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regcache: Zero-extend small registers described by a register map.

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When registers are supplied via regcache_supply_register from a
register block described by a register map, registers may be stored in
slots smaller than GDB's native register size (e.g. x86 segment
registers are 16 bits, but the GDB registers for those are 32-bits).
regcache_collect_regset is careful to zero-extend slots larger than a
register size, but regcache_supply_regset just used
regcache::raw_supply_part and did not initialize the upper bytes of a
register value.

trad_frame_set_reg_regmap assumes these semantics (zero-extending
short registers).  Upcoming patches also require these semantics for
handling x86 segment register values stored in 16-bit slots on
FreeBSD.  Note that architecturally x86 segment registers are 16 bits,
but the x86 gdb architectures treat these registers as 32 bits.
This commit is contained in:
John Baldwin 2022-01-28 11:14:37 -08:00
parent 5046f3c8c0
commit b623bbc9a5
1 changed files with 6 additions and 1 deletions
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7
gdb/regcache.c
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@ -1164,7 +1164,12 @@ regcache::transfer_regset_register (struct regcache *out_regcache, int regnum,
memset (out_buf + offs + reg_size, 0, slot_size - reg_size);
}
else if (in_buf != nullptr)
out_regcache->raw_supply_part (regnum, 0, reg_size, in_buf + offs);
{
/* Zero-extend the register value if the slot is smaller than the register. */
if (slot_size < register_size (gdbarch, regnum))
out_regcache->raw_supply_zeroed (regnum);
out_regcache->raw_supply_part (regnum, 0, reg_size, in_buf + offs);
}
else
{
/* Invalidate the register. */