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runtime: save context value in NetBSD sigtramp

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On NetBSD a signal handler returns to the kernel by calling the
setcontext system call with the context passed to the signal handler.
The implementation of runtime·sigreturn_tramp for amd64, copied from the
NetBSD libc, expects that context address to be in r15.  That works in
the NetBSD libc because r15 is preserved across the call to the signal
handler.  It fails in the Go library because r15 is not preserved.
There are various ways to fix this; this one uses the simple approach,
essentially identical to the one in the NetBSD libc, of preserving r15
across the signal handler proper.

Looking at the code for 386 and arm suggests that they are OK.  However,
I have not actually tested them.

Update #14052.

Change-Id: I2b516b1d05fe5d3b8911e65ca761d621dc37fa1b
Reviewed-on: https://go-review.googlesource.com/18815
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Ian Lance Taylor 2016-01-21 12:43:34 -08:00
parent 4c4476c297
commit 123510bf83
1 changed files with 3 additions and 1 deletions
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4
src/runtime/sys_netbsd_amd64.s
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@ -245,11 +245,13 @@ TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
CALL AX CALL AX
RET RET
TEXT runtime·sigtramp(SB),NOSPLIT,$24 TEXT runtime·sigtramp(SB),NOSPLIT,$32
MOVQ DI, 0(SP) // signum MOVQ DI, 0(SP) // signum
MOVQ SI, 8(SP) // info MOVQ SI, 8(SP) // info
MOVQ DX, 16(SP) // ctx MOVQ DX, 16(SP) // ctx
MOVQ R15, 24(SP) // for sigreturn
CALL runtime·sigtrampgo(SB) CALL runtime·sigtrampgo(SB)
MOVQ 24(SP), R15
RET RET
TEXT runtime·mmap(SB),NOSPLIT,$0 TEXT runtime·mmap(SB),NOSPLIT,$0