From 0004ccb885e534c386ceae21580fc59ec7ad0ede Mon Sep 17 00:00:00 2001
From: Tuan Le <ihnaut.if@gmail.com>
Date: Mon, 4 May 2020 16:40:01 +0200
Subject: [PATCH] llvmGen: Consider Relocatable read-only data as not
constantReferences: #18137
---
compiler/GHC/Cmm.hs | 40 +++++++++++++------
compiler/GHC/CmmToC.hs | 4 ++
compiler/GHC/CmmToLlvm/Data.hs | 3 +-
.../tests/codeGen/should_gen_asm/T18137.asm | 1 +
.../tests/codeGen/should_gen_asm/T18137.hs | 6 +++
testsuite/tests/codeGen/should_gen_asm/all.T | 1 +
6 files changed, 42 insertions(+), 13 deletions(-)
create mode 100644 testsuite/tests/codeGen/should_gen_asm/T18137.asm
create mode 100644 testsuite/tests/codeGen/should_gen_asm/T18137.hs
diff --git a/compiler/GHC/Cmm.hs b/compiler/GHC/Cmm.hs
index 48ffd25f1b1..440b6fd9d0d 100644
--- a/compiler/GHC/Cmm.hs
+++ b/compiler/GHC/Cmm.hs
@@ -12,7 +12,7 @@ module GHC.Cmm (
CmmBlock, RawCmmDecl,
Section(..), SectionType(..),
GenCmmStatics(..), type CmmStatics, type RawCmmStatics, CmmStatic(..),
- isSecConstant,
+ SectionProtection(..), sectionProtection,
-- ** Blocks containing lists
GenBasicBlock(..), blockId,
@@ -185,17 +185,33 @@ data SectionType
| OtherSection String
deriving (Show)
--- | Should a data in this section be considered constant
-isSecConstant :: Section -> Bool
-isSecConstant (Section t _) = case t of
- Text -> True
- ReadOnlyData -> True
- RelocatableReadOnlyData -> True
- ReadOnlyData16 -> True
- CString -> True
- Data -> False
- UninitialisedData -> False
- (OtherSection _) -> False
+data SectionProtection
+ = ReadWriteSection
+ | ReadOnlySection
+ | WriteProtectedSection -- See Note [Relocatable Read-Only Data]
+ deriving (Eq)
+
+-- | Should a data in this section be considered constant at runtime
+sectionProtection :: Section -> SectionProtection
+sectionProtection (Section t _) = case t of
+ Text -> ReadOnlySection
+ ReadOnlyData -> ReadOnlySection
+ RelocatableReadOnlyData -> WriteProtectedSection
+ ReadOnlyData16 -> ReadOnlySection
+ CString -> ReadOnlySection
+ Data -> ReadWriteSection
+ UninitialisedData -> ReadWriteSection
+ (OtherSection _) -> ReadWriteSection
+
+{-
+Note [Relocatable Read-Only Data]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Relocatable data are only read-only after relocation at the start of the
+program. They should be writable from the source code until then. Failure to
+do so would end up in segfaults at execution when using linkers that do not
+enforce writability of those sections, such as the gold linker.
+-}
data Section = Section SectionType CLabel
diff --git a/compiler/GHC/CmmToC.hs b/compiler/GHC/CmmToC.hs
index f4b8878fe29..d7b3fb05eb3 100644
--- a/compiler/GHC/CmmToC.hs
+++ b/compiler/GHC/CmmToC.hs
@@ -129,6 +129,10 @@ pprTop dflags = \case
pprDataExterns platform lits $$
pprWordArray dflags (isSecConstant section) lbl lits
where
+ isSecConstant section = case sectionProtection section of
+ ReadOnlySection -> True
+ WriteProtectedSection -> True
+ _ -> False
platform = targetPlatform dflags
-- --------------------------------------------------------------------------
diff --git a/compiler/GHC/CmmToLlvm/Data.hs b/compiler/GHC/CmmToLlvm/Data.hs
index b8db6ba4edf..aa91621cfdc 100644
--- a/compiler/GHC/CmmToLlvm/Data.hs
+++ b/compiler/GHC/CmmToLlvm/Data.hs
@@ -83,7 +83,8 @@ genLlvmData (sec, CmmStaticsRaw lbl xs) = do
Section CString _ -> if (platformArch platform == ArchS390X)
then Just 2 else Just 1
_ -> Nothing
- const = if isSecConstant sec then Constant else Global
+ const = if sectionProtection sec == ReadOnlySection
+ then Constant else Global
varDef = LMGlobalVar label tyAlias link lmsec align const
globDef = LMGlobal varDef struct
diff --git a/testsuite/tests/codeGen/should_gen_asm/T18137.asm b/testsuite/tests/codeGen/should_gen_asm/T18137.asm
new file mode 100644
index 00000000000..c38e425b946
--- /dev/null
+++ b/testsuite/tests/codeGen/should_gen_asm/T18137.asm
@@ -0,0 +1 @@
+\.section \.data\.rel\.ro\.RelocRoData_SomeData_closure_tbl,"aw",(?:%|@)progbits
\ No newline at end of file
diff --git a/testsuite/tests/codeGen/should_gen_asm/T18137.hs b/testsuite/tests/codeGen/should_gen_asm/T18137.hs
new file mode 100644
index 00000000000..f96960ba63c
--- /dev/null
+++ b/testsuite/tests/codeGen/should_gen_asm/T18137.hs
@@ -0,0 +1,6 @@
+module RelocRoData
+ ( SomeData(..)
+ )
+where
+
+data SomeData = SomeConstr
diff --git a/testsuite/tests/codeGen/should_gen_asm/all.T b/testsuite/tests/codeGen/should_gen_asm/all.T
index fbacf2b86bd..fa3ed1ccf5b 100644
--- a/testsuite/tests/codeGen/should_gen_asm/all.T
+++ b/testsuite/tests/codeGen/should_gen_asm/all.T
@@ -9,3 +9,4 @@ test('memcpy-unroll-conprop', is_amd64_codegen, compile_cmp_asm, ['cmm', ''])
test('memset-unroll', is_amd64_codegen, compile_cmp_asm, ['cmm', ''])
test('bytearray-memset-unroll', is_amd64_codegen, compile_grep_asm, ['hs', True, ''])
test('bytearray-memcpy-unroll', is_amd64_codegen, compile_grep_asm, ['hs', True, ''])
+test('T18137', [when(opsys('darwin'), skip), only_ways(llvm_ways)], compile_grep_asm, ['hs', False, '-fllvm -split-sections'])
--
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