| /**************************************************************************** |
| * * |
| * GNAT COMPILER COMPONENTS * |
| * * |
| * S I G T R A M P * |
| * * |
| * Asm Implementation File * |
| * * |
| * Copyright (C) 2013, Free Software Foundation, Inc. * |
| * * |
| * GNAT is free software; you can redistribute it and/or modify it under * |
| * terms of the GNU General Public License as published by the Free Soft- * |
| * ware Foundation; either version 3, or (at your option) any later ver- * |
| * sion. GNAT is distributed in the hope that it will be useful, but WITH- * |
| * OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY * |
| * or FITNESS FOR A PARTICULAR PURPOSE. * |
| * * |
| * As a special exception under Section 7 of GPL version 3, you are granted * |
| * additional permissions described in the GCC Runtime Library Exception, * |
| * version 3.1, as published by the Free Software Foundation. * |
| * * |
| * In particular, you can freely distribute your programs built with the * |
| * GNAT Pro compiler, including any required library run-time units, using * |
| * any licensing terms of your choosing. See the AdaCore Software License * |
| * for full details. * |
| * * |
| * GNAT was originally developed by the GNAT team at New York University. * |
| * Extensive contributions were provided by Ada Core Technologies Inc. * |
| * * |
| ****************************************************************************/ |
| |
| /****************************************************** |
| * ARM-VxWorks version of the __gnat_sigtramp service * |
| ******************************************************/ |
| |
| #include "sigtramp.h" |
| /* See sigtramp.h for a general explanation of functionality. */ |
| |
| #include <vxWorks.h> |
| #include <arch/../regs.h> |
| #include <sigLib.h> |
| |
| /* ---------------------- |
| -- General comments -- |
| ---------------------- |
| |
| Stubs are generated from toplevel asms and .cfi directives, much simpler |
| to use and check for correctness than manual encodings of CFI byte |
| sequences. The general idea is to establish CFA as sigcontext->sc_pregs |
| and state where to find the registers as offsets from there. |
| |
| As of today, we support a single stub, providing CFI info for common |
| registers (GPRs, LR, ...). We might need variants with support for floating |
| point or altivec registers as well at some point. |
| |
| Checking which variant should apply and getting at sc_pregs is simpler |
| to express in C (we can't use offsetof in toplevel asms and hardcoding |
| constants is not workable with the flurry of VxWorks variants), so this |
| is the choice for our toplevel interface. |
| |
| Note that the registers we "restore" here are those to which we have |
| direct access through the system sigcontext structure, which includes |
| only a partial set of the non-volatiles ABI-wise. */ |
| |
| /* ----------------------------------------- |
| -- Protypes for our internal asm stubs -- |
| ----------------------------------------- |
| |
| SC_PREGS is always expected to be SIGCONTEXT->sc_pregs. Eventhough our |
| symbols will remain local, the prototype claims "extern" and not |
| "static" to prevent compiler complaints about a symbol used but never |
| defined. */ |
| |
| /* sigtramp stub providing CFI info for common registers. */ |
| |
| extern void __gnat_sigtramp_common |
| (int signo, void *siginfo, void *sigcontext, |
| sighandler_t * handler, void * sc_pregs); |
| |
| |
| /* ------------------------------------- |
| -- Common interface implementation -- |
| ------------------------------------- |
| |
| We enforce optimization to minimize the overhead of the extra layer. */ |
| |
| void __gnat_sigtramp (int signo, void *si, void *sc, |
| sighandler_t * handler) |
| __attribute__((optimize(2))); |
| |
| void __gnat_sigtramp (int signo, void *si, void *sc, |
| sighandler_t * handler) |
| { |
| struct sigcontext * sctx = (struct sigcontext *) sc; |
| |
| __gnat_sigtramp_common (signo, si, sctx, handler, sctx->sc_pregs); |
| } |
| |
| |
| /* --------------------------- |
| -- And now the asm stubs -- |
| --------------------------- |
| |
| They all have a common structure with blocks of asm sequences queued one |
| after the others. Typically: |
| |
| SYMBOL_START |
| |
| CFI_DIRECTIVES |
| CFI_DEF_CFA, |
| CFI_COMMON_REGISTERS, |
| ... |
| |
| STUB_BODY |
| asm code to establish frame, setup the cfa reg value, |
| call the real signal handler, ... |
| |
| SYMBOL_END |
| */ |
| |
| /*-------------------------------- |
| -- Misc constants and helpers -- |
| -------------------------------- */ |
| |
| /* REGNO constants, dwarf column numbers for registers of interest. */ |
| |
| #define REGNO_G_REG_OFFSET(N) (N) |
| |
| #define REGNO_PC_OFFSET 15 /* PC_REGNUM */ |
| |
| /* asm string construction helpers. */ |
| |
| #define STR(TEXT) #TEXT |
| /* stringify expanded TEXT, surrounding it with double quotes. */ |
| |
| #define S(E) STR(E) |
| /* stringify E, which will resolve as text but may contain macros |
| still to be expanded. */ |
| |
| /* asm (TEXT) outputs <tab>TEXT. These facilitate the output of |
| multine contents: */ |
| #define TAB(S) "\t" S |
| #define CR(S) S "\n" |
| |
| #undef TCR |
| #define TCR(S) TAB(CR(S)) |
| |
| /*------------------------------ |
| -- Stub construction blocks -- |
| ------------------------------ */ |
| |
| /* CFA setup block |
| --------------- |
| Only non-volatile registers are suitable for a CFA base. These are the |
| only ones we can expect to be able retrieve from the unwinding context |
| while walking up the chain, saved by at least the bottom-most exception |
| propagation services. We use r8 here and set it to the value we need |
| in stub body that follows. Any of r4-r8 should work. */ |
| |
| #define CFA_REG 8 |
| |
| #define CFI_DEF_CFA \ |
| CR(".cfi_def_cfa " S(CFA_REG) ", 0") |
| |
| /* Register location blocks |
| ------------------------ |
| Rules to find registers of interest from the CFA. This should comprise |
| all the non-volatile registers relevant to the interrupted context. */ |
| |
| #define COMMON_CFI(REG) \ |
| ".cfi_offset " S(REGNO_##REG) "," S(REG_SET_##REG) |
| |
| #define CFI_COMMON_REGS \ |
| CR("# CFI for common registers\n") \ |
| TCR(COMMON_CFI(G_REG_OFFSET(0))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(1))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(2))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(3))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(4))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(5))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(6))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(7))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(8))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(9))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(10))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(11))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(12))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(13))) \ |
| TCR(COMMON_CFI(G_REG_OFFSET(14))) \ |
| TCR(COMMON_CFI(PC_OFFSET)) \ |
| TCR(".cfi_return_column " S(REGNO_PC_OFFSET)) |
| |
| /* Trampoline body block |
| --------------------- */ |
| |
| #define SIGTRAMP_BODY \ |
| CR("") \ |
| TCR("# Allocate frame and save the non-volatile") \ |
| TCR("# registers we're going to modify") \ |
| TCR("mov ip, sp") \ |
| TCR("stmfd sp!, {r"S(CFA_REG)", fp, ip, lr, pc}") \ |
| TCR("# Setup CFA_REG = sc_pregs, that we'll retrieve as our CFA value") \ |
| TCR("ldr r"S(CFA_REG)", [ip]") \ |
| TCR("") \ |
| TCR("# Call the real handler. The signo, siginfo and sigcontext") \ |
| TCR("# arguments are the same as those we received in r0, r1 and r2") \ |
| TCR("sub fp, ip, #4") \ |
| TCR("blx r3") \ |
| TCR("# Restore our callee-saved items, release our frame and return") \ |
| TCR("ldmfd sp, {r"S(CFA_REG)", fp, sp, pc}") |
| |
| |
| /* Symbol definition block |
| ----------------------- */ |
| |
| #define SIGTRAMP_START(SYM) \ |
| CR("# " S(SYM) " cfi trampoline") \ |
| TCR(".type " S(SYM) ", %function") \ |
| CR("") \ |
| CR(S(SYM) ":") \ |
| TCR(".cfi_startproc") \ |
| TCR(".cfi_signal_frame") |
| |
| /* Symbol termination block |
| ------------------------ */ |
| |
| #define SIGTRAMP_END(SYM) \ |
| CR(".cfi_endproc") \ |
| TCR(".size " S(SYM) ", .-" S(SYM)) |
| |
| /*---------------------------- |
| -- And now, the real code -- |
| ---------------------------- */ |
| |
| /* Text section start. The compiler isn't aware of that switch. */ |
| |
| asm (".text\n" |
| TCR(".align 2")); |
| |
| /* sigtramp stub for common registers. */ |
| |
| #define TRAMP_COMMON __gnat_sigtramp_common |
| |
| asm (SIGTRAMP_START(TRAMP_COMMON)); |
| asm (CFI_DEF_CFA); |
| asm (CFI_COMMON_REGS); |
| asm (SIGTRAMP_BODY); |
| asm (SIGTRAMP_END(TRAMP_COMMON)); |
| |
| |
