From 3e223185b3b6bf96b0b86a3be0ad626193ef85d4 Mon Sep 17 00:00:00 2001
From: Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
Date: Thu, 25 Nov 2021 20:15:02 +0100
Subject: [PATCH] Kernel+strace: Remove unnecessary indirection for PEEK

Also, remove incomplete, superfluous check.
Incomplete, because only the byte at the provided address was checked;
this misses the last bytes of the "jerk page".
Superfluous, because it is already correctly checked by peek_user_data
(which calls copy_from_user).

The caller/tracer should not typically attempt to read non-userspace
addresses, we don't need to "hot-path" it either.
---
 Kernel/API/Syscall.h                   |  5 -----
 Kernel/Syscalls/ptrace.cpp             | 16 ++++------------
 Userland/Libraries/LibC/sys/ptrace.cpp |  5 +----
 3 files changed, 5 insertions(+), 21 deletions(-)

diff --git a/Kernel/API/Syscall.h b/Kernel/API/Syscall.h
index 019a471db9..63d3050e2f 100644
--- a/Kernel/API/Syscall.h
+++ b/Kernel/API/Syscall.h
@@ -465,11 +465,6 @@ struct SC_ptrace_params {
     FlatPtr data;
 };
 
-struct SC_ptrace_peek_params {
-    const void* address;
-    FlatPtr* out_data;
-};
-
 struct SC_set_coredump_metadata_params {
     StringArgument key;
     StringArgument value;
diff --git a/Kernel/Syscalls/ptrace.cpp b/Kernel/Syscalls/ptrace.cpp
index adfcef8f70..9547725a33 100644
--- a/Kernel/Syscalls/ptrace.cpp
+++ b/Kernel/Syscalls/ptrace.cpp
@@ -114,26 +114,18 @@ static ErrorOr<FlatPtr> handle_ptrace(const Kernel::Syscall::SC_ptrace_params& p
     }
 
     case PT_PEEK: {
-        Kernel::Syscall::SC_ptrace_peek_params peek_params {};
-        TRY(copy_from_user(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)));
-        if (!Memory::is_user_address(VirtualAddress { peek_params.address }))
-            return EFAULT;
-        auto data = TRY(peer->process().peek_user_data(Userspace<const FlatPtr*> { (FlatPtr)peek_params.address }));
-        TRY(copy_to_user(peek_params.out_data, &data));
+        auto data = TRY(peer->process().peek_user_data(Userspace<const FlatPtr*> { (FlatPtr)params.addr }));
+        TRY(copy_to_user((FlatPtr*)params.data, &data));
         break;
     }
 
     case PT_POKE:
-        if (!Memory::is_user_address(VirtualAddress { params.addr }))
-            return EFAULT;
         TRY(peer->process().poke_user_data(Userspace<FlatPtr*> { (FlatPtr)params.addr }, params.data));
         return 0;
 
     case PT_PEEKDEBUG: {
-        Kernel::Syscall::SC_ptrace_peek_params peek_params {};
-        TRY(copy_from_user(&peek_params, reinterpret_cast<Kernel::Syscall::SC_ptrace_peek_params*>(params.addr)));
-        auto data = TRY(peer->peek_debug_register(reinterpret_cast<uintptr_t>(peek_params.address)));
-        TRY(copy_to_user(peek_params.out_data, &data));
+        auto data = TRY(peer->peek_debug_register(reinterpret_cast<uintptr_t>(params.addr)));
+        TRY(copy_to_user((FlatPtr*)params.data, &data));
         break;
     }
     case PT_POKEDEBUG:
diff --git a/Userland/Libraries/LibC/sys/ptrace.cpp b/Userland/Libraries/LibC/sys/ptrace.cpp
index e20f4ce1eb..61c3e41e12 100644
--- a/Userland/Libraries/LibC/sys/ptrace.cpp
+++ b/Userland/Libraries/LibC/sys/ptrace.cpp
@@ -18,12 +18,9 @@ long ptrace(int request, pid_t tid, void* addr, void* data)
     // by looking at errno rather than the return value.
 
     FlatPtr out_data;
-    Syscall::SC_ptrace_peek_params peek_params;
     auto is_peek_type = request == PT_PEEK || request == PT_PEEKDEBUG;
     if (is_peek_type) {
-        peek_params.address = reinterpret_cast<FlatPtr*>(addr);
-        peek_params.out_data = &out_data;
-        addr = &peek_params;
+        data = &out_data;
     }
 
     Syscall::SC_ptrace_params params {