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User space needs access to kernel BTF for many modern features of BPF. Right now each process needs to read the BTF blob either in pieces or as a whole. Allow mmaping the sysfs file so that processes can directly access the memory allocated for it in the kernel. remap_pfn_range is used instead of vm_insert_page due to aarch64 compatibility issues. Signed-off-by: Lorenz Bauer <lmb@isovalent.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Tested-by: Alan Maguire <alan.maguire@oracle.com> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev> Link: https://lore.kernel.org/bpf/20250520-vmlinux-mmap-v5-1-e8c941acc414@isovalent.com
69 lines
1.8 KiB
C
69 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Provide kernel BTF information for introspection and use by eBPF tools.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/init.h>
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#include <linux/sysfs.h>
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#include <linux/mm.h>
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#include <linux/io.h>
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#include <linux/btf.h>
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/* See scripts/link-vmlinux.sh, gen_btf() func for details */
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extern char __start_BTF[];
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extern char __stop_BTF[];
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static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,
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const struct bin_attribute *attr,
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struct vm_area_struct *vma)
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{
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unsigned long pages = PAGE_ALIGN(attr->size) >> PAGE_SHIFT;
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size_t vm_size = vma->vm_end - vma->vm_start;
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phys_addr_t addr = virt_to_phys(__start_BTF);
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unsigned long pfn = addr >> PAGE_SHIFT;
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if (attr->private != __start_BTF || !PAGE_ALIGNED(addr))
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return -EINVAL;
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if (vma->vm_pgoff)
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return -EINVAL;
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if (vma->vm_flags & (VM_WRITE | VM_EXEC | VM_MAYSHARE))
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return -EACCES;
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if (pfn + pages < pfn)
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return -EINVAL;
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if ((vm_size >> PAGE_SHIFT) > pages)
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return -EINVAL;
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vm_flags_mod(vma, VM_DONTDUMP, VM_MAYEXEC | VM_MAYWRITE);
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return remap_pfn_range(vma, vma->vm_start, pfn, vm_size, vma->vm_page_prot);
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}
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static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
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.attr = { .name = "vmlinux", .mode = 0444, },
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.read_new = sysfs_bin_attr_simple_read,
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.mmap = btf_sysfs_vmlinux_mmap,
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};
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struct kobject *btf_kobj;
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static int __init btf_vmlinux_init(void)
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{
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bin_attr_btf_vmlinux.private = __start_BTF;
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bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;
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if (bin_attr_btf_vmlinux.size == 0)
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return 0;
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btf_kobj = kobject_create_and_add("btf", kernel_kobj);
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if (!btf_kobj)
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return -ENOMEM;
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return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux);
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}
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subsys_initcall(btf_vmlinux_init);
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