Messages in this thread Patch in this message | | | Date | Wed, 15 Jan 2014 16:41:44 -0500 | From | Kyle McMartin <> | Subject | [PATCH] aarch64: always map VDSO at worst case alignment |
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Currently on ARM64 with 4K pages set, GDB fails to load the VDSO with the error "Failed to read a valid object file image from memory" as it is applying the phdr alignment to the vma, and attempting to read below where the VDSO is mapped. This is because our segment alignment is 64K in the ELF headers, but the VDSO only has PAGE_SIZE alignment from get_unmapped_area.
Work around this by calling vm_unmapped_area directly, and specifying the worst case alignment (64K) directly.
With this patch applied, I no longer have issues loading the VDSO in gdb (and no more error message every time I run a program inside it.)
Signed-off-by: Kyle McMartin <kyle@redhat.com>
--- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -163,7 +163,18 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, vdso_mapping_len = (vdso_pages + 1) << PAGE_SHIFT; down_write(&mm->mmap_sem); - vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); + { + /* the VDSO must be worst-case aligned to 64K */ + struct vm_unmapped_area_info info = + { + .flags = 0, + .length = vdso_mapping_len, + .low_limit = mm->mmap_base, + .high_limit = TASK_SIZE, + .align_mask = (1 << 16) - 1, + }; + vdso_base = vm_unmapped_area(&info); + } if (IS_ERR_VALUE(vdso_base)) { ret = vdso_base; goto up_fail;
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