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On Tue, 22 May 2018, Julien Grall wrote:
> This is part of XSA-263.
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
>
> ---
> I am aware of the missing commit message here. I wanted to send the
> series on the ML to get some feedback first.
> ---
> xen/arch/arm/alternative.c | 35 +++++++++++++----------------------
> 1 file changed, 13 insertions(+), 22 deletions(-)
>
> diff --git a/xen/arch/arm/alternative.c b/xen/arch/arm/alternative.c
> index 9ffdc475d6..bd62183def 100644
> --- a/xen/arch/arm/alternative.c
> +++ b/xen/arch/arm/alternative.c
> @@ -97,12 +97,16 @@ static u32 get_alt_insn(const struct alt_instr *alt,
> /*
> * The region patched should be read-write to allow __apply_alternatives
> * to replacing the instructions when necessary.
> + *
> + * @update_offset: Offset between the region patched and the writable
> + * region for the update. 0 if the patched region is writable.
> */
> -static int __apply_alternatives(const struct alt_region *region)
> +static int __apply_alternatives(const struct alt_region *region,
> + paddr_t update_offset)
> {
> const struct alt_instr *alt;
> - const u32 *replptr;
> - u32 *origptr;
> + const u32 *replptr, *origptr;
> + u32 *updptr;
>
> printk(XENLOG_INFO "alternatives: Patching with alt table %p -> %p\n",
> region->begin, region->end);
> @@ -118,6 +122,7 @@ static int __apply_alternatives(const struct alt_region *region)
> BUG_ON(alt->alt_len != alt->orig_len);
>
> origptr = ALT_ORIG_PTR(alt);
> + updptr = (void *)origptr + update_offset;
> replptr = ALT_REPL_PTR(alt);
>
> nr_inst = alt->alt_len / sizeof(insn);
> @@ -125,7 +130,7 @@ static int __apply_alternatives(const struct alt_region *region)
> for ( i = 0; i < nr_inst; i++ )
> {
> insn = get_alt_insn(alt, origptr + i, replptr + i);
> - *(origptr + i) = cpu_to_le32(insn);
> + *(updptr + i) = cpu_to_le32(insn);
> }
>
> /* Ensure the new instructions reached the memory and nuke */
> @@ -162,9 +167,6 @@ static int __apply_alternatives_multi_stop(void *unused)
> paddr_t xen_size = _end - _start;
> unsigned int xen_order = get_order_from_bytes(xen_size);
> void *xenmap;
> - struct virtual_region patch_region = {
> - .list = LIST_HEAD_INIT(patch_region.list),
> - };
>
> BUG_ON(patched);
>
> @@ -178,30 +180,19 @@ static int __apply_alternatives_multi_stop(void *unused)
> BUG_ON(!xenmap);
>
> /*
> - * If we generate a new branch instruction, the target will be
> - * calculated in this re-mapped Xen region. So we have to register
> - * this re-mapped Xen region as a virtual region temporarily.
> - */
> - patch_region.start = xenmap;
> - patch_region.end = xenmap + xen_size;
> - register_virtual_region(&patch_region);
> -
> - /*
> * Find the virtual address of the alternative region in the new
> * mapping.
> * alt_instr contains relative offset, so the function
> * __apply_alternatives will patch in the re-mapped version of
> * Xen.
> */
> - region.begin = (void *)__alt_instructions - (void *)_start + xenmap;
> - region.end = (void *)__alt_instructions_end - (void *)_start + xenmap;
> + region.begin = __alt_instructions;
> + region.end = __alt_instructions_end;
>
> - ret = __apply_alternatives(&region);
> + ret = __apply_alternatives(&region, xenmap - (void *)_start);
> /* The patching is not expected to fail during boot. */
> BUG_ON(ret != 0);
>
> - unregister_virtual_region(&patch_region);
> -
> vunmap(xenmap);
>
> /* Barriers provided by the cache flushing */
> @@ -235,7 +226,7 @@ int apply_alternatives(const struct alt_instr *start, const struct alt_instr *en
> .end = end,
> };
>
> - return __apply_alternatives(&region);
> + return __apply_alternatives(&region, 0);
> }
>
> /*
> --
> 2.11.0
>

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Re: [Xen-devel] [PATCH 07/13] xen/arm: Simplify alternative patching