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Update README

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This commit is contained in:
Gregory Nutt 2014-10-03 09:56:05 -06:00
parent 6030232354
commit 0e57b60cd1
1 changed files with 6 additions and 20 deletions
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26
configs/sim/README.txt
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@ -86,9 +86,12 @@ Issues
64-Bit Issues
-------------
As mentioned above, context switching is based on logic like setjmp and longjmp.
This context switching is only available for 32-bit targets. On 64-bit machines,
this context switching will fail.
As mentioned above, context switching is based on logic like setjmp() and
longjmp(). This context switching is available for 32-bit and 64-bit
targets. You must, however, set the correct target in the configuration
before you build: HOST_X86_64 or HOST_X86 for 62- and 32-bit targets,
respectively. On a 64-bit machine, you can also force the 32-bit build
with CONFIG_SIM_M32=y.
There are other 64-bit issues as well. For example, addresses are retained in
32-bit unsigned integer types in a few places. On a 64-bit machine, the 32-bit
@ -96,17 +99,6 @@ address storage may correcupt 64-bit addressing. NOTE: This is really a bug --
addresses should not be retained in uint32_t types but rather in uintptr_t types
to avoid issues just like this.
The workaround on 64-bit machines for now is to build for a 32-bit target on the
64-bit machine. The workaround for this issue has been included in NuttX 6.15 and
beyond. For thoses versions, you must add CONFIG_SIM_M32=y to the .config file in
order to enable building a 32-bit image on a 64-bit platform.
For older versions of NuttX, a patch also exists. The patch the Make.defs file in the
appropriate places so that -m32 is included in the CFLAGS and -m32 and -melf_386
are included in the LDFLAGS. See the patch
0001-Quick-hacks-to-build-sim-nsh-ostest-on-x86_64-as-32-.patch that can be found at
http://tech.groups.yahoo.com/group/nuttx/files.
Compiler differences
--------------------
@ -115,12 +107,6 @@ operator new:
Problem: "'operator new' takes size_t ('...') as first parameter"
Workaround: Add -fpermissive to the compilation flags
Continue up_setjmp() issues:
With some newer compilers, I am now getting segmentation faults in
up_setjmp.S (even when built with the -m32 option). I have not looked into
this yet.
Stack Size Issues
-----------------
When you run the NuttX simulation, it uses stacks allocated by NuttX from the