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Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix |
Date: |
Mon, 2 Nov 2015 14:09:36 +0000 |
On 2 November 2015 at 14:05, Paolo Bonzini <address@hidden> wrote:
> This is reported by Coverity. The algorithm description at
> ftp://ftp.icm.edu.pl/packages/ggi/doc/hw/sparc/Sparc.pdf suggests
> that the 32-bit parts of rs2, after the left shift, is treated
> as a 64-bit integer. Bits 32 and above are used to do the
> saturating truncation.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> target-sparc/vis_helper.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target-sparc/vis_helper.c b/target-sparc/vis_helper.c
> index 383cc8b..45fc7db 100644
> --- a/target-sparc/vis_helper.c
> +++ b/target-sparc/vis_helper.c
> @@ -447,7 +447,7 @@ uint32_t helper_fpackfix(uint64_t gsr, uint64_t rs2)
> for (word = 0; word < 2; word++) {
> uint32_t val;
> int32_t src = rs2 >> (word * 32);
> - int64_t scaled = src << scale;
> + int64_t scaled = (int64_t)src << scale;
> int64_t from_fixed = scaled >> 16;
This will now shift left into the sign bit of a signed integer,
which is undefined behaviour.
thanks
-- PMM
- [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/02
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix,
Peter Maydell <=
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/02
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Peter Maydell, 2015/11/02
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/02
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Richard Henderson, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Richard Henderson, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Markus Armbruster, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Paolo Bonzini, 2015/11/04
- Re: [Qemu-devel] [PATCH] target-sparc: fix 32-bit truncation in fpackfix, Markus Armbruster, 2015/11/04