linux-kernel - [PATCH v2 5/7] ptrace_get_syscall_info: factor out ptrace_get_syscall_info

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Message-ID: <20250113171201.GE589@strace.io>
Date: Mon, 13 Jan 2025 19:12:01 +0200
From: "Dmitry V. Levin" <ldv@...ace.io>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Eugene Syromyatnikov <evgsyr@...il.com>,
	Mike Frysinger <vapier@...too.org>,
	Renzo Davoli <renzo@...unibo.it>,
	Davide Berardi <berardi.dav@...il.com>,
	strace-devel@...ts.strace.io, linux-kernel@...r.kernel.org
Subject: [PATCH v2 5/7] ptrace_get_syscall_info: factor out
 ptrace_get_syscall_info_op

Move the code that calculates the type of the system call stop
out of ptrace_get_syscall_info() into a separate function
ptrace_get_syscall_info_op() which is going to be used later
to implement PTRACE_SET_SYSCALL_INFO API.

Signed-off-by: Dmitry V. Levin <ldv@...ace.io>
---
 kernel/ptrace.c | 58 +++++++++++++++++++++++++++++--------------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index d5f89f9ef29f..22e7d74cf4cd 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -921,7 +921,6 @@ ptrace_get_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
 	unsigned long args[ARRAY_SIZE(info->entry.args)];
 	int i;
 
-	info->op = PTRACE_SYSCALL_INFO_ENTRY;
 	info->entry.nr = syscall_get_nr(child, regs);
 	syscall_get_arguments(child, regs, args);
 	for (i = 0; i < ARRAY_SIZE(args); i++)
@@ -943,7 +942,6 @@ ptrace_get_syscall_info_seccomp(struct task_struct *child, struct pt_regs *regs,
 	 * diverge significantly enough.
 	 */
 	ptrace_get_syscall_info_entry(child, regs, info);
-	info->op = PTRACE_SYSCALL_INFO_SECCOMP;
 	info->seccomp.ret_data = child->ptrace_message;
 
 	/* ret_data is the last field in struct ptrace_syscall_info.seccomp */
@@ -954,7 +952,6 @@ static unsigned long
 ptrace_get_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
 			     struct ptrace_syscall_info *info)
 {
-	info->op = PTRACE_SYSCALL_INFO_EXIT;
 	info->exit.rval = syscall_get_error(child, regs);
 	info->exit.is_error = !!info->exit.rval;
 	if (!info->exit.is_error)
@@ -965,19 +962,8 @@ ptrace_get_syscall_info_exit(struct task_struct *child, struct pt_regs *regs,
 }
 
 static int
-ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
-			void __user *datavp)
+ptrace_get_syscall_info_op(struct task_struct *child)
 {
-	struct pt_regs *regs = task_pt_regs(child);
-	struct ptrace_syscall_info info = {
-		.op = PTRACE_SYSCALL_INFO_NONE,
-		.arch = syscall_get_arch(child),
-		.instruction_pointer = instruction_pointer(regs),
-		.stack_pointer = user_stack_pointer(regs),
-	};
-	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
-	unsigned long write_size;
-
 	/*
 	 * This does not need lock_task_sighand() to access
 	 * child->last_siginfo because ptrace_freeze_traced()
@@ -988,18 +974,42 @@ ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
 	case SIGTRAP | 0x80:
 		switch (child->ptrace_message) {
 		case PTRACE_EVENTMSG_SYSCALL_ENTRY:
-			actual_size = ptrace_get_syscall_info_entry(child, regs,
-								    &info);
-			break;
+			return PTRACE_SYSCALL_INFO_ENTRY;
 		case PTRACE_EVENTMSG_SYSCALL_EXIT:
-			actual_size = ptrace_get_syscall_info_exit(child, regs,
-								   &info);
-			break;
+			return PTRACE_SYSCALL_INFO_EXIT;
+		default:
+			return PTRACE_SYSCALL_INFO_NONE;
 		}
-		break;
 	case SIGTRAP | (PTRACE_EVENT_SECCOMP << 8):
-		actual_size = ptrace_get_syscall_info_seccomp(child, regs,
-							      &info);
+		return PTRACE_SYSCALL_INFO_SECCOMP;
+	default:
+		return PTRACE_SYSCALL_INFO_NONE;
+	}
+}
+
+static int
+ptrace_get_syscall_info(struct task_struct *child, unsigned long user_size,
+			void __user *datavp)
+{
+	struct pt_regs *regs = task_pt_regs(child);
+	struct ptrace_syscall_info info = {
+		.op = ptrace_get_syscall_info_op(child),
+		.arch = syscall_get_arch(child),
+		.instruction_pointer = instruction_pointer(regs),
+		.stack_pointer = user_stack_pointer(regs),
+	};
+	unsigned long actual_size = offsetof(struct ptrace_syscall_info, entry);
+	unsigned long write_size;
+
+	switch (info.op) {
+	case PTRACE_SYSCALL_INFO_ENTRY:
+		actual_size = ptrace_get_syscall_info_entry(child, regs, &info);
+		break;
+	case PTRACE_SYSCALL_INFO_EXIT:
+		actual_size = ptrace_get_syscall_info_exit(child, regs, &info);
+		break;
+	case PTRACE_SYSCALL_INFO_SECCOMP:
+		actual_size = ptrace_get_syscall_info_seccomp(child, regs, &info);
 		break;
 	}
 
-- 
ldv