[Lldb-commits] [lldb] [LLDB][LoongArch] Fix build errors and extend watchpoint numbers (PR #126020)

[via lldb-commits]

https://github.com/seehearfeel created https://github.com/llvm/llvm-project/pull/126020

1. [LLDB][LoongArch] Fix build errors about NT_LOONGARCH_HW_{BREAK,WATCH}
2. [LLDB][LoongArch] Extend the maximum number of watchpoints

>From 67dd4198073a2b87f7dbaa37cd6103f2230f326e Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <yangtiezhu at loongson.cn>
Date: Thu, 23 Jan 2025 15:30:20 +0800
Subject: [PATCH 1/2] [LLDB][LoongArch] Fix build errors about
 NT_LOONGARCH_HW_{BREAK,WATCH}

On some OS distros such as LoongArch Fedora 38 mate-5 [1], there are
no macro definitions NT_LOONGARCH_HW_BREAK and NT_LOONGARCH_HW_WATCH
in the system header, then there exist some errors when building LLDB
on LoongArch.

(1) Description of Problem:

llvm-project/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp:529:16:
error: 'NT_LOONGARCH_HW_WATCH' was not declared in this scope; did you mean 'NT_LOONGARCH_LBT'?
  529 |   int regset = NT_LOONGARCH_HW_WATCH;
      |                ^~~~~~~~~~~~~~~~~~~~~
      |                NT_LOONGARCH_LBT
llvm-project/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp:543:12:
error: 'NT_LOONGARCH_HW_BREAK' was not declared in this scope; did you mean 'NT_LOONGARCH_CSR'?
  543 |   regset = NT_LOONGARCH_HW_BREAK;
      |            ^~~~~~~~~~~~~~~~~~~~~
      |            NT_LOONGARCH_CSR

(2) Steps to Reproduce:

git clone https://github.com/llvm/llvm-project.git
mkdir -p llvm-project/llvm/build && cd llvm-project/llvm/build
cmake .. -G "Ninja" \
         -DCMAKE_BUILD_TYPE=Release \
         -DLLVM_BUILD_RUNTIME=OFF \
         -DLLVM_ENABLE_PROJECTS="clang;lldb" \
         -DCMAKE_INSTALL_PREFIX=/usr/local/llvm \
         -DLLVM_TARGETS_TO_BUILD="LoongArch" \
         -DLLVM_HOST_TRIPLE=loongarch64-redhat-linux
ninja

(3) Additional Info:

Maybe there are no problems on the OS distros with newer glibc devel
library, so this issue is related with OS distros.

(4) Root Cause Analysis:

This is because the related Linux kernel commit [3] was merged in
2023-02-25 and the glibc devel library has some delay with kernel,
the glibc version of specified OS distros is not updated in time.

(5) Final Solution:

One way is to ask the maintainer of OS distros to update glibc devel
library, but it is better to not depend on the glibc version.

In order to avoid the build errors, just define NT_LOONGARCH_HW_BREAK
and NT_LOONGARCH_HW_WATCH in LLDB if there are no these definitions in
the system header.

[1] https://mirrors.wsyu.edu.cn/fedora/linux/development/rawhide/Everything/loongarch64/iso/livecd-fedora-mate-5.loongarch64.iso
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1a69f7a161a7

Signed-off-by: Tiezhu Yang <yangtiezhu at loongson.cn>
---
 .../Linux/NativeRegisterContextLinux_loongarch64.cpp      | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
index b04018ee243fd7d..889c2083aa5b9b2 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
@@ -36,6 +36,14 @@
   0xa03 /* LoongArch Advanced SIMD eXtension registers */
 #endif
 
+#ifndef NT_LOONGARCH_HW_BREAK
+#define NT_LOONGARCH_HW_BREAK	0xa05   /* LoongArch hardware breakpoint registers */
+#endif
+
+#ifndef NT_LOONGARCH_HW_WATCH
+#define NT_LOONGARCH_HW_WATCH	0xa06   /* LoongArch hardware watchpoint registers */
+#endif
+
 #define REG_CONTEXT_SIZE                                                       \
   (GetGPRSize() + GetFPRSize() + sizeof(m_lsx) + sizeof(m_lasx))
 

>From 37ef08582098aac0eb19eb0d021a998563412c46 Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <yangtiezhu at loongson.cn>
Date: Thu, 6 Feb 2025 15:10:59 +0800
Subject: [PATCH 2/2] [LLDB][LoongArch] Extend the maximum number of
 watchpoints

The maximum number of load/store watchpoints and fetch instruction
watchpoints is 14 each according to LoongArch Reference Manual [1],
so extend the maximum number of watchpoints from 8 to 14 for ptrace.

A new struct user_watch_state_v2 was added into uapi in the related
kernel commit 531936dee53e ("LoongArch: Extend the maximum number of
watchpoints") [2], but there may be no struct user_watch_state_v2 in
the system header in time, so add the definition if not exist, then
replace user_watch_state with user_watch_state_v2.

[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=531936dee53e

Signed-off-by: Tiezhu Yang <yangtiezhu at loongson.cn>
---
 .../NativeRegisterContextLinux_loongarch64.cpp   | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
index 889c2083aa5b9b2..8eb2cb65c76d2ea 100644
--- a/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
+++ b/lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_loongarch64.cpp
@@ -47,6 +47,18 @@
 #define REG_CONTEXT_SIZE                                                       \
   (GetGPRSize() + GetFPRSize() + sizeof(m_lsx) + sizeof(m_lasx))
 
+#ifndef user_watch_state_v2
+struct user_watch_state_v2 {
+	uint64_t dbg_info;
+	struct {
+		uint64_t    addr;
+		uint64_t    mask;
+		uint32_t    ctrl;
+		uint32_t    pad;
+	} dbg_regs[14];
+};
+#endif
+
 using namespace lldb;
 using namespace lldb_private;
 using namespace lldb_private::process_linux;
@@ -536,7 +548,7 @@ llvm::Error NativeRegisterContextLinux_loongarch64::ReadHardwareDebugInfo() {
 
   int regset = NT_LOONGARCH_HW_WATCH;
   struct iovec ioVec;
-  struct user_watch_state dreg_state;
+  struct user_watch_state_v2 dreg_state;
   Status error;
 
   ioVec.iov_base = &dreg_state;
@@ -564,7 +576,7 @@ llvm::Error NativeRegisterContextLinux_loongarch64::ReadHardwareDebugInfo() {
 llvm::Error NativeRegisterContextLinux_loongarch64::WriteHardwareDebugRegs(
     DREGType hwbType) {
   struct iovec ioVec;
-  struct user_watch_state dreg_state;
+  struct user_watch_state_v2 dreg_state;
   int regset;
 
   memset(&dreg_state, 0, sizeof(dreg_state));