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From ddfee9d393af322938e4df466cd01b8f9570a1c9 Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Tue, 5 Apr 2022 10:20:59 +0200
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Subject: [PATCH 1/6] s390x/ipl: support extended kernel command line size
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RH-Author: Thomas Huth <thuth@redhat.com>
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RH-MergeRequest: 144: s390x/ipl: support extended kernel command line size
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RH-Commit: [1/1] be227e50af5dbe7802605f873db29ac5358aa196
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RH-Bugzilla: 2043830
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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Bugzilla: http://bugzilla.redhat.com/2043830
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commit b2173046a64beed76715f310f98538f159276af1
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Author: Marc Hartmayer <mhartmay@linux.ibm.com>
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Date:   Mon Nov 22 12:29:09 2021 +0100
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    s390x/ipl: support extended kernel command line size
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    In the past s390 used a fixed command line length of 896 bytes. This has changed
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    with the Linux commit 5ecb2da660ab ("s390: support command lines longer than 896
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    bytes"). There is now a parm area indicating the maximum command line size. This
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    parm area has always been initialized to zero, so with older kernels this field
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    would read zero and we must then assume that only 896 bytes are available.
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    Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
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    Reviewed-by: David Hildenbrand <david@redhat.com>
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    Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
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    Acked-by: Viktor Mihajlovski <mihajlov@de.ibm.com>
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    Message-Id: <20211122112909.18138-1-mhartmay@linux.ibm.com>
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    [thuth: Cosmetic fixes, and use PRIu64 instead of %lu]
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    Signed-off-by: Thomas Huth <thuth@redhat.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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---
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 hw/s390x/ipl.c | 27 +++++++++++++++++++++++----
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 1 file changed, 23 insertions(+), 4 deletions(-)
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diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
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index 7ddca0127f..eb7fc4c4ae 100644
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--- a/hw/s390x/ipl.c
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+++ b/hw/s390x/ipl.c
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@@ -37,8 +37,9 @@
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 #define KERN_IMAGE_START                0x010000UL
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 #define LINUX_MAGIC_ADDR                0x010008UL
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+#define KERN_PARM_AREA_SIZE_ADDR        0x010430UL
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 #define KERN_PARM_AREA                  0x010480UL
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-#define KERN_PARM_AREA_SIZE             0x000380UL
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+#define LEGACY_KERN_PARM_AREA_SIZE      0x000380UL
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 #define INITRD_START                    0x800000UL
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 #define INITRD_PARM_START               0x010408UL
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 #define PARMFILE_START                  0x001000UL
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@@ -110,6 +111,21 @@ static uint64_t bios_translate_addr(void *opaque, uint64_t srcaddr)
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     return srcaddr + dstaddr;
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 }
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+static uint64_t get_max_kernel_cmdline_size(void)
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+{
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+    uint64_t *size_ptr = rom_ptr(KERN_PARM_AREA_SIZE_ADDR, sizeof(*size_ptr));
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+
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+    if (size_ptr) {
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+        uint64_t size;
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+
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+        size = be64_to_cpu(*size_ptr);
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+        if (size) {
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+            return size;
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+        }
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+    }
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+    return LEGACY_KERN_PARM_AREA_SIZE;
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+}
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+
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 static void s390_ipl_realize(DeviceState *dev, Error **errp)
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 {
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     MachineState *ms = MACHINE(qdev_get_machine());
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@@ -197,10 +213,13 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
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             ipl->start_addr = KERN_IMAGE_START;
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             /* Overwrite parameters in the kernel image, which are "rom" */
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             if (parm_area) {
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-                if (cmdline_size > KERN_PARM_AREA_SIZE) {
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+                uint64_t max_cmdline_size = get_max_kernel_cmdline_size();
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+
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+                if (cmdline_size > max_cmdline_size) {
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                     error_setg(errp,
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-                               "kernel command line exceeds maximum size: %zu > %lu",
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-                               cmdline_size, KERN_PARM_AREA_SIZE);
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+                               "kernel command line exceeds maximum size:"
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+                               " %zu > %" PRIu64,
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+                               cmdline_size, max_cmdline_size);
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                     return;
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                 }
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-- 
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2.27.0
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