From 6aa392f6e413be166879c3fef3864905d3474aa4 Mon Sep 17 00:00:00 2001
From: Daniel Bertalan <dani@danielbertalan.dev>
Date: Mon, 24 Apr 2023 20:14:44 +0200
Subject: [PATCH] Kernel: Store the kernel command line in a `StringView`

The Raspberry Pi's mailbox interface does not guarantee that the
returned command line is null-terminated. This commit removes that
assumption from the current code, allowing the next commit to add
support for reading it on the Pi.

This also lets us eliminate a few manual `strlen()` calls :^)
---
 Kernel/Arch/init.cpp   |  9 +++++----
 Kernel/BootInfo.h      |  3 ++-
 Kernel/CommandLine.cpp | 10 ++--------
 Kernel/CommandLine.h   |  2 +-
 4 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/Kernel/Arch/init.cpp b/Kernel/Arch/init.cpp
index 8f7cf5381b..883e450d7d 100644
--- a/Kernel/Arch/init.cpp
+++ b/Kernel/Arch/init.cpp
@@ -133,7 +133,7 @@ READONLY_AFTER_INIT PhysicalAddress boot_pdpt;
 READONLY_AFTER_INIT PhysicalAddress boot_pd0;
 READONLY_AFTER_INIT PhysicalAddress boot_pd_kernel;
 READONLY_AFTER_INIT Memory::PageTableEntry* boot_pd_kernel_pt1023;
-READONLY_AFTER_INIT char const* kernel_cmdline;
+READONLY_AFTER_INIT StringView kernel_cmdline;
 READONLY_AFTER_INIT u32 multiboot_flags;
 READONLY_AFTER_INIT multiboot_memory_map_t* multiboot_memory_map;
 READONLY_AFTER_INIT size_t multiboot_memory_map_count;
@@ -166,7 +166,8 @@ extern "C" [[noreturn]] UNMAP_AFTER_INIT void init([[maybe_unused]] BootInfo con
     boot_pd0 = PhysicalAddress { boot_info.boot_pd0 };
     boot_pd_kernel = PhysicalAddress { boot_info.boot_pd_kernel };
     boot_pd_kernel_pt1023 = (Memory::PageTableEntry*)boot_info.boot_pd_kernel_pt1023;
-    kernel_cmdline = (char const*)boot_info.kernel_cmdline;
+    char const* cmdline = (char const*)boot_info.kernel_cmdline;
+    kernel_cmdline = StringView { cmdline, strlen(cmdline) };
     multiboot_flags = boot_info.multiboot_flags;
     multiboot_memory_map = (multiboot_memory_map_t*)boot_info.multiboot_memory_map;
     multiboot_memory_map_count = boot_info.multiboot_memory_map_count;
@@ -192,7 +193,7 @@ extern "C" [[noreturn]] UNMAP_AFTER_INIT void init([[maybe_unused]] BootInfo con
     multiboot_module_entry_t modules[] = {};
     multiboot_modules = modules;
     multiboot_modules_count = 0;
-    kernel_cmdline = "";
+    kernel_cmdline = ""sv;
 #endif
 
     setup_serial_debug();
@@ -442,7 +443,7 @@ UNMAP_AFTER_INIT void setup_serial_debug()
     // serial_debug will output all the dbgln() data to COM1 at
     // 8-N-1 57600 baud. this is particularly useful for debugging the boot
     // process on live hardware.
-    if (StringView { kernel_cmdline, strlen(kernel_cmdline) }.contains("serial_debug"sv)) {
+    if (kernel_cmdline.contains("serial_debug"sv)) {
         set_serial_debug_enabled(true);
     }
 }
diff --git a/Kernel/BootInfo.h b/Kernel/BootInfo.h
index 4724f0b12f..af3300f27a 100644
--- a/Kernel/BootInfo.h
+++ b/Kernel/BootInfo.h
@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/StringView.h>
 #include <Kernel/Multiboot.h>
 #include <Kernel/PhysicalAddress.h>
 #include <Kernel/VirtualAddress.h>
@@ -28,7 +29,7 @@ extern "C" PhysicalAddress boot_pdpt;
 extern "C" PhysicalAddress boot_pd0;
 extern "C" PhysicalAddress boot_pd_kernel;
 extern "C" Kernel::Memory::PageTableEntry* boot_pd_kernel_pt1023;
-extern "C" char const* kernel_cmdline;
+extern "C" StringView kernel_cmdline;
 extern "C" u32 multiboot_flags;
 extern "C" multiboot_memory_map_t* multiboot_memory_map;
 extern "C" size_t multiboot_memory_map_count;
diff --git a/Kernel/CommandLine.cpp b/Kernel/CommandLine.cpp
index 23245e044f..d52f4ce0e0 100644
--- a/Kernel/CommandLine.cpp
+++ b/Kernel/CommandLine.cpp
@@ -16,15 +16,9 @@ static char s_cmd_line[1024];
 static constexpr StringView s_embedded_cmd_line = ""sv;
 static CommandLine* s_the;
 
-UNMAP_AFTER_INIT void CommandLine::early_initialize(char const* cmd_line)
+UNMAP_AFTER_INIT void CommandLine::early_initialize(StringView cmd_line)
 {
-    if (!cmd_line)
-        return;
-    size_t length = strlen(cmd_line);
-    if (length >= sizeof(s_cmd_line))
-        length = sizeof(s_cmd_line) - 1;
-    memcpy(s_cmd_line, cmd_line, length);
-    s_cmd_line[length] = '\0';
+    (void)cmd_line.copy_characters_to_buffer(s_cmd_line, sizeof(s_cmd_line));
 }
 
 bool CommandLine::was_initialized()
diff --git a/Kernel/CommandLine.h b/Kernel/CommandLine.h
index af67aea472..decaf2aae2 100644
--- a/Kernel/CommandLine.h
+++ b/Kernel/CommandLine.h
@@ -52,7 +52,7 @@ enum class AHCIResetMode {
 class CommandLine {
 
 public:
-    static void early_initialize(char const* cmd_line);
+    static void early_initialize(StringView cmd_line);
     static void initialize();
     static bool was_initialized();