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6d5331054e
There is a special interface built in ARC simulators (such as
nSIM) called MetaWare hostlink IO which can be used to implement
system calls. This commit adds support for this interface to the
ARC port of libgloss.
Here is an example of using this interface:
$ arc-elf32-gcc -mcpu=hs -specs=hl.specs main.c -o main
$ nsimdrv -tcf $NSIM_HOME/etc/tcf/templates/hs48_full.tcf main
Hello, World!
Signed-off-by: Vladimir Isaev <vvisaev@gmail.com>
91 lines
4.1 KiB
Markdown
91 lines
4.1 KiB
Markdown
Metaware hostlink IO
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====================
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This directory includes target-side implementation of Metaware hostlink
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interface see Contents section. Target program can use Metaware hostlink
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interface to send messages to nsim simulator or mdb debugger (it can be
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attached to HW or nsim).
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Quick start
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-----------
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To link with this version of libgloss please add `-specs=hl.specs` to baremetal
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version of ARC gcc (arc-elf32).
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Lets build and run simple program:
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$ cat hello.c
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#include <stdio.h>
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int main()
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{
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printf("Hello World!\n");
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return 0;
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}
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$ arc-elf32-gcc -mcpu=hs -specs=hl.specs ./hello.c -o hello
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$ nsimdrv -prop=nsim_isa_family=av2hs -prop=nsim_hlink_gnu_io_ext=1 ./hello
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Hello World!
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Where `-mcpu` and `-prop=nsim_isa_family` is specific to your version of ARC CPU.
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Option `-prop=nsim_hlink_gnu_io_ext=1` enables GNU IO extension for nSIM which
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is used for some system calls. The `nsimdrv` option `-prop=nsim_emt={0,1,2}`
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enables trap emulation and should be disabled (removed or set to `0`) to use
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Metaware hostlink.
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**NB:** Metaware hostlink requires symbols `__HOSTLINK__` and `_hl_blockedPeek`
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to be present. So stripped binary won't work properly with Metaware hostlink.
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Contents
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--------
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* `hl/hl_gw.*` -- Hostlink gateway. This API is used in the `hl_api.*`.
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Please use `hl_message()` from `hl_api.*` for hostlink
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message exchange.
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* `hl/hl_api.*` -- High-level API to send hostlink messages, as well as
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functions to work with messages.
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* `hl/hl_<syscall>.*` -- Syscall implementations through hostlink API;
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* `arc-timer.*` -- Provides API to access ARC timers. Used by
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`hl/hl_clock.c` in `_clock()` implementation.
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* `arc-main-helper.c` -- Provides `__setup_argv_and_call_main()`. The function
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is called from `__start()` in `crt0.S`. It allows
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to setup `argc` and `arvg` as well as some custom
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things through `_setup_low_level()`.
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* `hl-setup.c` -- Provides `_setup_low_level()` for hostlink case.
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It just configures default timer if it exists. Default
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timer is used in the hostlink `clock()`
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implementation.
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* `hl-stub.c` -- Provides functions which are part of newlib but
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implemented without hostlink.
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e.g. `_kill()` and `_getpid()`.
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* `sbrk.c` -- Provides `_sbrk()`. It uses `__start_heap` and
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`__end_heap` variables.
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* `libcfunc.c` -- Additional C system calls.
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* `mcount.c` -- Profiler support.
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How it works
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------------
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Simulator looks for `__HOSTLINK__` and `_hl_blockedPeek()` symbols.
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`__HOSTLINK__` is the start of shared structure for message exchange and
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`_hl_blockedPeek()` is a function to be called when program is waiting
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for simulator response.
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When program wants to send a message it should follow:
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1. Fill `__HOSTLINK__.payload` with packed data.
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Packing format is following: `{u16 type, u16 size, char data[]}`.
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Supported types are `char`, `short`, `int`, `string` and `int64`.
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`hl_api` provides high-level API to this.
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2. Fill `__HOSTLINK__.pkt_hdr`. See `hl_pkt_init()` from `hl_gw.c`.
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3. Fill `__HOSTLINK__.hdr`. See `hl_send()` from `hl_gw.c`.
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4. Call `_hl_blockedPeek()` to get response.
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At this point message should be delivered to debugger.
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Some implementations uses change of `__HOSTLINK__.hdr.target2host_addr` as
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a signal that packet is sent and can be processed. Other implementations
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wait for `_hl_blockedPeek()` to be called.
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It means that portable implementation must fill
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`__HOSTLINK__.hdr.target2host_addr` at the last step and then call
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`_hl_blockedPeek()`.
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5. `_hl_blockedPeek()` returns pointer to debugger response which can be
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processed on target if needed. Because debugger and target share the same
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buffer the function actually returns `__HOSTLINK__.payload` that was
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filled with packed data (see step 1) by the debugger.
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