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Re: [Qemu-devel] [PATCH for-2.9 4/6] disas/microblaze: Avoid unintended
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH for-2.9 4/6] disas/microblaze: Avoid unintended sign extension |
Date: |
Fri, 3 Mar 2017 16:02:07 +0000 |
On 3 March 2017 at 15:58, Edgar E. Iglesias <address@hidden> wrote:
> On Fri, Mar 03, 2017 at 03:50:31PM +0000, Peter Maydell wrote:
>> In read_insn_microblaze() we assemble 4 bytes into an 'unsigned
>> long'. If 'unsigned long' is 64 bits and the high byte has its top
>> bit set, then C's implicit conversion from 'unsigned char' to 'int'
>> for the shift will result in an unintended sign extension which sets
>> the top 32 bits in 'inst'. Add casts to prevent this. (Spotted by
>> Coverity, CID 1005401.)
>
> I'm OK with this but perhaps it would have been more readable to
> change inst to uint32_t ? (All microblaze insns are 32bit).
I thought about that, but it was more invasive a change than
I was happy with: you'd want to change not just 'inst' but
also the return type of read_insn_microblaze, the opcode_mask
field of struct op_code_struct, 'inst' and 'prev_inst' in
print_insn_microblaze, the type of the instr arguments to
get_field, get_field_imm, etc...
thanks
-- PMM
- [Qemu-devel] [PATCH for-2.9 0/6] disas: Fix various coverity nits, Peter Maydell, 2017/03/03
- [Qemu-devel] [PATCH for-2.9 2/6] disas/i386: Avoid NULL pointer dereference in error case, Peter Maydell, 2017/03/03
- [Qemu-devel] [PATCH for-2.9 1/6] disas/hppa: Remove dead code, Peter Maydell, 2017/03/03
- [Qemu-devel] [PATCH for-2.9 5/6] disas/cris: Avoid unintended sign extension, Peter Maydell, 2017/03/03
- Re: [Qemu-devel] [PATCH for-2.9 0/6] disas: Fix various coverity nits, no-reply, 2017/03/03
- Re: [Qemu-devel] [PATCH for-2.9 0/6] disas: Fix various coverity nits, no-reply, 2017/03/03