From: Lorenz Bauer Date: Thu, 17 Jul 2025 16:49:49 +0000 (+0100) Subject: btf: Fix virt_to_phys() on arm64 when mmapping BTF X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=2e2713ae1a05eea7dda2f3b6988827196e33b25a;p=linux-block.git 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 Closes: https://lore.kernel.org/bpf/g2gqhkunbu43awrofzqb4cs4sxkxg2i4eud6p4qziwrdh67q4g@mtw3d3aqfgmb/ Signed-off-by: Lorenz Bauer Tested-by: Breno Leitao 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 --- diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index 941d0d2427e3..8e61dc555415 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -21,7 +21,7 @@ static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj, { unsigned long pages = PAGE_ALIGN(attr->size) >> PAGE_SHIFT; size_t vm_size = vma->vm_end - vma->vm_start; - phys_addr_t addr = virt_to_phys(__start_BTF); + phys_addr_t addr = __pa_symbol(__start_BTF); unsigned long pfn = addr >> PAGE_SHIFT; if (attr->private != __start_BTF || !PAGE_ALIGNED(addr))