Decorate the m68k signal trampoline with the appropriate .cfi

directives to allow exception unwind / backtrace across a signal
handler.
This commit is contained in:
thorpej 2021-11-21 23:58:09 +00:00
parent a2dfa8a4c3
commit 93b0ea009f
2 changed files with 75 additions and 2 deletions

View File

@ -1,4 +1,4 @@
# $NetBSD: genassym.cf,v 1.1 2013/07/17 01:41:17 matt Exp $
# $NetBSD: genassym.cf,v 1.2 2021/11/21 23:58:09 thorpej Exp $
#
# Copyright (c) 2013 The NetBSD Foundation, Inc.
@ -36,11 +36,32 @@ include <signal.h>
define UC_LINK offsetof(ucontext_t, uc_link)
define UC_SIGMASK offsetof(ucontext_t, uc_sigmask)
define UC_GREGS offsetof(ucontext_t, uc_mcontext.__gregs[0])
define UC_MCONTEXT_D0 offsetof(ucontext_t, uc_mcontext.__gregs[_REG_D0])
define UC_MCONTEXT_SP offsetof(ucontext_t, uc_mcontext.__gregs[_REG_A7])
define UC_MCONTEXT_PC offsetof(ucontext_t, uc_mcontext.__gregs[_REG_PC])
define UC_SIZE sizeof(ucontext_t)
define _REG_D0 _REG_D0
define _REG_D1 _REG_D1
define _REG_D2 _REG_D2
define _REG_D3 _REG_D3
define _REG_D4 _REG_D4
define _REG_D5 _REG_D5
define _REG_D6 _REG_D6
define _REG_D7 _REG_D7
define _REG_A0 _REG_A0
define _REG_A1 _REG_A1
define _REG_A2 _REG_A2
define _REG_A3 _REG_A3
define _REG_A4 _REG_A4
define _REG_A5 _REG_A5
define _REG_A6 _REG_A6
define _REG_A7 _REG_A7
define _REG_PC _REG_PC
define SIZEOF_SIGINFO sizeof(siginfo_t)
define SC_ONSTACK offsetof(struct sigcontext, sc_onstack)
define SC___MASK13 offsetof(struct sigcontext, __sc_mask13)
define SC_SP offsetof(struct sigcontext, sc_sp)

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@ -1,4 +1,4 @@
/* $NetBSD: __sigtramp2.S,v 1.4 2013/07/16 22:19:16 matt Exp $ */
/* $NetBSD: __sigtramp2.S,v 1.5 2021/11/21 23:58:09 thorpej Exp $ */
/*-
* Copyright (c) 2003 The NetBSD Foundation, Inc.
@ -27,6 +27,7 @@
*/
#include "SYS.h"
#include "assym.h"
/*
* The m68k signal trampoline is invoked only to return from
@ -39,7 +40,57 @@
* pointer to ucontext structure [8]
* pointer to siginfo structure [4]
* sp-> signal number [0]
*
* The DWARF register numbers are 0-7 (dX), 8-15 (aX), 16-23 (fpX),
* which maps nicely to _REG_D[0-7] and _REG_A[0-7]. For m68k, there
* is a DWARF pseudo-register for the return address, and additionally
* another DWARF pseudo-register for signal handler return addresses.
* We will specify both return address pseudo-registers (without
* explicitly specifying .cfi_return_column) to keep the compiler
* run-time happy with whichever one it decides to use.
*/
#define DWARF_RETURN_REG 24
#if defined(__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__)
#define DWARF_SIGRETURN_REG __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__
#else
#define DWARF_SIGRETURN_REG 25
#endif
#define CFI_OFFSET_DWARF_REG(d, r) .cfi_offset d, r * 4
#define CFI_OFFSET(r) CFI_OFFSET_DWARF_REG(r, r)
.text
.cfi_startproc simple
.cfi_signal_frame
.cfi_def_cfa _REG_A7, 12 + SIZEOF_SIGINFO + UC_GREGS
CFI_OFFSET(_REG_D0)
CFI_OFFSET(_REG_D1)
CFI_OFFSET(_REG_D2)
CFI_OFFSET(_REG_D3)
CFI_OFFSET(_REG_D4)
CFI_OFFSET(_REG_D5)
CFI_OFFSET(_REG_D6)
CFI_OFFSET(_REG_D7)
CFI_OFFSET(_REG_A0)
CFI_OFFSET(_REG_A1)
CFI_OFFSET(_REG_A2)
CFI_OFFSET(_REG_A3)
CFI_OFFSET(_REG_A4)
CFI_OFFSET(_REG_A5)
CFI_OFFSET(_REG_A6)
CFI_OFFSET(_REG_A7)
CFI_OFFSET_DWARF_REG(DWARF_RETURN_REG, _REG_PC)
CFI_OFFSET_DWARF_REG(DWARF_SIGRETURN_REG, _REG_PC)
/*
* The unwind entry includes one instruction slot prior to the trampoline
* because the unwinder will look up to (return PC - 1 insn) while unwinding.
* Normally this would be the jump / branch, but since there isn't one in
* this case, we place an explicit nop there instead.
*/
nop
ENTRY_NOPROFILE(__sigtramp_siginfo_2)
movl 8(%sp),%a0 /* get pointer to ucontext */
movl %a0,4(%sp) /* put it in the argument slot */
@ -47,4 +98,5 @@ ENTRY_NOPROFILE(__sigtramp_siginfo_2)
SYSTRAP(setcontext)
movl %d0,4(%sp) /* error code */
SYSTRAP(exit) /* exit */
.cfi_endproc
END(__sigtramp_siginfo_2)