[Qemu-devel] [PATCH 1/2] bswap.h: export bswap_le

[Qemu-devel] [PATCH 1/2] bswap.h: export bswap_le

[Michael S. Tsirkin]

it's a handy API for cases where we want to
get size in bits as a parameter.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/qemu/bswap.h | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
index 0cb7c05..4489ad9 100644
--- a/include/qemu/bswap.h
+++ b/include/qemu/bswap.h
@@ -423,9 +423,4 @@ static inline unsigned long leul_to_cpu(unsigned long v)
 #endif
 }
 
-#undef le_bswap
-#undef be_bswap
-#undef le_bswaps
-#undef be_bswaps
-
 #endif /* BSWAP_H */
-- 
MST

[Qemu-devel] [PATCH 2/2] acpi-build: don't access unaligned addresses

[Michael S. Tsirkin]

casting an unaligned address to e.g.
uint32_t can trigger undefined behaviour in C.
Replace cast + assignment with memcpy.

Reported-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/i386/acpi-build.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index b667d31..e08f514 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -466,9 +466,15 @@ static void acpi_align_size(GArray *blob, unsigned align)
     g_array_set_size(blob, ROUND_UP(acpi_data_len(blob), align));
 }
 
-/* Get pointer within table in a safe manner */
-#define ACPI_BUILD_PTR(table, size, off, type) \
-    ((type *)(acpi_data_get_ptr(table, size, off, sizeof(type))))
+/* Set a value within table in a safe manner */
+#define ACPI_BUILD_SET_LE(table, size, off, bits, val) \
+    do { \
+        uint64_t ACPI_BUILD_SET_LE_val = le_bswap(val, bits); \
+        memcpy(acpi_data_get_ptr(table, size, off, \
+                                 (bits) / BITS_PER_BYTE), \
+               &ACPI_BUILD_SET_LE_val, \
+               (bits) / BITS_PER_BYTE); \
+    } while (0)
 
 static inline void *acpi_data_get_ptr(uint8_t *table_data, unsigned table_size,
                                       unsigned off, unsigned size)
@@ -974,22 +980,17 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
 
 static void patch_pci_windows(PcPciInfo *pci, uint8_t *start, unsigned size)
 {
-    *ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t) =
-        cpu_to_le32(pci->w32.begin);
+    ACPI_BUILD_SET_LE(start, size, acpi_pci32_start[0], 32, pci->w32.begin);
 
-    *ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t) =
-        cpu_to_le32(pci->w32.end - 1);
+    ACPI_BUILD_SET_LE(start, size, acpi_pci32_end[0], 32, pci->w32.end - 1);
 
     if (pci->w64.end || pci->w64.begin) {
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t) = 1;
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_start[0], uint64_t) =
-            cpu_to_le64(pci->w64.begin);
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_end[0], uint64_t) =
-            cpu_to_le64(pci->w64.end - 1);
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_length[0], uint64_t) =
-            cpu_to_le64(pci->w64.end - pci->w64.begin);
+        ACPI_BUILD_SET_LE(start, size, acpi_pci64_valid[0], 8, 1);
+        ACPI_BUILD_SET_LE(start, size, acpi_pci64_start[0], 64, pci->w64.begin);
+        ACPI_BUILD_SET_LE(start, size, acpi_pci64_end[0], 64, pci->w64.end - 1);
+        ACPI_BUILD_SET_LE(start, size, acpi_pci64_length[0], 64, pci->w64.end - pci->w64.begin);
     } else {
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t) = 0;
+        ACPI_BUILD_SET_LE(start, size, acpi_pci64_valid[0], 8, 0);
     }
 }
 
-- 
MST

Re: [Qemu-devel] [PATCH 1/2] bswap.h: export bswap_le

[Richard Henderson]

On 03/10/2014 12:43 PM, Michael S. Tsirkin wrote:
> it's a handy API for cases where we want to
> get size in bits as a parameter.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  include/qemu/bswap.h | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h
> index 0cb7c05..4489ad9 100644
> --- a/include/qemu/bswap.h
> +++ b/include/qemu/bswap.h
> @@ -423,9 +423,4 @@ static inline unsigned long leul_to_cpu(unsigned long v)
>  #endif
>  }
>  
> -#undef le_bswap
> -#undef be_bswap
> -#undef le_bswaps
> -#undef be_bswaps

I don't like this because the bits "as parameter" must be constant
in order for token pasting to work.  Better to just use the existing
function calls.


r~

Re: [Qemu-devel] [PATCH 2/2] acpi-build: don't access unaligned addresses

[Richard Henderson]

On 03/10/2014 12:43 PM, Michael S. Tsirkin wrote:
> casting an unaligned address to e.g.
> uint32_t can trigger undefined behaviour in C.
> Replace cast + assignment with memcpy.
> 
> Reported-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  hw/i386/acpi-build.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b667d31..e08f514 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -466,9 +466,15 @@ static void acpi_align_size(GArray *blob, unsigned align)
>      g_array_set_size(blob, ROUND_UP(acpi_data_len(blob), align));
>  }
>  
> -/* Get pointer within table in a safe manner */
> -#define ACPI_BUILD_PTR(table, size, off, type) \
> -    ((type *)(acpi_data_get_ptr(table, size, off, sizeof(type))))
> +/* Set a value within table in a safe manner */
> +#define ACPI_BUILD_SET_LE(table, size, off, bits, val) \
> +    do { \
> +        uint64_t ACPI_BUILD_SET_LE_val = le_bswap(val, bits); \
> +        memcpy(acpi_data_get_ptr(table, size, off, \
> +                                 (bits) / BITS_PER_BYTE), \
> +               &ACPI_BUILD_SET_LE_val, \
> +               (bits) / BITS_PER_BYTE); \
> +    } while (0)
>  
>  static inline void *acpi_data_get_ptr(uint8_t *table_data, unsigned table_size,
>                                        unsigned off, unsigned size)
> @@ -974,22 +980,17 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
>  
>  static void patch_pci_windows(PcPciInfo *pci, uint8_t *start, unsigned size)
>  {
> -    *ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t) =
> -        cpu_to_le32(pci->w32.begin);
> +    ACPI_BUILD_SET_LE(start, size, acpi_pci32_start[0], 32, pci->w32.begin);

You're working too hard at this because you're using the wrong bswap interface.

Also, you missed one.

I'll follow up with a patch I wrote just recently, but hadn't yet gotten around
to posting.


r~

[Qemu-devel] [PATCH] hw/i386: Use unaligned store functions building acpi tables

[Richard Henderson]

Hosts that don't support native unaligned stores will SIGBUS
without additional help.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 hw/i386/acpi-build.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index b1a7ebb..d636115 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -886,22 +886,24 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
 
 static void patch_pci_windows(PcPciInfo *pci, uint8_t *start, unsigned size)
 {
-    *ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t) =
-        cpu_to_le32(pci->w32.begin);
+    /* Note that these pointers are unaligned, so we must use routines
+       that take care for unaligned stores on the host.  */
 
-    *ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t) =
-        cpu_to_le32(pci->w32.end - 1);
+    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t),
+             pci->w32.begin);
+    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t),
+             pci->w32.end - 1);
 
     if (pci->w64.end || pci->w64.begin) {
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t) = 1;
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_start[0], uint64_t) =
-            cpu_to_le64(pci->w64.begin);
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_end[0], uint64_t) =
-            cpu_to_le64(pci->w64.end - 1);
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_length[0], uint64_t) =
-            cpu_to_le64(pci->w64.end - pci->w64.begin);
+        stb_p(ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t), 1);
+        stq_le_p(ACPI_BUILD_PTR(start, size, acpi_pci64_start[0], uint64_t),
+                 pci->w64.begin);
+        stq_le_p(ACPI_BUILD_PTR(start, size, acpi_pci64_end[0], uint64_t),
+                 pci->w64.end - 1);
+        stq_le_p(ACPI_BUILD_PTR(start, size, acpi_pci64_length[0], uint64_t),
+                 pci->w64.end - pci->w64.begin);
     } else {
-        *ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t) = 0;
+        stb_p(ACPI_BUILD_PTR(start, size, acpi_pci64_valid[0], uint8_t), 0);
     }
 }
 
@@ -930,8 +932,7 @@ build_ssdt(GArray *table_data, GArray *linker,
 
     patch_pci_windows(pci, ssdt_ptr, sizeof(ssdp_misc_aml));
 
-    *(uint16_t *)(ssdt_ptr + *ssdt_isa_pest) =
-        cpu_to_le16(misc->pvpanic_port);
+    stw_le_p(ssdt_ptr + *ssdt_isa_pest, misc->pvpanic_port);
 
     {
         GArray *sb_scope = build_alloc_array();
-- 
1.8.5.3

Re: [Qemu-devel] [PATCH] hw/i386: Use unaligned store functions building acpi tables

[Peter Maydell]

On 12 March 2014 22:25, Richard Henderson <rth@twiddle.net> wrote:
> Hosts that don't support native unaligned stores will SIGBUS
> without additional help.
>
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  hw/i386/acpi-build.c | 29 +++++++++++++++--------------
>  1 file changed, 15 insertions(+), 14 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b1a7ebb..d636115 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -886,22 +886,24 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
>
>  static void patch_pci_windows(PcPciInfo *pci, uint8_t *start, unsigned size)
>  {
> -    *ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t) =
> -        cpu_to_le32(pci->w32.begin);
> +    /* Note that these pointers are unaligned, so we must use routines
> +       that take care for unaligned stores on the host.  */
>
> -    *ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t) =
> -        cpu_to_le32(pci->w32.end - 1);
> +    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t),
> +             pci->w32.begin);
> +    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t),
> +             pci->w32.end - 1);

See the mail thread on Michael's original patch -- he didn't like
this because we end up writing the size of the store twice
(once in the "l" suffix in the function name and once by passing
a type to the ACP_BUILD_PTR function.

(That thread also has my personal preferred option in the comments,
which uses stl_le_p and friends but via a wrapping macro.)

Also you'll find this doesn't apply because a fix has already been
committed on master...

> -    *(uint16_t *)(ssdt_ptr + *ssdt_isa_pest) =
> -        cpu_to_le16(misc->pvpanic_port);
> +    stw_le_p(ssdt_ptr + *ssdt_isa_pest, misc->pvpanic_port);

Patch on list to fix this too I think.

thanks
-- PMM

Re: [Qemu-devel] [PATCH] hw/i386: Use unaligned store functions building acpi tables

[Richard Henderson]

On 03/12/2014 04:26 PM, Peter Maydell wrote:
> On 12 March 2014 22:25, Richard Henderson <rth@twiddle.net> wrote:
>> Hosts that don't support native unaligned stores will SIGBUS
>> without additional help.
>>
>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>> ---
>>  hw/i386/acpi-build.c | 29 +++++++++++++++--------------
>>  1 file changed, 15 insertions(+), 14 deletions(-)
>>
>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>> index b1a7ebb..d636115 100644
>> --- a/hw/i386/acpi-build.c
>> +++ b/hw/i386/acpi-build.c
>> @@ -886,22 +886,24 @@ static void build_pci_bus_end(PCIBus *bus, void *bus_state)
>>
>>  static void patch_pci_windows(PcPciInfo *pci, uint8_t *start, unsigned size)
>>  {
>> -    *ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t) =
>> -        cpu_to_le32(pci->w32.begin);
>> +    /* Note that these pointers are unaligned, so we must use routines
>> +       that take care for unaligned stores on the host.  */
>>
>> -    *ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t) =
>> -        cpu_to_le32(pci->w32.end - 1);
>> +    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_start[0], uint32_t),
>> +             pci->w32.begin);
>> +    stl_le_p(ACPI_BUILD_PTR(start, size, acpi_pci32_end[0], uint32_t),
>> +             pci->w32.end - 1);
> 
> See the mail thread on Michael's original patch -- he didn't like
> this because we end up writing the size of the store twice
> (once in the "l" suffix in the function name and once by passing
> a type to the ACP_BUILD_PTR function.

I missed the original thread somewhere.

> (That thread also has my personal preferred option in the comments,
> which uses stl_le_p and friends but via a wrapping macro.)

I'm in favour of any solution that doesn't duplicate the bswap logic, like the
version I responded to did.

r~

> 
> Also you'll find this doesn't apply because a fix has already been
> committed on master...
> 
>> -    *(uint16_t *)(ssdt_ptr + *ssdt_isa_pest) =
>> -        cpu_to_le16(misc->pvpanic_port);
>> +    stw_le_p(ssdt_ptr + *ssdt_isa_pest, misc->pvpanic_port);
> 
> Patch on list to fix this too I think.
> 
> thanks
> -- PMM
>