diff mbox

Contribute FreeBSD unwind support (x86_64 and x86)

Message ID 555CE558.5070404@marino.st
State New
Headers show

Commit Message

John Marino May 20, 2015, 7:49 p.m. UTC
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 <gnugcc@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

Comments

Andreas Tobler May 20, 2015, 8:21 p.m. UTC | #1
On 20.05.15 21:49, John Marino wrote:
> 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.

It is, libjava uses it.


> 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 <gnugcc@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!

Testing patch locally now.

Thanks,
Andreas
Andreas Tobler May 25, 2015, 7:34 p.m. UTC | #2
On 20.05.15 22:21, Andreas Tobler wrote:
> On 20.05.15 21:49, John Marino wrote:
>> 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.
>
> It is, libjava uses it.
>
>
>> 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 <gnugcc@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!
>
> Testing patch locally now.

So, finally my findings. With some additional work on libjava for 
FreeBSD (pending patch on my side), I can confirm that this patch is a 
working prerequisite for proper signal handling in libjava. E.g, the 
magic Throw_2 test case succeeds.

I have not found any regressions on the FreeBSD side. And I really would 
like to see this patch go into trunk.

My tests were done on amd64 and i386 FreeBSD -CURRENT.

Thanks a lot!

Andreas
Jeff Law May 27, 2015, 4:17 p.m. UTC | #3
On 05/20/2015 01:49 PM, John Marino wrote:
> 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.
Happens.  I can't count how many things I've written but never finished 
for various reasons through the years.

>
> 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.
Seems reasonable.  We're not nearly as aggressive at dropping dead code 
as we perhaps could/should be.

> 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 )
Thanks for pointing that out.  It's a shame that the BSDs can't share 
this code, but such is life.

>
> Suggested text for libgcc/ChangeLog:
>
> 2015-05-XX  John Marino <gnugcc@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 for pointing that out.  Otherwise I'd probably have asked the 
redundant question :-)

Installed on the trunk.

Thanks,
jeff
John Marino May 27, 2015, 5:43 p.m. UTC | #4
On 5/27/2015 18:17, Jeff Law wrote:
> Thanks for pointing that out.  Otherwise I'd probably have asked the
> redundant question :-)
> 
> Installed on the trunk.
> 

Thanks a lot, Jeff!  Very painless this time. :)

By the way, I can't see any reason why this couldn't be backported to
the gcc-5 branch as well.  I don't know the procedure for that though.

Regards,
John
Jeff Law May 27, 2015, 5:46 p.m. UTC | #5
On 05/27/2015 11:43 AM, John Marino wrote:
> On 5/27/2015 18:17, Jeff Law wrote:
>> Thanks for pointing that out.  Otherwise I'd probably have asked the
>> redundant question :-)
>>
>> Installed on the trunk.
>>
>
> Thanks a lot, Jeff!  Very painless this time. :)
>
> By the way, I can't see any reason why this couldn't be backported to
> the gcc-5 branch as well.  I don't know the procedure for that though.
The procedure is pretty simple.  Ask Richi, Jakub or Joseph for 
permission.  They typically like to see patches on the trunk for a short 
period of time to help ensure there's no fallout.

jeff
diff mbox

Patch

--- /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 <gnugcc@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*)
 	;;