linux-kernel - [PATCH v2 2/2] LoongArch: Extend the maximum number of watchpoints

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20250122032310.26729-3-yangtiezhu@loongson.cn>
Date: Wed, 22 Jan 2025 11:23:10 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] 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, so
extend the maximum number of watchpoints from 8 to 14 for ptrace.

By the way, just simply change 8 to 14 for the definition in struct
user_watch_state at the beginning, but it may corrupt uapi, then add
a new struct user_watch_state_v2 directly.

As far as I can tell, the only users for this struct in the userspace
are GDB and LLDB, there are no any problems of software compatibility
between the application and kernel according to the analysis.

The compatibility problem has been considered when developing and testing
the patches, when the applications in the userspace get watchpoint state,
the length will be specified which will not bigger than the sizeof struct
user_watch_state or user_watch_state_v2, the actual length is assigned as
the minimal value of the application and kernel in the generic ptrace:

kernel/ptrace.c: ptrace_regset():

	kiov->iov_len = min(kiov->iov_len,
			    (__kernel_size_t) (regset->n * regset->size));

	if (req == PTRACE_GETREGSET)
		return copy_regset_to_user(task, view, regset_no, 0,
					   kiov->iov_len, kiov->iov_base);
	else
		return copy_regset_from_user(task, view, regset_no, 0,
					     kiov->iov_len, kiov->iov_base);

For example, there are four kind of combinations, all of them work well.

(1) "older kernel + older gdb", the actual length is 8+(8+8+4+4)*8=200;
(2) "newer kernel + newer gdb", the actual length is 8+(8+8+4+4)*14=344;
(3) "older kernel + newer gdb", the actual length is 8+(8+8+4+4)*8=200;
(4) "newer kernel + older gdb", the actual length is 8+(8+8+4+4)*8=200.

Link: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
Fixes: 1a69f7a161a7 ("LoongArch: ptrace: Expose hardware breakpoints to debuggers")
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 arch/loongarch/include/uapi/asm/ptrace.h | 10 ++++++++++
 arch/loongarch/kernel/ptrace.c           |  6 +++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/loongarch/include/uapi/asm/ptrace.h b/arch/loongarch/include/uapi/asm/ptrace.h
index ac915f841650..aafb3cd9e943 100644
--- a/arch/loongarch/include/uapi/asm/ptrace.h
+++ b/arch/loongarch/include/uapi/asm/ptrace.h
@@ -72,6 +72,16 @@ struct user_watch_state {
 	} dbg_regs[8];
 };
 
+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];
+};
+
 #define PTRACE_SYSEMU			0x1f
 #define PTRACE_SYSEMU_SINGLESTEP	0x20
 
diff --git a/arch/loongarch/kernel/ptrace.c b/arch/loongarch/kernel/ptrace.c
index 19dc6eff45cc..5e2402cfcab0 100644
--- a/arch/loongarch/kernel/ptrace.c
+++ b/arch/loongarch/kernel/ptrace.c
@@ -720,7 +720,7 @@ static int hw_break_set(struct task_struct *target,
 	unsigned int note_type = regset->core_note_type;
 
 	/* Resource info */
-	offset = offsetof(struct user_watch_state, dbg_regs);
+	offset = offsetof(struct user_watch_state_v2, dbg_regs);
 	user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, 0, offset);
 
 	/* (address, mask, ctrl) registers */
@@ -920,7 +920,7 @@ static const struct user_regset loongarch64_regsets[] = {
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 	[REGSET_HW_BREAK] = {
 		.core_note_type = NT_LOONGARCH_HW_BREAK,
-		.n = sizeof(struct user_watch_state) / sizeof(u32),
+		.n = sizeof(struct user_watch_state_v2) / sizeof(u32),
 		.size = sizeof(u32),
 		.align = sizeof(u32),
 		.regset_get = hw_break_get,
@@ -928,7 +928,7 @@ static const struct user_regset loongarch64_regsets[] = {
 	},
 	[REGSET_HW_WATCH] = {
 		.core_note_type = NT_LOONGARCH_HW_WATCH,
-		.n = sizeof(struct user_watch_state) / sizeof(u32),
+		.n = sizeof(struct user_watch_state_v2) / sizeof(u32),
 		.size = sizeof(u32),
 		.align = sizeof(u32),
 		.regset_get = hw_break_get,
-- 
2.42.0