[libunwind] Add an interface for dynamic .eh_frame registration
The libgcc runtime library provides __register_frame and
__deregister_frame functions, which can be used by dynamic code
generators to register an .eh_frame section, which contains one or
more Call Frame Information records, each consisting of a Common
Information Entry record followed by one or more Frame Description
Entry records. This libunwind library also provides __register_frame
and __deregister_frame functions, but they are aliases for
__unw_add_dynamic_fde and __unw_remove_dynamic_fde and thus can only
take a single FDE.
This patch adds __unw_add_dynamic_eh_frame_section and
__unw_remove_dynamic_eh_frame_section functions which explicitly use
the .eh_frame format. Clients such as the ORCv2 platform and runtime
can check for these functions and use them if unwinding is being
provided by libunwind, or fall back to __register_frame and
__deregister_frame if unwinding is provided by libgcc.
Reviewed By: lhames
Differential Revision: https://reviews.llvm.org/D111863
GitOrigin-RevId: bab39816085d715e52c2131fa249ccd10178764b
diff --git a/src/DwarfParser.hpp b/src/DwarfParser.hpp
index f9896ad..2153a71 100644
--- a/src/DwarfParser.hpp
+++ b/src/DwarfParser.hpp
@@ -154,7 +154,8 @@
uintptr_t sectionLength, pint_t fdeHint, FDE_Info *fdeInfo,
CIE_Info *cieInfo);
static const char *decodeFDE(A &addressSpace, pint_t fdeStart,
- FDE_Info *fdeInfo, CIE_Info *cieInfo);
+ FDE_Info *fdeInfo, CIE_Info *cieInfo,
+ bool useCIEInfo = false);
static bool parseFDEInstructions(A &addressSpace, const FDE_Info &fdeInfo,
const CIE_Info &cieInfo, pint_t upToPC,
int arch, PrologInfo *results);
@@ -162,10 +163,14 @@
static const char *parseCIE(A &addressSpace, pint_t cie, CIE_Info *cieInfo);
};
-/// Parse a FDE into a CIE_Info and an FDE_Info
+/// Parse a FDE into a CIE_Info and an FDE_Info. If useCIEInfo is
+/// true, treat cieInfo as already-parsed CIE_Info (whose start offset
+/// must match the one specified by the FDE) rather than parsing the
+/// one indicated within the FDE.
template <typename A>
const char *CFI_Parser<A>::decodeFDE(A &addressSpace, pint_t fdeStart,
- FDE_Info *fdeInfo, CIE_Info *cieInfo) {
+ FDE_Info *fdeInfo, CIE_Info *cieInfo,
+ bool useCIEInfo) {
pint_t p = fdeStart;
pint_t cfiLength = (pint_t)addressSpace.get32(p);
p += 4;
@@ -181,9 +186,14 @@
return "FDE is really a CIE"; // this is a CIE not an FDE
pint_t nextCFI = p + cfiLength;
pint_t cieStart = p - ciePointer;
- const char *err = parseCIE(addressSpace, cieStart, cieInfo);
- if (err != NULL)
- return err;
+ if (useCIEInfo) {
+ if (cieInfo->cieStart != cieStart)
+ return "CIE start does not match";
+ } else {
+ const char *err = parseCIE(addressSpace, cieStart, cieInfo);
+ if (err != NULL)
+ return err;
+ }
p += 4;
// Parse pc begin and range.
pint_t pcStart =
diff --git a/src/libunwind.cpp b/src/libunwind.cpp
index 2bf31b1..48750ce 100644
--- a/src/libunwind.cpp
+++ b/src/libunwind.cpp
@@ -292,6 +292,35 @@
// fde is own mh_group
DwarfFDECache<LocalAddressSpace>::removeAllIn((LocalAddressSpace::pint_t)fde);
}
+
+void __unw_add_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
+ // The eh_frame section start serves as the mh_group
+ unw_word_t mh_group = eh_frame_start;
+ CFI_Parser<LocalAddressSpace>::CIE_Info cieInfo;
+ CFI_Parser<LocalAddressSpace>::FDE_Info fdeInfo;
+ auto p = (LocalAddressSpace::pint_t)eh_frame_start;
+ while (true) {
+ if (CFI_Parser<LocalAddressSpace>::decodeFDE(
+ LocalAddressSpace::sThisAddressSpace, p, &fdeInfo, &cieInfo,
+ true) == NULL) {
+ DwarfFDECache<LocalAddressSpace>::add((LocalAddressSpace::pint_t)mh_group,
+ fdeInfo.pcStart, fdeInfo.pcEnd,
+ fdeInfo.fdeStart);
+ p += fdeInfo.fdeLength;
+ } else if (CFI_Parser<LocalAddressSpace>::parseCIE(
+ LocalAddressSpace::sThisAddressSpace, p, &cieInfo) == NULL) {
+ p += cieInfo.cieLength;
+ } else
+ return;
+ }
+}
+
+void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start) {
+ // The eh_frame section start serves as the mh_group
+ DwarfFDECache<LocalAddressSpace>::removeAllIn(
+ (LocalAddressSpace::pint_t)eh_frame_start);
+}
+
#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
#endif // !defined(__USING_SJLJ_EXCEPTIONS__)
diff --git a/src/libunwind_ext.h b/src/libunwind_ext.h
index a96ae6c..7065ffc 100644
--- a/src/libunwind_ext.h
+++ b/src/libunwind_ext.h
@@ -51,6 +51,9 @@
extern void __unw_add_dynamic_fde(unw_word_t fde);
extern void __unw_remove_dynamic_fde(unw_word_t fde);
+extern void __unw_add_dynamic_eh_frame_section(unw_word_t eh_frame_start);
+extern void __unw_remove_dynamic_eh_frame_section(unw_word_t eh_frame_start);
+
#if defined(_LIBUNWIND_ARM_EHABI)
extern const uint32_t* decode_eht_entry(const uint32_t*, size_t*, size_t*);
extern _Unwind_Reason_Code _Unwind_VRS_Interpret(_Unwind_Context *context,
