I have maintained unwind support for FreeBSD i386 and x86_64 in my "gnat-aux" repository for many years (I created it). I've always intended on contributing it back to GCC, but I never got around to "proving" it worked until now.
The version I've been using actually has two flavors: FreeBSD 8 and below and FreeBSD 9 and above. However, the last of the FreeBSD 8 releases reaches EOL at the end of June so the unwind support I've attached here drops the FreeBSD 8 variation for simplicity's sake. I was under the impression that MD unwinding was used for more than just GNAT but it looks like that impression was wrong. When I ran the testsuite, the only tests affected were Ada tests. FreeBSD 10.1 / gcc-6.0.0 before patch applied: http://leaf.dragonflybsd.org/~marino/freebsd/summary-100F64.txt FreeBSD 10.1 / gcc-6.0.0 after patch applied: http://leaf.dragonflybsd.org/~marino/freebsd/summary-unwind-100F64.txt Difference between runs: http://leaf.dragonflybsd.org/~marino/freebsd/unwind-diff-100F64.txt FreeBSD 11/amd64 with patch (Ada only): http://leaf.dragonflybsd.org/~marino/freebsd/summary-110F64.txt FreeBSD 11/i386 with patch (Ada only) http://leaf.dragonflybsd.org/~marino/freebsd/summary-110F32.txt Note that I provided a similar unwind support for DragonFly a few months ago. Please consider applying the attached patch to gcc trunk. (copy of patch found here: http://leaf.dragonflybsd.org/~marino/freebsd/freebsd-unwind-support.diff ) Suggested text for libgcc/ChangeLog: 2015-05-XX John Marino <gnu...@marino.st> * config.host (i[34567]86-*-freebsd*, x86_64-*-freebsd*): Set md_unwind_header * config/i386/freebsd-unwind.h: New. Also please recall that my copyright assignment to FSF is in order! Thanks, John Marino
--- /dev/null +++ libgcc/config/i386/freebsd-unwind.h @@ -0,0 +1,173 @@ +/* DWARF2 EH unwinding support for FreeBSD: AMD x86-64 and x86. + Copyright (C) 2015 Free Software Foundation, Inc. + Contributed by John Marino <gnu...@marino.st> + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 3, or (at your option) +any later version. + +GCC is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +Under Section 7 of GPL version 3, you are granted additional +permissions described in the GCC Runtime Library Exception, version +3.1, as published by the Free Software Foundation. + +You should have received a copy of the GNU General Public License and +a copy of the GCC Runtime Library Exception along with this program; +see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +<http://www.gnu.org/licenses/>. */ + +/* Do code reading to identify a signal frame, and set the frame + state data appropriately. See unwind-dw2.c for the structs. */ + +#include <sys/types.h> +#include <signal.h> +#include <sys/ucontext.h> +#include <machine/sigframe.h> + +#define REG_NAME(reg) sf_uc.uc_mcontext.mc_## reg + +#ifdef __x86_64__ +#define MD_FALLBACK_FRAME_STATE_FOR x86_64_freebsd_fallback_frame_state + +static _Unwind_Reason_Code +x86_64_freebsd_fallback_frame_state +(struct _Unwind_Context *context, _Unwind_FrameState *fs) +{ + struct sigframe *sf; + long new_cfa; + + /* Prior to FreeBSD 9, the signal trampoline was located immediately + before the ps_strings. To support non-executable stacks on AMD64, + the sigtramp was moved to a shared page for FreeBSD 9. Unfortunately + this means looking frame patterns again (sys/amd64/amd64/sigtramp.S) + rather than using the robust and convenient KERN_PS_STRINGS trick. + + <pc + 00>: lea 0x10(%rsp),%rdi + <pc + 05>: pushq $0x0 + <pc + 17>: mov $0x1a1,%rax + <pc + 14>: syscall + + If we can't find this pattern, we're at the end of the stack. + */ + + if (!( *(unsigned int *)(context->ra) == 0x247c8d48 + && *(unsigned int *)(context->ra + 4) == 0x48006a10 + && *(unsigned int *)(context->ra + 8) == 0x01a1c0c7 + && *(unsigned int *)(context->ra + 12) == 0x050f0000 )) + return _URC_END_OF_STACK; + + sf = (struct sigframe *) context->cfa; + new_cfa = sf->REG_NAME(rsp); + fs->regs.cfa_how = CFA_REG_OFFSET; + /* Register 7 is rsp */ + fs->regs.cfa_reg = 7; + fs->regs.cfa_offset = new_cfa - (long) context->cfa; + + /* The SVR4 register numbering macros aren't usable in libgcc. */ + fs->regs.reg[0].how = REG_SAVED_OFFSET; + fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(rax) - new_cfa; + fs->regs.reg[1].how = REG_SAVED_OFFSET; + fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(rdx) - new_cfa; + fs->regs.reg[2].how = REG_SAVED_OFFSET; + fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(rcx) - new_cfa; + fs->regs.reg[3].how = REG_SAVED_OFFSET; + fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(rbx) - new_cfa; + fs->regs.reg[4].how = REG_SAVED_OFFSET; + fs->regs.reg[4].loc.offset = (long)&sf->REG_NAME(rsi) - new_cfa; + fs->regs.reg[5].how = REG_SAVED_OFFSET; + fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(rdi) - new_cfa; + fs->regs.reg[6].how = REG_SAVED_OFFSET; + fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(rbp) - new_cfa; + fs->regs.reg[8].how = REG_SAVED_OFFSET; + fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(r8) - new_cfa; + fs->regs.reg[9].how = REG_SAVED_OFFSET; + fs->regs.reg[9].loc.offset = (long)&sf->REG_NAME(r9) - new_cfa; + fs->regs.reg[10].how = REG_SAVED_OFFSET; + fs->regs.reg[10].loc.offset = (long)&sf->REG_NAME(r10) - new_cfa; + fs->regs.reg[11].how = REG_SAVED_OFFSET; + fs->regs.reg[11].loc.offset = (long)&sf->REG_NAME(r11) - new_cfa; + fs->regs.reg[12].how = REG_SAVED_OFFSET; + fs->regs.reg[12].loc.offset = (long)&sf->REG_NAME(r12) - new_cfa; + fs->regs.reg[13].how = REG_SAVED_OFFSET; + fs->regs.reg[13].loc.offset = (long)&sf->REG_NAME(r13) - new_cfa; + fs->regs.reg[14].how = REG_SAVED_OFFSET; + fs->regs.reg[14].loc.offset = (long)&sf->REG_NAME(r14) - new_cfa; + fs->regs.reg[15].how = REG_SAVED_OFFSET; + fs->regs.reg[15].loc.offset = (long)&sf->REG_NAME(r15) - new_cfa; + fs->regs.reg[16].how = REG_SAVED_OFFSET; + fs->regs.reg[16].loc.offset = (long)&sf->REG_NAME(rip) - new_cfa; + fs->retaddr_column = 16; + fs->signal_frame = 1; + return _URC_NO_REASON; +} + +#else /* Next section is for i386 */ + +#define MD_FALLBACK_FRAME_STATE_FOR x86_freebsd_fallback_frame_state + +/* + * We can't use KERN_PS_STRINGS anymore if we want to support FreeBSD32 + * compat on AMD64. The sigtramp is in a shared page in that case so the + * x86_sigtramp_range only works on a true i386 system. We have to + * search for the sigtramp frame if we want it working everywhere. + */ + +static _Unwind_Reason_Code +x86_freebsd_fallback_frame_state +(struct _Unwind_Context *context, _Unwind_FrameState *fs) +{ + struct sigframe *sf; + long new_cfa; + +/* + * i386 sigtramp frame we are looking for follows. + * Apparently PSL_VM is variable, so we can't look past context->ra + 4 + * <sigcode>: + * 0: ff 54 24 10 call *0x10(%esp) *SIGF_HANDLER + * 4: 8d 44 24 20 lea 0x20(%esp),%eax SIGF_UC + * 8: 50 push %eax + * 9: f7 40 54 00 00 02 00 testl $0x20000,0x54(%eax) $PSL_VM + * 10: 75 03 jne 15 <sigcode+0x15> + * 12: 8e 68 14 mov 0x14(%eax),%gs UC_GS + * 15: b8 a1 01 00 00 mov 0x1a1,%eax $SYS_sigreturn + */ + + if (!( *(unsigned int *)(context->ra - 4) == 0x102454ff + && *(unsigned int *)(context->ra) == 0x2024448d )) + return _URC_END_OF_STACK; + + sf = (struct sigframe *) context->cfa; + new_cfa = sf->REG_NAME(esp); + fs->regs.cfa_how = CFA_REG_OFFSET; + fs->regs.cfa_reg = 4; + fs->regs.cfa_offset = new_cfa - (long) context->cfa; + + /* The SVR4 register numbering macros aren't usable in libgcc. */ + fs->regs.reg[0].how = REG_SAVED_OFFSET; + fs->regs.reg[0].loc.offset = (long)&sf->REG_NAME(eax) - new_cfa; + fs->regs.reg[3].how = REG_SAVED_OFFSET; + fs->regs.reg[3].loc.offset = (long)&sf->REG_NAME(ebx) - new_cfa; + fs->regs.reg[1].how = REG_SAVED_OFFSET; + fs->regs.reg[1].loc.offset = (long)&sf->REG_NAME(ecx) - new_cfa; + fs->regs.reg[2].how = REG_SAVED_OFFSET; + fs->regs.reg[2].loc.offset = (long)&sf->REG_NAME(edx) - new_cfa; + fs->regs.reg[6].how = REG_SAVED_OFFSET; + fs->regs.reg[6].loc.offset = (long)&sf->REG_NAME(esi) - new_cfa; + fs->regs.reg[7].how = REG_SAVED_OFFSET; + fs->regs.reg[7].loc.offset = (long)&sf->REG_NAME(edi) - new_cfa; + fs->regs.reg[5].how = REG_SAVED_OFFSET; + fs->regs.reg[5].loc.offset = (long)&sf->REG_NAME(ebp) - new_cfa; + fs->regs.reg[8].how = REG_SAVED_OFFSET; + fs->regs.reg[8].loc.offset = (long)&sf->REG_NAME(eip) - new_cfa; + fs->retaddr_column = 8; + fs->signal_frame = 1; + return _URC_NO_REASON; +} +#endif /* ifdef __x86_64__ */ --- libgcc/config.host.orig +++ libgcc/config.host @@ -578,9 +578,11 @@ ;; i[34567]86-*-freebsd*) tmake_file="${tmake_file} i386/t-freebsd i386/t-crtstuff" + md_unwind_header=i386/freebsd-unwind.h ;; x86_64-*-freebsd*) tmake_file="${tmake_file} i386/t-freebsd i386/t-crtstuff" + md_unwind_header=i386/freebsd-unwind.h ;; i[34567]86-*-netbsdelf*) ;;
