[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
NOKEYCHECK=True
GitOrigin-RevId: bab39816085d715e52c2131fa249ccd10178764b
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__)