Re: [PATCH] Powerpc: Add support for openat and fstatat syscalls

[Carl Love via Gdb-patches <gdb-patches@sourceware.org>]

Ulrich:

On Wed, 2021-10-13 at 15:08 +0200, Ulrich Weigand wrot
> 
> The two syscalls are similar, but not identical.  In particular, they
> differ in the amount of memory that is accessed:
> 
>  sys_newfstatat accesses a "struct stat"
>     (144 bytes on 64-bit / 88 bytes on 32-bit)
>  sys_fstatat64 accesses a "struct stat64"
>     (104 bytes on both 64-bit and 32-bit)
> 
> Since this affects the memory being recorded, it would actually be
> preferable to use the correct system call depending on ABI.
> 
> Note that in general, there are more cases of syscall numbers
> refering
> to different system calls depending on the ABI (64-bit vs. 32-bit),
> so it would make sense to add support for that in general.
> 
> As an example, you may want to look s390_canonicalize_syscall,
> which does make the distinction between 64-bit and 32-bit ABI

Thanks for the additional info and pointers.  I added a word size
argument to ppc_canonicalize_syscall.  The argument is then used to
select the correct 64-bit or 32-bit syscall.  

The updated patch has been retested on Power 10.  Please let me know if
it looks OK now.  Thanks.

                    Carl 


 --------------------------------------------------------
Powerpc: Add support for openat and fstatat syscalls

[gdb] update ppc-linux-tdep.c

Add argument to ppc_canonicalize_syscall for the wordsize.
Add syscall entries for the openat and fstatat system calls.
---
 gdb/ppc-linux-tdep.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index ea8e3b98fa4..1e0e9a0268a 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -1371,7 +1371,7 @@ static struct linux_record_tdep ppc64_linux_record_tdep;
    SYSCALL.  */
 
 static enum gdb_syscall
-ppc_canonicalize_syscall (int syscall)
+ppc_canonicalize_syscall (int syscall, int wordsize)
 {
   int result = -1;
 
@@ -1391,6 +1391,13 @@ ppc_canonicalize_syscall (int syscall)
     result = syscall += 259 - 240;
   else if (syscall >= 250 && syscall <= 251)	/* tgkill */
     result = syscall + 270 - 250;
+  else if (syscall == 286)
+    result = gdb_sys_openat;
+  else if (syscall == 291)
+    if (wordsize == 64)
+      result = gdb_sys_newfstatat;
+    else
+      result = gdb_sys_fstatat64;
   else if (syscall == 336)
     result = gdb_sys_recv;
   else if (syscall == 337)
@@ -1414,7 +1421,7 @@ ppc_linux_syscall_record (struct regcache *regcache)
   int ret;
 
   regcache_raw_read_unsigned (regcache, tdep->ppc_gp0_regnum, &scnum);
-  syscall_gdb = ppc_canonicalize_syscall (scnum);
+  syscall_gdb = ppc_canonicalize_syscall (scnum, tdep->wordsize);
 
   if (syscall_gdb < 0)
     {
-- 
2.30.2