On 13.03.2025 16:30, Roger Pau Monne wrote:
> When building Xen with GCC 12 with UBSAN and PVH_GUEST both enabled the
> compiler emits the following errors:
>
> arch/x86/setup.c: In function '__start_xen':
> arch/x86/setup.c:1504:19: error: 'consider_modules' reading 40 bytes from a
> region of size 4 [-Werror=stringop-overread]
> 1504 | end = consider_modules(s, e, reloc_size + mask,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 1505 | bi->mods, bi->nr_modules, -1);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/x86/setup.c:1504:19: note: referencing argument 4 of type 'const struct
> boot_module[0]'
> arch/x86/setup.c:686:24: note: in a call to function 'consider_modules'
> 686 | static uint64_t __init consider_modules(
> | ^~~~~~~~~~~~~~~~
> arch/x86/setup.c:1535:19: error: 'consider_modules' reading 40 bytes from a
> region of size 4 [-Werror=stringop-overread]
> 1535 | end = consider_modules(s, e, size, bi->mods,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 1536 | bi->nr_modules + relocated, j);
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/x86/setup.c:1535:19: note: referencing argument 4 of type 'const struct
> boot_module[0]'
> arch/x86/setup.c:686:24: note: in a call to function 'consider_modules'
> 686 | static uint64_t __init consider_modules(
> | ^~~~~~~~~~~~~~~~
>
> This seems to be the result of some function manipulation done by UBSAN
> triggering GCC stringops related errors. Placate the errors by declaring
> the function parameter as `const struct *boot_module` instead of `const
> struct boot_module[]`.
>
> Note that GCC 13 seems to be fixed, and doesn't trigger the error when
> using `[]`.
>
> Signed-off-by: Roger Pau Monné <roger....@citrix.com>
> ---
> xen/arch/x86/setup.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 4a32d8491186..bde5d75ea6ab 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -684,7 +684,7 @@ static void __init noinline move_xen(void)
> #undef BOOTSTRAP_MAP_LIMIT
>
> static uint64_t __init consider_modules(
> - uint64_t s, uint64_t e, uint32_t size, const struct boot_module mods[],
> + uint64_t s, uint64_t e, uint32_t size, const struct boot_module *mods,
> unsigned int nr_mods, unsigned int this_mod)
> {
> unsigned int i;
While I'm okay-ish with the change, how are we going to make sure it won't be
re-introduced? Or something similar be introduced elsewhere?
Jan
