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Re: [Qemu-devel] [PATCH] bios-tables-test: handle false-positive smbios


From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH] bios-tables-test: handle false-positive smbios signature matches
Date: Tue, 28 Apr 2015 21:42:57 +0200

On Tue, Apr 28, 2015 at 03:40:37PM -0400, Gabriel L. Somlo wrote:
> ping ?
> 
> On Tue, Mar 31, 2015 at 02:32:20PM -0400, Gabriel L. Somlo wrote:
> > Rather than stopping at the first match for the SMBIOS signature
> > ("_SM_") in the f-segment (0xF0000-0xFFFFF), continue scanning
> > until either a valid entry point table is found, or the f-segment
> > has been exhausted.
> > 
> > Signed-off-by: Gabriel Somlo <address@hidden>

I'm curious why do you want to do this.
Can you add this info in the commmit log?

> > ---
> >  tests/bios-tables-test.c | 76 
> > ++++++++++++++++++++++++++++--------------------
> >  1 file changed, 44 insertions(+), 32 deletions(-)
> > 
> > diff --git a/tests/bios-tables-test.c b/tests/bios-tables-test.c
> > index 735ac61..f79d89a 100644
> > --- a/tests/bios-tables-test.c
> > +++ b/tests/bios-tables-test.c
> > @@ -599,35 +599,15 @@ static void test_acpi_asl(test_data *data)
> >      free_test_data(&exp_data);
> >  }
> >  
> > -static void test_smbios_ep_address(test_data *data)
> > -{
> > -    uint32_t off;
> > -
> > -    /* find smbios entry point structure */
> > -    for (off = 0xf0000; off < 0x100000; off += 0x10) {
> > -        uint8_t sig[] = "_SM_";
> > -        int i;
> > -
> > -        for (i = 0; i < sizeof sig - 1; ++i) {
> > -            sig[i] = readb(off + i);
> > -        }
> > -
> > -        if (!memcmp(sig, "_SM_", sizeof sig)) {
> > -            break;
> > -        }
> > -    }
> > -
> > -    g_assert_cmphex(off, <, 0x100000);
> > -    data->smbios_ep_addr = off;
> > -}
> > -
> > -static void test_smbios_ep_table(test_data *data)
> > +static bool smbios_ep_table_ok(test_data *data)
> >  {
> >      struct smbios_entry_point *ep_table = &data->smbios_ep_table;
> >      uint32_t addr = data->smbios_ep_addr;
> >  
> >      ACPI_READ_ARRAY(ep_table->anchor_string, addr);
> > -    g_assert(!memcmp(ep_table->anchor_string, "_SM_", 4));
> > +    if (memcmp(ep_table->anchor_string, "_SM_", 4)) {
> > +        return false;
> > +    }
> >      ACPI_READ_FIELD(ep_table->checksum, addr);
> >      ACPI_READ_FIELD(ep_table->length, addr);
> >      ACPI_READ_FIELD(ep_table->smbios_major_version, addr);
> > @@ -636,17 +616,50 @@ static void test_smbios_ep_table(test_data *data)
> >      ACPI_READ_FIELD(ep_table->entry_point_revision, addr);
> >      ACPI_READ_ARRAY(ep_table->formatted_area, addr);
> >      ACPI_READ_ARRAY(ep_table->intermediate_anchor_string, addr);
> > -    g_assert(!memcmp(ep_table->intermediate_anchor_string, "_DMI_", 5));
> > +    if (memcmp(ep_table->intermediate_anchor_string, "_DMI_", 5)) {
> > +        return false;
> > +    }
> >      ACPI_READ_FIELD(ep_table->intermediate_checksum, addr);
> >      ACPI_READ_FIELD(ep_table->structure_table_length, addr);
> > -    g_assert_cmpuint(ep_table->structure_table_length, >, 0);
> > +    if (ep_table->structure_table_length == 0) {
> > +        return false;
> > +    }
> >      ACPI_READ_FIELD(ep_table->structure_table_address, addr);
> >      ACPI_READ_FIELD(ep_table->number_of_structures, addr);
> > -    g_assert_cmpuint(ep_table->number_of_structures, >, 0);
> > +    if (ep_table->number_of_structures == 0) {
> > +        return false;
> > +    }
> >      ACPI_READ_FIELD(ep_table->smbios_bcd_revision, addr);
> > -    g_assert(!acpi_checksum((uint8_t *)ep_table, sizeof *ep_table));
> > -    g_assert(!acpi_checksum((uint8_t *)ep_table + 0x10,
> > -                            sizeof *ep_table - 0x10));
> > +    if (acpi_checksum((uint8_t *)ep_table, sizeof *ep_table) ||
> > +        acpi_checksum((uint8_t *)ep_table + 0x10, sizeof *ep_table - 
> > 0x10)) {
> > +        return false;
> > +    }
> > +    return true;
> > +}
> > +
> > +static void test_smbios_entry_point(test_data *data)
> > +{
> > +    uint32_t off;
> > +
> > +    /* find smbios entry point structure */
> > +    for (off = 0xf0000; off < 0x100000; off += 0x10) {
> > +        uint8_t sig[] = "_SM_";
> > +        int i;
> > +
> > +        for (i = 0; i < sizeof sig - 1; ++i) {
> > +            sig[i] = readb(off + i);
> > +        }
> > +
> > +        if (!memcmp(sig, "_SM_", sizeof sig)) {
> > +            /* signature match, but is this a valid entry point? */
> > +            data->smbios_ep_addr = off;
> > +            if (smbios_ep_table_ok(data)) {
> > +                break;
> > +            }
> > +        }
> > +    }
> > +
> > +    g_assert_cmphex(off, <, 0x100000);
> >  }
> >  
> >  static inline bool smbios_single_instance(uint8_t type)
> > @@ -767,8 +780,7 @@ static void test_acpi_one(const char *params, test_data 
> > *data)
> >          }
> >      }
> >  
> > -    test_smbios_ep_address(data);
> > -    test_smbios_ep_table(data);
> > +    test_smbios_entry_point(data);
> >      test_smbios_structs(data);
> >  
> >      qtest_quit(global_qtest);
> > -- 
> > 2.1.0
> > 



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