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[rfc] Autoselect x86_64 or i386 based on the remote g packet size
- From: Daniel Jacobowitz <drow at false dot org>
- To: gdb-patches at sourceware dot org
- Date: Thu, 9 Nov 2006 15:57:55 -0500
- Subject: [rfc] Autoselect x86_64 or i386 based on the remote g packet size
The first useful thing to go on top of my previous infrastructure patches.
This patch is handy when using GDB without a binary; it will be even handier
if someone (I'll probably do this eventually) gets around to warning
when a binary and target have incompatible architectures.
Today:
This GDB was configured as "x86_64-linux-gnu".
(gdb) show architecture
The target architecture is set automatically (currently i386)
(gdb) tar rem :1234
Remote debugging using :1234
Remote register badly formatted:
T0506:0000000000000000;07:f0e1ffffff7f0000;10:80baaaaaaa2a0000;
here: 0000000;07:f0e1ffffff7f0000;10:80baaaaaaa2a0000;
After the patch:
(gdb) show architecture
The target architecture is set automatically (currently i386)
(gdb) tar rem :1234
Remote debugging using :1234
0x00002aaaaaaaba80 in ?? ()
(gdb) show architecture
The target architecture is set automatically (currently i386:x86-64)
Personally, I think that's pretty cool. I do this surprisingly
often, e.g. to kill an errant gdbserver; you have to connect to it
using the right architecture or you won't get far enough to send a
'k' packet.
The operating principle is that a target is free to send back a "short"
g packet, but some sizes are plausible and others are not. So I
enhanced the i386 backend to register the sizes of likely register
sets: core registers, core + i387, core + i387 + SSE. The Linux
backend adds the %orig_eax and %orig_rax pseudo-"registers" too
(which, if I were inventing them today, might be target objects like
the sparc WCOOKIE, but are currently in the g packet).
So if you have a GDB which defaults to i386-linux, and it connects to
an amd64 target and gets exactly the right number of bytes to be
a 64-bit register set, it'll assume that's what it's got.
There's deliberately no mechanism to say "more than X bytes must be amd64",
because I feel that's unsafe. The current registered guesses are
high-confidence, since e.g the amd64 guesses would be quite odd sizes for
an i386 target to return. For instance, the amd64 non-FP registers cut
off between fioff and foseg if interpreted as a 32-bit register set: not
very likely.
All comments welcome! Tested on x86_64-pc-linux-gnu, using gdbserver for
the testsuite and by hand.
--
Daniel Jacobowitz
CodeSourcery
2006-11-09 Daniel Jacobowitz <dan@codesourcery.com>
* remote.c (send_g_packet, process_g_packet): New functions, split
out from fetch_registers_using_g.
(fetch_registers_using_g): Use them.
(struct remote_g_packet_guess, remote_g_packet_guess_s)
(struct remote_g_packet_data, remote_g_packet_data_handle)
(remote_g_packet_data_init, register_remote_g_packet_guess)
(remote_read_description): New.
(init_remote_ops, init_remote_async_ops): Set to_read_description.
(_initialize_remote): Register remote_g_packet_data_handle.
* Makefile.in (amd64-linux-nat.o, i386-linux-tdep.o, i386-tdep.o):
Update.
* i386-tdep.c (tdesc_i386, tdesc_amd64): New variables.
(i386_register_g_packet_guesses): New function.
(i386_gdbarch_init): Call it.
* amd64-linux-tdep.c (amd64_linux_init_abi): Call
i386_linux_register_g_packet_guesses.
* i386-linux-tdep.c (i386_linux_register_g_packet_guesses): New.
(i386_linux_init_abi): Call it.
* i386-linux-tdep.h (i386_linux_register_g_packet_guesses): New
prototype.
* i386-tdep.h (tdesc_i386, tdesc_amd64): Declare.
* remote.h (register_remote_g_packet_guess): Declare.
---
gdb/Makefile.in | 8 +-
gdb/amd64-linux-tdep.c | 3 +
gdb/i386-linux-tdep.c | 25 ++++++++
gdb/i386-linux-tdep.h | 4 +
gdb/i386-tdep.c | 48 +++++++++++++++++
gdb/i386-tdep.h | 6 ++
gdb/remote.c | 137 ++++++++++++++++++++++++++++++++++++++++++-------
gdb/remote.h | 5 +
8 files changed, 214 insertions(+), 22 deletions(-)
Index: src/gdb/Makefile.in
===================================================================
--- src.orig/gdb/Makefile.in 2006-11-09 10:38:30.000000000 -0500
+++ src/gdb/Makefile.in 2006-11-09 10:40:16.000000000 -0500
@@ -1753,7 +1753,8 @@ amd64-linux-nat.o: amd64-linux-nat.c $(d
$(i386_linux_tdep_h) $(amd64_nat_h) $(target_h) $(amd64_linux_tdep_h)
amd64-linux-tdep.o: amd64-linux-tdep.c $(defs_h) $(frame_h) $(gdbcore_h) \
$(regcache_h) $(osabi_h) $(symtab_h) $(gdb_string_h) $(amd64_tdep_h) \
- $(solib_svr4_h) $(gdbtypes_h) $(reggroups_h) $(amd64_linux_tdep_h)
+ $(solib_svr4_h) $(gdbtypes_h) $(reggroups_h) $(amd64_linux_tdep_h) \
+ $(i386_linux_tdep_h)
amd64-nat.o: amd64-nat.c $(defs_h) $(gdbarch_h) $(regcache_h) \
$(gdb_assert_h) $(gdb_string_h) $(i386_tdep_h) $(amd64_tdep_h)
amd64nbsd-nat.o: amd64nbsd-nat.c $(defs_h) $(target_h) $(gdb_assert_h) \
@@ -2116,7 +2117,8 @@ i386-linux-nat.o: i386-linux-nat.c $(def
i386-linux-tdep.o: i386-linux-tdep.c $(defs_h) $(gdbcore_h) $(frame_h) \
$(value_h) $(regcache_h) $(inferior_h) $(osabi_h) $(reggroups_h) \
$(dwarf2_frame_h) $(gdb_string_h) $(i386_tdep_h) \
- $(i386_linux_tdep_h) $(glibc_tdep_h) $(solib_svr4_h)
+ $(i386_linux_tdep_h) $(glibc_tdep_h) $(solib_svr4_h) \
+ $(remote_h)
i386-nat.o: i386-nat.c $(defs_h) $(breakpoint_h) $(command_h) $(gdbcmd_h)
i386nbsd-nat.o: i386nbsd-nat.c $(defs_h) $(gdbcore_h) $(regcache_h) \
$(target_h) $(i386_tdep_h) $(i386bsd_nat_h) $(bsd_kvm_h)
@@ -2144,7 +2146,7 @@ i386-tdep.o: i386-tdep.c $(defs_h) $(arc
$(gdbcmd_h) $(gdbcore_h) $(objfiles_h) $(osabi_h) $(regcache_h) \
$(reggroups_h) $(regset_h) $(symfile_h) $(symtab_h) $(target_h) \
$(value_h) $(dis_asm_h) $(gdb_assert_h) $(gdb_string_h) \
- $(i386_tdep_h) $(i387_tdep_h)
+ $(i386_tdep_h) $(i387_tdep_h) $(remote_h) $(target_descriptions_h)
i386v4-nat.o: i386v4-nat.c $(defs_h) $(value_h) $(inferior_h) $(regcache_h) \
$(i386_tdep_h) $(i387_tdep_h) $(gregset_h)
i386v-nat.o: i386v-nat.c $(defs_h) $(frame_h) $(inferior_h) $(language_h) \
Index: src/gdb/i386-tdep.c
===================================================================
--- src.orig/gdb/i386-tdep.c 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/i386-tdep.c 2006-11-09 10:39:26.000000000 -0500
@@ -44,6 +44,8 @@
#include "target.h"
#include "value.h"
#include "dis-asm.h"
+#include "remote.h"
+#include "target-descriptions.h"
#include "gdb_assert.h"
#include "gdb_string.h"
@@ -2253,6 +2255,49 @@ i386_fetch_pointer_argument (struct fram
return read_memory_unsigned_integer (sp + (4 * (argi + 1)), 4);
}
+struct target_desc *tdesc_i386, *tdesc_amd64;
+
+static void
+i386_register_g_packet_guesses (struct gdbarch *gdbarch)
+{
+ int regs32, regs64, regs387, regs_sse32, regs_sse64;
+
+ if (tdesc_i386 == NULL)
+ {
+ const struct bfd_arch_info *arch;
+
+ tdesc_i386 = allocate_target_description ();
+ arch = bfd_lookup_arch (bfd_arch_i386, bfd_mach_i386_i386);
+ set_tdesc_architecture (tdesc_i386, arch);
+
+ tdesc_amd64 = allocate_target_description ();
+ arch = bfd_lookup_arch (bfd_arch_i386, bfd_mach_x86_64);
+ set_tdesc_architecture (tdesc_amd64, arch);
+ }
+
+ /* If the size matches the set of 32-bit or 64-bit integer registers,
+ assume that's what we've got. */
+ regs32 = 16 * 4;
+ register_remote_g_packet_guess (gdbarch, regs32, tdesc_i386);
+
+ regs64 = 17 * 8 + 7 * 4;
+ register_remote_g_packet_guess (gdbarch, regs64, tdesc_amd64);
+
+ /* Check for that plus i387 registers. */
+ regs387 = 8 * 10 + 8 * 4;
+ register_remote_g_packet_guess (gdbarch, regs32 + regs387, tdesc_i386);
+ register_remote_g_packet_guess (gdbarch, regs64 + regs387, tdesc_amd64);
+
+ /* Check for that plus SSE. */
+ regs_sse32 = 8 * 16 + 4;
+ register_remote_g_packet_guess (gdbarch, regs32 + regs387 + regs_sse32,
+ tdesc_i386);
+
+ regs_sse64 = 16 * 16 + 4;
+ register_remote_g_packet_guess (gdbarch, regs64 + regs387 + regs_sse64,
+ tdesc_amd64);
+}
+
static struct gdbarch *
i386_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
@@ -2418,6 +2463,9 @@ i386_gdbarch_init (struct gdbarch_info i
/* Helper for function argument information. */
set_gdbarch_fetch_pointer_argument (gdbarch, i386_fetch_pointer_argument);
+ /* Register likely sizes of the remote protocol 'g' packet. */
+ i386_register_g_packet_guesses (gdbarch);
+
/* Hook in the DWARF CFI frame unwinder. */
frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
Index: src/gdb/remote.c
===================================================================
--- src.orig/gdb/remote.c 2006-11-09 10:38:30.000000000 -0500
+++ src/gdb/remote.c 2006-11-09 10:39:26.000000000 -0500
@@ -3466,11 +3466,10 @@ fetch_register_using_p (struct packet_re
/* Fetch the registers included in the target's 'g' packet. */
-static void
-fetch_registers_using_g (void)
+static int
+send_g_packet (void)
{
struct remote_state *rs = get_remote_state ();
- struct remote_arch_state *rsa = get_remote_arch_state ();
int i, buf_len;
char *p;
char *regs;
@@ -3478,11 +3477,41 @@ fetch_registers_using_g (void)
sprintf (rs->buf, "g");
remote_send (&rs->buf, &rs->buf_size);
+ /* We can get out of synch in various cases. If the first character
+ in the buffer is not a hex character, assume that has happened
+ and try to fetch another packet to read. */
+ while ((rs->buf[0] < '0' || rs->buf[0] > '9')
+ && (rs->buf[0] < 'A' || rs->buf[0] > 'F')
+ && (rs->buf[0] < 'a' || rs->buf[0] > 'f')
+ && rs->buf[0] != 'x') /* New: unavailable register value. */
+ {
+ if (remote_debug)
+ fprintf_unfiltered (gdb_stdlog,
+ "Bad register packet; fetching a new packet\n");
+ getpkt (&rs->buf, &rs->buf_size, 0);
+ }
+
buf_len = strlen (rs->buf);
/* Sanity check the received packet. */
if (buf_len % 2 != 0)
error (_("Remote 'g' packet reply is of odd length: %s"), rs->buf);
+
+ return buf_len / 2;
+}
+
+static void
+process_g_packet (void)
+{
+ struct remote_state *rs = get_remote_state ();
+ struct remote_arch_state *rsa = get_remote_arch_state ();
+ int i, buf_len;
+ char *p;
+ char *regs;
+
+ buf_len = strlen (rs->buf);
+
+ /* Further sanity checks, with knowledge of the architecture. */
if (REGISTER_BYTES_OK_P () && !REGISTER_BYTES_OK (buf_len / 2))
error (_("Remote 'g' packet reply is wrong length: %s"), rs->buf);
if (buf_len > 2 * rsa->sizeof_g_packet)
@@ -3519,20 +3548,6 @@ fetch_registers_using_g (void)
/* Unimplemented registers read as all bits zero. */
memset (regs, 0, rsa->sizeof_g_packet);
- /* We can get out of synch in various cases. If the first character
- in the buffer is not a hex character, assume that has happened
- and try to fetch another packet to read. */
- while ((rs->buf[0] < '0' || rs->buf[0] > '9')
- && (rs->buf[0] < 'A' || rs->buf[0] > 'F')
- && (rs->buf[0] < 'a' || rs->buf[0] > 'f')
- && rs->buf[0] != 'x') /* New: unavailable register value. */
- {
- if (remote_debug)
- fprintf_unfiltered (gdb_stdlog,
- "Bad register packet; fetching a new packet\n");
- getpkt (&rs->buf, &rs->buf_size, 0);
- }
-
/* Reply describes registers byte by byte, each byte encoded as two
hex characters. Suck them all up, then supply them to the
register cacheing/storage mechanism. */
@@ -3580,6 +3595,13 @@ fetch_registers_using_g (void)
}
static void
+fetch_registers_using_g (void)
+{
+ send_g_packet ();
+ process_g_packet ();
+}
+
+static void
remote_fetch_registers (int regnum)
{
struct remote_state *rs = get_remote_state ();
@@ -5983,6 +6005,83 @@ remote_get_thread_local_address (ptid_t
return 0;
}
+/* Support for inferring a target description based on the current
+ architecture and the size of a 'g' packet. While the 'g' packet
+ can have any size (since optional registers can be left off the
+ end), some sizes are easily recognizable given knowledge of the
+ approximate architecture. */
+
+struct remote_g_packet_guess
+{
+ int bytes;
+ const struct target_desc *tdesc;
+};
+typedef struct remote_g_packet_guess remote_g_packet_guess_s;
+DEF_VEC_O(remote_g_packet_guess_s);
+
+struct remote_g_packet_data
+{
+ VEC(remote_g_packet_guess_s) *guesses;
+};
+
+static struct gdbarch_data *remote_g_packet_data_handle;
+
+static void *
+remote_g_packet_data_init (struct obstack *obstack)
+{
+ return OBSTACK_ZALLOC (obstack, struct remote_g_packet_data);
+}
+
+void
+register_remote_g_packet_guess (struct gdbarch *gdbarch, int bytes,
+ const struct target_desc *tdesc)
+{
+ struct remote_g_packet_data *data
+ = gdbarch_data (gdbarch, remote_g_packet_data_handle);
+ struct remote_g_packet_guess new_guess, *guess;
+ int ix;
+
+ gdb_assert (tdesc != NULL);
+
+ for (ix = 0;
+ VEC_iterate (remote_g_packet_guess_s, data->guesses, ix, guess);
+ ix++)
+ if (guess->bytes == bytes)
+ internal_error (__FILE__, __LINE__,
+ "Duplicate g packet description added for size %d",
+ bytes);
+
+ new_guess.bytes = bytes;
+ new_guess.tdesc = tdesc;
+ VEC_safe_push (remote_g_packet_guess_s, data->guesses, &new_guess);
+}
+
+static const struct target_desc *
+remote_read_description (struct target_ops *target)
+{
+ struct remote_g_packet_data *data
+ = gdbarch_data (current_gdbarch, remote_g_packet_data_handle);
+
+ if (!VEC_empty (remote_g_packet_guess_s, data->guesses))
+ {
+ struct remote_g_packet_guess *guess;
+ int ix;
+ int bytes = send_g_packet ();
+
+ for (ix = 0;
+ VEC_iterate (remote_g_packet_guess_s, data->guesses, ix, guess);
+ ix++)
+ if (guess->bytes == bytes)
+ return guess->tdesc;
+
+ /* We discard the g packet. A minor optimization would be to
+ hold on to it, and fill the register cache once we have selected
+ an architecture, but it's too tricky to do safely. */
+ }
+
+ return NULL;
+}
+
static void
init_remote_ops (void)
{
@@ -6034,6 +6133,7 @@ Specify the serial device it is connecte
remote_ops.to_memory_map = remote_memory_map;
remote_ops.to_flash_erase = remote_flash_erase;
remote_ops.to_flash_done = remote_flash_done;
+ remote_ops.to_read_description = remote_read_description;
}
/* Set up the extended remote vector by making a copy of the standard
@@ -6166,6 +6266,7 @@ Specify the serial device it is connecte
remote_async_ops.to_memory_map = remote_memory_map;
remote_async_ops.to_flash_erase = remote_flash_erase;
remote_async_ops.to_flash_done = remote_flash_done;
+ remote_ops.to_read_description = remote_read_description;
}
/* Set up the async extended remote vector by making a copy of the standard
@@ -6246,6 +6347,8 @@ _initialize_remote (void)
/* architecture specific data */
remote_gdbarch_data_handle =
gdbarch_data_register_post_init (init_remote_state);
+ remote_g_packet_data_handle =
+ gdbarch_data_register_pre_init (remote_g_packet_data_init);
/* Old tacky stuff. NOTE: This comes after the remote protocol so
that the remote protocol has been initialized. */
Index: src/gdb/amd64-linux-tdep.c
===================================================================
--- src.orig/gdb/amd64-linux-tdep.c 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/amd64-linux-tdep.c 2006-11-09 10:39:26.000000000 -0500
@@ -29,6 +29,7 @@
#include "gdbtypes.h"
#include "reggroups.h"
#include "amd64-linux-tdep.h"
+#include "i386-linux-tdep.h"
#include "gdb_string.h"
@@ -287,6 +288,8 @@ amd64_linux_init_abi (struct gdbarch_inf
/* Enable TLS support. */
set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map);
+
+ i386_linux_register_g_packet_guesses (gdbarch);
}
Index: src/gdb/i386-linux-tdep.c
===================================================================
--- src.orig/gdb/i386-linux-tdep.c 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/i386-linux-tdep.c 2006-11-09 10:39:26.000000000 -0500
@@ -1,6 +1,6 @@
/* Target-dependent code for GNU/Linux i386.
- Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005
+ Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006
Free Software Foundation, Inc.
This file is part of GDB.
@@ -28,6 +28,7 @@
#include "inferior.h"
#include "osabi.h"
#include "reggroups.h"
+#include "remote.h"
#include "dwarf2-frame.h"
#include "gdb_string.h"
@@ -403,6 +404,26 @@ static int i386_linux_sc_reg_offset[] =
0 * 4 /* %gs */
};
+void
+i386_linux_register_g_packet_guesses (struct gdbarch *gdbarch)
+{
+ int regs32, regs64, regs387, regs_sse32, regs_sse64;
+
+ /* Recognize the GNU/Linux %orig_eax and %orig_rax "registers". */
+ regs32 = 16 * 4;
+ regs64 = 17 * 8 + 7 * 4;
+
+ regs387 = 8 * 10 + 8 * 4;
+
+ regs_sse32 = 8 * 16 + 4;
+ regs_sse64 = 16 * 16 + 4;
+
+ register_remote_g_packet_guess (gdbarch, regs32 + regs387 + regs_sse32 + 4,
+ tdesc_i386);
+ register_remote_g_packet_guess (gdbarch, regs64 + regs387 + regs_sse64 + 8,
+ tdesc_amd64);
+}
+
static void
i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
@@ -442,6 +463,8 @@ i386_linux_init_abi (struct gdbarch_info
/* Enable TLS support. */
set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map);
+
+ i386_linux_register_g_packet_guesses (gdbarch);
}
/* Provide a prototype to silence -Wmissing-prototypes. */
Index: src/gdb/i386-linux-tdep.h
===================================================================
--- src.orig/gdb/i386-linux-tdep.h 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/i386-linux-tdep.h 2006-11-09 10:39:26.000000000 -0500
@@ -1,6 +1,6 @@
/* Target-dependent code for GNU/Linux x86.
- Copyright (C) 2002, 2003 Free Software Foundation, Inc.
+ Copyright (C) 2002, 2003, 2006 Free Software Foundation, Inc.
This file is part of GDB.
@@ -36,4 +36,6 @@
/* Total number of registers for GNU/Linux. */
#define I386_LINUX_NUM_REGS (I386_LINUX_ORIG_EAX_REGNUM + 1)
+void i386_linux_register_g_packet_guesses (struct gdbarch *gdbarch);
+
#endif /* i386-linux-tdep.h */
Index: src/gdb/i386-tdep.h
===================================================================
--- src.orig/gdb/i386-tdep.h 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/i386-tdep.h 2006-11-09 10:39:26.000000000 -0500
@@ -28,6 +28,7 @@ struct gdbarch;
struct reggroup;
struct regset;
struct regcache;
+struct target_desc;
/* GDB's i386 target supports both the 32-bit Intel Architecture
(IA-32) and the 64-bit AMD x86-64 architecture. Internally it uses
@@ -156,6 +157,11 @@ extern struct type *i386_mmx_type;
extern struct type *i386_sse_type;
extern struct type *i386_mxcsr_type;
+/* Minimal target descriptions for i386 and amd64 targets, which only
+ specify the architecture. */
+extern struct target_desc *tdesc_i386;
+extern struct target_desc *tdesc_amd64;
+
/* Segment selectors. */
#define I386_SEL_RPL 0x0003 /* Requester's Privilege Level mask. */
#define I386_SEL_UPL 0x0003 /* User Privilige Level. */
Index: src/gdb/remote.h
===================================================================
--- src.orig/gdb/remote.h 2006-11-09 10:34:53.000000000 -0500
+++ src/gdb/remote.h 2006-11-09 10:39:26.000000000 -0500
@@ -21,6 +21,8 @@
#ifndef REMOTE_H
#define REMOTE_H
+struct target_desc;
+
/* FIXME?: move this interface down to tgt vector) */
/* Read a packet from the remote machine, with error checking, and
@@ -63,4 +65,7 @@ extern int remote_read_bytes (CORE_ADDR
extern void (*deprecated_target_resume_hook) (void);
extern void (*deprecated_target_wait_loop_hook) (void);
+void register_remote_g_packet_guess (struct gdbarch *gdbarch, int bytes,
+ const struct target_desc *tdesc);
+
#endif