[llvm] bba7338 - BPF: generate BTF info for LD_imm64 loaded function pointer
Yonghong Song via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 26 17:23:49 PDT 2021
Author: Yonghong Song
Date: 2021-04-26T17:23:36-07:00
New Revision: bba7338b8f5df15a444aad8b3026aec869767b2b
URL: https://github.com/llvm/llvm-project/commit/bba7338b8f5df15a444aad8b3026aec869767b2b
DIFF: https://github.com/llvm/llvm-project/commit/bba7338b8f5df15a444aad8b3026aec869767b2b.diff
LOG: BPF: generate BTF info for LD_imm64 loaded function pointer
For an example like below,
extern int do_work(int);
long bpf_helper(void *callback_fn);
long prog() {
return bpf_helper(&do_work);
}
The final generated codes look like:
r1 = do_work ll
call bpf_helper
exit
where we have debuginfo for do_work() extern function:
!17 = !DISubprogram(name: "do_work", ...)
This patch implemented to add additional checking
in processing LD_imm64 operands for possible function pointers
so BTF for bpf function do_work() can be properly generated.
The original llvm function name processReloc() is renamed to
processGlobalValue() to better reflect what the function is doing.
Differential Revision: https://reviews.llvm.org/D100568
Added:
llvm/test/CodeGen/BPF/BTF/extern-func-ptr.ll
Modified:
llvm/lib/Target/BPF/BTFDebug.cpp
llvm/lib/Target/BPF/BTFDebug.h
Removed:
################################################################################
diff --git a/llvm/lib/Target/BPF/BTFDebug.cpp b/llvm/lib/Target/BPF/BTFDebug.cpp
index 37a5184893f3..c1f8ea99b959 100644
--- a/llvm/lib/Target/BPF/BTFDebug.cpp
+++ b/llvm/lib/Target/BPF/BTFDebug.cpp
@@ -1030,13 +1030,16 @@ void BTFDebug::generatePatchImmReloc(const MCSymbol *ORSym, uint32_t RootId,
FieldRelocTable[SecNameOff].push_back(FieldReloc);
}
-void BTFDebug::processReloc(const MachineOperand &MO) {
+void BTFDebug::processGlobalValue(const MachineOperand &MO) {
// check whether this is a candidate or not
if (MO.isGlobal()) {
const GlobalValue *GVal = MO.getGlobal();
auto *GVar = dyn_cast<GlobalVariable>(GVal);
- if (!GVar)
+ if (!GVar) {
+ // Not a global variable. Maybe an extern function reference.
+ processFuncPrototypes(dyn_cast<Function>(GVal));
return;
+ }
if (!GVar->hasAttribute(BPFCoreSharedInfo::AmaAttr) &&
!GVar->hasAttribute(BPFCoreSharedInfo::TypeIdAttr))
@@ -1087,12 +1090,12 @@ void BTFDebug::beginInstruction(const MachineInstr *MI) {
//
// If the insn is "r2 = LD_imm64 @<an TypeIdAttr global>",
// The LD_imm64 result will be replaced with a btf type id.
- processReloc(MI->getOperand(1));
+ processGlobalValue(MI->getOperand(1));
} else if (MI->getOpcode() == BPF::CORE_MEM ||
MI->getOpcode() == BPF::CORE_ALU32_MEM ||
MI->getOpcode() == BPF::CORE_SHIFT) {
// relocation insn is a load, store or shift insn.
- processReloc(MI->getOperand(3));
+ processGlobalValue(MI->getOperand(3));
} else if (MI->getOpcode() == BPF::JAL) {
// check extern function references
const MachineOperand &MO = MI->getOperand(0);
diff --git a/llvm/lib/Target/BPF/BTFDebug.h b/llvm/lib/Target/BPF/BTFDebug.h
index 76f1901779bb..2fdcf8500b7f 100644
--- a/llvm/lib/Target/BPF/BTFDebug.h
+++ b/llvm/lib/Target/BPF/BTFDebug.h
@@ -320,8 +320,9 @@ class BTFDebug : public DebugHandlerBase {
/// Populating unprocessed type on demand.
unsigned populateType(const DIType *Ty);
- /// Process relocation instructions.
- void processReloc(const MachineOperand &MO);
+ /// Process global variables referenced by relocation instructions
+ /// and extern function references.
+ void processGlobalValue(const MachineOperand &MO);
/// Emit common header of .BTF and .BTF.ext sections.
void emitCommonHeader();
diff --git a/llvm/test/CodeGen/BPF/BTF/extern-func-ptr.ll b/llvm/test/CodeGen/BPF/BTF/extern-func-ptr.ll
new file mode 100644
index 000000000000..c6da613f175f
--- /dev/null
+++ b/llvm/test/CodeGen/BPF/BTF/extern-func-ptr.ll
@@ -0,0 +1,76 @@
+; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+;
+; Source code:
+; extern int do_work(int) __attribute__((section(".callback_fn")));
+; long bpf_helper(void *callback_fn);
+; long prog() {
+; return bpf_helper(&do_work);
+; }
+; Compilation flag:
+; clang -target bpf -O2 -g -S -emit-llvm test.c
+
+; Function Attrs: nounwind
+define dso_local i64 @prog() local_unnamed_addr #0 !dbg !7 {
+entry:
+ %call = tail call i64 @bpf_helper(i8* bitcast (i32 (i32)* @do_work to i8*)) #2, !dbg !11
+ ret i64 %call, !dbg !12
+}
+
+; CHECK: .long 0 # BTF_KIND_FUNC_PROTO(id = 4)
+; CHECK-NEXT: .long 218103809 # 0xd000001
+; CHECK-NEXT: .long 5
+; CHECK-NEXT: .long 0
+; CHECK-NEXT: .long 5
+; CHECK-NEXT: .long 51 # BTF_KIND_INT(id = 5)
+; CHECK-NEXT: .long 16777216 # 0x1000000
+; CHECK-NEXT: .long 4
+; CHECK-NEXT: .long 16777248 # 0x1000020
+; CHECK-NEXT: .long 55 # BTF_KIND_FUNC(id = 6)
+; CHECK-NEXT: .long 201326594 # 0xc000002
+; CHECK-NEXT: .long 4
+
+; CHECK: .long 74 # BTF_KIND_DATASEC(id = 10)
+; CHECK-NEXT: .long 251658241 # 0xf000001
+; CHECK-NEXT: .long 0
+; CHECK-NEXT: .long 6
+; CHECK-NEXT: .long do_work
+; CHECK-NEXT: .long 0
+
+; CHECK: .ascii "int" # string offset=51
+; CHECK: .ascii "do_work" # string offset=55
+; CHECK: .ascii ".callback_fn" # string offset=74
+
+declare !dbg !13 dso_local i64 @bpf_helper(i8*) local_unnamed_addr #1
+
+declare !dbg !17 dso_local i32 @do_work(i32) #1 section ".callback_fn"
+
+attributes #0 = { nounwind "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #1 = { "frame-pointer"="all" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 13.0.0 (https://github.com/llvm/llvm-project.git aa382ed8a38d5efa118e1b2617544f5c253658a9)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/btf/core")
+!2 = !{}
+!3 = !{i32 7, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 13.0.0 (https://github.com/llvm/llvm-project.git aa382ed8a38d5efa118e1b2617544f5c253658a9)"}
+!7 = distinct !DISubprogram(name: "prog", scope: !1, file: !1, line: 3, type: !8, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
+!11 = !DILocation(line: 4, column: 12, scope: !7)
+!12 = !DILocation(line: 4, column: 5, scope: !7)
+!13 = !DISubprogram(name: "bpf_helper", scope: !1, file: !1, line: 2, type: !14, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
+!14 = !DISubroutineType(types: !15)
+!15 = !{!10, !16}
+!16 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
+!17 = !DISubprogram(name: "do_work", scope: !1, file: !1, line: 1, type: !18, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
+!18 = !DISubroutineType(types: !19)
+!19 = !{!20, !20}
+!20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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