UM0438 datasheet(13/50 Pages) STMICROELECTRONICS

13 / 50 page

UM0438

Application Binary Interface (ABI)

13/50

The VLE encodings also require additional relocation types, which allow the linker to resolve

immediate and branch displacement fields in the instruction encoding once a symbol or

label address is known (at link time). The VLE encodings require additional relocation types

to resolve fields not present in the PowerPC Book E encodings.

2.2.1

VLE information section

The e500 ABI defines an information section named .PPC.EMB.apuinfo having type

SHT_NOTE and attributes of 0, which matches the format of a typical ELF note section as

shown in Table 3. The information section allows disassemblers and debuggers to interpret

the instructions properly within the binary and can be used by operating systems to provide

emulation or error checking of the VLE extension revisions.

Table 3.

Typical Elf note section format

For the .PPC.EMB.apuinfo section, the name is APUinfo the type is 2 (as type 1 is already

reserved), and the data contains a series of words providing information about the APU or

extension, one per word. The information contains two unsigned half words: the upper half

contains the unique identifier, and the lower half contains the revision number. The VLE

identifier is shown in Table 4.

length of name (in bytes)

length of data (in bytes)

type

name (null-terminated, padded to 4-byte alignment)

data

Table 4.

VLE identifier

Identifier (16 Bits)

APU/Extension

0x0104

VLE

Example - Object file a.o

0x00000008

# 8 bytes in

"APUinfo\0"

0x0000000C

# 12 bytes (3 words)

of APU information

0x00000002

# NOTE type 2

0x41505569

# ASCII for "APUi"

0x6e666f00

# ASCII for "nfo\0"

0x00010001

# APU #1, revision 1

0x01040001

# VLE, revision 1

0x00040001

# APU #4, revision 1

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