Messages in this thread | | | From | "H.J. Lu" <> | Date | Thu, 30 Jan 2020 12:48:38 -0800 | Subject | [PATCH] Discard .note.gnu.property sections in generic NOTES |
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On Thu, Jan 30, 2020 at 12:20 PM H.J. Lu <hjl.tools@gmail.com> wrote: > > On Thu, Jan 30, 2020 at 12:08 PM Kees Cook <keescook@chromium.org> wrote: > > > > On Thu, Jan 30, 2020 at 12:04:54PM -0800, H.J. Lu wrote: > > > > I don't understand this. "may not be incompatible"? Is there an error > > > > generated? If so, what does it look like? > > > > > > When -mx86-used-note=yes is passed to assembler, with my patch, I got > > > > > > [hjl@gnu-skx-1 linux]$ readelf -n vmlinux > > > > > > Displaying notes found in: .notes > > > Owner Data size Description > > > Xen 0x00000006 Unknown note type: (0x00000006) > > > description data: 6c 69 6e 75 78 00 > > > Xen 0x00000004 Unknown note type: (0x00000007) > > > description data: 32 2e 36 00 > > > Xen 0x00000008 Unknown note type: (0x00000005) > > > description data: 78 65 6e 2d 33 2e 30 00 > > > Xen 0x00000008 Unknown note type: (0x00000003) > > > description data: 00 00 00 80 ff ff ff ff > > > Xen 0x00000008 Unknown note type: (0x0000000f) > > > description data: 00 00 00 00 80 00 00 00 > > > Xen 0x00000008 NT_VERSION (version) > > > description data: 80 a1 ba 82 ff ff ff ff > > > Xen 0x00000008 NT_ARCH (architecture) > > > description data: 00 10 00 81 ff ff ff ff > > > Xen 0x00000029 Unknown note type: (0x0000000a) > > > description data: 21 77 72 69 74 61 62 6c 65 5f 70 61 67 65 5f 74 > > > 61 62 6c 65 73 7c 70 61 65 5f 70 67 64 69 72 5f 61 62 6f 76 65 5f 34 > > > 67 62 > > > Xen 0x00000004 Unknown note type: (0x00000011) > > > description data: 01 88 00 00 > > > Xen 0x00000004 Unknown note type: (0x00000009) > > > description data: 79 65 73 00 > > > Xen 0x00000008 Unknown note type: (0x00000008) > > > description data: 67 65 6e 65 72 69 63 00 > > > Xen 0x00000010 Unknown note type: (0x0000000d) > > > description data: 01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 > > > Xen 0x00000004 Unknown note type: (0x0000000e) > > > description data: 01 00 00 00 > > > Xen 0x00000004 Unknown note type: (0x00000010) > > > description data: 01 00 00 00 > > > Xen 0x00000008 Unknown note type: (0x0000000c) > > > description data: 00 00 00 00 00 80 ff ff > > > Xen 0x00000008 Unknown note type: (0x00000004) > > > description data: 00 00 00 00 00 00 00 00 > > > GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) > > > Build ID: 11c73de2922f593e1b35b92ab3c70eaa1a80fa83 > > > Linux 0x00000018 OPEN > > > description data: 35 2e 33 2e 39 2d 32 30 30 2e 30 2e 66 63 33 30 > > > 2e 78 38 36 5f 36 34 00 > > > Xen 0x00000008 Unknown note type: (0x00000012) > > > description data: 70 04 00 01 00 00 00 00 > > > [hjl@gnu-skx-1 linux]$ > > > > > > Without my patch, > > > > > > [hjl@gnu-skx-1 linux]$ readelf -n vmlinux > > > > > > Displaying notes found in: .notes > > > Owner Data size Description > > > Xen 0x00000006 Unknown note type: (0x00000006) > > > description data: 6c 69 6e 75 78 00 > > > Xen 0x00000004 Unknown note type: (0x00000007) > > > description data: 32 2e 36 00 > > > xen-3.0 0x00000005 Unknown note type: (0x006e6558) > > > description data: 08 00 00 00 03 > > > readelf: Warning: note with invalid namesz and/or descsz found at offset 0x50 > > > readelf: Warning: type: 0xffffffff, namesize: 0x006e6558, descsize: > > > 0x80000000, alignment: 8 > > > [hjl@gnu-skx-1 linux]$ > > > > What is the source of this failure? Does readelf need updating instead? > > Is the linking step producing an invalid section? It seems like > > discarding the properties isn't the right solution here? > > With the command-line option, -mx86-used-note=yes, the x86 assembler > in binutils 2.32 and above generates a program property note in a note > section, .note.gnu.property, to encode used x86 ISAs and features. > But x86 kernel linker script only contains a signle NOTE segment: > > PHDRS { > text PT_LOAD FLAGS(5); > data PT_LOAD FLAGS(6); > percpu PT_LOAD FLAGS(6); > init PT_LOAD FLAGS(7); > note PT_NOTE FLAGS(0); > } > SECTIONS > { > ... > .notes : AT(ADDR(.notes) - 0xffffffff80000000) { __start_notes = .; KEEP(*(.not > e.*)) __stop_notes = .; } :text :note > ... > } > > But .note.gnu.property must be 8-byte aligned. Linker deals with it > by generating > 2 PT_NOTE segments, one has 4-byte alignment and the other has 8-byte alignment: > > [hjl@gnu-cfl-1 ~]$ readelf -l /usr/local/bin/ld > > Elf file type is EXEC (Executable file) > Entry point 0x404530 > There are 13 program headers, starting at offset 64 > > Program Headers: > Type Offset VirtAddr PhysAddr > FileSiz MemSiz Flags Align > PHDR 0x0000000000000040 0x0000000000400040 0x0000000000400040 > 0x00000000000002d8 0x00000000000002d8 R 0x8 > INTERP 0x0000000000000318 0x0000000000400318 0x0000000000400318 > 0x000000000000001c 0x000000000000001c R 0x1 > [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2] > LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000 > 0x0000000000002a30 0x0000000000002a30 R 0x1000 > LOAD 0x0000000000003000 0x0000000000403000 0x0000000000403000 > 0x00000000000d7b35 0x00000000000d7b35 R E 0x1000 > LOAD 0x00000000000db000 0x00000000004db000 0x00000000004db000 > 0x0000000000179248 0x0000000000179248 R 0x1000 > LOAD 0x0000000000254de0 0x0000000000655de0 0x0000000000655de0 > 0x00000000000062e8 0x000000000000ba68 RW 0x1000 > DYNAMIC 0x0000000000254df0 0x0000000000655df0 0x0000000000655df0 > 0x0000000000000200 0x0000000000000200 RW 0x8 > NOTE 0x0000000000000338 0x0000000000400338 0x0000000000400338 > 0x0000000000000030 0x0000000000000030 R 0x8 > NOTE 0x0000000000000368 0x0000000000400368 0x0000000000400368 > 0x0000000000000044 0x0000000000000044 R 0x4 > GNU_PROPERTY 0x0000000000000338 0x0000000000400338 0x0000000000400338 > 0x0000000000000030 0x0000000000000030 R 0x8 > GNU_EH_FRAME 0x0000000000233efc 0x0000000000633efc 0x0000000000633efc > 0x000000000000478c 0x000000000000478c R 0x4 > GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000 > 0x0000000000000000 0x0000000000000000 RW 0x10 > GNU_RELRO 0x0000000000254de0 0x0000000000655de0 0x0000000000655de0 > 0x0000000000000220 0x0000000000000220 R 0x1 > > Section to Segment mapping: > Segment Sections... > 00 > 01 .interp > 02 .interp .note.gnu.property .note.gnu.build-id .note.ABI-tag > .hash .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn > .rela.plt > 03 .init .plt .text .fini > 04 .rodata .eh_frame_hdr .eh_frame > 05 .init_array .fini_array .dynamic .got .got.plt .data .bss > 06 .dynamic > 07 .note.gnu.property > 08 .note.gnu.build-id .note.ABI-tag > 09 .note.gnu.property > 10 .eh_frame_hdr > 11 > 12 .init_array .fini_array .dynamic .got > [hjl@gnu-cfl-1 ~]$ > > Since .note.gnu.property in vmlinux is unused, it can be discarded. >
Here is a patch to discard .note.gnu.property sections in generic NOTES.
-- H.J. [unhandled content-type:application/x-patch] | |