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Peter patch simply removes >>>> that feature. >>> >>> Are you sure? He ends up with >> >> More than sure :) >> Just look at below. >> >>> static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, >>> u64 *ips, u32 trace_nr, bool user) >>> { >>> int i; >>> >>> /* cannot access current->mm, fall back to ips */ >>> for (i = 0; i < trace_nr; i++) { >>> id_offs[i].status = BPF_STACK_BUILD_ID_IP; >>> id_offs[i].ip = ips[i]; >>> memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX); >>> } >>> return; >>> } >>> >>> and you're saying that userspace won't like this because we didn't set >>> BPF_STACK_BUILD_ID_VALID? >> >> The patch forces the "fallback path" that in production is seen 0.001% >> Meaning that user space doesn't see build_id any more. It sees IPs only. >> The user space cannot correlate IPs to binaries. That's what build_id enabled. > > I was thinking of decomposing the checks in my first response to two > functions. > > Something like this: > -------------- > diff --git a/mm/mmap.c b/mm/mmap.c > index dce46105e3df..8afc1d22aa61 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2293,12 +2293,13 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, > EXPORT_SYMBOL(get_unmapped_area); > > /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */ > -struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) > +struct vm_area_struct *find_vma_non_owner(struct mm_struct *mm, > + unsigned long addr) > { > struct rb_node *rb_node; > struct vm_area_struct *vma; > > - mmap_assert_locked(mm); > + VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); > /* Check the cache first. */ > vma = vmacache_find(mm, addr); > if (likely(vma)) > @@ -2325,6 +2326,11 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) > return vma; > } > > +struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) > +{ > + lockdep_assert_held(&mm->mmap_lock); > + return find_vma_non_owner(mm, addr); > +} > EXPORT_SYMBOL(find_vma); > > /* > > -------------- > > Although this leaks more into the mm API and was referred to as ugly > previously, it does provide a working solution and still maintains the > same level of checking. > > Would it push the back actors to just switch to non_owner though? Thanks, Liam. This should work for bpf side as well as we can just call find_vma_no_owner(). I will submit v3 soon. > > > Thanks, > Liam >