[PATCH 4/5] multiboot2: parse console= option when setting GOP mode

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

Only set the GOP mode if vga is selected in the console option,
otherwise just fetch the information from the current mode in order to
make it available to dom0.

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

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
I'm unsure why the parsing of the multiboot2 tags is done in assembly,
it could very well be done in efi_multiboot2() in C, but I don't want
to switch that code now.
---
 xen/arch/x86/boot/head.S          | 15 ++++++++++++--
 xen/arch/x86/efi/efi-boot.h       | 33 +++++++++++++++++++++++++++++--
 xen/arch/x86/x86_64/asm-offsets.c |  1 +
 3 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 0fb7dd3029..6920ad08d1 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -221,9 +221,10 @@ __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
@@ -265,6 +266,15 @@ __efi64_mb2_start:
         cmpl    $MULTIBOOT2_TAG_TYPE_END,MB2_tag_type(%rcx)
         je      .Lrun_bs
 
+        /*
+         * Get command line from Multiboot2 information.
+         * Must be last parsed tag.
+         */
+        cmpl    $MULTIBOOT2_TAG_TYPE_CMDLINE,MB2_tag_type(%rcx)
+        jne     .Lefi_mb2_next_tag
+        mov     %rcx,%rdx
+        add     $(MB2_tag_string),%rdx
+
 .Lefi_mb2_next_tag:
         /* Go to next Multiboot2 information tag. */
         add     MB2_tag_size(%rcx),%ecx
@@ -324,7 +334,8 @@ __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 27f928ed3c..695491a5b7 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -786,7 +786,22 @@ 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 the last occurrence of opt in cmd. */
+static const char __init *get_option(const char *cmd, const char *opt)
+{
+    const char *s = cmd, *o = NULL;
+
+    while ( (s = strstr(s, opt)) != NULL )
+    {
+        s += strlen(opt);
+        o = s;
+    }
+
+    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;
@@ -807,7 +822,21 @@ 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 *opt = get_option(cmdline, "console=");
+        bool vga = false;
+
+        if ( opt )
+        {
+            const char *s = strstr(opt, "vga");
+
+            if ( s && s < strpbrk(opt, " \0"))
+                vga = true;
+        }
+
+        if ( vga )
+        {
+            gop_mode = efi_find_gop_mode(gop, 0, 0, 0);
+        }
 
         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 287dac101a..fbd6c54188 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);
-- 
2.37.3