Re: [Qemu-devel] [PATCH v3 3/5] hw/acpi: Use QEMU_NONSTRING for non NUL-terminated arrays

[Igor Mammedov]

On Tue, 18 Dec 2018 18:51:20 +0100
Philippe Mathieu-Daudé <address@hidden> wrote:

> GCC 8 added a -Wstringop-truncation warning:
> 
>   The -Wstringop-truncation warning added in GCC 8.0 via r254630 for
>   bug 81117 is specifically intended to highlight likely unintended
>   uses of the strncpy function that truncate the terminating NUL
>   character from the source string.
> 
> This new warning leads to compilation failures:
> 
>     CC      hw/acpi/core.o
>   In function 'acpi_table_install', inlined from 'acpi_table_add' at 
> qemu/hw/acpi/core.c:296:5:
>   qemu/hw/acpi/core.c:184:9: error: 'strncpy' specified bound 4 equals 
> destination size [-Werror=stringop-truncation]
>            strncpy(ext_hdr->sig, hdrs->sig, sizeof ext_hdr->sig);
>            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   make: *** [qemu/rules.mak:69: hw/acpi/core.o] Error 1
> 
> Use the QEMU_NONSTRING attribute, since ACPI tables don't require the
> strings to be NUL-terminated.
> 
> Suggested-by: Michael S. Tsirkin <address@hidden>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  hw/acpi/core.c              | 8 ++++----
>  include/hw/acpi/acpi-defs.h | 8 ++++----
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/acpi/core.c b/hw/acpi/core.c
> index aafdc61648..f60f750c3d 100644
> --- a/hw/acpi/core.c
> +++ b/hw/acpi/core.c
> @@ -35,14 +35,14 @@
>  struct acpi_table_header {
>      uint16_t _length;         /* our length, not actual part of the hdr */
>                                /* allows easier parsing for fw_cfg clients */
> -    char sig[4];              /* ACPI signature (4 ASCII characters) */
> +    char sig[4] QEMU_NONSTRING; /* ACPI signature (4 ASCII characters) */
>      uint32_t length;          /* Length of table, in bytes, including header 
> */
>      uint8_t revision;         /* ACPI Specification minor version # */
>      uint8_t checksum;         /* To make sum of entire table == 0 */
> -    char oem_id[6];           /* OEM identification */
> -    char oem_table_id[8];     /* OEM table identification */
> +    char oem_id[6] QEMU_NONSTRING; /* OEM identification */
> +    char oem_table_id[8] QEMU_NONSTRING; /* OEM table identification */
>      uint32_t oem_revision;    /* OEM revision number */
> -    char asl_compiler_id[4];  /* ASL compiler vendor ID */
> +    char asl_compiler_id[4] QEMU_NONSTRING; /* ASL compiler vendor ID */
>      uint32_t asl_compiler_revision; /* ASL compiler revision number */
>  } QEMU_PACKED;
>  
> diff --git a/include/hw/acpi/acpi-defs.h b/include/hw/acpi/acpi-defs.h
> index af8e023968..3bf0bec8ba 100644
> --- a/include/hw/acpi/acpi-defs.h
> +++ b/include/hw/acpi/acpi-defs.h
> @@ -43,7 +43,7 @@ enum {
>  struct AcpiRsdpDescriptor {        /* Root System Descriptor Pointer */
>      uint64_t signature;              /* ACPI signature, contains "RSD PTR " 
> */
>      uint8_t  checksum;               /* To make sum of struct == 0 */
> -    uint8_t  oem_id [6];             /* OEM identification */
> +    uint8_t  oem_id [6] QEMU_NONSTRING; /* OEM identification */
>      uint8_t  revision;               /* Must be 0 for 1.0, 2 for 2.0 */
>      uint32_t rsdt_physical_address;  /* 32-bit physical address of RSDT */
>      uint32_t length;                 /* XSDT Length in bytes including hdr */

you'll need to rebase this on top the latest Michael's pull request.
[PULL v2 25/30] hw: arm: Carry RSDP specific data through  AcpiRsdpData
[PULL v2 29/30] hw: acpi: Remove AcpiRsdpDescriptor and fix tests

> @@ -62,10 +62,10 @@ typedef struct AcpiRsdpDescriptor AcpiRsdpDescriptor;
>      uint32_t length;                 /* Length of table, in bytes, including 
> header */ \
>      uint8_t  revision;               /* ACPI Specification minor version # 
> */ \
>      uint8_t  checksum;               /* To make sum of entire table == 0 */ \
> -    uint8_t  oem_id [6];             /* OEM identification */ \
> -    uint8_t  oem_table_id [8];       /* OEM table identification */ \
> +    uint8_t  oem_id [6] QEMU_NONSTRING; /* OEM identification */ \
> +    uint8_t  oem_table_id [8] QEMU_NONSTRING; /* OEM table identification */ 
> \
>      uint32_t oem_revision;           /* OEM revision number */ \
> -    uint8_t  asl_compiler_id [4];    /* ASL compiler vendor ID */ \
> +    uint8_t  asl_compiler_id [4] QEMU_NONSTRING; /* ASL compiler vendor ID 
> */ \
>      uint32_t asl_compiler_revision;  /* ASL compiler revision number */
>  
>