Re: [Qemu-devel] [PATCH v4 15/23] i386: add bios linker/loader

[Paolo Bonzini <pbonzini@redhat.com>]

Il 23/09/2013 15:36, Michael S. Tsirkin ha scritto:
> On Mon, Sep 23, 2013 at 02:48:57PM +0200, Paolo Bonzini wrote:
>> Il 22/09/2013 15:37, Michael S. Tsirkin ha scritto:
>>> This adds a dynamic bios linker/loader.
>>> This will be used by acpi table generation
>>> code to:
>>>     - load each table in the appropriate memory segment
>>>     - link tables to each other
>>>     - fix up checksums after said linking
>>>
>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>> ---
>>>  include/hw/i386/bios-linker-loader.h |  26 ++++++
>>>  hw/i386/bios-linker-loader.c         | 156 +++++++++++++++++++++++++++++++++++
>>>  hw/i386/Makefile.objs                |   1 +
>>
>> Just a naming question...
>>
>> If this is ACPI-specific (or if there are no other uses in sight), it
>> should go in include/hw/acpi and hw/acpi, and renamed with s/bios/acpi/ etc.
>>
>> If this is i386-specific, it should go entirely in hw/i386 and the
>> headers should be included as "bios-linker-loader.h".
> 
> Definitely not ACPI specific.
> It's only used on i386 so I put it all under i386.
> You think we should replace
> #include "hw/i386/bios-linker-loader.h" with
> #include "bios-linker-loader.h"?
> 
> I don't really care, even though this makes headers
> hard to find. What's the benefit?

Private headers are outside include/, public headers within it.  Same
conventions as Linux.  But if it's not ACPI-specific, I don't feel too
strongly about it.

> It's not easy to find a good name for it.
> For now I'll just make all names bios_linker_loader_ consistently.
> We can always rename it later, it's not set in stone.

Ok.

>>> +struct BiosLinkerLoaderEntry {
>>> +    uint32_t command;
>>> +    union {
>>> +        /*
>>> +         * COMMAND_ALLOCATE - allocate a table from @alloc_file
>>> +         * subject to @alloc_align alignment (must be power of 2)
>>> +         * and @alloc_zone (can be HIGH or FSEG) requirements.
>>> +         *
>>> +         * Must appear exactly once for each file, and before
>>> +         * this file is referenced by any other command.
>>> +         */
>>> +        struct {
>>> +            char alloc_file[BIOS_LINKER_LOADER_FILESZ];
>>> +            uint32_t alloc_align;
>>> +            uint8_t alloc_zone;
>>> +        };
>>
>> I would prefer to have named structs, like
>>
>>         struct {
>>             char file[BIOS_LINKER_LOADER_FILESZ];
>>             uint32_t align;
>>             uint8_t zone;
>>         } alloc;
> 
> Why do you prefer this? It just makes code more verbose.

It doesn't, the names were already prefixed with alloc_/pointer_/cksum_.
 All it does is change underscores to periods.

Paolo

>>> +        /*
>>> +         * COMMAND_ADD_POINTER - patch the table (originating from
>>> +         * @dest_file) at @pointer_offset, by adding a pointer to the table
>>> +         * originating from @src_file. 1,2,4 or 8 byte unsigned
>>> +         * addition is used depending on @pointer_size.
>>> +         */
>>> +        struct {
>>> +            char pointer_dest_file[BIOS_LINKER_LOADER_FILESZ];
>>> +            char pointer_src_file[BIOS_LINKER_LOADER_FILESZ];
>>> +            uint32_t pointer_offset;
>>> +            uint8_t pointer_size;
>>> +        };
>>> +
>>> +        /*
>>> +         * COMMAND_ADD_CHECKSUM - calculate checksum of the range specified by
>>> +         * @cksum_start and @cksum_length fields,
>>> +         * and then add the value at @cksum_offset.
>>> +         * Checksum simply sums -X for each byte X in the range
>>> +         * using 8-bit math.
>>> +         */
>>> +        struct {
>>> +            char cksum_file[BIOS_LINKER_LOADER_FILESZ];
>>> +            uint32_t cksum_offset;
>>> +            uint32_t cksum_start;
>>> +            uint32_t cksum_length;
>>> +        };
>>> +
>>> +        /* padding */
>>> +        char pad[124];
>>> +    };
>>> +} QEMU_PACKED;
>>> +typedef struct BiosLinkerLoaderEntry BiosLinkerLoaderEntry;
>>> +
>>> +enum {
>>> +    BIOS_LINKER_LOADER_COMMAND_ALLOCATE     = 0x1,
>>> +    BIOS_LINKER_LOADER_COMMAND_ADD_POINTER  = 0x2,
>>> +    BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM = 0x3,
>>> +};
>>> +
>>> +enum {
>>> +    BIOS_LINKER_LOADER_ALLOC_ZONE_HIGH = 0x1,
>>> +    BIOS_LINKER_LOADER_ALLOC_ZONE_FSEG = 0x2,
>>> +};
>>> +
>>> +GArray *bios_linker_init(void)
>>> +{
>>> +    return g_array_new(false, true /* clear */, sizeof(BiosLinkerLoaderEntry));
>>> +}
>>> +
>>> +/* Free linker wrapper and return the linker array. */
>>> +void *bios_linker_cleanup(GArray *linker)
>>> +{
>>> +    return g_array_free(linker, false);
>>> +}
>>> +
>>> +void bios_linker_alloc(GArray *linker,
>>> +                       const char *file,
>>> +                       uint32_t alloc_align,
>>> +                       bool alloc_fseg)
>>> +{
>>> +    BiosLinkerLoaderEntry entry;
>>> +
>>> +    memset(&entry, 0, sizeof entry);
>>> +    strncpy(entry.alloc_file, file, sizeof entry.alloc_file - 1);
>>
>> Please use pstrcpy (also below).
> 
> OK.
> 
>>> +    entry.command = cpu_to_le32(BIOS_LINKER_LOADER_COMMAND_ALLOCATE);
>>> +    entry.alloc_align = cpu_to_le32(alloc_align);
>>> +    entry.alloc_zone = cpu_to_le32(alloc_fseg ?
>>> +                                    BIOS_LINKER_LOADER_ALLOC_ZONE_FSEG :
>>> +                                    BIOS_LINKER_LOADER_ALLOC_ZONE_HIGH);
>>> +
>>> +    /* Alloc entries must come first, so prepend them */
>>> +    g_array_prepend_val(linker, entry);
>>> +}
>>> +
>>> +void bios_linker_add_checksum(GArray *linker, const char *file, void *table,
>>> +                              void *start, unsigned size, uint8_t *checksum)
>>> +{
>>> +    BiosLinkerLoaderEntry entry;
>>> +
>>> +    memset(&entry, 0, sizeof entry);
>>> +    strncpy(entry.cksum_file, file, sizeof entry.cksum_file - 1);
>>> +    entry.command = cpu_to_le32(BIOS_LINKER_LOADER_COMMAND_ADD_CHECKSUM);
>>> +    entry.cksum_offset = cpu_to_le32(checksum - (uint8_t *)table);
>>> +    entry.cksum_start = cpu_to_le32((uint8_t *)start - (uint8_t *)table);
>>> +    entry.cksum_length = cpu_to_le32(size);
>>> +
>>> +    g_array_append_val(linker, entry);
>>> +}
>>> +
>>> +void bios_linker_add_pointer(GArray *linker,
>>> +                             const char *dest_file,
>>> +                             const char *src_file,
>>> +                             GArray *table, void *pointer,
>>> +                             uint8_t pointer_size)
>>> +{
>>> +    BiosLinkerLoaderEntry entry;
>>> +
>>> +    memset(&entry, 0, sizeof entry);
>>> +    strncpy(entry.pointer_dest_file, dest_file,
>>> +            sizeof entry.pointer_dest_file - 1);
>>> +    strncpy(entry.pointer_src_file, src_file,
>>> +            sizeof entry.pointer_src_file - 1);
>>> +    entry.command = cpu_to_le32(BIOS_LINKER_LOADER_COMMAND_ADD_POINTER);
>>> +    entry.pointer_offset = cpu_to_le32((gchar *)pointer - table->data);
>>> +    entry.pointer_size = pointer_size;
>>> +    assert(pointer_size == 1 || pointer_size == 2 ||
>>> +           pointer_size == 4 || pointer_size == 8);
>>> +
>>> +    g_array_append_val(linker, entry);
>>> +}
>>> diff --git a/hw/i386/Makefile.objs b/hw/i386/Makefile.objs
>>> index f950707..b9ca380 100644
>>> --- a/hw/i386/Makefile.objs
>>> +++ b/hw/i386/Makefile.objs
>>> @@ -5,6 +5,7 @@ obj-y += pc_sysfw.o
>>>  obj-$(CONFIG_XEN) += xen_domainbuild.o xen_machine_pv.o
>>>  
>>>  obj-y += kvmvapic.o
>>> +obj-y += bios-linker-loader.o
>>>  
>>>  iasl-option=$(shell if test -z "`$(1) $(2) 2>&1 > /dev/null`" \
>>>      ; then echo "$(2)"; else echo "$(3)"; fi ;)
>>>