Re: [Qemu-devel] [Qemu-arm] [PATCH v4 5/6] loader: Implement .hex file loader

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Hi Su,

On 08/03/2018 11:47 AM, Stefan Hajnoczi wrote:
> From: Su Hang <suhang16@mails.ucas.ac.cn>
> 
> This patch adds Intel Hexadecimal Object File format support to the
> generic loader device.  The file format specification is available here:
> http://www.piclist.com/techref/fileext/hex/intel.htm
> 
> This file format is often used with microcontrollers such as the
> micro:bit, Arduino, STM32, etc.  Users expect to be able to run .hex
> files directly with without first converting them to ELF.  Most
> micro:bit code is developed in web-based IDEs without direct user access
> to binutils so it is important for QEMU to handle this file format
> natively.
> 
> Signed-off-by: Su Hang <suhang16@mails.ucas.ac.cn>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  include/hw/loader.h      |  12 ++
>  hw/core/generic-loader.c |   4 +
>  hw/core/loader.c         | 243 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 259 insertions(+)
> 
> diff --git a/include/hw/loader.h b/include/hw/loader.h
> index 5235f119a3..3c112975f4 100644
> --- a/include/hw/loader.h
> +++ b/include/hw/loader.h
> @@ -28,6 +28,18 @@ ssize_t load_image_size(const char *filename, void *addr, size_t size);
>  int load_image_targphys_as(const char *filename,
>                             hwaddr addr, uint64_t max_sz, AddressSpace *as);
>  
> +/**load_targphys_hex_as:
> + * @filename: Path to the .hex file
> + * @entry: Store the entry point given by the .hex file
> + * @as: The AddressSpace to load the .hex file to. The value of
> + *      address_space_memory is used if nothing is supplied here.
> + *
> + * Load a fixed .hex file into memory.
> + *
> + * Returns the size of the loaded .hex file on success, -1 otherwise.
> + */
> +int load_targphys_hex_as(const char *filename, hwaddr *entry, AddressSpace *as);
> +
>  /** load_image_targphys:
>   * Same as load_image_targphys_as(), but doesn't allow the caller to specify
>   * an AddressSpace.
> diff --git a/hw/core/generic-loader.c b/hw/core/generic-loader.c
> index cb0e68486d..fde32cbda1 100644
> --- a/hw/core/generic-loader.c
> +++ b/hw/core/generic-loader.c
> @@ -147,6 +147,10 @@ static void generic_loader_realize(DeviceState *dev, Error **errp)
>                  size = load_uimage_as(s->file, &entry, NULL, NULL, NULL, NULL,
>                                        as);
>              }
> +
> +            if (size < 0) {
> +                size = load_targphys_hex_as(s->file, &entry, as);
> +            }
>          }
>  
>          if (size < 0 || s->force_raw) {
> diff --git a/hw/core/loader.c b/hw/core/loader.c
> index 612420b870..072bf8b434 100644
> --- a/hw/core/loader.c
> +++ b/hw/core/loader.c
> @@ -1321,3 +1321,246 @@ void hmp_info_roms(Monitor *mon, const QDict *qdict)
>          }
>      }
>  }
> +
> +typedef enum HexRecord HexRecord;
> +enum HexRecord {
> +    DATA_RECORD = 0,
> +    EOF_RECORD,
> +    EXT_SEG_ADDR_RECORD,
> +    START_SEG_ADDR_RECORD,
> +    EXT_LINEAR_ADDR_RECORD,
> +    START_LINEAR_ADDR_RECORD,
> +};
> +
> +#define DATA_FIELD_MAX_LEN 0xff
> +#define LEN_EXCEPT_DATA 0x5
> +/* 0x5 = sizeof(byte_count) + sizeof(address) + sizeof(record_type) +
> + *       sizeof(checksum) */
> +typedef struct {
> +    uint8_t byte_count;
> +    uint16_t address;
> +    uint8_t record_type;
> +    uint8_t data[DATA_FIELD_MAX_LEN];
> +    uint8_t checksum;
> +} HexLine;
> +
> +/* return 0 or -1 if error */
> +static bool parse_record(HexLine *line, uint8_t *our_checksum, const uint8_t c,
> +                         uint32_t *index, const bool in_process)
> +{
> +    /* +-------+---------------+-------+---------------------+--------+
> +     * | byte  |               |record |                     |        |
> +     * | count |    address    | type  |        data         |checksum|
> +     * +-------+---------------+-------+---------------------+--------+
> +     * ^       ^               ^       ^                     ^        ^
> +     * |1 byte |    2 bytes    |1 byte |     0-255 bytes     | 1 byte |
> +     */
> +    uint8_t value = 0;
> +    uint32_t idx = *index;
> +    /* ignore space */
> +    if (g_ascii_isspace(c)) {
> +        return true;
> +    }
> +    if (!g_ascii_isxdigit(c) || !in_process) {
> +        return false;
> +    }
> +    value = g_ascii_xdigit_value(c);
> +    value = idx & 0x1 ? value & 0xf : value << 4;

This construction is slightly easier to read as:

       value = (idx & 0x1) ? (value & 0xf) : (value << 4);

> +    if (idx < 2) {
> +        line->byte_count |= value;
> +    } else if (2 <= idx && idx < 6) {
> +        line->address <<= 4;
> +        line->address += g_ascii_xdigit_value(c);
> +    } else if (6 <= idx && idx < 8) {
> +        line->record_type |= value;
> +    } else if (8 <= idx && idx < 8 + 2 * line->byte_count) {
> +        line->data[(idx - 8) >> 1] |= value;
> +    } else if (8 + 2 * line->byte_count <= idx &&
> +               idx < 10 + 2 * line->byte_count) {
> +        line->checksum |= value;
> +    } else {
> +        return false;
> +    }
> +    *our_checksum += value;
> +    ++(*index);
> +    return true;
> +}
> +
> +typedef struct {
> +    const char *filename;
> +    HexLine line;
> +    uint8_t *bin_buf;
> +    hwaddr *start_addr;
> +    int total_size;
> +    uint32_t next_address_to_write;
> +    uint32_t current_address;
> +    uint32_t current_rom_index;
> +    uint32_t rom_start_address;
> +    AddressSpace *as;
> +} HexParser;
> +
> +/* return size or -1 if error */
> +static int handle_record_type(HexParser *parser)
> +{
> +    HexLine *line = &(parser->line);
> +    switch (line->record_type) {
> +    case DATA_RECORD:
> +        parser->current_address =
> +            (parser->next_address_to_write & 0xffff0000) | line->address;

Can you add a #define for this 0xffff0000? Maybe NEXT_ADDR_MASK 0xffff
and use ~NEXT_ADDR_MASK.

> +        /* verify this is a contiguous block of memory */
> +        if (parser->current_address != parser->next_address_to_write) {
> +            if (parser->current_rom_index != 0) {
> +                rom_add_blob_fixed_as(parser->filename, parser->bin_buf,
> +                                      parser->current_rom_index,
> +                                      parser->rom_start_address, parser->as);
> +            }
> +            parser->rom_start_address = parser->current_address;
> +            parser->current_rom_index = 0;
> +        }
> +
> +        /* copy from line buffer to output bin_buf */
> +        memcpy(parser->bin_buf + parser->current_rom_index, line->data,
> +               line->byte_count);
> +        parser->current_rom_index += line->byte_count;
> +        parser->total_size += line->byte_count;
> +        /* save next address to write */
> +        parser->next_address_to_write =
> +            parser->current_address + line->byte_count;
> +        break;
> +
> +    case EOF_RECORD:
> +        if (parser->current_rom_index != 0) {
> +            rom_add_blob_fixed_as(parser->filename, parser->bin_buf,
> +                                  parser->current_rom_index,
> +                                  parser->rom_start_address, parser->as);
> +        }
> +        return parser->total_size;
> +    case EXT_SEG_ADDR_RECORD:
> +    case EXT_LINEAR_ADDR_RECORD:
> +        if (line->byte_count != 2 && line->address != 0) {
> +            return -1;
> +        }
> +
> +        if (parser->current_rom_index != 0) {
> +            rom_add_blob_fixed_as(parser->filename, parser->bin_buf,
> +                                  parser->current_rom_index,
> +                                  parser->rom_start_address, parser->as);
> +        }
> +
> +        /* save next address to write,
> +         * in case of non-contiguous block of memory */
> +        parser->next_address_to_write =
> +            line->record_type == EXT_SEG_ADDR_RECORD
> +                ? ((line->data[0] << 12) | (line->data[1] << 4))
> +                : ((line->data[0] << 24) | (line->data[1] << 16));

Hard to read IMHO, what about this?

           parser->next_address_to_write = (line->data[0] << 12)
                                         | (line->data[1] << 4);
           if (line->record_type != EXT_SEG_ADDR_RECORD) {
               parser->next_address_to_write <<= 12;
           }

> +        parser->rom_start_address = parser->next_address_to_write;
> +        parser->current_rom_index = 0;
> +        break;
> +
> +    case START_SEG_ADDR_RECORD:
> +        if (line->byte_count != 4 && line->address != 0) {
> +            return -1;
> +        }
> +
> +        /* x86 16-bit CS:IP segmented addressing */
> +        *(parser->start_addr) = (((line->data[0] << 8) | line->data[1]) << 4) |
> +                                (line->data[2] << 8) | line->data[3];

Can you add a qtest for this case?
For the HEX loader I understand the specs as this is the same parsing as
the START_LINEAR_ADDR_RECORD case; so I disagree with data[0] and
data[1] shifts.
This is different for the consumer (i386 expects 2 16-bit registers but
HexParser->start_addr is a hwaddr, used as a single (at least) 32-bit
register.

> +        break;
> +
> +    case START_LINEAR_ADDR_RECORD:
> +        if (line->byte_count != 4 && line->address != 0) {
> +            return -1;
> +        }
> +
> +        *(parser->start_addr) = (line->data[0] << 24) | (line->data[1] << 16) |
> +                                (line->data[2] << 8)  | (line->data[3]);

You can use this helper:

           *(parser->start_addr) = ldl_be_p(line->data);

> +        break;
> +
> +    default:
> +        return -1;
> +    }
> +
> +    return parser->total_size;
> +}
> +
> +/* return size or -1 if error */
> +static int parse_hex_blob(const char *filename, hwaddr *addr, uint8_t *hex_blob,
> +                          size_t hex_blob_size, AddressSpace *as)
> +{
> +    bool in_process = false; /* avoid re-enter and
> +                              * check whether record begin with ':' */
> +    uint8_t *end = hex_blob + hex_blob_size;
> +    uint8_t our_checksum = 0;
> +    uint32_t record_index = 0;
> +    HexParser parser = {
> +        .filename = filename,
> +        .bin_buf = g_malloc(hex_blob_size),
> +        .start_addr = addr,
> +        .as = as,
> +    };
> +
> +    rom_transaction_begin();
> +
> +    for (; hex_blob < end; ++hex_blob) {
> +        switch (*hex_blob) {
> +        case '\r':
> +        case '\n':
> +            if (!in_process) {
> +                break;
> +            }
> +
> +            in_process = false;
> +            if ((LEN_EXCEPT_DATA + parser.line.byte_count) * 2 !=
> +                    record_index ||
> +                our_checksum != 0) {
> +                parser.total_size = -1;
> +                goto out;
> +            }
> +
> +            if (handle_record_type(&parser) == -1) {
> +                parser.total_size = -1;
> +                goto out;
> +            }
> +            break;
> +
> +        /* start of a new record. */
> +        case ':':
> +            memset(&parser.line, 0, sizeof(HexLine));
> +            in_process = true;
> +            record_index = 0;
> +            break;
> +
> +        /* decoding lines */
> +        default:
> +            if (!parse_record(&parser.line, &our_checksum, *hex_blob,
> +                              &record_index, in_process)) {
> +                parser.total_size = -1;
> +                goto out;
> +            }
> +            break;
> +        }
> +    }
> +
> +out:
> +    g_free(parser.bin_buf);
> +    rom_transaction_end(parser.total_size != -1);
> +    return parser.total_size;
> +}
> +
> +/* return size or -1 if error */
> +int load_targphys_hex_as(const char *filename, hwaddr *entry, AddressSpace *as)
> +{
> +    gsize hex_blob_size;
> +    gchar *hex_blob;
> +    int total_size = 0;
> +
> +    if (!g_file_get_contents(filename, &hex_blob, &hex_blob_size, NULL)) {
> +        return -1;
> +    }
> +
> +    total_size = parse_hex_blob(filename, entry, (uint8_t *)hex_blob,
> +                                hex_blob_size, as);
> +
> +    g_free(hex_blob);
> +    return total_size;
> +}
> 

Regards,

Phil.