hexagon-add-syscall_set_return_value.patch removed from -mm tree

The quilt patch titled
Subject: hexagon: add syscall_set_return_value()
has been removed from the -mm tree. Its filename was
hexagon-add-syscall_set_return_value.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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From: "Dmitry V. Levin" <[email protected]>
Subject: hexagon: add syscall_set_return_value()
Date: Mon, 3 Mar 2025 13:19:53 +0200

Patch series "ptrace: introduce PTRACE_SET_SYSCALL_INFO API", v7.

PTRACE_SET_SYSCALL_INFO is a generic ptrace API that complements PTRACE_GET_SYSCALL_INFO by letting the ptracer modify details of system calls the tracee is blocked in.

This API allows ptracers to obtain and modify system call details in a straightforward and architecture-agnostic way, providing a consistent way of manipulating the system call number and arguments across architectures.

As in case of PTRACE_GET_SYSCALL_INFO, PTRACE_SET_SYSCALL_INFO also does not aim to address numerous architecture-specific system call ABI peculiarities, like differences in the number of system call arguments for such system calls as pread64 and preadv.

The current implementation supports changing only those bits of system call information that are used by strace system call tampering, namely, syscall number, syscall arguments, and syscall return value.

Support of changing additional details returned by PTRACE_GET_SYSCALL_INFO, such as instruction pointer and stack pointer, could be added later if needed, by using struct ptrace_syscall_info.flags to specify the additional details that should be set. Currently, "flags" and "reserved" fields of struct ptrace_syscall_info must be initialized with zeroes; "arch", "instruction_pointer", and "stack_pointer" fields are currently ignored.

PTRACE_SET_SYSCALL_INFO currently supports only PTRACE_SYSCALL_INFO_ENTRY, PTRACE_SYSCALL_INFO_EXIT, and PTRACE_SYSCALL_INFO_SECCOMP operations. Other operations could be added later if needed.

Ideally, PTRACE_SET_SYSCALL_INFO should have been introduced along with PTRACE_GET_SYSCALL_INFO, but it didn't happen. The last straw that convinced me to implement PTRACE_SET_SYSCALL_INFO was apparent failure to provide an API of changing the first system call argument on riscv architecture [1].

ptrace(2) man page:

long ptrace(enum __ptrace_request request, pid_t pid, void *addr, void *data);
...
PTRACE_SET_SYSCALL_INFO
Modify information about the system call that caused the stop. The "data" argument is a pointer to struct ptrace_syscall_info that specifies the system call information to be set.
The "addr" argument should be set to sizeof(struct ptrace_syscall_info)).

This patch (of 6):

hexagon is the only architecture that provides HAVE_ARCH_TRACEHOOK but doesn't define syscall_set_return_value(). Since this function is going to be needed on all HAVE_ARCH_TRACEHOOK architectures to implement PTRACE_SET_SYSCALL_INFO API, add it on hexagon, too.

---

 arch/hexagon/include/asm/syscall.h |    7 +++++++
 1 file changed, 7 insertions(+)

@@ -45,6 +45,13 @@ static inline long syscall_get_return_va
 	return regs->r00;
 }
 
+static inline void syscall_set_return_value(struct task_struct *task,
+					    struct pt_regs *regs,
+					    int error, long val)
+{
+	regs->r00 = (long) error ?: val;
+}
+
 static inline int syscall_get_arch(struct task_struct *task)
 {
 	return AUDIT_ARCH_HEXAGON;

_

Patches currently in -mm which might be from [email protected] are