[PATCH] libcxxabi/unwind: Add support for ARM EHABI in AddressSpace.hpp
Dana Jansens
danakj at google.com
Tue Jun 3 18:27:39 PDT 2014
Here's an updated patch that uses LIBCXX_API_EHABI. Since this is in
AddressSpace.hpp which is part of the "libunwind" layer, I've duplicated
the #define for this from the unwind.h which is part of the "_Unwind" layer
to avoid including the unwind.h header which doesn't belong in
AddressSpace.hpp.
On Wed, Jun 4, 2014 at 2:29 AM, Dana Jansens <danakj at google.com> wrote:
> On Wed, Jun 4, 2014 at 2:09 AM, Nick Kledzik <kledzik at apple.com> wrote:
>
>>
>> On Jun 3, 2014, at 4:58 PM, Dana Jansens <danakj at google.com> wrote:
>>
>>
>>> The setjump-longjump is similar to this. It does not use the lower
>>> level libunwind APIs and it has its own phase1/phase2 unwinding code
>>> separate from the Itanium style. So, it makes sense to me for the ARM
>>> EHABI implementation to be in its own Unwind-ehabi.c file and do not use
>>> libunwind under it. This was part of why I thought of EHABI as being a
>>> different unwinder than the zero-cost unwinder in terms of
>>> _LIBUNWIND_BUILD_blah.
>>>
>>
>> We discussed making a change like that, but we're more concerned with
>> upstreaming first right now, rather than keeping this all on a private
>> repo. Since the way we developed this was sharing code with the itanium
>> implementation as much as possible, are you okay with upstreaming it in
>> this fashion and then looking at moving it away in the future?
>>
>>
>> Can you be more specific about what you mean by “in this fashion” and
>> “moving it away in the future”.
>>
>
> Sure! What we have in our repo[1] is an implementation of ARM EHABI on top
> of the Itanium APIs. Initially we felt that made a lot of sense, though
> more recently we've started thinking about doing something different to fit
> the ARM EHABI requirements better. So, currently we are sharing code in
> unwind_level1, and AddressSpace and so on, as much as possible. This also
> helps keep our diffs smaller, I think.
>
> In the future (maybe 6 months out) we could consider moving the
> implementation away from sharing code with itanium with #ifdefs, and moving
> to something more separate like SJLJ. But this isn't something we can
> realistically commit to doing right now, so it would make upstreaming a lot
> more difficult.
>
> What we have is a functioning implementation that passes the tests, so I
> think it's not unreasonable. Concretely, this means using #if
> LIBCXX_ARM_EHABI throughout each of the three cxxabi, Unwind, and libunwind
> layers.
>
> [1]
> https://github.com/awong-dev/ndk/compare/upstream-llvm-ndkpatched...master#commit_comments_bucket
>
>
>>
>> -Nick
>>
>
>
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commit 0e3bc35b917eee440e838e3d7841617342f39aaf
Author: Dana Jansens <danakj at chromium.org>
Date: Mon Jun 2 08:39:12 2014 -0400
unwind: Add support for ARM EHABI in LocalAddressSpace.
When building on non-apple, define _LIBUNWIND_SUPPORT_ARM_EHABI_UNWIND.
Then use this define to make LocalAddressSpace::findUnwindSections()
find the exidx section, and store that in the UnwindInfoSections.
Since ARM EHABI does not need a dso_base variable in the
UnwindInfoSections, move it into each of the other platform blocks
to avoid it when implementing ARM EHABI.
Change-Id: I525e5a0b917a036511eb59a0631af7fb663d6b66
diff --git a/libcxxabi/include/libunwind.h b/libcxxabi/include/libunwind.h
index eaeab39..4c1415e 100644
--- a/libcxxabi/include/libunwind.h
+++ b/libcxxabi/include/libunwind.h
@@ -17,6 +17,14 @@
#include <stdint.h>
#include <stddef.h>
+// FIXME: This is also in unwind.h, can we consolidate?
+#if !defined(__USING_SJLJ_EXCEPTIONS__) && defined(__arm__) && \
+ !defined(__ARM_DWARF_EH__) && !defined(__APPLE__)
+#define LIBCXXABI_ARM_EHABI 1
+#else
+#define LIBCXXABI_ARM_EHABI 0
+#endif
+
#if __APPLE__
#include <Availability.h>
#if __arm__
diff --git a/libcxxabi/include/unwind.h b/libcxxabi/include/unwind.h
index 131657d..03f5f4c 100644
--- a/libcxxabi/include/unwind.h
+++ b/libcxxabi/include/unwind.h
@@ -23,6 +23,7 @@
#define LIBUNWIND_UNAVAIL
#endif
+// FIXME: This is also in libunwind.h, can we consolidate?
#if !defined(__USING_SJLJ_EXCEPTIONS__) && defined(__arm__) && \
!defined(__ARM_DWARF_EH__) && !defined(__APPLE__)
#define LIBCXXABI_ARM_EHABI 1
diff --git a/libcxxabi/src/Unwind/AddressSpace.hpp b/libcxxabi/src/Unwind/AddressSpace.hpp
index 283f14e..332bc51 100644
--- a/libcxxabi/src/Unwind/AddressSpace.hpp
+++ b/libcxxabi/src/Unwind/AddressSpace.hpp
@@ -31,23 +31,42 @@ namespace libunwind {
#include "dwarf2.h"
#include "Registers.hpp"
+#if LIBCXXABI_ARM_EHABI
+#if __LINUX__
+ // Emulate the BSD dl_unwind_find_exidx API when on a GNU libdl system.
+ typedef long unsigned int *_Unwind_Ptr;
+ extern "C" _Unwind_Ptr __gnu_Unwind_Find_exidx(_Unwind_Ptr targetAddr, int *length);
+ _Unwind_Ptr (*dl_unwind_find_exidx)(_Unwind_Ptr targetAddr, int *length) =
+ __gnu_Unwind_Find_exidx;
+#else
+ #include <link.h>
+#endif
+#endif // LIBCXXABI_ARM_EHABI
+
namespace libunwind {
/// Used by findUnwindSections() to return info about needed sections.
struct UnwindInfoSections {
- uintptr_t dso_base;
#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
+ uintptr_t dso_base;
uintptr_t dwarf_section;
uintptr_t dwarf_section_length;
#endif
#if _LIBUNWIND_SUPPORT_DWARF_INDEX
+ uintptr_t dso_base;
uintptr_t dwarf_index_section;
uintptr_t dwarf_index_section_length;
#endif
#if _LIBUNWIND_SUPPORT_COMPACT_UNWIND
+ uintptr_t dso_base;
uintptr_t compact_unwind_section;
uintptr_t compact_unwind_section_length;
#endif
+#if LIBCXXABI_ARM_EHABI
+ // No dso_base for ARM EHABI.
+ uintptr_t arm_section;
+ uintptr_t arm_section_length;
+#endif
};
@@ -303,9 +322,15 @@ inline bool LocalAddressSpace::findUnwindSections(pint_t targetAddr,
info.compact_unwind_section_length = dyldInfo.compact_unwind_section_length;
return true;
}
-#else
- // TO DO
-
+#elif LIBCXXABI_ARM_EHABI
+ int length = 0;
+ info.arm_section = (uintptr_t) dl_unwind_find_exidx(
+ (_Unwind_Ptr) targetAddr, &length);
+ info.arm_section_length = length;
+ _LIBUNWIND_TRACE_UNWINDING("findUnwindSections: section %X length %x\n",
+ info.arm_section, info.arm_section_length);
+ if (info.arm_section && info.arm_section_length)
+ return true;
#endif
return false;
diff --git a/libcxxabi/src/Unwind/config.h b/libcxxabi/src/Unwind/config.h
index 7d7e6bf..638dab2 100644
--- a/libcxxabi/src/Unwind/config.h
+++ b/libcxxabi/src/Unwind/config.h
@@ -57,16 +57,24 @@
#endif
#else
- // #define _LIBUNWIND_BUILD_ZERO_COST_APIS
- // #define _LIBUNWIND_BUILD_SJLJ_APIS
- // #define _LIBUNWIND_SUPPORT_FRAME_APIS
- // #define _LIBUNWIND_EXPORT
- // #define _LIBUNWIND_HIDDEN
- // #define _LIBUNWIND_LOG()
- // #define _LIBUNWIND_ABORT()
- // #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND
- // #define _LIBUNWIND_SUPPORT_DWARF_UNWIND
- // #define _LIBUNWIND_SUPPORT_DWARF_INDEX
+ // ARM EHABI.
+ static inline void assert_rtn(const char* func, const char* file, int line, const char* msg) __attribute__ ((noreturn));
+ static inline void assert_rtn(const char* func, const char* file, int line, const char* msg) {
+ fprintf(stderr, "libunwind: %s %s:%d - %s\n", func, file, line, msg);
+ assert(false);
+ abort();
+ }
+ #define _LIBUNWIND_BUILD_ZERO_COST_APIS (__i386__ || __x86_64__ || __arm64__ || __arm__)
+ #define _LIBUNWIND_BUILD_SJLJ_APIS 0
+ #define _LIBUNWIND_SUPPORT_FRAME_APIS (__i386__ || __x86_64__)
+ #define _LIBUNWIND_EXPORT __attribute__((visibility("default")))
+ #define _LIBUNWIND_HIDDEN __attribute__((visibility("hidden")))
+ #define _LIBUNWIND_LOG(msg, ...) fprintf(stderr, "libuwind: " msg, __VA_ARGS__)
+ #define _LIBUNWIND_ABORT(msg) assert_rtn(__func__, __FILE__, __LINE__, msg)
+
+ #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 0
+ #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 0
+ #define _LIBUNWIND_SUPPORT_DWARF_INDEX 0
#endif
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