[PATCH v4 1/3] multiboot2: parse vga= option when setting GOP mode

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Introduce support for passing the command line to the efi_multiboot2()
helper, and parse the vga= option if present.

Add support for the 'gfx' and 'current' vga options, ignore the 'keep'
option, and print a warning message about other options not being
currently implemented.

Note that the multboot2 command line string must always be
zero-terminated according to the multiboot2 specification, and hence
there's no need to pass the string size to efi_multiboot2().

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v3:
 - s/last/cur/
 - asm style fixes.
 - Add note about cmdline always being 0 terminated.
 - Also allow \t as valid option separator (as space).
 - Expand comment about expected get_option() behavior.
 - Always check for valid option terminator.

Changes since v2:
 - Do not parse console=.
 - Allow width or height to be 0 as long as the gfx- option is well
   formed.

Changes since v1:
 - Do not return the last occurrence of a command line.
 - Rearrange the code for assembly processing of the cmdline and use
   lea.
 - Merge patches handling console= and vga= together.
---
 xen/arch/x86/boot/head.S          | 13 +++++-
 xen/arch/x86/efi/efi-boot.h       | 74 ++++++++++++++++++++++++++++++-
 xen/arch/x86/x86_64/asm-offsets.c |  1 +
 3 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index e03f52c75535..1eb829ab419f 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -237,9 +237,10 @@ __efi64_mb2_start:
         jmp     x86_32_switch
 
 .Lefi_multiboot2_proto:
-        /* Zero EFI SystemTable and EFI ImageHandle addresses. */
+        /* Zero EFI SystemTable, EFI ImageHandle addresses and cmdline. */
         xor     %esi,%esi
         xor     %edi,%edi
+        xor     %edx,%edx
 
         /* Skip Multiboot2 information fixed part. */
         lea     (MB2_fixed_sizeof+MULTIBOOT2_TAG_ALIGN-1)(%rbx),%ecx
@@ -277,6 +278,13 @@ __efi64_mb2_start:
         cmove   MB2_efi64_ih(%rcx),%rdi
         je      .Lefi_mb2_next_tag
 
+        /* Get command line from Multiboot2 information. */
+        cmpl    $MULTIBOOT2_TAG_TYPE_CMDLINE, MB2_tag_type(%rcx)
+        jne     .Lno_cmdline
+        lea     MB2_tag_string(%rcx), %rdx
+        jmp     .Lefi_mb2_next_tag
+.Lno_cmdline:
+
         /* Is it the end of Multiboot2 information? */
         cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
         je      .Lrun_bs
@@ -340,7 +348,8 @@ __efi64_mb2_start:
 
         /*
          * efi_multiboot2() is called according to System V AMD64 ABI:
-         *   - IN:  %rdi - EFI ImageHandle, %rsi - EFI SystemTable.
+         *   - IN:  %rdi - EFI ImageHandle, %rsi - EFI SystemTable,
+         *          %rdx - MB2 cmdline
          */
         call    efi_multiboot2
 
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 64c1a02cf10a..4394c7276aa3 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -795,7 +795,30 @@ static bool __init 
efi_arch_use_config_file(EFI_SYSTEM_TABLE *SystemTable)
 
 static void __init efi_arch_flush_dcache_area(const void *vaddr, UINTN size) { 
}
 
-void __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable)
+/* Return a pointer to the character after the first occurrence of opt in cmd 
*/
+static const char __init *get_option(const char *cmd, const char *opt)
+{
+    const char *s = cmd, *o = NULL;
+
+    if ( !cmd || !opt )
+        return NULL;
+
+    while ( (s = strstr(s, opt)) != NULL )
+    {
+        if ( s == cmd || *(s - 1) == ' ' || *(s - 1) == '\t' )
+        {
+            o = s + strlen(opt);
+            break;
+        }
+
+        s += strlen(opt);
+    }
+
+    return o;
+}
+
+void __init efi_multiboot2(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE 
*SystemTable,
+                           const char *cmdline)
 {
     EFI_GRAPHICS_OUTPUT_PROTOCOL *gop;
     EFI_HANDLE gop_handle;
@@ -816,7 +839,54 @@ void __init efi_multiboot2(EFI_HANDLE ImageHandle, 
EFI_SYSTEM_TABLE *SystemTable
 
     if ( gop )
     {
-        gop_mode = efi_find_gop_mode(gop, 0, 0, 0);
+        const char *cur = cmdline;
+        unsigned int width = 0, height = 0, depth = 0;
+        bool keep_current = false;
+
+        while ( (cur = get_option(cur, "vga=")) != NULL )
+        {
+#define VALID_TERMINATOR(c) \
+    (*(c) == ' ' || *(c) == '\t' || *(c) == '\0' || *(c) == ',')
+            if ( !strncmp(cur, "gfx-", 4) )
+            {
+                width = simple_strtoul(cur + 4, &cur, 10);
+
+                if ( *cur == 'x' )
+                    height = simple_strtoul(cur + 1, &cur, 10);
+                else
+                    goto error;
+
+                if ( *cur == 'x' )
+                    depth = simple_strtoul(cur + 1, &cur, 10);
+                else
+                    goto error;
+
+                if ( !VALID_TERMINATOR(cur) )
+                {
+error:
+                    PrintStr(L"Warning: Invalid gfx- option detected.\r\n");
+                    width = height = depth = 0;
+                }
+                keep_current = false;
+            }
+            else if ( !strncmp(cur, "current", 7) && VALID_TERMINATOR(cur + 7) 
)
+                keep_current = true;
+            else if ( !strncmp(cur, "keep", 4) && VALID_TERMINATOR(cur + 4) )
+            {
+                /* Ignore, handled in later vga= parsing. */
+            }
+            else
+            {
+                /* Fallback to defaults if unimplemented. */
+                width = height = depth = 0;
+                keep_current = false;
+                PrintStr(L"Warning: Cannot use selected vga option.\r\n");
+            }
+#undef VALID_TERMINATOR
+        }
+
+        if ( !keep_current )
+            gop_mode = efi_find_gop_mode(gop, width, height, depth);
 
         efi_arch_edid(gop_handle);
     }
diff --git a/xen/arch/x86/x86_64/asm-offsets.c 
b/xen/arch/x86/x86_64/asm-offsets.c
index 287dac101ad4..fbd6c54188db 100644
--- a/xen/arch/x86/x86_64/asm-offsets.c
+++ b/xen/arch/x86/x86_64/asm-offsets.c
@@ -175,6 +175,7 @@ void __dummy__(void)
     OFFSET(MB2_mem_lower, multiboot2_tag_basic_meminfo_t, mem_lower);
     OFFSET(MB2_efi64_st, multiboot2_tag_efi64_t, pointer);
     OFFSET(MB2_efi64_ih, multiboot2_tag_efi64_ih_t, pointer);
+    OFFSET(MB2_tag_string, multiboot2_tag_string_t, string);
     BLANK();
 
     OFFSET(DOMAIN_vm_assist, struct domain, vm_assist);
-- 
2.41.0