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From 2ee2492513f9685cb716dc1cb4cf5b580da43e07 Mon Sep 17 00:00:00 2001
From: Bandan Das <bsd@redhat.com>
Date: Wed, 25 Jan 2017 03:36:07 +0100
Subject: [PATCH 01/11] memory: Allow access only upto the maximum alignment
 for memory_region_* functions

RH-Author: Bandan Das <bsd@redhat.com>
Message-id: <jpgefzrn74o.fsf@linux.bootlegged.copy>
Patchwork-id: 73367
O-Subject: [RHEL-7.4 qemu-kvm PATCH] memory: Allow access only upto the maximum alignment for memory_region_* functions
Bugzilla: 1342768
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1342768
Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=12437870
Upstream: N/A, upstream doesn't exhibit this behavior

Currently, there is no check in memory_region_iorange_* functions for whether
the size requested is greater than the maximum alignment. This causes
an abort with a specific version of the Linux kernel (4.7.0-RC1):
/usr/libexec/qemu-kvm -kernel ~/vmlinuz-4.7.0-rc1 --enable-kvm -m 1G -vnc :2 -monitor stdio

0  0x00007fb057cb65f7 in raise () from /lib64/libc.so.6
1  0x00007fb057cb7ce8 in abort () from /lib64/libc.so.6
2  0x00007fb05eca5537 in acpi_gpe_ioport_readb ()
3  0x00007fb05eca5ff0 in gpe_readb ()
4  0x00007fb05ede6f4c in memory_region_read_accessor ()
5  0x00007fb05ede6993 in access_with_adjusted_size ()
6  0x00007fb05ede7ce8 in memory_region_iorange_read ()
7  0x00007fb05ede2ac7 in ioport_readl_thunk ()
8  0x00007fb05ede3141 in cpu_inl ()
9  0x00007fb05ede5c49 in kvm_cpu_exec ()
10 0x00007fb05ed98485 in qemu_kvm_cpu_thread_fn ()
11 0x00007fb05bcc9dc5 in start_thread () from /lib64/libpthread.so.0
12 0x00007fb057d77ced in clone () from /lib64/libc.so.6

This happens because guest code tries to read(l=4) from 0xafe2
with GPE base being 0xafe0 which causes the abort in
acpi_gpe_ioport_get_ptr() to trigger. This change adds a
memory_access_size() which is similar to the one in upstream that
forces size to be equal to the maximum alignment if it's greater.
It also keeps the other checks present in upstream for safety and
is called from the memory_region_read/write functions before
calling the call specific access functions.

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 memory.c | 44 ++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 40 insertions(+), 4 deletions(-)

diff --git a/memory.c b/memory.c
index 7bd6e87..573ecdd 100644
--- a/memory.c
+++ b/memory.c
@@ -381,6 +381,33 @@ static const MemoryRegionPortio *find_portio(MemoryRegion *mr, uint64_t offset,
     return NULL;
 }
 
+static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
+{
+  unsigned access_size_max = mr->ops->valid.max_access_size;
+
+  /* Regions are assumed to support 1-4 byte accesses unless
+     otherwise specified.  */
+  if (access_size_max == 0) {
+    access_size_max = 4;
+  }
+
+  /* Bound the maximum access by the alignment of the address.  */
+  if (!mr->ops->impl.unaligned) {
+    unsigned align_size_max = addr & -addr;
+    if (align_size_max != 0 && align_size_max < access_size_max) {
+        access_size_max = align_size_max;
+    }
+  }
+
+  /* Don't attempt accesses larger than the maximum.  */
+  if (l > access_size_max) {
+    l = access_size_max;
+  }
+  l = pow2floor(l);
+
+  return l;
+}
+
 static void memory_region_iorange_read(IORange *iorange,
                                        uint64_t offset,
                                        unsigned width,
@@ -389,6 +416,7 @@ static void memory_region_iorange_read(IORange *iorange,
     MemoryRegionIORange *mrio
         = container_of(iorange, MemoryRegionIORange, iorange);
     MemoryRegion *mr = mrio->mr;
+    unsigned l;
 
     offset += mrio->offset;
     if (mr->ops->old_portio) {
@@ -407,7 +435,8 @@ static void memory_region_iorange_read(IORange *iorange,
         return;
     }
     *data = 0;
-    access_with_adjusted_size(offset, data, width,
+    l = memory_access_size(mr, width, offset);
+    access_with_adjusted_size(offset, data, l,
                               mr->ops->impl.min_access_size,
                               mr->ops->impl.max_access_size,
                               memory_region_read_accessor, mr);
@@ -421,6 +450,7 @@ static void memory_region_iorange_write(IORange *iorange,
     MemoryRegionIORange *mrio
         = container_of(iorange, MemoryRegionIORange, iorange);
     MemoryRegion *mr = mrio->mr;
+    unsigned l;
 
     offset += mrio->offset;
     if (mr->ops->old_portio) {
@@ -437,7 +467,8 @@ static void memory_region_iorange_write(IORange *iorange,
         }
         return;
     }
-    access_with_adjusted_size(offset, &data, width,
+    l = memory_access_size(mr, width, offset);
+    access_with_adjusted_size(offset, &data, l,
                               mr->ops->impl.min_access_size,
                               mr->ops->impl.max_access_size,
                               memory_region_write_accessor, mr);
@@ -850,6 +881,7 @@ static uint64_t memory_region_dispatch_read1(MemoryRegion *mr,
                                              unsigned size)
 {
     uint64_t data = 0;
+    unsigned l;
 
     if (!memory_region_access_valid(mr, addr, size, false)) {
         return -1U; /* FIXME: better signalling */
@@ -859,8 +891,9 @@ static uint64_t memory_region_dispatch_read1(MemoryRegion *mr,
         return mr->ops->old_mmio.read[ctz32(size)](mr->opaque, addr);
     }
 
+    l = memory_access_size(mr, size, addr);
     /* FIXME: support unaligned access */
-    access_with_adjusted_size(addr, &data, size,
+    access_with_adjusted_size(addr, &data, l,
                               mr->ops->impl.min_access_size,
                               mr->ops->impl.max_access_size,
                               memory_region_read_accessor, mr);
@@ -902,6 +935,8 @@ static void memory_region_dispatch_write(MemoryRegion *mr,
                                          uint64_t data,
                                          unsigned size)
 {
+    unsigned l;
+
     if (!memory_region_access_valid(mr, addr, size, true)) {
         return; /* FIXME: better signalling */
     }
@@ -913,8 +948,9 @@ static void memory_region_dispatch_write(MemoryRegion *mr,
         return;
     }
 
+    l = memory_access_size(mr, size, addr);
     /* FIXME: support unaligned access */
-    access_with_adjusted_size(addr, &data, size,
+    access_with_adjusted_size(addr, &data, l,
                               mr->ops->impl.min_access_size,
                               mr->ops->impl.max_access_size,
                               memory_region_write_accessor, mr);
-- 
1.8.3.1