1 // Copyright 2015 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 "textflag.h" 6 7 // xx_cgo_panicmem is the entrypoint for SIGSEGV as intercepted via a 8 // mach thread port as EXC_BAD_ACCESS. As the segfault may have happened 9 // in C code, we first need to load_g then call xx_cgo_panicmem. 10 // 11 // R1 - LR at moment of fault 12 // R2 - PC at moment of fault 13 TEXT xx_cgo_panicmem(SB),NOSPLIT,$-8 14 // If in external C code, we need to load the g register. 15 BL runtimeload_g(SB) 16 CMP $0, g 17 BNE ongothread 18 19 // On a foreign thread. 20 // TODO(crawshaw): call badsignal 21 MOVD.W $0, -16(RSP) 22 MOVW $139, R1 23 MOVW R1, 8(RSP) 24 B runtimeexit(SB) 25 26 ongothread: 27 // Trigger a SIGSEGV panic. 28 // 29 // The goal is to arrange the stack so it looks like the runtime 30 // function sigpanic was called from the PC that faulted. It has 31 // to be sigpanic, as the stack unwinding code in traceback.go 32 // looks explicitly for it. 33 // 34 // To do this we call into runtimesetsigsegv, which sets the 35 // appropriate state inside the g object. We give it the faulting 36 // PC on the stack, then put it in the LR before calling sigpanic. 37 38 // Build a 32-byte stack frame for us for this call. 39 // Saved LR (none available) is at the bottom, 40 // then the PC argument for setsigsegv, 41 // then a copy of the LR for us to restore. 42 MOVD.W $0, -32(RSP) 43 MOVD R1, 8(RSP) 44 MOVD R2, 16(RSP) 45 BL runtimesetsigsegv(SB) 46 MOVD 8(RSP), R1 47 MOVD 16(RSP), R2 48 49 // Build a 16-byte stack frame for the simulated 50 // call to sigpanic, by taking 16 bytes away from the 51 // 32-byte stack frame above. 52 // The saved LR in this frame is the LR at time of fault, 53 // and the LR on entry to sigpanic is the PC at time of fault. 54 MOVD.W R1, 16(RSP) 55 MOVD R2, R30 56 B runtimesigpanic(SB) 57
