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[lld][COFF] Remove incorrect flag from EHcont table
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Fixes EHCont implementation in LLD. Closes #64570

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D157623
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@namazso @duk-37
namazso authored and duk-37 committed Aug 10, 2023
1 parent 8ee6c0e commit e335c78
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Showing 3 changed files with 55 additions and 187 deletions.
2 changes: 1 addition & 1 deletion lld/COFF/Writer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1796,7 +1796,7 @@ void Writer::createGuardCFTables() {
// Add the ehcont target table unless the user told us not to.
if (config->guardCF & GuardCFLevel::EHCont)
maybeAddRVATable(std::move(ehContTargets), "__guard_eh_cont_table",
"__guard_eh_cont_count", true);
"__guard_eh_cont_count");

// Set __guard_flags, which will be used in the load config to indicate that
// /guard:cf was enabled.
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210 changes: 40 additions & 170 deletions lld/test/COFF/guard-ehcont.s
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@
# CHECK: GuardCFCheckFunction: 0x0
# CHECK: GuardCFCheckDispatch: 0x0
# CHECK: GuardCFFunctionTable: 0x14000{{.*}}
# CHECK: GuardCFFunctionCount: 4
# CHECK: GuardCFFunctionCount: 1
# CHECK: GuardFlags [ (0x400500)
# CHECK: CF_FUNCTION_TABLE_PRESENT (0x400)
# CHECK: CF_INSTRUMENTED (0x100)
Expand All @@ -19,25 +19,13 @@
# CHECK: GuardAddressTakenIatEntryTable: 0x0
# CHECK: GuardAddressTakenIatEntryCount: 0
# CHECK: GuardEHContinuationTable: 0x14000{{.*}}
# CHECK: GuardEHContinuationCount: 1
# CHECK: GuardEHContinuationCount: 2
# CHECK: ]
# CHECK: GuardEHContTable [
# CHECK-NEXT: 0x14000{{.*}}
# CHECK-NEXT: 0x14000{{.*}}
# CHECK-NEXT: ]


# This assembly is reduced from C code like:
# int main()
# {
# try {
# throw 3;
# }
# catch (int e) {
# return e != 3;
# }
# return 2;
# }

# We need @feat.00 to have 0x4000 to indicate /guard:ehcont.
.def @feat.00;
.scl 3;
Expand All @@ -48,168 +36,50 @@
.def main; .scl 2; .type 32; .endef
.globl main # -- Begin function main
.p2align 4, 0x90
main: # @main
.Lfunc_begin0:
main:
.seh_proc main
.intel_syntax
.seh_handler __CxxFrameHandler3, @unwind, @except
# %bb.0: # %entry
push rbp
.seh_pushreg rbp
sub rsp, 64
.seh_stackalloc 64
lea rbp, [rsp + 64]
.seh_setframe rbp, 64
.seh_endprologue
mov qword ptr [rbp - 16], -2
mov dword ptr [rbp - 20], 0
mov dword ptr [rbp - 24], 3
.Ltmp0:
lea rdx, [rip + _TI1H]
lea rcx, [rbp - 24]
call _CxxThrowException
.Ltmp1:
jmp .LBB0_3
.LBB0_2: # Block address taken
# %catchret.dest
$ehgcr_0_2:
mov eax, dword ptr [rbp - 20]
add rsp, 64
pop rbp
ret
.LBB0_3: # %unreachable
int3
.seh_handlerdata
.long ($cppxdata$main)@IMGREL
.text
.seh_endproc
.def "?catch$1@?0?main@4HA";
.scl 3;
.type 32;
.endef
.p2align 4, 0x90
"?catch$1@?0?main@4HA":
.seh_proc "?catch$1@?0?main@4HA"
.seh_handler __CxxFrameHandler3, @unwind, @except
.LBB0_1: # %catch
mov qword ptr [rsp + 16], rdx
push rbp
.seh_pushreg rbp
sub rsp, 32
.seh_stackalloc 32
lea rbp, [rdx + 64]
.seh_endprologue
mov eax, dword ptr [rbp - 4]
sub eax, 3
setne al
movzx eax, al
mov dword ptr [rbp - 20], eax
lea rax, [rip + .LBB0_2]
add rsp, 32
pop rbp
ret # CATCHRET
.def free; .scl 2; .type 32; .endef
.globl free
free:
ret
.def __CxxFrameHandler3; .scl 2; .type 32; .endef
.globl __CxxFrameHandler3
__CxxFrameHandler3:
ret
.def _CxxThrowException; .scl 2; .type 32; .endef
.globl _CxxThrowException
_CxxThrowException:
ret
.Lfunc_end0:
.seh_handler __C_specific_handler, @unwind, @except
.seh_handlerdata
.long ($cppxdata$main)@IMGREL
.long 2
.long (seh_begin)@IMGREL
.long (seh_end)@IMGREL
.long 1
.long (seh_except)@IMGREL
.long (seh2_begin)@IMGREL
.long (seh2_end)@IMGREL
.long 1
.long (seh2_except)@IMGREL
.text
.seh_endproc
.section .xdata,"dr"
.p2align 2
$cppxdata$main:
.long 429065506 # MagicNumber
.long 2 # MaxState
.long ($stateUnwindMap$main)@IMGREL # UnwindMap
.long 1 # NumTryBlocks
.long ($tryMap$main)@IMGREL # TryBlockMap
.long 4 # IPMapEntries
.long ($ip2state$main)@IMGREL # IPToStateXData
.long 48 # UnwindHelp
.long 0 # ESTypeList
.long 1 # EHFlags
$stateUnwindMap$main:
.long -1 # ToState
.long 0 # Action
.long -1 # ToState
.long 0 # Action
$tryMap$main:
.long 0 # TryLow
.long 0 # TryHigh
.long 1 # CatchHigh
.long 1 # NumCatches
.long ($handlerMap$0$main)@IMGREL # HandlerArray
$handlerMap$0$main:
.long 0 # Adjectives
.long "??_R0H@8"@IMGREL # Type
.long 60 # CatchObjOffset
.long "?catch$1@?0?main@4HA"@IMGREL # Handler
.long 56 # ParentFrameOffset
$ip2state$main:
.long .Lfunc_begin0@IMGREL # IP
.long -1 # ToState
.long .Ltmp0@IMGREL+1 # IP
.long 0 # ToState
.long .Ltmp1@IMGREL+1 # IP
.long -1 # ToState
.long "?catch$1@?0?main@4HA"@IMGREL # IP
.long 1 # ToState
.text
# -- End function
.section .data,"dw",discard,"??_R0H@8"
.globl "??_R0H@8" # @"??_R0H@8"
.p2align 4
"??_R0H@8":
.quad 0
.quad 0
.asciz ".H"
.zero 5
seh_begin:
nop
int3
nop
seh_end:
nop
seh_except:
nop

.section .xdata,"dr",discard,"_CT??_R0H@84"
.globl "_CT??_R0H@84" # @"_CT??_R0H@84"
.p2align 4
"_CT??_R0H@84":
.long 1 # 0x1
.long "??_R0H@8"@IMGREL
.long 0 # 0x0
.long 4294967295 # 0xffffffff
.long 0 # 0x0
.long 4 # 0x4
.long 0 # 0x0
seh2_begin:
nop
int3
nop
seh2_end:
nop
seh2_except:
nop

xor %eax, %eax
ret
.seh_endproc

.section .xdata,"dr",discard,_CTA1H
.globl _CTA1H # @_CTA1H
.p2align 3
_CTA1H:
.long 1 # 0x1
.long "_CT??_R0H@84"@IMGREL
__C_specific_handler:
ret

.section .xdata,"dr",discard,_TI1H
.globl _TI1H # @_TI1H
.p2align 3
_TI1H:
.long 0 # 0x0
.long 0 # 0x0
.long 0 # 0x0
.long _CTA1H@IMGREL
.section .gehcont$y,"dr"
.symidx seh_except
.symidx seh2_except

.section .gehcont$y,"dr"
.symidx $ehgcr_0_2
.addrsig_sym _CxxThrowException
.addrsig_sym __CxxFrameHandler3
.addrsig_sym "??_R0H@8"
.addrsig_sym __ImageBase
.section .rdata,"dr"
.section .rdata,"dr"
.globl _load_config_used
_load_config_used:
.long 312
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30 changes: 14 additions & 16 deletions llvm/tools/llvm-readobj/COFFDumper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -940,36 +940,34 @@ void COFFDumper::printCOFFLoadConfig() {
OS << " flags " << utohexstr(Flags);
};

// The stride gives the number of extra bytes in addition to the 4-byte
// RVA of each entry in the table. As of writing only a 1-byte extra flag
// has been defined.
uint32_t Stride = Tables.GuardFlags >> 28;
PrintExtraCB PrintExtra = Stride == 1 ? PrintGuardFlags : nullptr;

if (Tables.GuardFidTableVA) {
ListScope LS(W, "GuardFidTable");
if (uint32_t Size =
Tables.GuardFlags &
uint32_t(COFF::GuardFlags::CF_FUNCTION_TABLE_SIZE_MASK)) {
// The size mask gives the number of extra bytes in addition to the 4-byte
// RVA of each entry in the table. As of writing only a 1-byte extra flag
// has been defined.
Size = (Size >> 28) + 4;
printRVATable(Tables.GuardFidTableVA, Tables.GuardFidTableCount, Size,
PrintGuardFlags);
} else {
printRVATable(Tables.GuardFidTableVA, Tables.GuardFidTableCount, 4);
}
printRVATable(Tables.GuardFidTableVA, Tables.GuardFidTableCount,
4 + Stride, PrintExtra);
}

if (Tables.GuardIatTableVA) {
ListScope LS(W, "GuardIatTable");
printRVATable(Tables.GuardIatTableVA, Tables.GuardIatTableCount, 4);
printRVATable(Tables.GuardIatTableVA, Tables.GuardIatTableCount,
4 + Stride, PrintExtra);
}

if (Tables.GuardLJmpTableVA) {
ListScope LS(W, "GuardLJmpTable");
printRVATable(Tables.GuardLJmpTableVA, Tables.GuardLJmpTableCount, 4);
printRVATable(Tables.GuardLJmpTableVA, Tables.GuardLJmpTableCount,
4 + Stride, PrintExtra);
}

if (Tables.GuardEHContTableVA) {
ListScope LS(W, "GuardEHContTable");
printRVATable(Tables.GuardEHContTableVA, Tables.GuardEHContTableCount, 5,
PrintGuardFlags);
printRVATable(Tables.GuardEHContTableVA, Tables.GuardEHContTableCount,
4 + Stride, PrintExtra);
}
}

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