Fix inconsistent reg struct layout for 64bit tracer and 32bit tracee

changelog/2448.changed.md

@@ -0,0 +1 @@
+Module sys/ptrace changes `ptrace::getregs` for x86_64/x86 to be unsafe function.

src/sys/ptrace/linux.rs

@@ -304,12 +304,17 @@ fn ptrace_peek(
     }
 }
 
-/// Get user registers, as with `ptrace(PTRACE_GETREGS, ...)`
+/// Get user registers, as with `ptrace(PTRACE_GETREGS, ...)`. Call `getregset` for safe version
 ///
 /// Note that since `PTRACE_GETREGS` are not available on all platforms (as in [ptrace(2)]),
 /// `ptrace(PTRACE_GETREGSET, pid, NT_PRSTATUS, ...)` is used instead to achieve the same effect
 /// on aarch64 and riscv64.
 ///
+/// # Safety
+///
+/// Currently, in x86_64 platform, if the tracer is 64bit and tracee is 32bit, the return value is
+/// undefined.
+///
 /// [ptrace(2)]: https://www.man7.org/linux/man-pages/man2/ptrace.2.html
 #[cfg(all(
     target_os = "linux",
@@ -321,7 +326,7 @@ fn ptrace_peek(
         all(target_arch = "x86", target_env = "gnu")
     )
 ))]
-pub fn getregs(pid: Pid) -> Result<user_regs_struct> {
+pub unsafe fn getregs(pid: Pid) -> Result<user_regs_struct> {
     ptrace_get_data::<user_regs_struct>(Request::PTRACE_GETREGS, pid)
 }
 
@@ -342,6 +347,9 @@ pub fn getregs(pid: Pid) -> Result<user_regs_struct> {
 }
 
 /// Get a particular set of user registers, as with `ptrace(PTRACE_GETREGSET, ...)`
+///
+/// Currently, in x86_64 platform, if the tracer is 64bit and tracee is 32bit, this function
+/// will return EIO error.
 #[cfg(all(
     target_os = "linux",
     target_env = "gnu",
@@ -367,6 +375,9 @@ pub fn getregset<S: RegisterSet>(pid: Pid) -> Result<S::Regs> {
             (&mut iov as *mut libc::iovec).cast(),
         )?;
     };
+    if iov.iov_len != mem::size_of::<S::Regs>() {
+        return Err(Errno::EIO);
+    }
     Ok(unsafe { data.assume_init() })
 }
 

test/sys/test_ptrace.rs

@@ -224,12 +224,16 @@ fn test_ptrace_syscall() {
                 .unwrap();
 
             #[cfg(target_arch = "x86_64")]
-            let get_syscall_id =
-                || ptrace::getregs(child).unwrap().orig_rax as libc::c_long;
+            let get_syscall_id = || {
+                unsafe { ptrace::getregs(child) }.unwrap().orig_rax
+                    as libc::c_long
+            };
 
             #[cfg(target_arch = "x86")]
-            let get_syscall_id =
-                || ptrace::getregs(child).unwrap().orig_eax as libc::c_long;
+            let get_syscall_id = || {
+                unsafe { ptrace::getregs(child) }.unwrap().orig_eax
+                    as libc::c_long
+            };
 
             #[cfg(target_arch = "aarch64")]
             let get_syscall_id =