[PATCH 01/24] gdb: don't handle i386 k registers as pseudo registers

Simon Marchi
2023-11-08T05:12:50Z

From: Simon Marchi <simon.marchi@efficios.com>

I think that i386 k registers are raw registers, and therefore shouldn't
be handled in the various functions handling pseudo registers.

What tipped me off is the code in i386_pseudo_register_read_into_value:

else if (i386_k_regnum_p (gdbarch, regnum))
{
regnum -= tdep->k0_regnum;

/* Extract (always little endian). */
status = regcache->raw_read (tdep->k0_regnum + regnum, raw_buf);

We take regnum (the pseudo register number we want to read), subtract
k0_regnum, add k0_regnum, and pass the result to raw_read. So we would
end up calling raw_read with the same regnum as the function received
which is supposedly a pseudo register number.

Other hints are:

- The command `maint print raw-registers` shows the k registers.
- Printing $k0 doesn't cause i386_pseudo_register_read_into_value to be
called.
- There's code in i387-tdep.c to save/restore the k registers.

Remove handling of the k registers from:

- i386_pseudo_register_read_into_value
- i386_pseudo_register_write
- i386_ax_pseudo_register_collect

Change-Id: Ic97956ed59af6099fef6d36a0b61464172694562
---
gdb/i386-tdep.c | 23 -----------------------
1 file changed, 23 deletions(-)

diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 1ddca2410fdf..2759c1a558c5 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -3464,17 +3464,6 @@ i386_pseudo_register_read_into_value (struct gdbarch *gdbarch,
memcpy (buf + size, &upper, size);
}
}
- else if (i386_k_regnum_p (gdbarch, regnum))
- {
- regnum -= tdep->k0_regnum;
-
- /* Extract (always little endian). */
- status = regcache->raw_read (tdep->k0_regnum + regnum, raw_buf);
- if (status != REG_VALID)
- result_value->mark_bytes_unavailable (0, 8);
- else
- memcpy (buf, raw_buf, 8);
- }
else if (i386_zmm_regnum_p (gdbarch, regnum))
{
regnum -= tdep->zmm0_regnum;
@@ -3656,12 +3645,6 @@ i386_pseudo_register_write (struct gdbarch *gdbarch, struct regcache *regcache,

regcache->raw_write (I387_BND0R_REGNUM (tdep) + regnum, raw_buf);
}
- else if (i386_k_regnum_p (gdbarch, regnum))
- {
- regnum -= tdep->k0_regnum;
-
- regcache->raw_write (tdep->k0_regnum + regnum, buf);
- }
else if (i386_zmm_regnum_p (gdbarch, regnum))
{
regnum -= tdep->zmm0_regnum;
@@ -3758,12 +3741,6 @@ i386_ax_pseudo_register_collect (struct gdbarch *gdbarch,
ax_reg_mask (ax, I387_BND0R_REGNUM (tdep) + regnum);
return 0;
}
- else if (i386_k_regnum_p (gdbarch, regnum))
- {
- regnum -= tdep->k0_regnum;
- ax_reg_mask (ax, tdep->k0_regnum + regnum);
- return 0;
- }
else if (i386_zmm_regnum_p (gdbarch, regnum))
{
regnum -= tdep->zmm0_regnum;
--
2.42.1