binutils-gdb/gdb/proc-service.c
Pedro Alves 6d30ada87b Fix gdb.Inferior.read_memory without execution (PR dap/30644)
Andrew reported that the previous change to gdb.Inferior.read_memory &
friends introducing scoped_restore_current_inferior_for_memory broke
gdb.dap/stop-at-main.exp.  This is also reported as PR dap/30644.

The root of the problem is that all the methods that now use
scoped_restore_current_inferior_for_memory cause GDB to crash with a
failed assert if they are run on an inferior that is not yet started.

E.g.:

 (gdb) python i = gdb.selected_inferior ()
 (gdb) python i.read_memory (4,4)
 gdb/thread.c:626: internal-error: any_thread_of_inferior: Assertion `inf->pid != 0' failed.

This patch fixes the problem by removing
scoped_restore_current_inferior_for_memory's ctor ptid parameter and
the any_thread_of_inferior calls completely, and making
scoped_restore_current_inferior_for_memory switch inferior_ptid to a
pid ptid.

I was a little worried that some port might be assuming inferior_ptid
points at a thread in the xfer_partial memory access routines.  We
know that anything that supports forks must not assume that, due to
how detach_breakpoints works.  I looked at a number of xfer_partial
implementations, and didn't see anything that is looking at
inferior_ptid in a way that would misbehave.  I'm thinking that we
could go forward with this and just fix ports if they break.

While on some ports like on AMD GPU we have thread-specific address
spaces, and so when accessing memory for those address spaces, we must
have the right thread context (via inferior_ptid) selected, in
Inferior.read_memory, we only have the inferior to work with, so this
API as is can't be used to access thread-specific address spaces.
IOW, it can only be used to access the global address space that is
visible to both the CPU and the GPUs.

In proc-service.c:ps_xfer_memory, the other spot using
scoped_restore_current_inferior_for_memory, we're always accessing
per-inferior memory.

If we end up using scoped_restore_current_inferior_for_memory later to
set up the context to read memory from a specific thread, then we can
add an alternative ctor that takes a thread_info pointer, and make
inferior_ptid point to the thread, for example.

New test added to gdb.python/py-inferior.exp, exercising
Inferior.read_memory without execution.

No regressions on native and extended-gdbserver x86_64 GNU/Linux.

Reviewed-By: Tom Tromey <tom@tromey.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30644
Change-Id: I11309c5ddbbb51a4594cf63c21b3858bfd9aed19
2023-07-19 14:10:19 +01:00

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/* <proc_service.h> implementation.
Copyright (C) 1999-2023 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 "gdbcore.h"
#include "inferior.h"
#include "gdbthread.h"
#include "symtab.h"
#include "target.h"
#include "regcache.h"
#include "objfiles.h"
#include "gdb_proc_service.h"
#include <sys/procfs.h>
/* Prototypes for supply_gregset etc. */
#include "gregset.h"
/* Helper functions. */
/* Convert a psaddr_t to a CORE_ADDR. */
static CORE_ADDR
ps_addr_to_core_addr (psaddr_t addr)
{
if (current_program_space->exec_bfd ()
&& bfd_get_sign_extend_vma (current_program_space->exec_bfd ()))
return (intptr_t) addr;
else
return (uintptr_t) addr;
}
/* Convert a CORE_ADDR to a psaddr_t. */
static psaddr_t
core_addr_to_ps_addr (CORE_ADDR addr)
{
if (current_program_space->exec_bfd ()
&& bfd_get_sign_extend_vma (current_program_space->exec_bfd ()))
return (psaddr_t) (intptr_t) addr;
else
return (psaddr_t) (uintptr_t) addr;
}
/* Transfer LEN bytes of memory between BUF and address ADDR in the
process specified by PH. If WRITE, transfer them to the process,
else transfer them from the process. Returns PS_OK for success,
PS_ERR on failure.
This is a helper function for ps_pdread and ps_pdwrite. */
static ps_err_e
ps_xfer_memory (const struct ps_prochandle *ph, psaddr_t addr,
gdb_byte *buf, size_t len, int write)
{
scoped_restore_current_inferior_for_memory save_inferior (ph->thread->inf);
CORE_ADDR core_addr = ps_addr_to_core_addr (addr);
int ret;
if (write)
ret = target_write_memory (core_addr, buf, len);
else
ret = target_read_memory (core_addr, buf, len);
return (ret == 0 ? PS_OK : PS_ERR);
}
/* Search for the symbol named NAME within the object named OBJ within
the target process PH. If the symbol is found the address of the
symbol is stored in SYM_ADDR. */
ps_err_e
ps_pglobal_lookup (struct ps_prochandle *ph, const char *obj,
const char *name, psaddr_t *sym_addr)
{
inferior *inf = ph->thread->inf;
scoped_restore_current_program_space restore_pspace;
set_current_program_space (inf->pspace);
/* FIXME: kettenis/2000-09-03: What should we do with OBJ? */
bound_minimal_symbol ms = lookup_minimal_symbol (name, NULL, NULL);
if (ms.minsym == NULL)
return PS_NOSYM;
*sym_addr = core_addr_to_ps_addr (ms.value_address ());
return PS_OK;
}
/* Read SIZE bytes from the target process PH at address ADDR and copy
them into BUF. */
ps_err_e
ps_pdread (struct ps_prochandle *ph, psaddr_t addr, void *buf, size_t size)
{
return ps_xfer_memory (ph, addr, (gdb_byte *) buf, size, 0);
}
/* Write SIZE bytes from BUF into the target process PH at address ADDR. */
ps_err_e
ps_pdwrite (struct ps_prochandle *ph, psaddr_t addr,
const void *buf, size_t size)
{
return ps_xfer_memory (ph, addr, (gdb_byte *) buf, size, 1);
}
/* Get a regcache for LWPID using its inferior's "main" architecture,
which is the register set libthread_db expects to be using. In
multi-arch debugging scenarios, the thread's architecture may
differ from the inferior's "main" architecture. */
static struct regcache *
get_ps_regcache (struct ps_prochandle *ph, lwpid_t lwpid)
{
inferior *inf = ph->thread->inf;
return get_thread_arch_regcache (inf->process_target (),
ptid_t (inf->pid, lwpid),
inf->gdbarch);
}
/* Get the general registers of LWP LWPID within the target process PH
and store them in GREGSET. */
ps_err_e
ps_lgetregs (struct ps_prochandle *ph, lwpid_t lwpid, prgregset_t gregset)
{
struct regcache *regcache = get_ps_regcache (ph, lwpid);
target_fetch_registers (regcache, -1);
fill_gregset (regcache, (gdb_gregset_t *) gregset, -1);
return PS_OK;
}
/* Set the general registers of LWP LWPID within the target process PH
from GREGSET. */
ps_err_e
ps_lsetregs (struct ps_prochandle *ph, lwpid_t lwpid, const prgregset_t gregset)
{
struct regcache *regcache = get_ps_regcache (ph, lwpid);
supply_gregset (regcache, (const gdb_gregset_t *) gregset);
target_store_registers (regcache, -1);
return PS_OK;
}
/* Get the floating-point registers of LWP LWPID within the target
process PH and store them in FPREGSET. */
ps_err_e
ps_lgetfpregs (struct ps_prochandle *ph, lwpid_t lwpid,
prfpregset_t *fpregset)
{
struct regcache *regcache = get_ps_regcache (ph, lwpid);
target_fetch_registers (regcache, -1);
fill_fpregset (regcache, (gdb_fpregset_t *) fpregset, -1);
return PS_OK;
}
/* Set the floating-point registers of LWP LWPID within the target
process PH from FPREGSET. */
ps_err_e
ps_lsetfpregs (struct ps_prochandle *ph, lwpid_t lwpid,
const prfpregset_t *fpregset)
{
struct regcache *regcache = get_ps_regcache (ph, lwpid);
supply_fpregset (regcache, (const gdb_fpregset_t *) fpregset);
target_store_registers (regcache, -1);
return PS_OK;
}
/* Return overall process id of the target PH. Special for GNU/Linux
-- not used on Solaris. */
pid_t
ps_getpid (struct ps_prochandle *ph)
{
return ph->thread->ptid.pid ();
}
void _initialize_proc_service ();
void
_initialize_proc_service ()
{
/* This function solely exists to make sure this module is linked
into the final binary. */
}