Messages in this thread Patch in this message | | | Date | Thu, 16 Jan 2014 12:53:18 -0500 | From | Kyle McMartin <> | Subject | Re: [PATCH] aarch64: always map VDSO at worst case alignment |
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On Thu, Jan 16, 2014 at 05:43:44PM +0000, Will Deacon wrote: > > + 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); > > + } > > I don't like this fix. The kernel is perfectly alright mapping the vdso at > the actual page size, as opposed to the maximum. Since the vdso isn't > demand-paged, we can actually just tell the linker not to bother forcing 64k > (worst case) alignment for PT_LOAD segments. Please can you try the patch > below? >
Me either, tbh. ;-)
I was testing out using -Wl,-z,max-page-size for the !CONFIG_ARM64_64K_PAGES case, and that seemed to work. A quick compile check shows the segment alignment being 0x10 with -Wl,-n:
kmcmarti ~/linux $ eu-readelf -l arch/arm64/kernel/vdso/vdso.so Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x000700 0x000700 R E 0x10
so I think that should work nicely!
I'll reboot a machine with this fix to test it as soon as possible.
Acked-by: Kyle McMartin <kyle@redhat.com>
> --- a/arch/arm64/kernel/vdso/Makefile > +++ b/arch/arm64/kernel/vdso/Makefile > @@ -48,7 +48,7 @@ $(obj-vdso): %.o: %.S > > # Actual build commands > quiet_cmd_vdsold = VDSOL $@ > - cmd_vdsold = $(CC) $(c_flags) -Wl,-T $^ -o $@ > + cmd_vdsold = $(CC) $(c_flags) -Wl,-n -Wl,-T $^ -o $@ > quiet_cmd_vdsoas = VDSOA $@ > cmd_vdsoas = $(CC) $(a_flags) -c -o $@ $< >
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