[PATCH 13/78] hw/i386/pc: fix regression in parsing vga cmdline parameter

[Michael Roth]

From: Peter Wu <peter@lekensteyn.nl>

When the 'vga=' parameter is succeeded by another parameter, QEMU 4.2.0
would refuse to start with a rather cryptic message:

    $ qemu-system-x86_64 -kernel /boot/vmlinuz-linux -append 'vga=792 quiet'
    qemu: can't parse 'vga' parameter: Invalid argument

It was not clear whether this applied to the '-vga std' parameter or the
'-append' one. Fix the parsing regression and clarify the error.

Fixes: 133ef074bd ("hw/i386/pc: replace use of strtol with qemu_strtoui in 
x86_load_linux()")
Cc: Sergio Lopez <slp@redhat.com>
Signed-off-by: Peter Wu <peter@lekensteyn.nl>
Message-Id: <20191221162124.1159291-1-peter@lekensteyn.nl>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit a88c40f02ace88f09b2a85a64831b277b2ebc88c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 hw/i386/x86.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index 394edc2f72..121650ae51 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -508,6 +508,7 @@ void x86_load_linux(X86MachineState *x86ms,
     vmode = strstr(kernel_cmdline, "vga=");
     if (vmode) {
         unsigned int video_mode;
+        const char *end;
         int ret;
         /* skip "vga=" */
         vmode += 4;
@@ -518,10 +519,9 @@ void x86_load_linux(X86MachineState *x86ms,
         } else if (!strncmp(vmode, "ask", 3)) {
             video_mode = 0xfffd;
         } else {
-            ret = qemu_strtoui(vmode, NULL, 0, &video_mode);
-            if (ret != 0) {
-                fprintf(stderr, "qemu: can't parse 'vga' parameter: %s\n",
-                        strerror(-ret));
+            ret = qemu_strtoui(vmode, &end, 0, &video_mode);
+            if (ret != 0 || (*end && *end != ' ')) {
+                fprintf(stderr, "qemu: invalid 'vga=' kernel parameter.\n");
                 exit(1);
             }
         }
-- 
2.17.1