UM0438 datasheet(14/50 Pages) STMICROELECTRONICS

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Application Binary Interface (ABI)

UM0438

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Linkers merge all .PPC.EMB.apuinfo sections in individual object files into one, with merging

of per-APU information. For example, after linking file a.o and b.o, the merged

.PPC.EMB.apuinfo is as shown in example below.

Note that it is assumed that a later revision of any APU or extension is compatible with an

earlier one, but not vice versa. Thus, the resultant .PPC.EMB.apuinfo section requires APU

#1 revision 2 or greater to work, and does not work on APU #1 revision 1. If a revision

breaks backwards compatibility, it must be given a new unique identifier.

A linker may optionally warn when different objects require different revisions, because

moving the revision up may make the executable no longer work on processors with the

older revision. In this example, the linker could emit a warning like “Warning: bumping APU

#1 revision number to 2, required by b.o.”

2.2.2

VLE identification

The executable and linking format (ELF) allows processor-specific section header and

program header flag attributes to be defined. The following section header and program

header flag attribute definitions are used to mark ELF sections containing VLE instruction

encodings.

Example - Object file b.o

0x00000008

# 8 bytes in

"APUinfo\0"

0x00000008

# 8 bytes (2 words)

of APU information

0x00000002

# NOTE type 2

0x41505569

# ASCII for "APUi"

0x6e666f00

# ASCII for "nfo\0"

0x00010002

# APU #1, revision 2

0x00040001

# APU #4, revision 1

Example - PPC.EMB.apuinfo

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"

0x00010002

# APU #1, revision 2

0x01040001

# VLE, revision 1

0x00040001

# APU #4, revision 1

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