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FuncUnwinders: prefer debug_frame over eh_frame 

The two sections usually contain the same information, and we rarely
have both kinds of entries for a single function. However, in theory the
debug_frame plan can be more complete, whereas eh_frame is only required
to be correct at places where exceptions can be thrown.

Reviewers: jasonmolenda, clayborg

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D62374

llvm-svn: 361758
This commit is contained in:
Pavel Labath 2019-05-27 11:53:24 +00:00
parent a53d48b7f4
commit ae4ec62cc9
3 changed files with 65 additions and 4 deletions
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38
lldb/lit/Unwind/Inputs/prefer-debug-over-eh-frame.s Normal file
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@ -0,0 +1,38 @@
.cfi_sections .eh_frame, .debug_frame
.text
.globl bar
bar:
.cfi_startproc
leal (%edi, %edi), %eax
ret
.cfi_endproc
.globl foo
foo:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
call bar
addl $1, %eax
popq %rbp
ret
.cfi_endproc
.globl asm_main
asm_main:
.cfi_startproc
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset 6, -16
movq %rsp, %rbp
.cfi_def_cfa_register 6
movl $47, %edi
call foo
popq %rbp
.cfi_def_cfa 7, 8
ret
.cfi_endproc

23
lldb/lit/Unwind/prefer-debug-over-eh-frame.test Normal file
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@ -0,0 +1,23 @@
# Test that we prefer debug_frame over eh_frame unwind plans. They usually
# contain the same information, and we rarely have both kinds of entries for a
# single function. However, in theory the debug_frame plan can be more complete,
# whereas eh_frame is only required to be correct at places where exceptions can
# be thrown.
# UNSUPPORTED: system-windows
# REQUIRES: target-x86_64, native
# RUN: %clang %p/Inputs/call-asm.c %p/Inputs/prefer-debug-over-eh-frame.s -o %t
# RUN: %lldb %t -s %s -o exit | FileCheck %s
breakpoint set -n bar
# CHECK: Breakpoint 1: where = {{.*}}`bar
process launch
# CHECK: stop reason = breakpoint 1.1
target modules show-unwind -n foo
# CHECK: Asynchronous (not restricted to call-sites) UnwindPlan is 'DWARF CFI plus augmentation from assembly parsing'
# CHECK: Synchronous (restricted to call-sites) UnwindPlan is 'DWARF CFI'
# CHECK: eh_frame UnwindPlan:
# CHECK: debug_frame UnwindPlan:

8
lldb/source/Symbol/FuncUnwinders.cpp
View File

@ -60,10 +60,10 @@ UnwindPlanSP FuncUnwinders::GetUnwindPlanAtCallSite(Target &target,
if (UnwindPlanSP plan_sp = GetSymbolFileUnwindPlan(thread))
return plan_sp;
if (UnwindPlanSP plan_sp = GetEHFrameUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetDebugFrameUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetEHFrameUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetCompactUnwindUnwindPlan(target))
return plan_sp;
if (UnwindPlanSP plan_sp = GetArmUnwindUnwindPlan(target))
@ -362,10 +362,10 @@ UnwindPlanSP FuncUnwinders::GetUnwindPlanAtNonCallSite(Target &target,
if (UnwindPlanSP plan_sp = GetSymbolFileUnwindPlan(thread))
return plan_sp;
if (UnwindPlanSP plan_sp = GetEHFrameAugmentedUnwindPlan(target, thread))
return plan_sp;
if (UnwindPlanSP plan_sp = GetDebugFrameAugmentedUnwindPlan(target, thread))
return plan_sp;
if (UnwindPlanSP plan_sp = GetEHFrameAugmentedUnwindPlan(target, thread))
return plan_sp;
return assembly_sp;
}