108 lines
3.4 KiB
Diff
108 lines
3.4 KiB
Diff
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From e83074ea52287115b85002a6b72137c72f6d7ecc Mon Sep 17 00:00:00 2001
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From: Cherry Zhang <cherryyz@google.com>
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Date: Sun, 10 Nov 2019 13:18:06 -0500
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Subject: [PATCH 5/6] runtime: don't save G during VDSO if we're handling
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signal
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On some platforms (currently ARM and ARM64), when calling into
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VDSO we store the G to the gsignal stack, if there is one, so if
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we receive a signal during VDSO we can find the G.
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If we receive a signal during VDSO, and within the signal handler
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we call nanotime again (e.g. when handling profiling signal),
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we'll save/clear the G slot on the gsignal stack again, which
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clobbers the original saved G. If we receive a second signal
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during the same VDSO execution, we will fetch a nil G, which will
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lead to bad things such as deadlock.
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Don't save G if we're calling VDSO code from the gsignal stack.
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Saving G is not necessary as we won't receive a nested signal.
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Fixes #35473.
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Change-Id: Ibfd8587a3c70c2f1533908b056e81b94d75d65a5
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Reviewed-on: https://go-review.googlesource.com/c/go/+/206397
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Run-TryBot: Cherry Zhang <cherryyz@google.com>
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TryBot-Result: Gobot Gobot <gobot@golang.org>
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Reviewed-by: Bryan C. Mills <bcmills@google.com>
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---
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src/runtime/sys_linux_arm.s | 8 ++++++++
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src/runtime/sys_linux_arm64.s | 8 ++++++++
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2 files changed, 16 insertions(+)
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diff --git a/src/runtime/sys_linux_arm.s b/src/runtime/sys_linux_arm.s
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index a47ac5f..577faac 100644
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--- a/src/runtime/sys_linux_arm.s
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+++ b/src/runtime/sys_linux_arm.s
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@@ -252,12 +252,16 @@ noswitch:
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// so don't bother saving g.
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// When using cgo, we already saved g on TLS, also don't save
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// g here.
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+ // Also don't save g if we are already on the signal stack.
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+ // We won't get a nested signal.
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MOVB runtime·iscgo(SB), R6
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CMP $0, R6
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BNE nosaveg
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MOVW m_gsignal(R5), R6 // g.m.gsignal
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CMP $0, R6
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BEQ nosaveg
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+ CMP g, R6
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+ BEQ nosaveg
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MOVW (g_stack+stack_lo)(R6), R6 // g.m.gsignal.stack.lo
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MOVW g, (R6)
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@@ -326,12 +330,16 @@ noswitch:
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// so don't bother saving g.
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// When using cgo, we already saved g on TLS, also don't save
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// g here.
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+ // Also don't save g if we are already on the signal stack.
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+ // We won't get a nested signal.
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MOVB runtime·iscgo(SB), R6
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CMP $0, R6
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BNE nosaveg
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MOVW m_gsignal(R5), R6 // g.m.gsignal
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CMP $0, R6
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BEQ nosaveg
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+ CMP g, R6
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+ BEQ nosaveg
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MOVW (g_stack+stack_lo)(R6), R6 // g.m.gsignal.stack.lo
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MOVW g, (R6)
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diff --git a/src/runtime/sys_linux_arm64.s b/src/runtime/sys_linux_arm64.s
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index 94c93ca..a076744 100644
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--- a/src/runtime/sys_linux_arm64.s
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+++ b/src/runtime/sys_linux_arm64.s
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@@ -214,10 +214,14 @@ noswitch:
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// so don't bother saving g.
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// When using cgo, we already saved g on TLS, also don't save
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// g here.
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+ // Also don't save g if we are already on the signal stack.
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+ // We won't get a nested signal.
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MOVBU runtime·iscgo(SB), R22
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CBNZ R22, nosaveg
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MOVD m_gsignal(R21), R22 // g.m.gsignal
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CBZ R22, nosaveg
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+ CMP g, R22
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+ BEQ nosaveg
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MOVD (g_stack+stack_lo)(R22), R22 // g.m.gsignal.stack.lo
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MOVD g, (R22)
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@@ -278,10 +282,14 @@ noswitch:
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// so don't bother saving g.
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// When using cgo, we already saved g on TLS, also don't save
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// g here.
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+ // Also don't save g if we are already on the signal stack.
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+ // We won't get a nested signal.
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MOVBU runtime·iscgo(SB), R22
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CBNZ R22, nosaveg
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MOVD m_gsignal(R21), R22 // g.m.gsignal
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CBZ R22, nosaveg
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+ CMP g, R22
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+ BEQ nosaveg
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MOVD (g_stack+stack_lo)(R22), R22 // g.m.gsignal.stack.lo
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MOVD g, (R22)
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--
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2.17.1
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