[metal] Some minor fixes and tweaks (#933)

* [metal] Ensure DF is clear when calling C from exception handler
* [metal] Mark some internal routines and declarations as `@internal`
* [metal] Fix crash under UEFI when command line string is NULL
* [metal] Fix argc & argv[] setting, & VM page freeing, for UEFI

Part of the memory occupied by the argv[] contents was
erroneously used for page tables & then later erroneously
freed.  The symptom was that argv[0] would show up as an
empty string ("").

Author: tkchia

libc/intrin/interrupts.S

@@ -92,6 +92,7 @@ __excep0_isr:
 	mov	%eax,%ss
 	mov	%eax,%ds
 	mov	%eax,%es
+	cld				# make sure DF is reset, for C code
 	ezlea	.excep_msg,di		# stack should be 16-byte aligned now
 	xor	%eax,%eax		# kprintf is variadic, remember to
 					# pass no. of vector regs. used (= 0)

libc/intrin/mman.greg.c

@@ -59,6 +59,7 @@ struct ReclaimedPage {
 };
 
 /**
+ * @internal
  * Allocates new page of physical memory.
  */
 texthead uint64_t __new_page(struct mman *mm) {
@@ -85,6 +86,7 @@ texthead uint64_t __new_page(struct mman *mm) {
 }
 
 /**
+ * @internal
  * Returns pointer to page table entry for page at virtual address.
  * Additional page tables are allocated if needed as a side-effect.
  */
@@ -106,6 +108,7 @@ textreal uint64_t *__get_virtual(struct mman *mm, uint64_t *t, int64_t vaddr,
 }
 
 /**
+ * @internal
  * Sorts, rounds, and filters BIOS memory map.
  */
 static textreal void __normalize_e820(struct mman *mm, uint64_t top) {
@@ -139,6 +142,7 @@ static textreal void __normalize_e820(struct mman *mm, uint64_t top) {
 }
 
 /**
+ * @internal
  * Identity maps an area of physical memory to its negative address.
  */
 textreal uint64_t *__invert_memory_area(struct mman *mm, uint64_t *pml4t,
@@ -157,6 +161,7 @@ textreal uint64_t *__invert_memory_area(struct mman *mm, uint64_t *pml4t,
 }
 
 /**
+ * @internal
  * Increments the reference count for a page of physical memory.
  */
 void __ref_page(struct mman *mm, uint64_t *pml4t, uint64_t p) {
@@ -172,6 +177,7 @@ void __ref_page(struct mman *mm, uint64_t *pml4t, uint64_t p) {
 }
 
 /**
+ * @internal
  * Increments the reference counts for an area of physical memory.
  */
 void __ref_pages(struct mman *mm, uint64_t *pml4t, uint64_t ps, uint64_t size) {
@@ -183,6 +189,7 @@ void __ref_pages(struct mman *mm, uint64_t *pml4t, uint64_t ps, uint64_t size) {
 }
 
 /**
+ * @internal
  * Reclaims a page of physical memory for later use.
  */
 static void __reclaim_page(struct mman *mm, uint64_t p) {
@@ -193,6 +200,7 @@ static void __reclaim_page(struct mman *mm, uint64_t p) {
 }
 
 /**
+ * @internal
  * Decrements the reference count for a page of physical memory.  Frees the
  * page if there are no virtual addresses (excluding the negative space)
  * referring to it.
@@ -211,6 +219,7 @@ void __unref_page(struct mman *mm, uint64_t *pml4t, uint64_t p) {
 }
 
 /**
+ * @internal
  * Identity maps all usable physical memory to its negative address.
  */
 static textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
@@ -224,6 +233,7 @@ static textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
 }
 
 /**
+ * @internal
  * Exports information about the offset of a field within a structure type,
  * so that assembly language routines can use it.  This macro can be invoked
  * from inside a function whose code is known to be emitted.
@@ -284,6 +294,7 @@ static textreal uint64_t __map_phdr(struct mman *mm, uint64_t *pml4t,
 }
 
 /**
+ * @internal
  * Maps APE-defined ELF program headers into memory and clears BSS.
  */
 textreal void __map_phdrs(struct mman *mm, uint64_t *pml4t, uint64_t b,
@@ -315,6 +326,7 @@ textreal void __map_phdrs(struct mman *mm, uint64_t *pml4t, uint64_t b,
 }
 
 /**
+ * @internal
  * Reclaims memory pages which were used at boot time but which can now be
  * made available for the application.
  */

libc/irq/acpi.internal.h

@@ -5,6 +5,17 @@
 #include "libc/log/color.internal.h"
 
 /**
+ * @internal
+ * @fileoverview Declarations for bare metal code to interact with ACPI
+ *
+ * @see UEFI Forum, Inc.  Advanced Configuration and Power Interface (ACPI)
+ *      Specification, Version 6.5, 2022.  https://uefi.org/specifications
+ * @see Intel Corporation.  ACPI Component Architecture: User Guide and
+ *      Programmer Reference, Revision 6.2, 2017.  https://acpica.org
+ */
+
+/**
+ * @internal
  * AcpiStatus values.
  */
 #define kAcpiOk             0x0000
@@ -13,11 +24,13 @@
 #define kAcpiExBadChecksum  0x2003
 
 /**
+ * @internal
  * Flags for AcpiTableMadt::Flags.
  */
 #define kAcpiMadtPcAtCompat 0x0001
 
 /**
+ * @internal
  * Flags for AcpiTableFadt::BootFlags.
  */
 #define kAcpiFadtLegacyDevices 0x0001
@@ -28,6 +41,7 @@
 #define kAcpiFadtNoCmosRtc     0x0020
 
 /**
+ * @internal
  * Values for AcpiSubtableHeader::Type under an AcpiTableMadt.
  */
 #define kAcpiMadtLocalApic    0
@@ -36,15 +50,6 @@
 
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 
-/**
- * @fileoverview Declarations for bare metal code to interact with ACPI
- *
- * @see UEFI Forum, Inc.  Advanced Configuration and Power Interface (ACPI)
- *      Specification, Version 6.5, 2022.  https://uefi.org/specifications
- * @see Intel Corporation.  ACPI Component Architecture: User Guide and
- *      Programmer Reference, Revision 6.2, 2017.  https://acpica.org
- */
-
 COSMOPOLITAN_C_START_
 
 /**

libc/runtime/efimain.greg.c

@@ -173,6 +173,7 @@ __msabi EFI_STATUS EfiMain(EFI_HANDLE ImageHandle,
   uint64_t Address;
   uintptr_t Args, MapKey, DescSize;
   uint64_t *pd, *pml4t, *pdt1, *pdt2, *pdpt1, *pdpt2;
+  const char16_t *CmdLine;
 
   extern char os asm("__hostos");
   os = _HOSTMETAL;
@@ -194,26 +195,28 @@ __msabi EFI_STATUS EfiMain(EFI_HANDLE ImageHandle,
   Address = 0x79000;
   SystemTable->BootServices->AllocatePages(
       AllocateAddress, EfiRuntimeServicesData,
-      (0x7e000 - 0x79000 + sizeof(struct EfiArgs) + 4095) / 4096, &Address);
+      (0x7f000 - 0x79000 + sizeof(struct EfiArgs) + 4095) / 4096, &Address);
   Address = IMAGE_BASE_PHYSICAL;
   SystemTable->BootServices->AllocatePages(
       AllocateAddress, EfiRuntimeServicesData,
       ((_end - __executable_start) + 4095) / 4096, &Address);
   mm = __get_mm_phy();
   SystemTable->BootServices->SetMem(mm, sizeof(*mm), 0);
   SystemTable->BootServices->SetMem(
-      (void *)0x79000, 0x7e000 - 0x79000 + sizeof(struct EfiArgs), 0);
+      (void *)0x79000, 0x7f000 - 0x79000 + sizeof(struct EfiArgs), 0);
   SystemTable->BootServices->CopyMem((void *)IMAGE_BASE_PHYSICAL,
                                      __executable_start,
                                      _end - __executable_start);
 
   /*
    * Converts UEFI shell arguments to argv.
    */
-  ArgBlock = (struct EfiArgs *)0x7e000;
+  ArgBlock = (struct EfiArgs *)0x7f000;
   SystemTable->BootServices->HandleProtocol(ImageHandle,
                                             &kEfiLoadedImageProtocol, &ImgInfo);
-  Args = GetDosArgv(ImgInfo->LoadOptions, ArgBlock->ArgBlock,
+  CmdLine = (const char16_t *)ImgInfo->LoadOptions;
+  if (!CmdLine || !CmdLine[0]) CmdLine = u"BOOTX64.EFI";
+  Args = GetDosArgv(CmdLine, ArgBlock->ArgBlock,
                     sizeof(ArgBlock->ArgBlock), ArgBlock->Args,
                     ARRAYLEN(ArgBlock->Args));
 

libc/vga/tty-graph.c

@@ -30,6 +30,7 @@
 #include "libc/vga/vga.internal.h"
 
 /**
+ * @internal
  * @fileoverview Instantiation of routines for normal console output in
  * graphical video modes.
  *

libc/vga/tty-graph.inc

@@ -31,6 +31,7 @@
 #include "libc/vga/vga.internal.h"
 
 /**
+ * @internal
  * @fileoverview Template for routines to support output in graphical video
  * modes for bare metal VGA.
  *

libc/vga/tty.greg.c

@@ -33,6 +33,7 @@
 #ifdef __x86_64__
 
 /**
+ * @internal
  * @fileoverview ECMA-48 / VT100 video terminal implementation for bare
  * metal VGA.
  *
@@ -325,6 +326,7 @@ static void TtySetCodepage(struct Tty *tty, char id) {
 }
 
 /**
+ * @internal
  * Map the given direct color value to one of the 16 basic foreground colors
  * or one of the 16 background colors.
  *
@@ -344,6 +346,7 @@ static uint8_t TtyGetTextColor(TtyCanvasColor color) {
 }
 
 /**
+ * @internal
  * Map the currently active foreground & background colors & terminal
  * configuration to a VGA text character attribute byte.
  *
@@ -794,12 +797,18 @@ static void TtyCsiN(struct Tty *tty) {
   }
 }
 
-/** Create a direct color pixel value. */
+/**
+ * @internal
+ * Create a direct color pixel value.
+ */
 static TtyCanvasColor TtyMapTrueColor(uint8_t r, uint8_t g, uint8_t b) {
   return (TtyCanvasColor){.bgr.r = r, .bgr.g = g, .bgr.b = b, .bgr.x = 0xff};
 }
 
-/** Map the given 256-color code to a direct color. */
+/**
+ * @internal
+ * Map the given 256-color code to a direct color.
+ */
 static TtyCanvasColor TtyMapXtermColor(uint8_t color) {
   uint8_t r, g, b;
   if (color < 8) {
@@ -822,7 +831,10 @@ static TtyCanvasColor TtyMapXtermColor(uint8_t color) {
   return TtyMapTrueColor(r, g, b);
 }
 
-/** Map the given ECMA-48 / VT100 SGR color code to a direct color. */
+/**
+ * @internal
+ * Map the given ECMA-48 / VT100 SGR color code to a direct color.
+ */
 static TtyCanvasColor TtyMapEcma48Color(uint8_t color) {
   return TtyMapXtermColor(color % 16);
 }

libc/vga/vga.internal.h

@@ -2,11 +2,20 @@
 #define COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
 #include "libc/runtime/mman.internal.h"
 
-/** Preferred width of the video screen, in character units. */
+/**
+ * @internal
+ * Preferred width of the video screen, in character units.
+ */
 #define VGA_PREFER_TTY_HEIGHT 30
-/** Preferred width of the video screen, in character units. */
+/**
+ * @internal
+ * Preferred width of the video screen, in character units.
+ */
 #define VGA_PREFER_TTY_WIDTH 80
-/** Assumed height of each character in pixels, in graphics modes. */
+/**
+ * @internal
+ * Assumed height of each character in pixels, in graphics modes.
+ */
 #define VGA_ASSUME_CHAR_HEIGHT_PX 16
 /** Assumed width of each character in pixels, in graphics modes. */
 #define VGA_ASSUME_CHAR_WIDTH_PX 8
@@ -18,6 +27,7 @@
  */
 
 /**
+ * @internal
  * If VGA_USE_WCS is defined, the tty code can maintain an array of the
  * Unicode characters "underlying" the 8-bit (or 9-bit) characters that are
  * actually displayed on the text screen.  This Unicode character
@@ -33,6 +43,7 @@
  */
 #undef VGA_USE_WCS
 /**
+ * @internal
  * The VGA hardware can be configured — via the IBM BIOS, or via port I/O —
  * to either support blinking characters, or support the use of bright
  * background colors, but not both.  There is a hardware setting that
@@ -67,6 +78,7 @@
  */
 #undef VGA_USE_BLINK
 /**
+ * @internal
  * If VGA_PERSNICKETY_STATUS is defined, then when deciding how to return
  * status response codes (e.g. "\e[0n"), the tty code will pay attention to
  * the terminal's termios mode (TODO).  If undefined, the tty code will
@@ -75,7 +87,10 @@
  */
 #undef VGA_PERSNICKETY_STATUS
 
-/* Flags which are passed to _StartTty(). */
+/**
+ * @internal
+ * Flags which are passed to _StartTty().
+ */
 #define kTtyAllocWcs                       \
   0x01 /* allocate Unicode character array \
           (if VGA_USE_WCS also defined) */
@@ -85,6 +100,7 @@
           to show system messages */
 
 /**
+ * @internal
  * Flags for Tty::pr.  These govern properties of individual character cells.
  */
 #define kTtyFg      0x0001
@@ -102,6 +118,7 @@
 #define kTtyConceal 0x1000
 
 /**
+ * @internal
  * Flags for Tty::conf.  These govern the current state of the teletypewriter
  * as a whole.
  */
@@ -153,6 +170,10 @@ typedef union {
 typedef TtyBgrxColor TtyCanvasColor;
 struct Tty;
 
+/**
+ * @internal
+ * Video console object type.
+ */
 struct Tty {
   /**
    * Cursor position.  (y, x) = (0, 0) means the cursor is on the top left