[OHOS]After -mbranch-protection=pac-ret is enabled, sign-return-addres… · Pull Request !739 · OpenHarmony/third_party_llvm-project

【任务描述】
[Description]
支持-mbranch-protection=pac-ret使能后对编译单元的所有函数添加sign-return-address，同时支持-mbranch-protection=pac-ret-strong命令且-mbranch-protection=pac-ret优先于-mbranch-protection=pac-ret-strong

After -mbranch-protection=pac-ret is enabled, sign-return-address can be added to functions. The -mbranch-protection=pac-ret-strong command is also supported, and -mbranch-protection=pac-ret takes precedence over -mbranch-protection=pac-ret-strong.
效果如下：
The effect is as follows：
attribute((noinline)) void TestSArray()
{
char array[5];
array[1]='2';

printf("%s\n",array);
return;
}
上述代码使用如下编译：
The preceding code is compiled as follows:
clang -Xclang -no-opaque-pointers -mbranch-protection=pac-ret --target=aarch64-linux-gnu -march=armv8.3-a --sysroot=$ARM_SYSROOT -v -g BeCfiTestIR.c -o beCfi -fuse-ld=lld -rtlib=libgcc -mllvm -print-after-all 2>BeCfiTestIR.ll

生成的IR中会对每个函数添加attribute(sign-return-address)
The attribute(sign-return-address) is added to each function in the generated IR.

; Function Attrs: noinline nounwind uwtable
define dso_local void @TestArray() #2 !dbg !61:[OHOS] Add mipsel-linux-ohos target {
entry:
%array = alloca [5 x i8], align 1
%0 = bitcast [5 x i8]* %array to i8*, !dbg !67:Add riscv64 target for ohos
call void @llvm.lifetime.start.p0i8(i64 5, i8* %0) #6, !dbg !67:Add riscv64 target for ohos
call void @llvm.dbg.declare(metadata [5 x i8]* %array, metadata !63:[BUILD][MUSL]Ignore musl build warnings, metadata !DIExpression()), !dbg !68:Add riscv64 target for ohos
%arrayidx = getelementptr inbounds [5 x i8], [5 x i8]* %array, i64 0, i64 1, !dbg !69:Sync patch "Fix rendezvous for rebase_exec=true case"
store i8 50, i8* %arrayidx, align 1, !dbg !70:Fix longtime waiting while attach remote process, !tbaa !71:[ohos-build][clang][LLDB] Add an optional build of lldb-server for hos target triples
%arraydecay = getelementptr inbounds [5 x i8], [5 x i8]* %array, i64 0, i64 0, !dbg !72:fix issues after enabling emutls feature
%call = call i32 (i8*, ...) @printf(i8* noundef getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), i8* noundef %arraydecay) #7, !dbg !73:Disable LUA and LIBNCURSES
call void @llvm.lifetime.end.p0i8(i64 5, i8* %0) #6, !dbg !74:[OHOS] Fix tests for code checker
ret void, !dbg !74:[OHOS] Fix tests for code checker
}
attributes #2 = { noinline nounwind uwtable "frame-pointer"="non-leaf" "min-legal-vector-width"="0" "no-trapping-math"="true" 
 **"sign-return-address"="non-leaf" "sign-return-address-key"="a_key"**  "sign-return-address-strong"="non-leaf;a_key" "stack-protector-buffer-size"="8" "target-cpu"="generic" "target-features"="+neon,+v8.3a" }

生成的汇编：TestArray已加pacia
Generated assembly: TestSArray has added pacia
00000000000112ec :
112ec: dac103fe pacia x30, sp
112f0: d10083ff sub sp, sp, #32
112f4: a9017bfd stp x29, x30, [sp, #16]
112f8: 910043fd add x29, sp, #16
112fc: 52800648 mov w8, #50
11300: 910023e0 add x0, sp, #8
11304: 390027e8 strb w8, [sp, #9]
11308: 9400005e bl 0x11480 puts@plt
1130c: a9417bfd ldp x29, x30, [sp, #16]
11310: 910083ff add sp, sp, #32
11314: d65f0bff retaa

【解决方案】
当有-mbranch-protection=pac-ret时为每个函数添加atrribute，当同时具有pac-ret和pac-ret-strong时pac-ret的优先级更高，若同时具有多个pac-ret/pac-ret-strong时同等优先级以后一个为准
When -mbranch-protection is set to pac-ret, atrribute is added for each function. When both pac-ret and pac-ret-strong are set, the priority of pac-ret is higher. If multiple pac-retpac-ret-strong commands are configured, the next one takes effect.

类型	指派人员	状态
审查	hhj 已审查通过 Pavel Kosov	已完成 (1/1人)
测试	openharmony_ci 已测试通过 public_ARKCIAccount	已完成 (1/1人)

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