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Re: [PATCH-for-4.17] xen: fix generated code for calling hypercall handlers
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 3 Nov 2022 17:45:37 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Henry Wang <Henry.Wang@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 03 Nov 2022 16:45:46 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 03.11.2022 17:36, Juergen Gross wrote:
> The code generated for the call_handlers_*() macros needs to avoid
> undefined behavior when multiple handlers share the same priority.
> The issue is the hypercall number being unverified fed into the macros
> and then used to set a mask via "mask = 1ULL << <hypercall-number>".
>
> Avoid a shift amount of more than 63 by setting mask to zero in case
> the hypercall number is too large.
>
> Fixes: eca1f00d0227 ("xen: generate hypercall interface related code")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit preferably with ...
> --- a/xen/scripts/gen_hypercall.awk
> +++ b/xen/scripts/gen_hypercall.awk
> @@ -263,7 +263,7 @@ END {
> printf("#define call_handlers_%s(num, ret, a1, a2, a3, a4, a5)
> \\\n", ca);
> printf("({ \\\n");
> if (need_mask)
> - printf(" uint64_t mask = 1ULL << num; \\\n");
> + printf(" uint64_t mask = (num > 63) ? 0 : 1ULL << num; \\\n");
... "num" also properly parenthesized (this is part of a macro definition
in the output after all). Easy enough to take care of while committing.
Jan
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