[clang] Pack relocations for Android API >= 28 (PR #117624)

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https://github.com/hiraditya created https://github.com/llvm/llvm-project/pull/117624

Patch copied from: https://github.com/android/ndk/issues/909#issuecomment-649872696
Fixes: https://github.com/android/ndk/issues/909


>From ae0074af2125871b79b8fac7e2433fa56e60f4bd Mon Sep 17 00:00:00 2001
From: AdityaK <hiraditya at msn.com>
Date: Mon, 25 Nov 2024 11:05:53 -0800
Subject: [PATCH 1/2] Add no-rosegment by default for API 29 and earlier.

Details in: https://github.com/android/ndk/issues/1196
Fixes: https://github.com/android/ndk/issues/1294
---
 clang/lib/Driver/ToolChains/Linux.cpp |  8 ++++++++
 clang/test/Driver/linux-ld.c          | 14 ++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index d1cb625613415b..5cc3d6feaa434f 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -256,6 +256,14 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
       ExtraOpts.push_back("-z");
       ExtraOpts.push_back("max-page-size=16384");
     }
+    if (Triple.isAndroidVersionLT(29)) {
+      // https://github.com/android/ndk/issues/1196
+      // The unwinder used by the crash handler on versions of Android prior to
+      // API 29 did not correctly handle binaries built with rosegment, which is
+      // enabled by default for LLD. Android only supports LLD, so it's not an
+      // issue that this flag is not accepted by other linkers.
+      ExtraOpts.push_back("--no-rosegment");
+    }
   }
 
   if (GCCInstallation.getParentLibPath().contains("opt/rh/"))
diff --git a/clang/test/Driver/linux-ld.c b/clang/test/Driver/linux-ld.c
index 28fb075a80dbbc..50facb6a03ac20 100644
--- a/clang/test/Driver/linux-ld.c
+++ b/clang/test/Driver/linux-ld.c
@@ -940,6 +940,20 @@
 // CHECK-ANDROID-HASH-STYLE-M: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ANDROID-HASH-STYLE-M: "--hash-style=gnu"
 
+// Check that we pass --no-rosegment for pre-29 Android versions and do not for
+// 29+.
+// RUN: %clang %s -### -o %t.o 2>&1 \
+// RUN:     --target=armv7-linux-android28 \
+// RUN:   | FileCheck --check-prefix=CHECK-ANDROID-ROSEGMENT-28 %s
+// CHECK-ANDROID-ROSEGMENT-28: "{{.*}}ld{{(.exe)?}}"
+// CHECK-ANDROID-ROSEGMENT-28: "--no-rosegment"
+//
+// RUN: %clang %s -### -o %t.o 2>&1 \
+// RUN:     --target=armv7-linux-android29 \
+// RUN:   | FileCheck --check-prefix=CHECK-ANDROID-ROSEGMENT-29 %s
+// CHECK-ANDROID-ROSEGMENT-29: "{{.*}}ld{{(.exe)?}}"
+// CHECK-ANDROID-ROSEGMENT-29-NOT: "--no-rosegment"
+
 // RUN: %clang -### %s -no-pie 2>&1 --target=mips64-linux-gnuabin32 \
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS64EL-GNUABIN32 %s
 // CHECK-MIPS64EL-GNUABIN32: "{{.*}}ld{{(.exe)?}}"

>From 0940f24788e9398dfbd8cc92d12d7c803693a172 Mon Sep 17 00:00:00 2001
From: AdityaK <hiraditya at msn.com>
Date: Mon, 25 Nov 2024 12:03:41 -0800
Subject: [PATCH 2/2] Pack relocations for Android API >= 28

Patch copied from: https://github.com/android/ndk/issues/909#issuecomment-649872696
Fixes: https://github.com/android/ndk/issues/909
---
 clang/lib/Driver/ToolChains/Linux.cpp | 10 ++++++++++
 clang/test/Driver/linux-ld.c          | 16 ++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/clang/lib/Driver/ToolChains/Linux.cpp b/clang/lib/Driver/ToolChains/Linux.cpp
index 5cc3d6feaa434f..83f4df19d43fd4 100644
--- a/clang/lib/Driver/ToolChains/Linux.cpp
+++ b/clang/lib/Driver/ToolChains/Linux.cpp
@@ -264,6 +264,16 @@ Linux::Linux(const Driver &D, const llvm::Triple &Triple, const ArgList &Args)
       // issue that this flag is not accepted by other linkers.
       ExtraOpts.push_back("--no-rosegment");
     }
+    if (!Triple.isAndroidVersionLT(28)) {
+      // Android supports relr packing starting with API 28 and had its own flavor
+      // (--pack-dyn-relocs=android) starting in API 23.
+      // TODO: It's possible to use both with --pack-dyn-relocs=android+relr,
+      // but we need to gather some data on the impact of that form before we
+      // can know if it's a good default.
+      // On the other hand, relr should always be an improvement.
+      ExtraOpts.push_back("--use-android-relr-tags");
+      ExtraOpts.push_back("--pack-dyn-relocs=relr");
+    }
   }
 
   if (GCCInstallation.getParentLibPath().contains("opt/rh/"))
diff --git a/clang/test/Driver/linux-ld.c b/clang/test/Driver/linux-ld.c
index 50facb6a03ac20..4d641c8f1b46e9 100644
--- a/clang/test/Driver/linux-ld.c
+++ b/clang/test/Driver/linux-ld.c
@@ -954,6 +954,22 @@
 // CHECK-ANDROID-ROSEGMENT-29: "{{.*}}ld{{(.exe)?}}"
 // CHECK-ANDROID-ROSEGMENT-29-NOT: "--no-rosegment"
 
+// Check that we pass --pack-dyn-relocs=relr for API 28+ and not before.
+// RUN: %clang %s -### -o %t.o 2>&1 \
+// RUN:     --target=armv7-linux-android27 \
+// RUN:   | FileCheck --check-prefix=CHECK-ANDROID-RELR-27 %s
+// CHECK-ANDROID-RELR-27: "{{.*}}ld{{(.exe)?}}"
+// CHECK-ANDROID-RELR-27-NOT: "--pack-dyn-relocs=relr"
+// CHECK-ANDROID-RELR-27-NOT: "--pack-dyn-relocs=android+relr"
+//
+// RUN: %clang %s -### -o %t.o 2>&1 \
+// RUN:     --target=armv7-linux-android28 \
+// RUN:   | FileCheck --check-prefix=CHECK-ANDROID-RELR-28 %s
+// CHECK-ANDROID-RELR-28: "{{.*}}ld{{(.exe)?}}"
+// CHECK-ANDROID-RELR-28: "--use-android-relr-tags"
+// CHECK-ANDROID-RELR-28: "--pack-dyn-relocs=relr"
+// CHECK-ANDROID-RELR-28-NOT: "--pack-dyn-relocs=android+relr"
+
 // RUN: %clang -### %s -no-pie 2>&1 --target=mips64-linux-gnuabin32 \
 // RUN:   | FileCheck --check-prefix=CHECK-MIPS64EL-GNUABIN32 %s
 // CHECK-MIPS64EL-GNUABIN32: "{{.*}}ld{{(.exe)?}}"