| /* Target-dependent code for BPF. |
| |
| Copyright (C) 2020-2021 Free Software Foundation, Inc. |
| |
| This file is part of GDB. |
| |
| This program 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 of the License, or |
| (at your option) any later version. |
| |
| This program 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 this program. If not, see <http://www.gnu.org/licenses/>. */ |
| |
| #include "defs.h" |
| #include "arch-utils.h" |
| #include "dis-asm.h" |
| #include "frame.h" |
| #include "frame-unwind.h" |
| #include "trad-frame.h" |
| #include "symtab.h" |
| #include "value.h" |
| #include "gdbcmd.h" |
| #include "breakpoint.h" |
| #include "inferior.h" |
| #include "regcache.h" |
| #include "target.h" |
| #include "dwarf2/frame.h" |
| #include "osabi.h" |
| #include "target-descriptions.h" |
| #include "remote.h" |
| |
| |
| /* eBPF registers. */ |
| |
| enum bpf_regnum |
| { |
| BPF_R0_REGNUM, /* return value */ |
| BPF_R1_REGNUM, |
| BPF_R2_REGNUM, |
| BPF_R3_REGNUM, |
| BPF_R4_REGNUM, |
| BPF_R5_REGNUM, |
| BPF_R6_REGNUM, |
| BPF_R7_REGNUM, |
| BPF_R8_REGNUM, |
| BPF_R9_REGNUM, |
| BPF_R10_REGNUM, /* sp */ |
| BPF_PC_REGNUM, |
| }; |
| |
| #define BPF_NUM_REGS (BPF_PC_REGNUM + 1) |
| |
| /* Target-dependent structure in gdbarch. */ |
| struct gdbarch_tdep |
| { |
| }; |
| |
| |
| /* Internal debugging facilities. */ |
| |
| /* When this is set to non-zero debugging information will be |
| printed. */ |
| |
| static unsigned int bpf_debug_flag = 0; |
| |
| /* The show callback for 'show debug bpf'. */ |
| |
| static void |
| show_bpf_debug (struct ui_file *file, int from_tty, |
| struct cmd_list_element *c, const char *value) |
| { |
| fprintf_filtered (file, _("Debugging of BPF is %s.\n"), value); |
| } |
| |
| |
| /* BPF registers. */ |
| |
| static const char *bpf_register_names[] = |
| { |
| "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", |
| "r8", "r9", "r10", "pc" |
| }; |
| |
| /* Return the name of register REGNUM. */ |
| |
| static const char * |
| bpf_register_name (struct gdbarch *gdbarch, int reg) |
| { |
| if (reg >= 0 && reg < BPF_NUM_REGS) |
| return bpf_register_names[reg]; |
| return NULL; |
| } |
| |
| /* Return the GDB type of register REGNUM. */ |
| |
| static struct type * |
| bpf_register_type (struct gdbarch *gdbarch, int reg) |
| { |
| if (reg == BPF_R10_REGNUM) |
| return builtin_type (gdbarch)->builtin_data_ptr; |
| else if (reg == BPF_PC_REGNUM) |
| return builtin_type (gdbarch)->builtin_func_ptr; |
| return builtin_type (gdbarch)->builtin_int64; |
| } |
| |
| /* Return the GDB register number corresponding to DWARF's REG. */ |
| |
| static int |
| bpf_dwarf2_reg_to_regnum (struct gdbarch *gdbarch, int reg) |
| { |
| if (reg >= 0 && reg < BPF_NUM_REGS) |
| return reg; |
| return -1; |
| } |
| |
| /* Implement the "print_insn" gdbarch method. */ |
| |
| static int |
| bpf_gdb_print_insn (bfd_vma memaddr, disassemble_info *info) |
| { |
| info->symbols = NULL; |
| return default_print_insn (memaddr, info); |
| } |
| |
| |
| /* Return PC of first real instruction of the function starting at |
| START_PC. */ |
| |
| static CORE_ADDR |
| bpf_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc) |
| { |
| fprintf_unfiltered (gdb_stdlog, |
| "Skipping prologue: start_pc=%s\n", |
| paddress (gdbarch, start_pc)); |
| /* XXX: to be completed. */ |
| return start_pc + 0; |
| } |
| |
| |
| /* Frame unwinder. |
| |
| XXX it is not clear how to unwind in eBPF, since the stack is not |
| guaranteed to be contiguous, and therefore no relative stack |
| addressing can be done in the callee in order to access the |
| caller's stack frame. To explore with xBPF, which will relax this |
| restriction. */ |
| |
| /* Given THIS_FRAME, return its ID. */ |
| |
| static void |
| bpf_frame_this_id (struct frame_info *this_frame, |
| void **this_prologue_cache, |
| struct frame_id *this_id) |
| { |
| /* Note that THIS_ID defaults to the outermost frame if we don't set |
| anything here. See frame.c:compute_frame_id. */ |
| } |
| |
| /* Return the reason why we can't unwind past THIS_FRAME. */ |
| |
| static enum unwind_stop_reason |
| bpf_frame_unwind_stop_reason (struct frame_info *this_frame, |
| void **this_cache) |
| { |
| return UNWIND_OUTERMOST; |
| } |
| |
| /* Ask THIS_FRAME to unwind its register. */ |
| |
| static struct value * |
| bpf_frame_prev_register (struct frame_info *this_frame, |
| void **this_prologue_cache, int regnum) |
| { |
| return frame_unwind_got_register (this_frame, regnum, regnum); |
| } |
| |
| /* Frame unwinder machinery for BPF. */ |
| |
| static const struct frame_unwind bpf_frame_unwind = |
| { |
| "bpf prologue", |
| NORMAL_FRAME, |
| bpf_frame_unwind_stop_reason, |
| bpf_frame_this_id, |
| bpf_frame_prev_register, |
| NULL, |
| default_frame_sniffer |
| }; |
| |
| |
| /* Breakpoints. */ |
| |
| /* Enum describing the different kinds of breakpoints. We currently |
| just support one, implemented by the brkpt xbpf instruction. */ |
| |
| enum bpf_breakpoint_kinds |
| { |
| BPF_BP_KIND_BRKPT = 0, |
| }; |
| |
| /* Implement the breakpoint_kind_from_pc gdbarch method. */ |
| |
| static int |
| bpf_breakpoint_kind_from_pc (struct gdbarch *gdbarch, CORE_ADDR *start_pc) |
| { |
| /* We support just one kind of breakpoint. */ |
| return BPF_BP_KIND_BRKPT; |
| } |
| |
| /* Implement the sw_breakpoint_from_kind gdbarch method. */ |
| |
| static const gdb_byte * |
| bpf_sw_breakpoint_from_kind (struct gdbarch *gdbarch, int kind, int *size) |
| { |
| static unsigned char brkpt_insn[] |
| = {0x8c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}; |
| |
| switch (kind) |
| { |
| case BPF_BP_KIND_BRKPT: |
| *size = 8; |
| return brkpt_insn; |
| default: |
| gdb_assert_not_reached ("unexpected BPF breakpoint kind"); |
| } |
| } |
| |
| |
| /* Assuming THIS_FRAME is a dummy frame, return its frame ID. */ |
| |
| static struct frame_id |
| bpf_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame) |
| { |
| CORE_ADDR sp = get_frame_register_unsigned (this_frame, |
| gdbarch_sp_regnum (gdbarch)); |
| return frame_id_build (sp, get_frame_pc (this_frame)); |
| } |
| |
| /* Implement the push dummy call gdbarch callback. */ |
| |
| static CORE_ADDR |
| bpf_push_dummy_call (struct gdbarch *gdbarch, struct value *function, |
| struct regcache *regcache, CORE_ADDR bp_addr, |
| int nargs, struct value **args, CORE_ADDR sp, |
| function_call_return_method return_method, |
| CORE_ADDR struct_addr) |
| { |
| fprintf_unfiltered (gdb_stdlog, "Pushing dummy call: sp=%s\n", |
| paddress (gdbarch, sp)); |
| /* XXX writeme */ |
| return sp; |
| } |
| |
| /* Extract a function return value of TYPE from REGCACHE, |
| and copy it into VALBUF. */ |
| |
| static void |
| bpf_extract_return_value (struct type *type, struct regcache *regcache, |
| gdb_byte *valbuf) |
| { |
| int len = TYPE_LENGTH (type); |
| gdb_byte vbuf[8]; |
| |
| gdb_assert (len <= 8); |
| regcache->cooked_read (BPF_R0_REGNUM, vbuf); |
| memcpy (valbuf, vbuf + 8 - len, len); |
| } |
| |
| /* Store the function return value of type TYPE from VALBUF into REGNAME. */ |
| |
| static void |
| bpf_store_return_value (struct type *type, struct regcache *regcache, |
| const gdb_byte *valbuf) |
| { |
| int len = TYPE_LENGTH (type); |
| gdb_byte vbuf[8]; |
| |
| gdb_assert (len <= 8); |
| memset (vbuf, 0, sizeof (vbuf)); |
| memcpy (vbuf + 8 - len, valbuf, len); |
| regcache->cooked_write (BPF_R0_REGNUM, vbuf); |
| } |
| |
| /* Handle function's return value. */ |
| |
| static enum return_value_convention |
| bpf_return_value (struct gdbarch *gdbarch, struct value *function, |
| struct type *type, struct regcache *regcache, |
| gdb_byte *readbuf, const gdb_byte *writebuf) |
| { |
| int len = TYPE_LENGTH (type); |
| |
| if (len > 8) |
| return RETURN_VALUE_STRUCT_CONVENTION; |
| |
| if (readbuf != NULL) |
| bpf_extract_return_value (type, regcache, readbuf); |
| if (writebuf != NULL) |
| bpf_store_return_value (type, regcache, writebuf); |
| |
| return RETURN_VALUE_REGISTER_CONVENTION; |
| } |
| |
| |
| /* Initialize the current architecture based on INFO. If possible, re-use an |
| architecture from ARCHES, which is a list of architectures already created |
| during this debugging session. */ |
| |
| static struct gdbarch * |
| bpf_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches) |
| { |
| /* If there is already a candidate, use it. */ |
| arches = gdbarch_list_lookup_by_info (arches, &info); |
| if (arches != NULL) |
| return arches->gdbarch; |
| |
| /* Allocate space for the new architecture. */ |
| struct gdbarch_tdep *tdep = XCNEW (struct gdbarch_tdep); |
| struct gdbarch *gdbarch = gdbarch_alloc (&info, tdep); |
| |
| /* Information about registers, etc. */ |
| set_gdbarch_num_regs (gdbarch, BPF_NUM_REGS); |
| set_gdbarch_register_name (gdbarch, bpf_register_name); |
| set_gdbarch_register_type (gdbarch, bpf_register_type); |
| |
| /* Register numbers of various important registers. */ |
| set_gdbarch_sp_regnum (gdbarch, BPF_R10_REGNUM); |
| set_gdbarch_pc_regnum (gdbarch, BPF_PC_REGNUM); |
| |
| /* Map DWARF2 registers to GDB registers. */ |
| set_gdbarch_dwarf2_reg_to_regnum (gdbarch, bpf_dwarf2_reg_to_regnum); |
| |
| /* Call dummy code. */ |
| set_gdbarch_call_dummy_location (gdbarch, ON_STACK); |
| set_gdbarch_dummy_id (gdbarch, bpf_dummy_id); |
| set_gdbarch_push_dummy_call (gdbarch, bpf_push_dummy_call); |
| |
| /* Returning results. */ |
| set_gdbarch_return_value (gdbarch, bpf_return_value); |
| |
| /* Advance PC across function entry code. */ |
| set_gdbarch_skip_prologue (gdbarch, bpf_skip_prologue); |
| |
| /* Stack grows downward. */ |
| set_gdbarch_inner_than (gdbarch, core_addr_lessthan); |
| |
| /* Breakpoint manipulation. */ |
| set_gdbarch_breakpoint_kind_from_pc (gdbarch, bpf_breakpoint_kind_from_pc); |
| set_gdbarch_sw_breakpoint_from_kind (gdbarch, bpf_sw_breakpoint_from_kind); |
| |
| /* Frame handling. */ |
| set_gdbarch_frame_args_skip (gdbarch, 8); |
| |
| /* Disassembly. */ |
| set_gdbarch_print_insn (gdbarch, bpf_gdb_print_insn); |
| |
| /* Hook in ABI-specific overrides, if they have been registered. */ |
| gdbarch_init_osabi (info, gdbarch); |
| |
| /* Install unwinders. */ |
| frame_unwind_append_unwinder (gdbarch, &bpf_frame_unwind); |
| |
| return gdbarch; |
| } |
| |
| void _initialize_bpf_tdep (); |
| void |
| _initialize_bpf_tdep () |
| { |
| register_gdbarch_init (bfd_arch_bpf, bpf_gdbarch_init); |
| |
| /* Add commands 'set/show debug bpf'. */ |
| add_setshow_zuinteger_cmd ("bpf", class_maintenance, |
| &bpf_debug_flag, |
| _("Set BPF debugging."), |
| _("Show BPF debugging."), |
| _("Enables BPF specific debugging output."), |
| NULL, |
| &show_bpf_debug, |
| &setdebuglist, &showdebuglist); |
| } |