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lmbAlexei Starovoitov
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btf: Fix virt_to_phys() on arm64 when mmapping BTF
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 <[email protected]> Closes: https://lore.kernel.org/bpf/g2gqhkunbu43awrofzqb4cs4sxkxg2i4eud6p4qziwrdh67q4g@mtw3d3aqfgmb/ Signed-off-by: Lorenz Bauer <[email protected]> Tested-by: Breno Leitao <leitao@debian> Fixes: a539e2a ("btf: Allow mmap of vmlinux btf") Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Alexei Starovoitov <[email protected]>
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kernel/bpf/sysfs_btf.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -21,7 +21,7 @@ static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,
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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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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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