+++ /dev/null
-// crt1-sim.S
-// For the Xtensa simulator target, this code sets up the C calling context
-// and calls main() (via __clibrary_start).
-// Control arrives here at _start from the reset vector or from crt0-app.S.
-
-// Copyright (c) 1998-2010 Tensilica Inc.
-//
-// Permission is hereby granted, free of charge, to any person obtaining
-// a copy of this software and associated documentation files (the
-// "Software"), to deal in the Software without restriction, including
-// without limitation the rights to use, copy, modify, merge, publish,
-// distribute, sublicense, and/or sell copies of the Software, and to
-// permit persons to whom the Software is furnished to do so, subject to
-// the following conditions:
-//
-// The above copyright notice and this permission notice shall be included
-// in all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
-// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
-// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
-#include <xtensa/simboard.h>
-#include <xtensa/simcall.h>
-#include <xtensa/coreasm.h>
-#include "xtos-internal.h"
-
-
-// Exports
-.global _start
-
-// Imports
-// __clibrary_init from C library (eg. newlib or uclibc)
-// exit from C library
-// main from user application
-// __stack from linker script (see LSP Ref Manual)
-
-.type __clibrary_init, @function
-.type main, @function
-.type exit, @function
-
-
-// Macros to abstract away ABI differences
-
-#if __XTENSA_CALL0_ABI__
-# define CALL call0
-# define ARG1 a2 /* 1st outgoing call argument */
-# define ARG2 a3 /* 2nd outgoing call argument */
-# define ARG3 a4 /* 3rd outgoing call argument */
-# define ARG4 a5 /* 4th outgoing call argument */
-# define ARG5 a6 /* 5th outgoing call argument */
-#else
-# define CALL call4
-# define ARG1 a6 /* 1st outgoing call argument */
-# define ARG2 a7 /* 2nd outgoing call argument */
-# define ARG3 a8 /* 3rd outgoing call argument */
-# define ARG4 a9 /* 4th outgoing call argument */
-# define ARG5 a10 /* 5th outgoing call argument */
-#endif
-
- .data
- .weak _start_envp // allow overriding
- .align 4
-_start_envp: .word 0 // empty environ
-
-
-
- .text
- .align 4
-
-_start:
- // _start is typically NOT at the beginning of the text segment --
- // it is always called from either the reset vector or other code
- // that does equivalent initialization (such as crt0-app.S).
- //
- // Assumptions on entry to _start:
- // - low (level-one) and medium priority interrupts are disabled
- // via PS.INTLEVEL and/or INTENABLE (PS.INTLEVEL is expected to
- // be zeroed, to potentially enable them, before calling main)
- // - C calling context not initialized:
- // - PS not initialized
- // - SP not initialized
- // - the following are initialized:
- // - LITBASE, cache attributes, WindowBase, WindowStart,
- // CPENABLE, FP's FCR and FSR, EXCSAVE[n]
-
- // Keep a0 zero. It is used to initialize a few things.
- // It is also the return address, where zero indicates
- // that the frame used by _start is the bottommost frame.
- //
- movi a0, 0 // keep this register zero.
-
-#if XTOS_RESET_UNNEEDED
-#include "reset-unneeded.S"
-#endif
-
-
- // Initialize the stack pointer.
- // See the "ABI and Software Conventions" chapter in the
- // Xtensa ISA Reference manual for details.
-
- // NOTE: Because the _start routine does not use any memory in its
- // stack frame, and because all of its CALL instructions use a
- // window size of 4, the stack frame for _start can be empty.
- movi sp, __stack
-
- // reserve stack space for
- // - argv array
- // - argument strings
- movi a2, SYS_iss_argv_size
- simcall // returns size of argv[] + its strings in a2
-#if XCHAL_HAVE_PIF
- // The stack only needs 16-byte alignment.
- // However, here we round up the argv size further to 128 byte multiples
- // so that in most cases, variations in argv[0]'s path do not result in
- // different stack allocation. Otherwise, such variations can impact
- // execution timing (eg. due to cache effects etc) for the same code and data.
- // If we have a PIF, it's more likely the extra required space is okay.
- addi a2, a2, 127
- srli a2, a2, 7
- slli a2, a2, 7
-#else
- // Keep stack 16-byte aligned.
- addi a2, a2, 15
- srli a2, a2, 4
- slli a2, a2, 4
-#endif
- // No need to use MOVSP because we have no caller (we're the
- // base caller); in fact it's better not to use MOVSP in this
- // context, to avoid unnecessary ALLOCA exceptions and copying
- // from undefined memory:
- // sub a3, sp, a2
- // movsp sp, a3
- sub sp, sp, a2
-
-
- /*
- * Now that sp (a1) is set, we can set PS as per the application
- * (user vector mode, enable interrupts, enable window exceptions if applicable).
- */
-#if XCHAL_HAVE_EXCEPTIONS
-# ifdef __XTENSA_CALL0_ABI__
- movi a3, PS_UM // PS.WOE = 0, PS.UM = 1, PS.EXCM = 0, PS.INTLEVEL = 0
-# else
- movi a3, PS_UM|PS_WOE // PS.WOE = 1, PS.UM = 1, PS.EXCM = 0, PS.INTLEVEL = 0
-# endif
- wsr a3, PS
- rsync
-#endif
-
-
- /* The new ISS simcall only appeared after RB-2007.2: */
-#if !XCHAL_HAVE_BOOTLOADER && (XCHAL_HW_MAX_VERSION > XTENSA_HWVERSION_RB_2007_2) /* pre-LX2 cores only */
- /*
- * Clear the BSS (uninitialized data) segments.
- * This code supports multiple zeroed sections (*.bss).
- * For speed, we clear memory using an ISS simcall
- * (see crt1-boards.S for more generic BSS clearing code).
- */
- movi a6, _bss_table_start
- movi a7, _bss_table_end
- bgeu a6, a7, .Lnobss
-.Lbssloop:
- movi a2, SYS_memset
- l32i a3, a6, 0 // arg1 = fill start address
- movi a4, 0 // arg2 = fill pattern
- l32i a5, a6, 4 // get end address
- addi a6, a6, 8 // next bss table entry
- sub a5, a5, a3 // arg3 = fill size in bytes
- simcall // memset(a3,a4,a5)
- bltu a6, a7, .Lbssloop // loop until end of bss table
-.Lnobss:
-#endif
-
-
- /*
- * Call __clibrary_init to initialize the C library:
- *
- * void __clibrary_init(int argc, char ** argv, char ** environ,
- * void(*init_func)(void), void(*fini_func)(void));
- */
-
- // Get argv with the arguments from the ISS
- mov a3, sp // tell simcall where to write argv[]
- movi a2, SYS_iss_set_argv
- simcall // write argv[] array at a3
-
- movi a2, SYS_iss_argc
- simcall // put argc in a2
-
-
-// Alternative smaller code for Xtensa TX.
-// Many starting with simulation assume a full C env, so NOT DONE FOR NOW.
-//
-//#if XCHAL_HAVE_HALT
-//
-// // Assume minimalist environment for memory-constrained TX cores.
-// // No C library or board initialization, and no call to exit().
-// // However, in the interest of software regressions, for now we
-// // still pass parameters to main (but not the rarely used envp).
-//
-// //mov ARG1, a2 // argc already in a2.
-// mov ARG2, sp // argv
-// CALL main
-// halt
-//
-//#else /* !HALT */
-// ...
-
-
-#if __XTENSA_CALL0_ABI__
- mov a12, a2 // save argc (a2 is ARG1)
-#else
- mov ARG1, a2 // argc
-#endif
- mov ARG2, sp // argv
- movi ARG3, _start_envp // envp
- movi ARG4, _init // _init
- movi ARG5, _fini // _fini
- CALL __clibrary_init
-
- // Call: int main(int argc, char ** argv, char ** environ);
-#if __XTENSA_CALL0_ABI__
- mov ARG1, a12 // argc
-#else
- mov ARG1, a2 // argc
-#endif
- mov ARG2, sp // argv
- movi ARG3, _start_envp // envp = [0]
- CALL main
- // The return value is the same register as the first outgoing argument.
- CALL exit // exit with main's return value
- // Does not return here.
-
- .size _start, . - _start
-
-\f
-// Local Variables:
-// mode:fundamental
-// comment-start: "// "
-// comment-start-skip: "// *"
-// End:
projects / open-ath9k-htc-firmware.git / blobdiff