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2e2713ae1a
Breno Leitao reports that arm64 emits the following warning
with CONFIG_DEBUG_VIRTUAL:
[ 58.896157] virt_to_phys used for non-linear address: 000000009fea9737
(__start_BTF+0x0/0x685530)
[ 23.988669] WARNING: CPU: 25 PID: 1442 at arch/arm64/mm/physaddr.c:15
__virt_to_phys (arch/arm64/mm/physaddr.c:?)
...
[ 24.075371] Tainted: [E]=UNSIGNED_MODULE, [N]=TEST
[ 24.080276] Hardware name: Quanta S7GM 20S7GCU0010/S7G MB (CG1), BIOS 3D22
07/03/2024
[ 24.088295] pstate: 63400009 (nZCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
[ 24.098440] pc : __virt_to_phys (arch/arm64/mm/physaddr.c:?)
[ 24.105398] lr : __virt_to_phys (arch/arm64/mm/physaddr.c:?)
...
[ 24.197257] Call trace:
[ 24.199761] __virt_to_phys (arch/arm64/mm/physaddr.c:?) (P)
[ 24.206883] btf_sysfs_vmlinux_mmap (kernel/bpf/sysfs_btf.c:27)
[ 24.214264] sysfs_kf_bin_mmap (fs/sysfs/file.c:179)
[ 24.218536] kernfs_fop_mmap (fs/kernfs/file.c:462)
[ 24.222461] mmap_region (./include/linux/fs.h:? mm/internal.h:167
mm/vma.c:2405 mm/vma.c:2467 mm/vma.c:2622 mm/vma.c:2692)
It seems that the memory layout on arm64 maps the kernel image in vmalloc space
which is different than x86. This makes virt_to_phys emit the warning.
Fix this by translating the address using __pa_symbol as suggested by
Breno instead.
Reported-by: Breno Leitao <leitao@debian.org>
Closes: https://lore.kernel.org/bpf/g2gqhkunbu43awrofzqb4cs4sxkxg2i4eud6p4qziwrdh67q4g@mtw3d3aqfgmb/
Signed-off-by: Lorenz Bauer <lmb@isovalent.com>
Tested-by: Breno Leitao <leitao@debian>
Fixes: a539e2a6d51d ("btf: Allow mmap of vmlinux btf")
Link: https://lore.kernel.org/r/20250717-vmlinux-mmap-pa-symbol-v1-1-970be6681158@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
70 lines
1.8 KiB
C
70 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 = __pa_symbol(__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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