Fuxin Zhang 写道:
Hello,
My goal is to compile a simple assembly program and boot it on top
of pmon2000 on a Yeeloong laptop.
But I am missing information such as the address range to write to
memory.
Where are mapped the 1GBytes of memory?
low 256MB is at physical address 0-0x10000000, can be accessed from
0x80000000-0x90000000 or 0xa0000000-0xb0000000
all mem is mapped at physical address start from 0x80000000(can differ
with pmon versions), can be accessed only via 64bit address or tlb mapped
addresses.
Does the pmon mt command provide a good answer?
probably it can access only the low part.
Does pmon load the program at the start of this space?
can't remember the details, but it should be no. Pmon itself is normally
loaded at 0x80020000. the top part is used for stack and malloc etc.
Pmon first analysis target executable file's program headers , loads
neccessory program sections,
then jumps to target file's entrypiont(descript in elf headerd).
Pmon not assume anything, but entry point usually fix to 0x8020_0000
(compressed kernel usually use 0x80Fx_xxxx)
In fact ,pmon can only use low 256MB(0x8000_0000 ~ 0x8fff_ffff) now.
Since low and high part memory are allocated by pmon,so I think all
addresses
between 0x8020_0000 and 0x8E00_0000 can be used as entrypoint, but not
guarantee.
Example :
my-laptop$ readelf -l fl-vmlinux
Elf file type is EXEC (Executable file)
Entry point 0xffffffff802063e0
There are 2 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000004000 0xffffffff80200000 0xffffffff80200000
0x0000000000480085 0x00000000004cfca0 RWE 4000
NOTE 0x0000000000352c30 0xffffffff8054ec30 0xffffffff8054ec30
0x0000000000000024 0x0000000000000024 R 4
Pmon only load program sections with "LOAD" type, and copy the section
to VirtAddr (0x8020_0000)
then jump to Entry piont address(0x802063eo).
Addresses like 0x82000000 should be unused. But why do you want to use raw
addresses?
BTW: the topic does not directly related to Loongson2F manual? The address
mapping can be changed for different implementations.
Freely
Sebastien
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