[PATCH v2 5/7] ptrace_get_syscall_info: factor out ptrace_get_syscall_info_op

Dmitry V. Levin
2025-01-13T17:12:02Z

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@strace.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