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[rfc] Add syscall restart handling for MIPS GNU/Linux
- From: Daniel Jacobowitz <drow at false dot org>
- To: gdb-patches at sourceware dot org
- Date: Mon, 21 May 2007 09:56:47 -0400
- Subject: [rfc] Add syscall restart handling for MIPS GNU/Linux
This patch fixes the interrupt.exp and mi*-syn-frame.exp tests for
native MIPS GNU/Linux. Just like i386 (and most other Linux
platforms), MIPS has a ptrace-accessible "register" which stores the
error code for restartable syscalls. If a signal handler is run then
this becomes an EINTR return value; if no signal handler is run, then
the syscall is restarted by backing up $pc two instructions. This
causes obvious trouble if GDB tries to call a function at some other
location during a restartable syscall. We have to clear the register
before changing $pc.
This patch touches a fair number of files but is quite simple. It has
two parts:
- If the target can describe registers, then the MIPS GNU/Linux
OSABI reserves a register number for $restart, and maps the
supplied restart register to that address if it is found.
- Native MIPS GNU/Linux debugging supplies an XML description
including this register. It is stored in the ptrace slot that
would otherwise be used for $0. The kernel has done this for years.
Target parts tested mips64-linux all three ABIs; native parts tested
o32. I'll commit this after the MIPS register description support,
which it requires.
--
Daniel Jacobowitz
CodeSourcery
2007-05-18 Daniel Jacobowitz <dan@codesourcery.com>
* config/mips/linux.mh (TDEP_XML): New.
* features/mips-linux.xml, features/mips64-linux.xml: New files.
* mips-linux-nat.c (mips_linux_register_addr): Handle
MIPS_RESTART_REGNUM.
(mips64_linux_register_addr): Likewise.
(super_xfer_partial, mips_linux_xfer_partial): New.
(_initialize_mips_linux_nat): Add them to the target_ops.
* mips-linux-tdep.c (mips_supply_gregset): Handle MIPS_RESTART_REGNUM.
(mips_fill_gregset, mips64_supply_gregset, mips64_fill_gregset)
(mips_linux_o32_sigframe_init)
(mips_linux_n32n64_sigframe_init): Likewise.
(mips_linux_write_pc, mips_linux_restart_reg_p): New.
(mips_linux_init_abi): Use mips_linux_write_pc. Check for the
"org.gnu.gdb.mips.linux" feature.
* mips-linux-tdep.h (MIPS_RESTART_REGNUM): New constant.
(mips_linux_restart_reg_p): New prototype.
* mips-tdep.c (mips_gdbarch_init): Pass tdesc_data to the OS/ABI
initialization routine.
* Makefile.in (mips-linux-tdep.o, mips-linux-nat.o): Update.
* gdb.texinfo (MIPS Features): Document org.gnu.gdb.mips.linux.
---
Makefile.in | 6 +-
config/mips/linux.mh | 9 ++++
doc/gdb.texinfo | 4 +
features/mips-linux.xml | 18 ++++++++
features/mips64-linux.xml | 18 ++++++++
mips-linux-nat.c | 41 ++++++++++++++++++++
mips-linux-tdep.c | 93 ++++++++++++++++++++++++++++++++++++++--------
mips-linux-tdep.h | 10 ++++
mips-tdep.c | 1
9 files changed, 182 insertions(+), 18 deletions(-)
Index: gdb/config/mips/linux.mh
===================================================================
--- gdb.orig/config/mips/linux.mh 2007-05-21 09:00:01.000000000 -0400
+++ gdb/config/mips/linux.mh 2007-05-21 09:43:16.000000000 -0400
@@ -5,3 +5,12 @@ NATDEPFILES= inf-ptrace.o fork-child.o m
linux-nat.o linux-fork.o
LOADLIBES = -ldl -rdynamic
+
+TDEP_XML = $(srcdir)/features/mips-cpu.xml \
+ $(srcdir)/features/mips-cp0.xml \
+ $(srcdir)/features/mips-fpu.xml \
+ $(srcdir)/features/mips-linux.xml \
+ $(srcdir)/features/mips64-cpu.xml \
+ $(srcdir)/features/mips64-cp0.xml \
+ $(srcdir)/features/mips64-fpu.xml \
+ $(srcdir)/features/mips64-linux.xml
Index: gdb/features/mips-linux.xml
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gdb/features/mips-linux.xml 2007-05-21 09:43:16.000000000 -0400
@@ -0,0 +1,18 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2007 Free Software Foundation, Inc.
+
+ Copying and distribution of this file, with or without modification,
+ are permitted in any medium without royalty provided the copyright
+ notice and this notice are preserved. -->
+
+<!DOCTYPE target SYSTEM "gdb-target.dtd">
+<target>
+ <architecture>mips</architecture>
+ <xi:include href="mips-cpu.xml"/>
+ <xi:include href="mips-cp0.xml"/>
+ <xi:include href="mips-fpu.xml"/>
+
+ <feature name="org.gnu.gdb.mips.linux">
+ <reg name="restart" bitsize="32" group="system"/>
+ </feature>
+</target>
Index: gdb/features/mips64-linux.xml
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ gdb/features/mips64-linux.xml 2007-05-21 09:43:16.000000000 -0400
@@ -0,0 +1,18 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2007 Free Software Foundation, Inc.
+
+ Copying and distribution of this file, with or without modification,
+ are permitted in any medium without royalty provided the copyright
+ notice and this notice are preserved. -->
+
+<!DOCTYPE target SYSTEM "gdb-target.dtd">
+<target>
+ <architecture>mips</architecture>
+ <xi:include href="mips64-cpu.xml"/>
+ <xi:include href="mips64-cp0.xml"/>
+ <xi:include href="mips64-fpu.xml"/>
+
+ <feature name="org.gnu.gdb.mips.linux">
+ <reg name="restart" bitsize="64" group="system"/>
+ </feature>
+</target>
Index: gdb/mips-linux-nat.c
===================================================================
--- gdb.orig/mips-linux-nat.c 2007-05-21 09:00:01.000000000 -0400
+++ gdb/mips-linux-nat.c 2007-05-21 09:43:16.000000000 -0400
@@ -27,10 +27,13 @@
#include "regcache.h"
#include "linux-nat.h"
#include "mips-linux-tdep.h"
+#include "target-descriptions.h"
+#include "xml-support.h"
#include "gdb_proc_service.h"
#include "gregset.h"
+#include <sgidefs.h>
#include <sys/ptrace.h>
#ifndef PTRACE_GET_THREAD_AREA
@@ -81,6 +84,8 @@ mips_linux_register_addr (struct gdbarch
regaddr = FPC_CSR;
else if (regno == mips_regnum (gdbarch)->fp_implementation_revision)
regaddr = store? (CORE_ADDR) -1 : FPC_EIR;
+ else if (mips_linux_restart_reg_p (gdbarch) && regno == MIPS_RESTART_REGNUM)
+ regaddr = 0;
else
regaddr = (CORE_ADDR) -1;
@@ -114,6 +119,8 @@ mips64_linux_register_addr (struct gdbar
regaddr = MIPS64_FPC_CSR;
else if (regno == mips_regnum (gdbarch)->fp_implementation_revision)
regaddr = store? (CORE_ADDR) -1 : MIPS64_FPC_EIR;
+ else if (mips_linux_restart_reg_p (gdbarch) && regno == MIPS_RESTART_REGNUM)
+ regaddr = 0;
else
regaddr = (CORE_ADDR) -1;
@@ -335,6 +342,36 @@ mips_linux_register_u_offset (struct gdb
return mips_linux_register_addr (gdbarch, regno, store_p);
}
+static LONGEST (*super_xfer_partial) (struct target_ops *, enum target_object,
+ const char *, gdb_byte *, const gdb_byte *,
+ ULONGEST, LONGEST);
+
+static LONGEST
+mips_linux_xfer_partial (struct target_ops *ops,
+ enum target_object object,
+ const char *annex,
+ gdb_byte *readbuf, const gdb_byte *writebuf,
+ ULONGEST offset, LONGEST len)
+{
+ if (object == TARGET_OBJECT_AVAILABLE_FEATURES)
+ {
+ if (annex != NULL && strcmp (annex, "target.xml") == 0)
+ {
+ /* Report that target registers are a size we know for sure
+ that we can get from ptrace. */
+ if (_MIPS_SIM == _ABIO32)
+ annex = "mips-linux.xml";
+ else
+ annex = "mips64-linux.xml";
+ }
+
+ return xml_builtin_xfer_partial (annex, readbuf, writebuf, offset, len);
+ }
+
+ return super_xfer_partial (ops, object, annex, readbuf, writebuf,
+ offset, len);
+}
+
void _initialize_mips_linux_nat (void);
void
@@ -348,5 +385,9 @@ _initialize_mips_linux_nat (void)
t->to_fetch_registers = mips64_linux_fetch_registers;
t->to_store_registers = mips64_linux_store_registers;
+ /* Override the default to_xfer_partial. */
+ super_xfer_partial = t->to_xfer_partial;
+ t->to_xfer_partial = mips_linux_xfer_partial;
+
linux_nat_add_target (t);
}
Index: gdb/mips-linux-tdep.c
===================================================================
--- gdb.orig/mips-linux-tdep.c 2007-05-21 09:00:02.000000000 -0400
+++ gdb/mips-linux-tdep.c 2007-05-21 09:43:16.000000000 -0400
@@ -37,6 +37,7 @@
#include "solib-svr4.h"
#include "solist.h"
#include "symtab.h"
+#include "target-descriptions.h"
#include "mips-linux-tdep.h"
static struct target_so_ops mips_svr4_so_ops;
@@ -93,9 +94,12 @@ mips_supply_gregset (struct regcache *re
memset (zerobuf, 0, MAX_REGISTER_SIZE);
- for (regi = EF_REG0; regi <= EF_REG31; regi++)
+ for (regi = EF_REG0 + 1; regi <= EF_REG31; regi++)
supply_32bit_reg (regcache, regi - EF_REG0, regp + regi);
+ if (mips_linux_restart_reg_p (current_gdbarch))
+ supply_32bit_reg (regcache, MIPS_RESTART_REGNUM, regp + EF_REG0);
+
supply_32bit_reg (regcache, mips_regnum (current_gdbarch)->lo,
regp + EF_LO);
supply_32bit_reg (regcache, mips_regnum (current_gdbarch)->hi,
@@ -110,9 +114,10 @@ mips_supply_gregset (struct regcache *re
regp + EF_CP0_CAUSE);
/* Fill inaccessible registers with zero. */
+ regcache_raw_supply (regcache, MIPS_ZERO_REGNUM, zerobuf);
regcache_raw_supply (regcache, MIPS_UNUSED_REGNUM, zerobuf);
for (regi = MIPS_FIRST_EMBED_REGNUM;
- regi < MIPS_LAST_EMBED_REGNUM;
+ regi <= MIPS_LAST_EMBED_REGNUM;
regi++)
regcache_raw_supply (regcache, regi, zerobuf);
}
@@ -130,7 +135,7 @@ mips_fill_gregset (const struct regcache
if (regno == -1)
{
memset (regp, 0, sizeof (mips_elf_gregset_t));
- for (regi = 0; regi < 32; regi++)
+ for (regi = 1; regi < 32; regi++)
mips_fill_gregset (regcache, gregsetp, regi);
mips_fill_gregset (regcache, gregsetp,
mips_regnum (current_gdbarch)->lo);
@@ -143,10 +148,11 @@ mips_fill_gregset (const struct regcache
mips_fill_gregset (regcache, gregsetp, MIPS_PS_REGNUM);
mips_fill_gregset (regcache, gregsetp,
mips_regnum (current_gdbarch)->cause);
+ mips_fill_gregset (regcache, gregsetp, MIPS_RESTART_REGNUM);
return;
}
- if (regno < 32)
+ if (regno > 0 && regno < 32)
{
dst = regp + regno + EF_REG0;
regcache_raw_collect (regcache, regno, dst);
@@ -165,6 +171,9 @@ mips_fill_gregset (const struct regcache
regaddr = EF_CP0_STATUS;
else if (regno == mips_regnum (current_gdbarch)->cause)
regaddr = EF_CP0_CAUSE;
+ else if (mips_linux_restart_reg_p (current_gdbarch)
+ && regno == MIPS_RESTART_REGNUM)
+ regaddr = EF_REG0;
else
regaddr = -1;
@@ -288,10 +297,14 @@ mips64_supply_gregset (struct regcache *
memset (zerobuf, 0, MAX_REGISTER_SIZE);
- for (regi = MIPS64_EF_REG0; regi <= MIPS64_EF_REG31; regi++)
+ for (regi = MIPS64_EF_REG0 + 1; regi <= MIPS64_EF_REG31; regi++)
supply_64bit_reg (regcache, regi - MIPS64_EF_REG0,
(const gdb_byte *)(regp + regi));
+ if (mips_linux_restart_reg_p (current_gdbarch))
+ supply_64bit_reg (regcache, MIPS_RESTART_REGNUM,
+ (const gdb_byte *)(regp + MIPS64_EF_REG0));
+
supply_64bit_reg (regcache, mips_regnum (current_gdbarch)->lo,
(const gdb_byte *) (regp + MIPS64_EF_LO));
supply_64bit_reg (regcache, mips_regnum (current_gdbarch)->hi,
@@ -307,9 +320,10 @@ mips64_supply_gregset (struct regcache *
(const gdb_byte *) (regp + MIPS64_EF_CP0_CAUSE));
/* Fill inaccessible registers with zero. */
+ regcache_raw_supply (regcache, MIPS_ZERO_REGNUM, zerobuf);
regcache_raw_supply (regcache, MIPS_UNUSED_REGNUM, zerobuf);
for (regi = MIPS_FIRST_EMBED_REGNUM;
- regi < MIPS_LAST_EMBED_REGNUM;
+ regi <= MIPS_LAST_EMBED_REGNUM;
regi++)
regcache_raw_supply (regcache, regi, zerobuf);
}
@@ -327,7 +341,7 @@ mips64_fill_gregset (const struct regcac
if (regno == -1)
{
memset (regp, 0, sizeof (mips64_elf_gregset_t));
- for (regi = 0; regi < 32; regi++)
+ for (regi = 1; regi < 32; regi++)
mips64_fill_gregset (regcache, gregsetp, regi);
mips64_fill_gregset (regcache, gregsetp,
mips_regnum (current_gdbarch)->lo);
@@ -340,10 +354,11 @@ mips64_fill_gregset (const struct regcac
mips64_fill_gregset (regcache, gregsetp, MIPS_PS_REGNUM);
mips64_fill_gregset (regcache, gregsetp,
mips_regnum (current_gdbarch)->cause);
+ mips64_fill_gregset (regcache, gregsetp, MIPS_RESTART_REGNUM);
return;
}
- if (regno < 32)
+ if (regno > 0 && regno < 32)
regaddr = regno + MIPS64_EF_REG0;
else if (regno == mips_regnum (current_gdbarch)->lo)
regaddr = MIPS64_EF_LO;
@@ -357,6 +372,9 @@ mips64_fill_gregset (const struct regcac
regaddr = MIPS64_EF_CP0_STATUS;
else if (regno == mips_regnum (current_gdbarch)->cause)
regaddr = MIPS64_EF_CP0_CAUSE;
+ else if (mips_linux_restart_reg_p (current_gdbarch)
+ && regno == MIPS_RESTART_REGNUM)
+ regaddr = MIPS64_EF_REG0;
else
regaddr = -1;
@@ -830,10 +848,9 @@ mips_linux_o32_sigframe_init (const stru
else
regs_base = sigcontext_base;
-#if 0
- trad_frame_set_reg_addr (this_cache, ORIG_ZERO_REGNUM + NUM_REGS,
- regs_base + SIGCONTEXT_REGS);
-#endif
+ if (mips_linux_restart_reg_p (current_gdbarch))
+ trad_frame_set_reg_addr (this_cache, MIPS_RESTART_REGNUM + NUM_REGS,
+ regs_base + SIGCONTEXT_REGS);
for (ireg = 1; ireg < 32; ireg++)
trad_frame_set_reg_addr (this_cache,
@@ -968,10 +985,9 @@ mips_linux_n32n64_sigframe_init (const s
else
sigcontext_base += N64_SIGFRAME_SIGCONTEXT_OFFSET;
-#if 0
- trad_frame_set_reg_addr (this_cache, ORIG_ZERO_REGNUM + NUM_REGS,
- sigcontext_base + N64_SIGCONTEXT_REGS);
-#endif
+ if (mips_linux_restart_reg_p (current_gdbarch))
+ trad_frame_set_reg_addr (this_cache, MIPS_RESTART_REGNUM + NUM_REGS,
+ sigcontext_base + N64_SIGCONTEXT_REGS);
for (ireg = 1; ireg < 32; ireg++)
trad_frame_set_reg_addr (this_cache,
@@ -1005,6 +1021,30 @@ mips_linux_n32n64_sigframe_init (const s
func));
}
+static void
+mips_linux_write_pc (CORE_ADDR pc, ptid_t ptid)
+{
+ write_register_pid (PC_REGNUM, pc, ptid);
+
+ /* Clear the syscall restart flag. */
+ if (mips_linux_restart_reg_p (current_gdbarch))
+ write_register_pid (MIPS_RESTART_REGNUM, 0, ptid);
+}
+
+/* Return 1 if MIPS_RESTART_REGNUM is usable. */
+
+int
+mips_linux_restart_reg_p (struct gdbarch *gdbarch)
+{
+ /* If we do not have a target description with registers, then
+ MIPS_RESTART_REGNUM will not be included in the register set. */
+ if (!tdesc_has_registers (gdbarch_target_desc (gdbarch)))
+ return 0;
+
+ /* If we do, then MIPS_RESTART_REGNUM is safe to check; it will
+ either be GPR-sized or missing. */
+ return register_size (gdbarch, MIPS_RESTART_REGNUM) > 0;
+}
/* Initialize one of the GNU/Linux OS ABIs. */
@@ -1014,6 +1054,7 @@ mips_linux_init_abi (struct gdbarch_info
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
enum mips_abi abi = mips_abi (gdbarch);
+ struct tdesc_arch_data *tdesc_data = (void *) info.tdep_info;
switch (abi)
{
@@ -1074,6 +1115,26 @@ mips_linux_init_abi (struct gdbarch_info
= mips_linux_in_dynsym_resolve_code;
}
set_solib_ops (gdbarch, &mips_svr4_so_ops);
+
+ set_gdbarch_write_pc (gdbarch, mips_linux_write_pc);
+
+ if (tdesc_data)
+ {
+ const struct tdesc_feature *feature;
+
+ /* If we have target-described registers, then we can safely
+ reserve a number for MIPS_RESTART_REGNUM (whether it is
+ described or not). */
+ gdb_assert (gdbarch_num_regs (gdbarch) <= MIPS_RESTART_REGNUM);
+ set_gdbarch_num_regs (gdbarch, MIPS_RESTART_REGNUM + 1);
+
+ /* If it's present, then assign it to the reserved number. */
+ feature = tdesc_find_feature (info.target_desc,
+ "org.gnu.gdb.mips.linux");
+ if (feature != NULL)
+ tdesc_numbered_register (feature, tdesc_data, MIPS_RESTART_REGNUM,
+ "restart");
+ }
}
void
Index: gdb/mips-linux-tdep.h
===================================================================
--- gdb.orig/mips-linux-tdep.h 2007-05-21 09:00:02.000000000 -0400
+++ gdb/mips-linux-tdep.h 2007-05-21 09:43:16.000000000 -0400
@@ -92,3 +92,13 @@ void mips64_supply_gregset (struct regca
void mips64_fill_gregset (const struct regcache *, mips64_elf_gregset_t *, int);
void mips64_supply_fpregset (struct regcache *, const mips64_elf_fpregset_t *);
void mips64_fill_fpregset (const struct regcache *, mips64_elf_fpregset_t *, int);
+
+enum {
+ /* The Linux kernel stores an error code from any interrupted
+ syscall in a "register" (in $0's save slot). */
+ MIPS_RESTART_REGNUM = MIPS_LAST_EMBED_REGNUM + 1
+};
+
+/* Return 1 if MIPS_RESTART_REGNUM is usable. */
+
+int mips_linux_restart_reg_p (struct gdbarch *gdbarch);
Index: gdb/mips-tdep.c
===================================================================
--- gdb.orig/mips-tdep.c 2007-05-21 09:43:14.000000000 -0400
+++ gdb/mips-tdep.c 2007-05-21 09:43:16.000000000 -0400
@@ -5372,6 +5372,7 @@ mips_gdbarch_init (struct gdbarch_info i
mips_register_g_packet_guesses (gdbarch);
/* Hook in OS ABI-specific overrides, if they have been registered. */
+ info.tdep_info = (void *) tdesc_data;
gdbarch_init_osabi (info, gdbarch);
/* Unwind the frame. */
Index: gdb/Makefile.in
===================================================================
--- gdb.orig/Makefile.in 2007-05-21 09:43:14.000000000 -0400
+++ gdb/Makefile.in 2007-05-21 09:43:16.000000000 -0400
@@ -2337,12 +2337,14 @@ mips64obsd-tdep.o: mips64obsd-tdep.c $(d
mips-irix-tdep.o: mips-irix-tdep.c $(defs_h) $(osabi_h) $(elf_bfd_h)
mips-linux-nat.o: mips-linux-nat.c $(defs_h) $(mips_tdep_h) $(target_h) \
$(regcache_h) $(linux_nat_h) $(gdb_proc_service_h) $(gregset_h) \
- $(mips_linux_tdep_h) $(inferior_h)
+ $(mips_linux_tdep_h) $(inferior_h) $(target_descriptions_h) \
+ $(xml_support_h)
mips-linux-tdep.o: mips-linux-tdep.c $(defs_h) $(gdbcore_h) $(target_h) \
$(solib_svr4_h) $(osabi_h) $(mips_tdep_h) $(gdb_string_h) \
$(gdb_assert_h) $(frame_h) $(regcache_h) $(trad_frame_h) \
$(tramp_frame_h) $(gdbtypes_h) $(solib_h) $(symtab_h) \
- $(mips_linux_tdep_h) $(solist_h) $(solib_svr4_h)
+ $(mips_linux_tdep_h) $(solist_h) $(solib_svr4_h) \
+ $(target_descriptions_h)
mipsnbsd-nat.o: mipsnbsd-nat.c $(defs_h) $(inferior_h) $(regcache_h) \
$(target_h) $(mips_tdep_h) $(mipsnbsd_tdep_h) $(inf_ptrace_h)
mipsnbsd-tdep.o: mipsnbsd-tdep.c $(defs_h) $(gdbcore_h) $(regcache_h) \
Index: gdb/doc/gdb.texinfo
===================================================================
--- gdb.orig/doc/gdb.texinfo 2007-05-21 09:44:34.000000000 -0400
+++ gdb/doc/gdb.texinfo 2007-05-21 09:46:44.000000000 -0400
@@ -25688,6 +25688,10 @@ it may be optional in a future version o
contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
@samp{fir}. They may be 32-bit or 64-bit depending on the target.
+The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
+contain a single register, @samp{restart}, which is used by the
+Linux kernel to control restartable syscalls.
+
@include gpl.texi
@raisesections