Re: [PATCH v5] Add support for NetBSD threads in sparc-nat.c

[Simon Marchi <simark@simark.ca>]

On 2020-03-17 3:07 p.m., Simon Marchi wrote:
> On 2020-03-17 2:18 p.m., Kamil Rytarowski wrote:
>> NetBSD ptrace(2) accepts thread id (LWP) as the 4th argument for threads.
>>
>> Define gdb_ptrace() a wrapper function for ptrace(2) that properly passes
>> the pid,lwp pair on NetBSD and the result of get_ptrace_pid() for others.
>> ---
>>  gdb/sparc-nat.c | 50 ++++++++++++++++++++++---------------------------
>>  1 file changed, 22 insertions(+), 28 deletions(-)
>>
>> diff --git a/gdb/sparc-nat.c b/gdb/sparc-nat.c
>> index dff0f521565..fadcfd34474 100644
>> --- a/gdb/sparc-nat.c
>> +++ b/gdb/sparc-nat.c
>> @@ -78,6 +78,19 @@ typedef struct fp_status fpregset_t;
>>  #define PTRACE_SETFPREGS PT_SETFPREGS
>>  #endif
>>
>> +static int
>> +gdb_ptrace (PTRACE_TYPE_ARG1 request, ptid_t ptid, PTRACE_TYPE_ARG3 addr)
>> +{
>> +#ifdef __NetBSD__
>> +  /* Support for NetBSD threads: unlike other ptrace implementations in this
>> +     file, NetBSD requires that we pass both the pid and lwp.  */
>> +  return ptrace (request, ptid.pid (), addr, ptid.lwp ());
>> +#else
>> +  pid_t pid = get_ptrace_pid (ptid);
>> +  return ptrace (request, pid, addr, 0);
>> +#endif
>> +}
>> +
>>  /* Register set description.  */
>>  const struct sparc_gregmap *sparc_gregmap;
>>  const struct sparc_fpregmap *sparc_fpregmap;
>> @@ -137,22 +150,7 @@ void
>>  sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
>>  {
>>    struct gdbarch *gdbarch = regcache->arch ();
>> -  pid_t pid;
>> -
>> -  /* NOTE: cagney/2002-12-03: This code assumes that the currently
>> -     selected light weight processes' registers can be written
>> -     directly into the selected thread's register cache.  This works
>> -     fine when given an 1:1 LWP:thread model (such as found on
>> -     GNU/Linux) but will, likely, have problems when used on an N:1
>> -     (userland threads) or N:M (userland multiple LWP) model.  In the
>> -     case of the latter two, the LWP's registers do not necessarily
>> -     belong to the selected thread (the LWP could be in the middle of
>> -     executing the thread switch code).
>> -
>> -     These functions should instead be parameterized with an explicit
>> -     object (struct regcache, struct thread_info?) into which the LWPs
>> -     registers can be written.  */
>> -  pid = get_ptrace_pid (regcache->ptid ());
>> +  ptid_t ptid = regcache->ptid ();
>>
>>    if (regnum == SPARC_G0_REGNUM)
>>      {
>> @@ -166,7 +164,7 @@ sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
>>      {
>>        gregset_t regs;
>>
>> -      if (ptrace (PTRACE_GETREGS, pid, (PTRACE_TYPE_ARG3) &regs, 0) == -1)
>> +      if (gdb_ptrace (PTRACE_GETREGS, ptid, (PTRACE_TYPE_ARG3) &regs) == -1)
>>  	perror_with_name (_("Couldn't get registers"));
>>
>>        sparc_supply_gregset (sparc_gregmap, regcache, -1, &regs);
>> @@ -178,7 +176,7 @@ sparc_fetch_inferior_registers (struct regcache *regcache, int regnum)
>>      {
>>        fpregset_t fpregs;
>>
>> -      if (ptrace (PTRACE_GETFPREGS, pid, (PTRACE_TYPE_ARG3) &fpregs, 0) == -1)
>> +      if (gdb_ptrace (PTRACE_GETFPREGS, ptid, (PTRACE_TYPE_ARG3) &fpregs) == -1)
>>  	perror_with_name (_("Couldn't get floating point status"));
>>
>>        sparc_supply_fpregset (sparc_fpregmap, regcache, -1, &fpregs);
>> @@ -189,22 +187,18 @@ void
>>  sparc_store_inferior_registers (struct regcache *regcache, int regnum)
>>  {
>>    struct gdbarch *gdbarch = regcache->arch ();
>> -  pid_t pid;
>> -
>> -  /* NOTE: cagney/2002-12-02: See comment in fetch_inferior_registers
>> -     about threaded assumptions.  */
>> -  pid = get_ptrace_pid (regcache->ptid ());
>> +  ptid_t ptid = regcache->ptid ();
>>
>>    if (regnum == -1 || sparc_gregset_supplies_p (gdbarch, regnum))
>>      {
>>        gregset_t regs;
>>
>> -      if (ptrace (PTRACE_GETREGS, pid, (PTRACE_TYPE_ARG3) &regs, 0) == -1)
>> +      if (gdb_ptrace (PTRACE_GETREGS, ptid, (PTRACE_TYPE_ARG3) &regs) == -1)
>>  	perror_with_name (_("Couldn't get registers"));
>>
>>        sparc_collect_gregset (sparc_gregmap, regcache, regnum, &regs);
>>
>> -      if (ptrace (PTRACE_SETREGS, pid, (PTRACE_TYPE_ARG3) &regs, 0) == -1)
>> +      if (gdb_ptrace (PTRACE_SETREGS, ptid, (PTRACE_TYPE_ARG3) &regs) == -1)
>>  	perror_with_name (_("Couldn't write registers"));
>>
>>        /* Deal with the stack regs.  */
>> @@ -225,7 +219,7 @@ sparc_store_inferior_registers (struct regcache *regcache, int regnum)
>>      {
>>        fpregset_t fpregs, saved_fpregs;
>>
>> -      if (ptrace (PTRACE_GETFPREGS, pid, (PTRACE_TYPE_ARG3) &fpregs, 0) == -1)
>> +      if (gdb_ptrace (PTRACE_GETFPREGS, ptid, (PTRACE_TYPE_ARG3) &fpregs) == -1)
>>  	perror_with_name (_("Couldn't get floating-point registers"));
>>
>>        memcpy (&saved_fpregs, &fpregs, sizeof (fpregs));
>> @@ -237,8 +231,8 @@ sparc_store_inferior_registers (struct regcache *regcache, int regnum)
>>  	 to write the registers if nothing changed.  */
>>        if (memcmp (&saved_fpregs, &fpregs, sizeof (fpregs)) != 0)
>>  	{
>> -	  if (ptrace (PTRACE_SETFPREGS, pid,
>> -		      (PTRACE_TYPE_ARG3) &fpregs, 0) == -1)
>> +	  if (gdb_ptrace (PTRACE_SETFPREGS, ptid,
>> +			  (PTRACE_TYPE_ARG3) &fpregs) == -1)
>>  	    perror_with_name (_("Couldn't write floating-point registers"));
>>  	}
>>
>> --
>> 2.25.0
>>
> 
> Thanks, this version LGTM.
> 
> Simon

Don't forget the ChangeLog entry though.

Simon