220653f21c
Author: anchao <anchao@pinecone.net>
apps/, most main() function: Correct CONFIG_BUILD_LOADABLE usage
Loadable apps/: Correct loadable symbol table generate
apps/system/ubloxmodem: Fix build break
apps/examples/ostest: start restart/waitpid/user test from main loop
apps/nshlib: Expand reboot and poweroff commands to include a second, optional mode argument
Author: Gregory Nutt <gnutt@nuttx.org>
An attempt to fix build issues. Does not work.
apps/examples/ostest: Fix some inappropriate renaming of static functions introduced with recent patches.
apps/builtin/exec_builtin.c: Fix a error introduced by recent comments. Found in build testing.
Author: anchao <anchao@pinecone.net>
apps/builtin/exec_builtin.c: Try posix_spawn if builtin apps do not have have an entry point.
apps/Application.mk: introduce MODULE config to simplify tristate(m)
apps/nsh: Change the nuttx shell module type to tristate
apps: Add loadable application support
script/mksymtab: Generate symbol table name by default
apps/builtin: Allow loadable applications can register with apps/builtin.
62 lines
2.5 KiB
Plaintext
62 lines
2.5 KiB
Plaintext
symtab
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======
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Symbol Tables and Build Modes
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-----------------------------
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This directory provide support for a symbol table which provides all/most of
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system and C library services/functions to the application and NSH.
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Symbol tables have differing usefulness in different NuttX build modes:
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1. In the FLAT build (CONFIG_BUILD_FLAT), symbol tables are used to bind
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addresses in loaded ELF or NxFLAT modules to base code that usually
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resides in FLASH memory. Both OS interfaces and user/application
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libraries are made available to the loaded module via symbol tables.
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2. Symbol tables may be of value in a protected build
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(CONFIG_BUILD_PROTECTED) where the newly started user task must
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share resources with other user code (but should use system calls to
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interact with the OS).
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3. But in the kernel build mode (CONFIG_BUILD_LOADABLE), only fully linked
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executables loadable via execl(), execv(), or posix_spawan() can used.
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There is no use for a symbol table with the kernel build since all
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memory resources are separate; nothing is share-able with the newly
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started process.
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Creating the Canned Symbol Table
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--------------------------------
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The support is selected by CONFIG_SYSTEM_SYMTAB option and table has to be
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prepared in advance manually. It can be prepared from NuttX top level
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directory by using the following commands:
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cd <nuttx-path>
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cat syscall/syscall.csv libc/libc.csv | sort > <apps-path>/symtab/symtab.csv
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tools/mksymtab <apps-path>/symtab/symtab.csv <apps-path>/symtab/symtab.inc
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where:
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<nuttx-path> is the path to the NuttX top level build directory
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<apps-path> is the path to the top level application directory
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You may want omit syscall/syscall.csv in the above command in the protected
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mode. It is optional since the system calls are provided through system
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call traps.
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Your board-level start up code code then needs to select the symbol table
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by calling the function symtab_initialize():
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#include "system/symtab.h"
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...
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symtab_initialize();
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Code/Text Size Implications
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---------------------------
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The option can have substantial effect on system image size, mainly
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code/text. That is because the instructions to generate symtab.inc
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above will cause EVERY interface in the NuttX RTOS and the C library to be
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included into build. Add to that the size of a huge symbol table.
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In order to reduce the code/text size, you may want to manually prune the
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auto-generated symtab.inc file to remove all interfaces that you do
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not wish to include into the base FLASH image.
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