[V3,1/3] gdb: support for eBPF

Message ID 20200703124650.15272-2-jose.marchesi@oracle.com
State New
Headers show
Series
  • eBPF support
Related show

Commit Message

Simon Marchi via Gdb-patches July 3, 2020, 12:46 p.m.
This patch adds basic support for the eBPF target: tdep and build
machinery.  The accompanying simulator is introduced in subsequent
patches.

gdb/ChangeLog:

2020-07-03  Weimin Pan <weimin.pan@oracle.com>
	    Jose E. Marchesi  <jose.marchesi@oracle.com>

	* configure.tgt: Add entry for bpf-*-*.
	* Makefile.in (ALL_TARGET_OBS): Add bpf-tdep.o
	(HFILES_NO_SRCDIR): Add bpf-tdep.h.
	(ALLDEPFILES): Add bpf-tdep.c.
	* bpf-tdep.h: New file.
	* bpf-tdep.c: Likewise.

gdb/doc/ChangeLog:

2020-07-03  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* gdb.texinfo (Contributors): Add information for the eBPF
	support.
	(BPF): New section.
---
 gdb/ChangeLog       |  10 ++
 gdb/Makefile.in     |   3 +
 gdb/bpf-tdep.c      | 331 ++++++++++++++++++++++++++++++++++++++++++++
 gdb/bpf-tdep.h      |  46 ++++++
 gdb/configure.tgt   |   6 +
 gdb/doc/ChangeLog   |   6 +
 gdb/doc/gdb.texinfo |  21 +++
 7 files changed, 423 insertions(+)
 create mode 100644 gdb/bpf-tdep.c
 create mode 100644 gdb/bpf-tdep.h

-- 
2.25.0.2.g232378479e

Patch

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 9ae9fe2d1e..bce77b693d 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -717,6 +717,7 @@  ALL_TARGET_OBS = \
 	avr-tdep.o \
 	bfin-linux-tdep.o \
 	bfin-tdep.o \
+	bpf-tdep.o \
 	bsd-uthread.o \
 	cris-linux-tdep.o \
 	cris-tdep.o \
@@ -1221,6 +1222,7 @@  HFILES_NO_SRCDIR = \
 	bcache.h \
 	bfd-target.h \
 	bfin-tdep.h \
+	bpf-tdep.h \
 	block.h \
 	breakpoint.h \
 	bsd-kvm.h \
@@ -2145,6 +2147,7 @@  ALLDEPFILES = \
 	avr-tdep.c \
 	bfin-linux-tdep.c \
 	bfin-tdep.c \
+	bpf-tdep.c \
 	bsd-kvm.c \
 	bsd-uthread.c \
 	csky-linux-tdep.c \
diff --git a/gdb/bpf-tdep.c b/gdb/bpf-tdep.c
new file mode 100644
index 0000000000..ebaf8f8cf3
--- /dev/null
+++ b/gdb/bpf-tdep.c
@@ -0,0 +1,331 @@ 
+/* Target-dependent code for eBPF.
+
+   Copyright (C) 2020 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 "bpf-tdep.h"
+#include "remote.h"
+
+
+static unsigned int ebpf_debug_flag = 0;
+
+static void ATTRIBUTE_PRINTF (1, 2)
+ebpf_debug (const char *fmt, ...)
+{
+  if (ebpf_debug_flag)
+    {
+       va_list args;
+
+       va_start (args, fmt);
+       printf_unfiltered ("eBPF: ");
+       vprintf_unfiltered (fmt, args);
+       va_end (args);
+    }
+}
+
+
+/* eBPF registers */
+
+static const char *ebpf_register_names[] =
+{
+  "r0",   "r1",  "r2",    "r3",   "r4",   "r5",   "r6",   "r7",
+  "r8",   "r9",  "r10",   "pc"
+};
+
+/* Return the name of register REGNUM.  */
+
+static const char *
+ebpf_register_name (struct gdbarch *gdbarch, int reg)
+{
+  if (reg >= 0 && reg < EBPF_NUM_REGS)
+    return ebpf_register_names[reg];
+  return NULL;
+}
+
+/* Return the GDB type of register REGNUM.  */
+
+static struct type *
+ebpf_register_type (struct gdbarch *gdbarch, int reg)
+{
+  if (reg == EBPF_R10_REGNUM)
+    return builtin_type (gdbarch)->builtin_data_ptr;
+  else if (reg == EBPF_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
+ebpf_dwarf2_reg_to_regnum (struct gdbarch *gdbarch, int reg)
+{
+  if (reg >= 0 && reg < EBPF_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);
+}
+
+
+/* Implement the "unwind_pc" gdbarch method.  */
+
+static CORE_ADDR
+ebpf_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
+{
+  return frame_unwind_register_unsigned (next_frame,
+					 gdbarch_pc_regnum (gdbarch));
+}
+
+/* Return PC of first real instruction of the function starting at
+   START_PC.  */
+
+static CORE_ADDR
+ebpf_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
+{
+  ebpf_debug ("Skipping prologue: start_pc=%s\n",
+	      paddress (gdbarch, start_pc));
+  /* XXX */
+  return start_pc+0;
+}
+
+
+/* Frame unwinder.  */
+
+static void
+bpf_frame_this_id (struct frame_info *this_frame,
+		   void **this_prologue_cache,
+		   struct frame_id *this_id)
+{
+  /* XXX */
+}
+
+static enum unwind_stop_reason
+bpf_frame_unwind_stop_reason (struct frame_info *this_frame,
+			      void **this_cache)
+{
+  return UNWIND_OUTERMOST; /* XXX */
+}
+
+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); /* XXX */
+}
+
+static const struct frame_unwind bpf_frame_unwind =
+{
+ NORMAL_FRAME,
+ bpf_frame_unwind_stop_reason,
+ bpf_frame_this_id,
+ bpf_frame_prev_register,
+ NULL,
+ default_frame_sniffer
+};
+
+
+/* Breakpoints.  */
+
+/* Implement the breakpoint_kind_from_pc gdbarch method.  */
+
+static int
+ebpf_breakpoint_kind_from_pc (struct gdbarch *gdbarch, CORE_ADDR *start_pc)
+{
+  /* We support just one kind of breakpoint.  */
+  return 8;
+}
+
+/* Implement the sw_breakpoint_from_kind gdbarch method.  */
+
+static const gdb_byte *
+ebpf_sw_breakpoint_from_kind (struct gdbarch *gdbarch, int kind, int *size)
+{
+  static unsigned char ebpf_breakpoint[]
+    = {0x8c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+  *size = kind;
+  return ebpf_breakpoint;
+}
+
+
+/* Assuming THIS_FRAME is a dummy frame, return its frame ID.  */
+
+static struct frame_id
+ebpf_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));
+}
+
+static CORE_ADDR
+ebpf_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)
+{
+  ebpf_debug ("Pushing dummy call: sp=%s\n", paddress (gdbarch, sp));
+  /* XXX */
+  return sp;
+}
+
+/* Extract a function return value of TYPE from REGCACHE,
+   and copy it into VALBUF.  */
+
+static void
+ebpf_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 (EBPF_R0_REGNUM, vbuf);
+  memcpy (valbuf, vbuf + 8 - len, len);
+}
+
+/* Store the function return value of type TYPE from VALBUF into REGNAME.  */
+
+static void
+ebpf_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 (EBPF_R0_REGNUM, vbuf);
+}
+
+/* Handle function's return value.  */
+
+static enum return_value_convention
+ebpf_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)
+    ebpf_extract_return_value (type, regcache, readbuf);
+  if (writebuf)
+    ebpf_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 *
+ebpf_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
+{
+  struct gdbarch_tdep *tdep;
+  struct gdbarch *gdbarch;
+
+  /* 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.  */
+  tdep = XCNEW (struct gdbarch_tdep);
+  gdbarch = gdbarch_alloc (&info, tdep);
+
+  /* Information about registers, etc.  */
+  set_gdbarch_num_regs (gdbarch, EBPF_NUM_REGS);
+  set_gdbarch_register_name (gdbarch, ebpf_register_name);
+  set_gdbarch_register_type (gdbarch, ebpf_register_type);
+
+  /* Register numbers of various important registers.  */
+  set_gdbarch_sp_regnum (gdbarch, EBPF_R10_REGNUM);
+  set_gdbarch_pc_regnum (gdbarch, EBPF_PC_REGNUM);
+
+  /* Map DWARF2 registers to GDB registers.  */
+  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, ebpf_dwarf2_reg_to_regnum);
+
+  /* Call dummy code.  */
+  set_gdbarch_call_dummy_location (gdbarch, ON_STACK);
+  set_gdbarch_dummy_id (gdbarch, ebpf_dummy_id);
+  set_gdbarch_push_dummy_call (gdbarch, ebpf_push_dummy_call);
+
+  /* Returning results.  */
+  set_gdbarch_return_value (gdbarch, ebpf_return_value);
+
+  /* Advance PC across function entry code.  */
+  set_gdbarch_skip_prologue (gdbarch, ebpf_skip_prologue);
+
+  /* Stack grows downward.  */
+  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
+
+  /* Breakpoint manipulation.  */
+  set_gdbarch_breakpoint_kind_from_pc (gdbarch, ebpf_breakpoint_kind_from_pc);
+  set_gdbarch_sw_breakpoint_from_kind (gdbarch, ebpf_sw_breakpoint_from_kind);
+
+  /* Frame handling.  */
+  set_gdbarch_frame_args_skip (gdbarch, 8);
+  set_gdbarch_unwind_pc (gdbarch, ebpf_unwind_pc);
+
+  /* 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_ebpf_tdep ();
+void
+_initialize_ebpf_tdep (void)
+{
+  register_gdbarch_init (bfd_arch_bpf, ebpf_gdbarch_init);
+}
diff --git a/gdb/bpf-tdep.h b/gdb/bpf-tdep.h
new file mode 100644
index 0000000000..3cfab9cd43
--- /dev/null
+++ b/gdb/bpf-tdep.h
@@ -0,0 +1,46 @@ 
+/* Target-dependent code for eBPF, for GDB.
+
+   Copyright (C) 2020 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/>.  */
+
+#ifndef BPF_TDEP_H
+#define BPF_TDEP_H
+
+enum ebpf_regnum {
+  EBPF_R0_REGNUM,		/* return value */
+  EBPF_R1_REGNUM,
+  EBPF_R2_REGNUM,
+  EBPF_R3_REGNUM,
+  EBPF_R4_REGNUM,
+  EBPF_R5_REGNUM,
+  EBPF_R6_REGNUM,
+  EBPF_R7_REGNUM,
+  EBPF_R8_REGNUM,
+  EBPF_R9_REGNUM,
+  EBPF_R10_REGNUM,		/* sp */
+  EBPF_PC_REGNUM,
+};
+
+#define EBPF_NUM_REGS	(EBPF_PC_REGNUM + 1)
+
+/* Target-dependent structure in gdbarch.  */
+struct gdbarch_tdep
+{
+  /* XXX */
+};
+
+#endif /* BPF_TDEP_H */
diff --git a/gdb/configure.tgt b/gdb/configure.tgt
index d66f01bb9f..8a26bdeb87 100644
--- a/gdb/configure.tgt
+++ b/gdb/configure.tgt
@@ -205,6 +205,12 @@  bfin-*-*)
 	gdb_sim=../sim/bfin/libsim.a
 	;;
 
+bpf-*-*)
+	# Target: eBPF
+	gdb_target_obs="bpf-tdep.o"
+	gdb_sim=../sim/bpf/libsim.a
+	;;
+
 cris*)
 	# Target: CRIS
 	gdb_target_obs="cris-tdep.o cris-linux-tdep.o linux-tdep.o solib-svr4.o"
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index c591934508..a134c0fdcf 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@ 
+2020-07-03  Jose E. Marchesi  <jose.marchesi@oracle.com>
+
+	* gdb.texinfo (Contributors): Add information for the eBPF
+	support.
+	(BPF): New section.
+
 2020-06-26  Eli Zaretskii  <eliz@gnu.org>
 
 	* gdb.texinfo (Shell Commands): More accurate description of use
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index fbe9f850af..b9df9cdf95 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -557,6 +557,10 @@  Alessandro Forin and Per Bothner.  More recent ports have been the work
 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
 Stafford Horne.
 
+Weimin Pan, David Faust and Jose E. Marchesi contributed support for
+the Linux kernel BPF virtual architecture.  This work was sponsored by
+Oracle.
+
 @node Sample Session
 @chapter A Sample @value{GDBN} Session
 
@@ -24379,6 +24383,7 @@  acceptable commands.
 @menu
 * ARC::                         Synopsys ARC
 * ARM::                         ARM
+* BPF::				eBPF
 * M68K::                        Motorola M68K
 * MicroBlaze::			Xilinx MicroBlaze
 * MIPS Embedded::               MIPS Embedded
@@ -24513,6 +24518,22 @@  The default value is @code{all}.
 @end table
 @end table
 
+@node BPF
+@subsection BPF
+
+@table @code
+@item target sim @r{[}@var{simargs}@r{]} @dots{} 
+The @value{GDBN} BPF simulator accepts the following optional arguments.
+
+@table @code
+@item --skb-data-offset=@var{offset}
+Tell the simulator the offset, measured in bytes, of the
+@code{skb_data} field in the kernel @code{struct sk_buff} structure.
+This offset is used by some BPF specific-purpose load/store
+instructions.  Defaults to 0.
+@end table
+@end table
+
 @node M68K
 @subsection M68k