| /**************************************************************************** |
| * * |
| * GNAT COMPILER COMPONENTS * |
| * * |
| * S I G T R A M P * |
| * * |
| * Asm Implementation File * |
| * * |
| * Copyright (C) 2015-2021, 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. * |
| * * |
| ****************************************************************************/ |
| |
| /**************************************************** |
| * ARM64/IOS version of the __gnat_sigtramp service * |
| ****************************************************/ |
| |
| #include <sys/ucontext.h> |
| |
| #include "sigtramp.h" |
| /* See sigtramp.h for a general explanation of functionality. */ |
| |
| /* ---------------------- |
| -- General comments -- |
| ---------------------- |
| |
| Unfortunately the libunwind library used on this platform comes with severe |
| limitations that make the implementation convoluted: |
| |
| 1. At each step, the stack pointer register SP is restored with the CFA. |
| This makes it impossible to set the CFA to an arbitrary value, for |
| example to the address of the context saved on the stack, which means |
| that the simple CFI directives cannot be used for the registers. |
| |
| 2. For the ARM64 architecture (and only it), DWARF expressions are not |
| supported to compute the CFA. Only DW_CFA_def_cfa is supported, which |
| means that the CFA (modulo offset) must be loaded into a register. |
| |
| 3. The return column cannot be changed (30 for the ARM64 architecture). |
| Since column 30 is that of the LR register, this makes it impossible |
| to restore both the LR register and the PC. |
| |
| Therefore we need 2 distinct call-saved registers in the trampoline and |
| we resort to manual encoding of CFI byte sequences. */ |
| |
| /* ----------------------------------------- |
| -- Protypes for our internal asm stubs -- |
| ----------------------------------------- |
| |
| Even though 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 unwind info for common registers. */ |
| |
| extern void __gnat_sigtramp_common |
| (int signo, void *siginfo, void *sigcontext, |
| __sigtramphandler_t * handler); |
| |
| void __gnat_sigtramp (int signo, void *si, void *ucontext, |
| __sigtramphandler_t * handler) |
| __attribute__((optimize(2))); |
| |
| void __gnat_sigtramp (int signo, void *si, void *ucontext, |
| __sigtramphandler_t * handler) |
| { |
| mcontext_t mcontext = ((ucontext_t *) ucontext)->uc_mcontext; |
| |
| __gnat_sigtramp_common (signo, si, mcontext, handler); |
| } |
| |
| /* 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 |
| multiline contents: */ |
| #define TAB(S) "\t" S |
| #define CR(S) S "\n" |
| |
| #undef TCR |
| #define TCR(S) TAB(CR(S)) |
| |
| /* Offset in uc_mcontext of the __ss structure containing the registers. */ |
| #define UC_MCONTEXT_SS 16 |
| |
| #define CFA_REG 19 |
| #define BASE_REG 20 |
| |
| #define DW_CFA_def_cfa 0x0c |
| #define DW_CFA_expression 0x10 |
| |
| #define DW_OP_breg(n) 0x70+(n) |
| |
| #define REG_REGNO_GR(n) n |
| #define REG_REGNO_PC 30 |
| |
| /* The first byte of the SLEB128 value of the offset. */ |
| #define REG_OFFSET_GR(n) (UC_MCONTEXT_SS + n * 8) |
| #define REG_OFFSET_LONG_GR(n) (UC_MCONTEXT_SS + n * 8 + 128) |
| #define REG_OFFSET_LONG128_GR(n) (UC_MCONTEXT_SS + (n - 16) * 8 + 128) |
| #define REG_OFFSET_LONG256_GR(n) (UC_MCONTEXT_SS + (n - 32) * 8 + 128) |
| |
| #define REG_OFFSET_LONG256_PC REG_OFFSET_LONG256_GR(32) |
| |
| #define CFI_DEF_CFA \ |
| TCR(".cfi_def_cfa " S(CFA_REG) ", 0") |
| |
| /* We need 4 variants depending on the offset: 0+, 64+, 128+, 256+. */ |
| #define COMMON_CFI(REG) \ |
| ".cfi_escape " S(DW_CFA_expression) "," S(REG_REGNO_##REG) ",2," \ |
| S(DW_OP_breg(BASE_REG)) "," S(REG_OFFSET_##REG) |
| |
| #define COMMON_LONG_CFI(REG) \ |
| ".cfi_escape " S(DW_CFA_expression) "," S(REG_REGNO_##REG) ",3," \ |
| S(DW_OP_breg(BASE_REG)) "," S(REG_OFFSET_LONG_##REG) ",0" |
| |
| #define COMMON_LONG128_CFI(REG) \ |
| ".cfi_escape " S(DW_CFA_expression) "," S(REG_REGNO_##REG) ",3," \ |
| S(DW_OP_breg(BASE_REG)) "," S(REG_OFFSET_LONG128_##REG) ",1" |
| |
| #define COMMON_LONG256_CFI(REG) \ |
| ".cfi_escape " S(DW_CFA_expression) "," S(REG_REGNO_##REG) ",3," \ |
| S(DW_OP_breg(BASE_REG)) "," S(REG_OFFSET_LONG256_##REG) ",2" |
| |
| #define CFI_COMMON_REGS \ |
| CR("# CFI for common registers\n") \ |
| TCR(COMMON_CFI(GR(0))) \ |
| TCR(COMMON_CFI(GR(1))) \ |
| TCR(COMMON_CFI(GR(2))) \ |
| TCR(COMMON_CFI(GR(3))) \ |
| TCR(COMMON_CFI(GR(4))) \ |
| TCR(COMMON_CFI(GR(5))) \ |
| TCR(COMMON_LONG_CFI(GR(6))) \ |
| TCR(COMMON_LONG_CFI(GR(7))) \ |
| TCR(COMMON_LONG_CFI(GR(8))) \ |
| TCR(COMMON_LONG_CFI(GR(9))) \ |
| TCR(COMMON_LONG_CFI(GR(10))) \ |
| TCR(COMMON_LONG_CFI(GR(11))) \ |
| TCR(COMMON_LONG_CFI(GR(12))) \ |
| TCR(COMMON_LONG_CFI(GR(13))) \ |
| TCR(COMMON_LONG128_CFI(GR(14))) \ |
| TCR(COMMON_LONG128_CFI(GR(15))) \ |
| TCR(COMMON_LONG128_CFI(GR(16))) \ |
| TCR(COMMON_LONG128_CFI(GR(17))) \ |
| TCR(COMMON_LONG128_CFI(GR(18))) \ |
| TCR(COMMON_LONG128_CFI(GR(19))) \ |
| TCR(COMMON_LONG128_CFI(GR(20))) \ |
| TCR(COMMON_LONG128_CFI(GR(21))) \ |
| TCR(COMMON_LONG128_CFI(GR(22))) \ |
| TCR(COMMON_LONG128_CFI(GR(23))) \ |
| TCR(COMMON_LONG128_CFI(GR(24))) \ |
| TCR(COMMON_LONG128_CFI(GR(25))) \ |
| TCR(COMMON_LONG128_CFI(GR(26))) \ |
| TCR(COMMON_LONG128_CFI(GR(27))) \ |
| TCR(COMMON_LONG128_CFI(GR(28))) \ |
| TCR(COMMON_LONG128_CFI(GR(29))) \ |
| TCR(COMMON_LONG256_CFI(PC)) |
| |
| /* Trampoline body block |
| --------------------- */ |
| |
| #define SIGTRAMP_BODY \ |
| TCR("stp fp, lr, [sp, #-32]!") \ |
| TCR("stp x" S(CFA_REG) ", x" S(BASE_REG) ", [sp, #16]") \ |
| TCR("mov fp, sp") \ |
| TCR("# Load the saved value of the stack pointer as CFA") \ |
| TCR("ldr x" S(CFA_REG) ", [x2, #" S(REG_OFFSET_GR(31)) "]") \ |
| TCR("# Use x" S(BASE_REG) " as base register for the CFI") \ |
| TCR("mov x" S(BASE_REG) ", x2") \ |
| TCR("# Call the handler") \ |
| TCR("blr x3") \ |
| TCR("# Release our frame and return (should never get here!).") \ |
| TCR("ldp x" S(CFA_REG) ", x" S(BASE_REG)" , [sp, #16]") \ |
| TCR("ldp fp, lr, [sp], 32") \ |
| TCR("ret") |
| |
| /* ----------------------------- |
| -- Symbol definition block -- |
| ----------------------------- */ |
| |
| #define SIGTRAMP_START(SYM) \ |
| CR("# " S(SYM) " signal trampoline") \ |
| CR(S(SYM) ":") \ |
| TCR(".cfi_startproc") \ |
| TCR(".cfi_signal_frame") |
| |
| /* ------------------------------ |
| -- Symbol termination block -- |
| ------------------------------ */ |
| |
| #define SIGTRAMP_END(SYM) \ |
| TCR(".cfi_endproc") |
| |
| /*---------------------------- |
| -- And now, the real code -- |
| ---------------------------- */ |
| |
| 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)); |
