeBarrier(SB), $0
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SHLXQ AX, CX, R15
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ADDQ $1, R15
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RET
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@ -1254,29 +1254,6 @@ func progMentionsR15(p *obj.Prog) bool {
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return addrMentionsR15(&p.From) || addrMentionsR15(&p.To) || isR15(p.Reg) || addrMentionsR15(p.GetFrom3())
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}
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// progOverwritesR15 reports whether p writes to R15 and does not depend on
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// the previous value of R15.
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func progOverwritesR15(p *obj.Prog) bool {
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if !(p.To.Type == obj.TYPE_REG && isR15(p.To.Reg)) {
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// Not writing to R15.
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return false
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}
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if (p.As == AXORL || p.As == AXORQ) && p.From.Type == obj.TYPE_REG && isR15(p.From.Reg) {
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// These look like uses of R15, but aren't, so we must detect these
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// before the use check below.
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return true
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}
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if addrMentionsR15(&p.From) || isR15(p.Reg) || addrMentionsR15(p.GetFrom3()) {
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// use before overwrite
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return false
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}
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if p.As == AMOVL || p.As == AMOVQ || p.As == APOPQ {
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return true
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// TODO: MOVB might be ok if we only ever use R15B.
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}
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return false
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}
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func addrUsesGlobal(a *obj.Addr) bool {
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if a == nil {
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return false
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@ -1296,6 +1273,114 @@ func progUsesGlobal(p *obj.Prog) bool {
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return addrUsesGlobal(&p.From) || addrUsesGlobal(&p.To) || addrUsesGlobal(p.GetFrom3())
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}
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type rwMask int
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const (
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readFrom rwMask = 1 << iota
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readTo
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readReg
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readFrom3
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writeFrom
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writeTo
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writeReg
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writeFrom3
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)
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// progRW returns a mask describing the effects of the instruction p.
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// Note: this isn't exhaustively accurate. It is only currently used for detecting
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// reads/writes to R15, so SSE register behavior isn't fully correct, and
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// other weird cases (e.g. writes to DX by CLD) also aren't captured.
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func progRW(p *obj.Prog) rwMask {
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var m rwMask
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// Default for most instructions
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if p.From.Type != obj.TYPE_NONE {
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m |= readFrom
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}
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if p.To.Type != obj.TYPE_NONE {
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// Most x86 instructions update the To value
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m |= readTo | writeTo
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}
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if p.Reg != 0 {
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m |= readReg
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}
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if p.GetFrom3() != nil {
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m |= readFrom3
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}
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// Lots of exceptions to the above defaults.
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name := p.As.String()
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if strings.HasPrefix(name, "MOV") || strings.HasPrefix(name, "PMOV") {
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// MOV instructions don't read To.
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m &^= readTo
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}
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switch p.As {
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case APOPW, APOPL, APOPQ,
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ALEAL, ALEAQ,
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AIMUL3W, AIMUL3L, AIMUL3Q,
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APEXTRB, APEXTRW, APEXTRD, APEXTRQ, AVPEXTRB, AVPEXTRW, AVPEXTRD, AVPEXTRQ, AEXTRACTPS,
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ABSFW, ABSFL, ABSFQ, ABSRW, ABSRL, ABSRQ, APOPCNTW, APOPCNTL, APOPCNTQ, ALZCNTW, ALZCNTL, ALZCNTQ,
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ASHLXL, ASHLXQ, ASHRXL, ASHRXQ, ASARXL, ASARXQ:
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// These instructions are pure writes to To. They don't use its old value.
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m &^= readTo
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case AXORL, AXORQ:
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// Register-clearing idiom doesn't read previous value.
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if p.From.Type == obj.TYPE_REG && p.To.Type == obj.TYPE_REG && p.From.Reg == p.To.Reg {
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m &^= readFrom | readTo
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}
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case AMULXL, AMULXQ:
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// These are write-only to both To and From3.
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m &^= readTo | readFrom3
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m |= writeFrom3
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}
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return m
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}
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// progReadsR15 reports whether p reads the register R15.
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func progReadsR15(p *obj.Prog) bool {
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m := progRW(p)
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if m&readFrom != 0 && p.From.Type == obj.TYPE_REG && isR15(p.From.Reg) {
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return true
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}
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if m&readTo != 0 && p.To.Type == obj.TYPE_REG && isR15(p.To.Reg) {
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return true
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}
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if m&readReg != 0 && isR15(p.Reg) {
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return true
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}
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if m&readFrom3 != 0 && p.GetFrom3().Type == obj.TYPE_REG && isR15(p.GetFrom3().Reg) {
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return true
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}
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// reads of the index registers
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if p.From.Type == obj.TYPE_MEM && (isR15(p.From.Reg) || isR15(p.From.Index)) {
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return true
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}
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if p.To.Type == obj.TYPE_MEM && (isR15(p.To.Reg) || isR15(p.To.Index)) {
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return true
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}
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if f3 := p.GetFrom3(); f3 != nil && f3.Type == obj.TYPE_MEM && (isR15(f3.Reg) || isR15(f3.Index)) {
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return true
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}
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return false
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}
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// progWritesR15 reports whether p writes the register R15.
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func progWritesR15(p *obj.Prog) bool {
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m := progRW(p)
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if m&writeFrom != 0 && p.From.Type == obj.TYPE_REG && isR15(p.From.Reg) {
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return true
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}
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if m&writeTo != 0 && p.To.Type == obj.TYPE_REG && isR15(p.To.Reg) {
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return true
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}
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if m&writeReg != 0 && isR15(p.Reg) {
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return true
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}
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if m&writeFrom3 != 0 && p.GetFrom3().Type == obj.TYPE_REG && isR15(p.GetFrom3().Reg) {
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return true
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}
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return false
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}
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func errorCheck(ctxt *obj.Link, s *obj.LSym) {
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// When dynamic linking, R15 is used to access globals. Reject code that
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// uses R15 after a global variable access.
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@ -1320,6 +1405,15 @@ func errorCheck(ctxt *obj.Link, s *obj.LSym) {
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for len(work) > 0 {
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p := work[len(work)-1]
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work = work[:len(work)-1]
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if progReadsR15(p) {
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pos := ctxt.PosTable.Pos(p.Pos)
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ctxt.Diag("%s:%s: when dynamic linking, R15 is clobbered by a global variable access and is used here: %v", path.Base(pos.Filename()), pos.LineNumber(), p)
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break // only report one error
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}
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if progWritesR15(p) {
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// R15 is overwritten by this instruction. Its value is not junk any more.
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continue
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}
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if q := p.To.Target(); q != nil && q.Mark&markBit == 0 {
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q.Mark |= markBit
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work = append(work, q)
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@ -1327,15 +1421,6 @@ func errorCheck(ctxt *obj.Link, s *obj.LSym) {
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if p.As == obj.AJMP || p.As == obj.ARET {
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continue // no fallthrough
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}
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if progMentionsR15(p) {
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if progOverwritesR15(p) {
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// R15 is overwritten by this instruction. Its value is not junk any more.
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continue
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}
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pos := ctxt.PosTable.Pos(p.Pos)
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ctxt.Diag("%s:%s: when dynamic linking, R15 is clobbered by a global variable access and is used here: %v", path.Base(pos.Filename()), pos.LineNumber(), p)
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break // only report one error
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}
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if q := p.Link; q != nil && q.Mark&markBit == 0 {
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q.Mark |= markBit
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work = append(work, q)
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