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Re: [Qemu-devel] [PATCH RFC 4/7] hw/apci: fix pcihp io initialization


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH RFC 4/7] hw/apci: fix pcihp io initialization
Date: Tue, 21 Jun 2016 11:57:29 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

On 06/17/2016 12:04 PM, Igor Mammedov wrote:
On Tue, 31 May 2016 20:48:35 +0300
Marcel Apfelbaum <address@hidden> wrote:

The pm initialization code assigns the pcihp IO base and length to -1 on error,
but the later code will assume 0 as invalid value.

Fix it initializing the above value to 0 as expected.

Signed-off-by: Marcel Apfelbaum <address@hidden>
---
  hw/i386/acpi-build.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 0c329fb..2097c4c 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -124,17 +124,19 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
      Object *lpc = ich9_lpc_find();
      Object *obj = NULL;
      QObject *o;
+    int pcihp_io_len, pcihp_io_base;

      pm->cpu_hp_io_base = 0;
-    pm->pcihp_io_base = 0;
-    pm->pcihp_io_len = 0;
this introduces uninitialized memory access in q35 case


How? We are always checking pcihp_io_len/pcihp_io_base.

      if (piix) {
          obj = piix;
          pm->cpu_hp_io_base = PIIX4_CPU_HOTPLUG_IO_BASE;
-        pm->pcihp_io_base =
+        pcihp_io_base =
              object_property_get_int(obj, ACPI_PCIHP_IO_BASE_PROP, NULL);
-        pm->pcihp_io_len =
+        pcihp_io_len =
              object_property_get_int(obj, ACPI_PCIHP_IO_LEN_PROP, NULL);
+
+        pm->pcihp_io_base = (pcihp_io_base == -1) ? 0 : pcihp_io_base;
+        pm->pcihp_io_len = (pcihp_io_len == -1) ? 0 : pcihp_io_len;
      }
      if (lpc) {
          obj = lpc;

how about something like that:

Please see the next patch. It is only  a temporary measure, the next patch
initialize it right to ACPI_PCIHP_IO_BASE_PROP/ACPI_PCIHP_IO_LEN_PROP.
If the properties are not there, they will be 0, but we are checking this 
everywhere.

Also I'll prefer pm->pcihp_io_len 0 length to mean "unused" because it is used 
widely.
If you still think is a real issue, I'll change this, of course.


Thanks,
Marcel


diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 4f9aec6..d753e25 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -125,7 +125,7 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)

      pm->cpu_hp_io_base = 0;
      pm->pcihp_io_base = 0;
-    pm->pcihp_io_len = 0;
+    pm->pcihp_io_len = UINT16_MAX;
      if (piix) {
          obj = piix;
          pm->cpu_hp_io_base = PIIX4_CPU_HOTPLUG_IO_BASE;
@@ -2053,7 +2053,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
      g_ptr_array_free(mem_ranges, true);

      /* reserve PCIHP resources */
-    if (pm->pcihp_io_len) {
+    if (pm->pcihp_io_len != UINT16_MAX) {
          dev = aml_device("PHPR");
          aml_append(dev, aml_name_decl("_HID", aml_string("PNP0A06")));
          aml_append(dev,





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