/* tc-bpf.c -- Assembler for the Linux eBPF. Copyright (C) 2019-2021 Free Software Foundation, Inc. Contributed by Oracle, Inc. This file is part of GAS, the GNU Assembler. GAS is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GAS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GAS; see the file COPYING. If not, write to the Free Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */ #include "as.h" #include "subsegs.h" #include "symcat.h" #include "opcodes/bpf-desc.h" #include "opcodes/bpf-opc.h" #include "cgen.h" #include "elf/common.h" #include "elf/bpf.h" #include "dwarf2dbg.h" const char comment_chars[] = ";"; const char line_comment_chars[] = "#"; const char line_separator_chars[] = "`"; const char EXP_CHARS[] = "eE"; const char FLT_CHARS[] = "fFdD"; /* Like s_lcomm_internal in gas/read.c but the alignment string is allowed to be optional. */ static symbolS * pe_lcomm_internal (int needs_align, symbolS *symbolP, addressT size) { addressT align = 0; SKIP_WHITESPACE (); if (needs_align && *input_line_pointer == ',') { align = parse_align (needs_align - 1); if (align == (addressT) -1) return NULL; } else { if (size >= 8) align = 3; else if (size >= 4) align = 2; else if (size >= 2) align = 1; else align = 0; } bss_alloc (symbolP, size, align); return symbolP; } static void pe_lcomm (int needs_align) { s_comm_internal (needs_align * 2, pe_lcomm_internal); } /* The target specific pseudo-ops which we support. */ const pseudo_typeS md_pseudo_table[] = { { "half", cons, 2 }, { "word", cons, 4 }, { "dword", cons, 8 }, { "lcomm", pe_lcomm, 1 }, { NULL, NULL, 0 } }; /* ISA handling. */ static CGEN_BITSET *bpf_isa; /* Command-line options processing. */ enum options { OPTION_LITTLE_ENDIAN = OPTION_MD_BASE, OPTION_BIG_ENDIAN, OPTION_XBPF }; struct option md_longopts[] = { { "EL", no_argument, NULL, OPTION_LITTLE_ENDIAN }, { "EB", no_argument, NULL, OPTION_BIG_ENDIAN }, { "mxbpf", no_argument, NULL, OPTION_XBPF }, { NULL, no_argument, NULL, 0 }, }; size_t md_longopts_size = sizeof (md_longopts); const char * md_shortopts = ""; extern int target_big_endian; /* Whether target_big_endian has been set while parsing command-line arguments. */ static int set_target_endian = 0; static int target_xbpf = 0; static int set_xbpf = 0; int md_parse_option (int c, const char * arg ATTRIBUTE_UNUSED) { switch (c) { case OPTION_BIG_ENDIAN: set_target_endian = 1; target_big_endian = 1; break; case OPTION_LITTLE_ENDIAN: set_target_endian = 1; target_big_endian = 0; break; case OPTION_XBPF: set_xbpf = 1; target_xbpf = 1; break; default: return 0; } return 1; } void md_show_usage (FILE * stream) { fprintf (stream, _("\nBPF options:\n")); fprintf (stream, _("\ --EL generate code for a little endian machine\n\ --EB generate code for a big endian machine\n\ -mxbpf generate xBPF instructions\n")); } void md_begin (void) { /* Initialize the `cgen' interface. */ /* If not specified in the command line, use the host endianness. */ if (!set_target_endian) { #ifdef WORDS_BIGENDIAN target_big_endian = 1; #else target_big_endian = 0; #endif } /* If not specified in the command line, use eBPF rather than xBPF. */ if (!set_xbpf) target_xbpf = 0; /* Set the ISA, which depends on the target endianness. */ bpf_isa = cgen_bitset_create (ISA_MAX); if (target_big_endian) { if (target_xbpf) cgen_bitset_set (bpf_isa, ISA_XBPFBE); else cgen_bitset_set (bpf_isa, ISA_EBPFBE); } else { if (target_xbpf) cgen_bitset_set (bpf_isa, ISA_XBPFLE); else cgen_bitset_set (bpf_isa, ISA_EBPFLE); } /* Set the machine number and endian. */ gas_cgen_cpu_desc = bpf_cgen_cpu_open (CGEN_CPU_OPEN_ENDIAN, target_big_endian ? CGEN_ENDIAN_BIG : CGEN_ENDIAN_LITTLE, CGEN_CPU_OPEN_INSN_ENDIAN, CGEN_ENDIAN_LITTLE, CGEN_CPU_OPEN_ISAS, bpf_isa, CGEN_CPU_OPEN_END); bpf_cgen_init_asm (gas_cgen_cpu_desc); /* This is a callback from cgen to gas to parse operands. */ cgen_set_parse_operand_fn (gas_cgen_cpu_desc, gas_cgen_parse_operand); /* Set the machine type. */ bfd_default_set_arch_mach (stdoutput, bfd_arch_bpf, bfd_mach_bpf); } valueT md_section_align (segT segment, valueT size) { int align = bfd_section_alignment (segment); return ((size + (1 << align) - 1) & -(1 << align)); } /* Functions concerning relocs. */ /* The location from which a PC relative jump should be calculated, given a PC relative reloc. */ long md_pcrel_from_section (fixS *fixP, segT sec) { if (fixP->fx_addsy != (symbolS *) NULL && (! S_IS_DEFINED (fixP->fx_addsy) || (S_GET_SEGMENT (fixP->fx_addsy) != sec) || S_IS_EXTERNAL (fixP->fx_addsy) || S_IS_WEAK (fixP->fx_addsy))) { /* The symbol is undefined (or is defined but not in this section). Let the linker figure it out. */ return 0; } return fixP->fx_where + fixP->fx_frag->fr_address; } /* Write a value out to the object file, using the appropriate endianness. */ void md_number_to_chars (char * buf, valueT val, int n) { if (target_big_endian) number_to_chars_bigendian (buf, val, n); else number_to_chars_littleendian (buf, val, n); } arelent * tc_gen_reloc (asection *sec, fixS *fix) { return gas_cgen_tc_gen_reloc (sec, fix); } /* Return the bfd reloc type for OPERAND of INSN at fixup FIXP. This is called when the operand is an expression that couldn't be fully resolved. Returns BFD_RELOC_NONE if no reloc type can be found. *FIXP may be modified if desired. */ bfd_reloc_code_real_type md_cgen_lookup_reloc (const CGEN_INSN *insn ATTRIBUTE_UNUSED, const CGEN_OPERAND *operand, fixS *fixP) { switch (operand->type) { case BPF_OPERAND_OFFSET16: return BFD_RELOC_BPF_16; case BPF_OPERAND_IMM32: return BFD_RELOC_BPF_32; case BPF_OPERAND_IMM64: return BFD_RELOC_BPF_64; case BPF_OPERAND_DISP16: fixP->fx_pcrel = 1; return BFD_RELOC_BPF_DISP16; case BPF_OPERAND_DISP32: fixP->fx_pcrel = 1; return BFD_RELOC_BPF_DISP32; default: break; } return BFD_RELOC_NONE; } /* *FRAGP has been relaxed to its final size, and now needs to have the bytes inside it modified to conform to the new size. Called after relaxation is finished. fragP->fr_type == rs_machine_dependent. fragP->fr_subtype is the subtype of what the address relaxed to. */ void md_convert_frag (bfd *abfd ATTRIBUTE_UNUSED, segT sec ATTRIBUTE_UNUSED, fragS *fragP ATTRIBUTE_UNUSED) { as_fatal (_("convert_frag called")); } int md_estimate_size_before_relax (fragS *fragP ATTRIBUTE_UNUSED, segT segment ATTRIBUTE_UNUSED) { as_fatal (_("estimate_size_before_relax called")); return 0; } void md_apply_fix (fixS *fixP, valueT *valP, segT seg) { /* Some fixups for instructions require special attention. This is handled in the code block below. */ if ((int) fixP->fx_r_type >= (int) BFD_RELOC_UNUSED) { int opindex = (int) fixP->fx_r_type - (int) BFD_RELOC_UNUSED; const CGEN_OPERAND *operand = cgen_operand_lookup_by_num (gas_cgen_cpu_desc, opindex); char *where; switch (operand->type) { case BPF_OPERAND_DISP32: /* eBPF supports two kind of CALL instructions: the so called pseudo calls ("bpf to bpf") and external calls ("bpf to kernel"). Both kind of calls use the same instruction (CALL). However, external calls are constructed by passing a constant argument to the instruction, whereas pseudo calls result from expressions involving symbols. In practice, instructions requiring a fixup are interpreted as pseudo-calls. If we are executing this code, this is a pseudo call. The kernel expects for pseudo-calls to be annotated by having BPF_PSEUDO_CALL in the SRC field of the instruction. But beware the infamous nibble-swapping of eBPF and take endianness into account here. Note that the CALL instruction has only one operand, so this code is executed only once per instruction. */ where = fixP->fx_frag->fr_literal + fixP->fx_where + 1; where[0] = target_big_endian ? 0x01 : 0x10; /* Fallthrough. */ case BPF_OPERAND_DISP16: /* The PC-relative displacement fields in jump instructions shouldn't be in bytes. Instead, they hold the number of 64-bit words to the target, _minus one_. */ *valP = (((long) (*valP)) - 8) / 8; break; default: break; } } /* And now invoke CGEN's handler, which will eventually install *valP into the corresponding operand. */ gas_cgen_md_apply_fix (fixP, valP, seg); } void md_assemble (char *str) { const CGEN_INSN *insn; char *errmsg; CGEN_FIELDS fields; #if CGEN_INT_INSN_P CGEN_INSN_INT buffer[CGEN_MAX_INSN_SIZE / sizeof (CGEN_INT_INSN_P)]; #else unsigned char buffer[CGEN_MAX_INSN_SIZE]; #endif gas_cgen_init_parse (); insn = bpf_cgen_assemble_insn (gas_cgen_cpu_desc, str, &fields, buffer, &errmsg); if (insn == NULL) { as_bad ("%s", errmsg); return; } gas_cgen_finish_insn (insn, buffer, CGEN_FIELDS_BITSIZE (&fields), 0, /* zero to ban relaxable insns. */ NULL); /* NULL so results not returned here. */ } void md_operand (expressionS *expressionP) { gas_cgen_md_operand (expressionP); } symbolS * md_undefined_symbol (char *name ATTRIBUTE_UNUSED) { return NULL; } /* Turn a string in input_line_pointer into a floating point constant of type TYPE, and store the appropriate bytes in *LITP. The number of LITTLENUMS emitted is stored in *SIZEP. An error message is returned, or NULL on OK. */ const char * md_atof (int type, char *litP, int *sizeP) { return ieee_md_atof (type, litP, sizeP, FALSE); }