From 9473d9a241827b90b7f6db32b93e12bc77e2e44f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= <roger.pau@citrix.com>
Date: Mon, 10 Jul 2023 12:19:03 +0200
Subject: [PATCH] cmdline: parse multiple instances of the vga option
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Parse all instances of the vga= option on the command line, in order
to always enforce the last selection on the command line.

Note that it's not safe to parse just the last occurrence of the vga=
option, as then a command line with `vga=current vga=keep` would
result in current being ignored.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/boot/cmdline.c | 83 +++++++++++++++++++------------------
 1 file changed, 42 insertions(+), 41 deletions(-)

diff --git a/xen/arch/x86/boot/cmdline.c b/xen/arch/x86/boot/cmdline.c
index fc11c6d3c5..10dcc6142c 100644
--- a/xen/arch/x86/boot/cmdline.c
+++ b/xen/arch/x86/boot/cmdline.c
@@ -277,59 +277,60 @@ static u16 rows2vmode(unsigned int rows)
 
 static void vga_parse(const char *cmdline, early_boot_opts_t *ebo)
 {
-    const char *c;
-    unsigned int tmp, vesa_depth, vesa_height, vesa_width;
-
-    c = find_opt(cmdline, "vga=", true);
-
-    if ( !c )
-        return;
+    const char *c = cmdline;
 
     ebo->boot_vid_mode = ASK_VGA;
 
-    if ( !strmaxcmp(c, "current", delim_chars_comma) )
-        ebo->boot_vid_mode = VIDEO_CURRENT_MODE;
-    else if ( !strsubcmp(c, "text-80x") )
+    while ( (c = find_opt(c, "vga=", true)) != NULL )
     {
-        c += strlen("text-80x");
-        ebo->boot_vid_mode = rows2vmode(strtoui(c, delim_chars_comma, NULL));
-    }
-    else if ( !strsubcmp(c, "gfx-") )
-    {
-        vesa_width = strtoui(c + strlen("gfx-"), "x", &c);
+        unsigned int tmp, vesa_depth, vesa_height, vesa_width;
 
-        if ( vesa_width > U16_MAX )
-            return;
+        if ( !strmaxcmp(c, "current", delim_chars_comma) )
+            ebo->boot_vid_mode = VIDEO_CURRENT_MODE;
+        else if ( !strsubcmp(c, "text-80x") )
+        {
+            c += strlen("text-80x");
+            ebo->boot_vid_mode = rows2vmode(strtoui(c, delim_chars_comma, NULL));
+        }
+        else if ( !strsubcmp(c, "gfx-") )
+        {
+            vesa_width = strtoui(c + strlen("gfx-"), "x", &c);
 
-        /*
-         * Increment c outside of strtoui() because otherwise some
-         * compiler may complain with following message:
-         * warning: operation on 'c' may be undefined.
-         */
-        ++c;
-        vesa_height = strtoui(c, "x", &c);
+            if ( vesa_width > U16_MAX )
+                return;
 
-        if ( vesa_height > U16_MAX )
-            return;
+            /*
+             * Increment c outside of strtoui() because otherwise some
+             * compiler may complain with following message:
+             * warning: operation on 'c' may be undefined.
+             */
+            ++c;
+            vesa_height = strtoui(c, "x", &c);
 
-        vesa_depth = strtoui(++c, delim_chars_comma, NULL);
+            if ( vesa_height > U16_MAX )
+                return;
 
-        if ( vesa_depth > U16_MAX )
-            return;
+            vesa_depth = strtoui(++c, delim_chars_comma, NULL);
 
-        ebo->vesa_width = vesa_width;
-        ebo->vesa_height = vesa_height;
-        ebo->vesa_depth = vesa_depth;
-        ebo->boot_vid_mode = VIDEO_VESA_BY_SIZE;
-    }
-    else if ( !strsubcmp(c, "mode-") )
-    {
-        tmp = strtoui(c + strlen("mode-"), delim_chars_comma, NULL);
+            if ( vesa_depth > U16_MAX )
+                return;
 
-        if ( tmp > U16_MAX )
-            return;
+            ebo->vesa_width = vesa_width;
+            ebo->vesa_height = vesa_height;
+            ebo->vesa_depth = vesa_depth;
+            ebo->boot_vid_mode = VIDEO_VESA_BY_SIZE;
+        }
+        else if ( !strsubcmp(c, "mode-") )
+        {
+            tmp = strtoui(c + strlen("mode-"), delim_chars_comma, NULL);
 
-        ebo->boot_vid_mode = tmp;
+            if ( tmp > U16_MAX )
+                return;
+
+            ebo->boot_vid_mode = tmp;
+        }
+        else if ( !strmaxcmp(c, "ask", delim_chars_comma) )
+            ebo->boot_vid_mode = ASK_VGA;
     }
 }
 #endif