| Michael Munday | e6f36f0 | 2016-03-18 19:09:39 -0400 | [diff] [blame] | 1 | // Copyright 2016 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | #include "go_asm.h" |
| 6 | #include "go_tls.h" |
| 7 | #include "funcdata.h" |
| 8 | #include "textflag.h" |
| 9 | |
| 10 | // We have to resort to TLS variable to save g (R13). |
| 11 | // One reason is that external code might trigger |
| 12 | // SIGSEGV, and our runtime.sigtramp don't even know we |
| 13 | // are in external code, and will continue to use R13, |
| 14 | // this might well result in another SIGSEGV. |
| 15 | |
| 16 | // save_g saves the g register into pthread-provided |
| 17 | // thread-local memory, so that we can call externally compiled |
| 18 | // s390x code that will overwrite this register. |
| 19 | // |
| 20 | // If !iscgo, this is a no-op. |
| 21 | // |
| 22 | // NOTE: setg_gcc<> assume this clobbers only R10 and R11. |
| 23 | TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0-0 |
| 24 | MOVB runtime·iscgo(SB), R10 |
| 25 | CMPBEQ R10, $0, nocgo |
| 26 | MOVW AR0, R11 |
| 27 | SLD $32, R11 |
| 28 | MOVW AR1, R11 |
| 29 | MOVD runtime·tls_g(SB), R10 |
| 30 | MOVD g, 0(R10)(R11*1) |
| 31 | nocgo: |
| 32 | RET |
| 33 | |
| 34 | // load_g loads the g register from pthread-provided |
| 35 | // thread-local memory, for use after calling externally compiled |
| 36 | // s390x code that overwrote those registers. |
| 37 | // |
| 38 | // This is never called directly from C code (it doesn't have to |
| 39 | // follow the C ABI), but it may be called from a C context, where the |
| 40 | // usual Go registers aren't set up. |
| 41 | // |
| 42 | // NOTE: _cgo_topofstack assumes this only clobbers g (R13), R10 and R11. |
| 43 | TEXT runtime·load_g(SB),NOSPLIT|NOFRAME,$0-0 |
| 44 | MOVW AR0, R11 |
| 45 | SLD $32, R11 |
| 46 | MOVW AR1, R11 |
| 47 | MOVD runtime·tls_g(SB), R10 |
| 48 | MOVD 0(R10)(R11*1), g |
| 49 | RET |
| 50 | |
| 51 | GLOBL runtime·tls_g+0(SB),TLSBSS,$8 |
