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

[Simon Marchi <simark@simark.ca>]

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