* [PATCH 0/2] x86: Discard .note.gnu.property sections
@ 2020-01-24 18:18 H.J. Lu
2020-01-24 18:18 ` [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO H.J. Lu
2020-01-24 18:18 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux H.J. Lu
0 siblings, 2 replies; 12+ messages in thread
From: H.J. Lu @ 2020-01-24 18:18 UTC (permalink / raw)
To: linux-kernel
Cc: Andy Lutomirski, Thomas Gleixner, Kees Cook, Thomas Lendacky,
Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov,
H . Peter Anvin, x86, Yu-cheng Yu
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 vmlinux and vDSO linker scripts only contain a signle NOTE
segment which may not be incompatible with note.gnu.property sections.
Since note.gnu.property section from kernel are unused, they should be
discarded by adding
/DISCARD/ : {
*(.note.gnu.property)
}
before .notes sections.
H.J. Lu (2):
x86: Discard .note.gnu.property sections in vDSO
x86: Discard .note.gnu.property sections in vmlinux
arch/x86/entry/vdso/vdso-layout.lds.S | 4 ++++
arch/x86/kernel/vmlinux.lds.S | 11 +++++++++++
2 files changed, 15 insertions(+)
--
2.24.1
^ permalink raw reply [flat|nested] 12+ messages in thread* [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO 2020-01-24 18:18 [PATCH 0/2] x86: Discard .note.gnu.property sections H.J. Lu @ 2020-01-24 18:18 ` H.J. Lu 2020-01-24 18:18 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux H.J. Lu 1 sibling, 0 replies; 12+ messages in thread From: H.J. Lu @ 2020-01-24 18:18 UTC (permalink / raw) To: linux-kernel Cc: Andy Lutomirski, Thomas Gleixner, Kees Cook, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, x86, Yu-cheng Yu 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. X86 kernel vDSO linker script only contains a signle NOTE segment: PHDRS { text PT_LOAD FLAGS(5) FILEHDR PHDRS; /* PF_R|PF_X */ dynamic PT_DYNAMIC FLAGS(4); /* PF_R */ note PT_NOTE FLAGS(4); /* PF_R */ eh_frame_hdr 0x6474e550; } which may not be incompatible with note.gnu.property sections. Since note.gnu.property section in vDSO is not used by dynamic linker, this patch discards .note.gnu.property sections in vDSO by adding /DISCARD/ : { *(.note.gnu.property) } before .notes sections. Signed-off-by: H.J. Lu <hjl.tools@gmail.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> --- arch/x86/entry/vdso/vdso-layout.lds.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S index 93c6dc7812d0..b604da6cc024 100644 --- a/arch/x86/entry/vdso/vdso-layout.lds.S +++ b/arch/x86/entry/vdso/vdso-layout.lds.S @@ -52,6 +52,10 @@ SECTIONS *(.gnu.linkonce.b.*) } :text + /* .note.gnu.property sections should be discarded */ + /DISCARD/ : { + *(.note.gnu.property) + } .note : { *(.note.*) } :text :note .eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr -- 2.24.1 ^ permalink raw reply related [flat|nested] 12+ messages in thread
* [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-24 18:18 [PATCH 0/2] x86: Discard .note.gnu.property sections H.J. Lu 2020-01-24 18:18 ` [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO H.J. Lu @ 2020-01-24 18:18 ` H.J. Lu 2020-01-27 23:34 ` Kees Cook 1 sibling, 1 reply; 12+ messages in thread From: H.J. Lu @ 2020-01-24 18:18 UTC (permalink / raw) To: linux-kernel Cc: Andy Lutomirski, Thomas Gleixner, Kees Cook, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, x86, Yu-cheng Yu 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 ... } which may not be incompatible with note.gnu.property sections. Since note.gnu.property section in kernel image is unused, this patch discards .note.gnu.property sections in kernel linker script by adding /DISCARD/ : { *(.note.gnu.property) } before .notes sections. Since .exit.text and .exit.data sections are discarded at runtime, it undefines EXIT_TEXT and EXIT_DATA to exclude .exit.text and .exit.data sections from default discarded sections. Signed-off-by: H.J. Lu <hjl.tools@gmail.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> --- arch/x86/kernel/vmlinux.lds.S | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 3a1a819da137..6c6cc26b0177 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -150,6 +150,11 @@ SECTIONS _etext = .; . = ALIGN(PAGE_SIZE); + /* .note.gnu.property sections should be discarded */ + /DISCARD/ : { + *(.note.gnu.property) + } + X86_ALIGN_RODATA_BEGIN RO_DATA(PAGE_SIZE) X86_ALIGN_RODATA_END @@ -413,6 +418,12 @@ SECTIONS STABS_DEBUG DWARF_DEBUG + /* Sections to be discarded. EXIT_TEXT and EXIT_DATA discard at runtime. + * not link time. */ +#undef EXIT_TEXT +#define EXIT_TEXT +#undef EXIT_DATA +#define EXIT_DATA DISCARDS /DISCARD/ : { *(.eh_frame) -- 2.24.1 ^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-24 18:18 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux H.J. Lu @ 2020-01-27 23:34 ` Kees Cook 2020-01-30 17:51 ` H.J. Lu 0 siblings, 1 reply; 12+ messages in thread From: Kees Cook @ 2020-01-27 23:34 UTC (permalink / raw) To: H.J. Lu Cc: linux-kernel, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, x86, Yu-cheng Yu On Fri, Jan 24, 2020 at 10:18:19AM -0800, H.J. Lu wrote: > 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 > ... > } > > which may not be incompatible with note.gnu.property sections. Since > note.gnu.property section in kernel image is unused, this patch discards > .note.gnu.property sections in kernel linker script by adding > > /DISCARD/ : { > *(.note.gnu.property) > } I think this is happening in the wrong place? Shouldn't this be in the DISCARDS macro in include/asm-generic/vmlinux.lds.h instead? > before .notes sections. Since .exit.text and .exit.data sections are > discarded at runtime, it undefines EXIT_TEXT and EXIT_DATA to exclude > .exit.text and .exit.data sections from default discarded sections. This looks like a separate issue (though maybe related to DISCARDS)? -Kees > > Signed-off-by: H.J. Lu <hjl.tools@gmail.com> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> > --- > arch/x86/kernel/vmlinux.lds.S | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 3a1a819da137..6c6cc26b0177 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -150,6 +150,11 @@ SECTIONS > _etext = .; > . = ALIGN(PAGE_SIZE); > > + /* .note.gnu.property sections should be discarded */ > + /DISCARD/ : { > + *(.note.gnu.property) > + } > + > X86_ALIGN_RODATA_BEGIN > RO_DATA(PAGE_SIZE) > X86_ALIGN_RODATA_END > @@ -413,6 +418,12 @@ SECTIONS > STABS_DEBUG > DWARF_DEBUG > > + /* Sections to be discarded. EXIT_TEXT and EXIT_DATA discard at runtime. > + * not link time. */ > +#undef EXIT_TEXT > +#define EXIT_TEXT > +#undef EXIT_DATA > +#define EXIT_DATA > DISCARDS > /DISCARD/ : { > *(.eh_frame) > -- > 2.24.1 > -- Kees Cook ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-27 23:34 ` Kees Cook @ 2020-01-30 17:51 ` H.J. Lu 2020-01-30 19:51 ` Kees Cook 0 siblings, 1 reply; 12+ messages in thread From: H.J. Lu @ 2020-01-30 17:51 UTC (permalink / raw) To: Kees Cook Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu [-- Attachment #1: Type: text/plain, Size: 1834 bytes --] On Mon, Jan 27, 2020 at 3:34 PM Kees Cook <keescook@chromium.org> wrote: > > On Fri, Jan 24, 2020 at 10:18:19AM -0800, H.J. Lu wrote: > > 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 > > ... > > } > > > > which may not be incompatible with note.gnu.property sections. Since > > note.gnu.property section in kernel image is unused, this patch discards > > .note.gnu.property sections in kernel linker script by adding > > > > /DISCARD/ : { > > *(.note.gnu.property) > > } > > I think this is happening in the wrong place? Shouldn't this be in the > DISCARDS macro in include/asm-generic/vmlinux.lds.h instead? Please read my commit message closely. We can't discard .note.gnu.property sections by adding .note.gnu.property to default discarded sections since default discarded sections are placed AFTER .notes sections in x86 kernel linker scripts. > > before .notes sections. Since .exit.text and .exit.data sections are > > discarded at runtime, it undefines EXIT_TEXT and EXIT_DATA to exclude > > .exit.text and .exit.data sections from default discarded sections. > > This looks like a separate issue (though maybe related to DISCARDS)? Here is the updated patch without EXIT_TEXT and EXIT_DATA change. I will submit a separate patch for it. Thanks. -- H.J. [-- Attachment #2: 0002-x86-Discard-.note.gnu.property-sections-in-vmlinux.patch --] [-- Type: text/x-patch, Size: 1814 bytes --] From 6397008c2c295cd58a052acf9fc6411a3d68e46d Mon Sep 17 00:00:00 2001 From: "H.J. Lu" <hjl.tools@gmail.com> Date: Thu, 30 Jan 2020 09:25:54 -0800 Subject: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 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 ... } which may not be incompatible with note.gnu.property sections. Since note.gnu.property section in kernel image is never used, this patch discards .note.gnu.property sections in kernel linker script by adding /DISCARD/ : { *(.note.gnu.property) } before .notes sections. NB: We can't discard .note.gnu.property sections by adding .note.gnu.property to default discarded sections since default discarded sections are placed AFTER .notes sections in x86 kernel linker scripts. Signed-off-by: H.J. Lu <hjl.tools@gmail.com> --- arch/x86/kernel/vmlinux.lds.S | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index e3296aa028fe..d1b942365d27 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -150,6 +150,11 @@ SECTIONS _etext = .; . = ALIGN(PAGE_SIZE); + /* .note.gnu.property sections should be discarded */ + /DISCARD/ : { + *(.note.gnu.property) + } + X86_ALIGN_RODATA_BEGIN RO_DATA(PAGE_SIZE) X86_ALIGN_RODATA_END -- 2.24.1 ^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-30 17:51 ` H.J. Lu @ 2020-01-30 19:51 ` Kees Cook 2020-01-30 20:04 ` H.J. Lu 0 siblings, 1 reply; 12+ messages in thread From: Kees Cook @ 2020-01-30 19:51 UTC (permalink / raw) To: H.J. Lu Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu On Thu, Jan 30, 2020 at 09:51:38AM -0800, H.J. Lu wrote: > On Mon, Jan 27, 2020 at 3:34 PM Kees Cook <keescook@chromium.org> wrote: > > > > On Fri, Jan 24, 2020 at 10:18:19AM -0800, H.J. Lu wrote: > > > 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 > > > ... > > > } > > > > > > which may not be incompatible with note.gnu.property sections. Since I don't understand this. "may not be incompatible"? Is there an error generated? If so, what does it look like? > > > note.gnu.property section in kernel image is unused, this patch discards > > > .note.gnu.property sections in kernel linker script by adding > > > > > > /DISCARD/ : { > > > *(.note.gnu.property) > > > } > > > > I think this is happening in the wrong place? Shouldn't this be in the > > DISCARDS macro in include/asm-generic/vmlinux.lds.h instead? > > Please read my commit message closely. We can't discard .note.gnu.property > sections by adding .note.gnu.property to default discarded sections > since default > discarded sections are placed AFTER .notes sections in x86 kernel > linker scripts. I see what you mean now, /DISCARD/ happens after the NOTES macro (now in the RO_DATA macro). To this end, I think this should be in include/asm-generic/vmlinux.lds.h in the NOTES macro? It's x86-specific right now, but why not make this future-proof? I'd like to avoid as much arch-specific linker stuff as we can. I spent a lot of time trying to clean up NOTES specifically. :) > + /* .note.gnu.property sections should be discarded */ This comment should say _why_ -- the script already shows _what_ is happening... > + /DISCARD/ : { > + *(.note.gnu.property) > + } -Kees -- Kees Cook ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-30 19:51 ` Kees Cook @ 2020-01-30 20:04 ` H.J. Lu 2020-01-30 20:08 ` Kees Cook 0 siblings, 1 reply; 12+ messages in thread From: H.J. Lu @ 2020-01-30 20:04 UTC (permalink / raw) To: Kees Cook Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu On Thu, Jan 30, 2020 at 11:51 AM Kees Cook <keescook@chromium.org> wrote: > > On Thu, Jan 30, 2020 at 09:51:38AM -0800, H.J. Lu wrote: > > On Mon, Jan 27, 2020 at 3:34 PM Kees Cook <keescook@chromium.org> wrote: > > > > > > On Fri, Jan 24, 2020 at 10:18:19AM -0800, H.J. Lu wrote: > > > > 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 > > > > ... > > > > } > > > > > > > > which may not be incompatible with note.gnu.property sections. Since > > 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]$ > > > > note.gnu.property section in kernel image is unused, this patch discards > > > > .note.gnu.property sections in kernel linker script by adding > > > > > > > > /DISCARD/ : { > > > > *(.note.gnu.property) > > > > } > > > > > > I think this is happening in the wrong place? Shouldn't this be in the > > > DISCARDS macro in include/asm-generic/vmlinux.lds.h instead? > > > > Please read my commit message closely. We can't discard .note.gnu.property > > sections by adding .note.gnu.property to default discarded sections > > since default > > discarded sections are placed AFTER .notes sections in x86 kernel > > linker scripts. > > I see what you mean now, /DISCARD/ happens after the NOTES macro (now in > the RO_DATA macro). To this end, I think this should be in > include/asm-generic/vmlinux.lds.h in the NOTES macro? It's x86-specific > right now, but why not make this future-proof? I am trying to avoid touching generic parts. I will give it a try. > I'd like to avoid as much arch-specific linker stuff as we can. I spent > a lot of time trying to clean up NOTES specifically. :) > > > + /* .note.gnu.property sections should be discarded */ > > This comment should say _why_ -- the script already shows _what_ is > happening... I will update comments. > > + /DISCARD/ : { > > + *(.note.gnu.property) > > + } > Thanks. -- H.J. ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-30 20:04 ` H.J. Lu @ 2020-01-30 20:08 ` Kees Cook 2020-01-30 20:20 ` H.J. Lu 0 siblings, 1 reply; 12+ messages in thread From: Kees Cook @ 2020-01-30 20:08 UTC (permalink / raw) To: H.J. Lu Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu 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? -- Kees Cook ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-30 20:08 ` Kees Cook @ 2020-01-30 20:20 ` H.J. Lu 2020-01-30 20:48 ` [PATCH] Discard .note.gnu.property sections in generic NOTES H.J. Lu 2020-01-30 22:06 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux Kees Cook 0 siblings, 2 replies; 12+ messages in thread From: H.J. Lu @ 2020-01-30 20:20 UTC (permalink / raw) To: Kees Cook Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu 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. -- H.J. ^ permalink raw reply [flat|nested] 12+ messages in thread
* [PATCH] Discard .note.gnu.property sections in generic NOTES 2020-01-30 20:20 ` H.J. Lu @ 2020-01-30 20:48 ` H.J. Lu 2020-01-30 22:09 ` Kees Cook 2020-01-30 22:06 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux Kees Cook 1 sibling, 1 reply; 12+ messages in thread From: H.J. Lu @ 2020-01-30 20:48 UTC (permalink / raw) To: Kees Cook Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu [-- Attachment #1: Type: text/plain, Size: 7826 bytes --] 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. [-- Attachment #2: 0001-Discard-.note.gnu.property-sections-in-generic-NOTES.patch --] [-- Type: application/x-patch, Size: 2447 bytes --] ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] Discard .note.gnu.property sections in generic NOTES 2020-01-30 20:48 ` [PATCH] Discard .note.gnu.property sections in generic NOTES H.J. Lu @ 2020-01-30 22:09 ` Kees Cook 0 siblings, 0 replies; 12+ messages in thread From: Kees Cook @ 2020-01-30 22:09 UTC (permalink / raw) To: H.J. Lu Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu On Thu, Jan 30, 2020 at 12:48:38PM -0800, H.J. Lu wrote: > Here is a patch to discard .note.gnu.property sections in generic NOTES. Thanks! This looks good, though please send not as an attachment. :) Also, one more nit: the comment style should be: /* * First line of text, blah blah ... * ... blah blah, end of text. */ -- Kees Cook ^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux 2020-01-30 20:20 ` H.J. Lu 2020-01-30 20:48 ` [PATCH] Discard .note.gnu.property sections in generic NOTES H.J. Lu @ 2020-01-30 22:06 ` Kees Cook 1 sibling, 0 replies; 12+ messages in thread From: Kees Cook @ 2020-01-30 22:06 UTC (permalink / raw) To: H.J. Lu Cc: LKML, Andy Lutomirski, Thomas Gleixner, Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov, H . Peter Anvin, the arch/x86 maintainers, Yu-cheng Yu On Thu, Jan 30, 2020 at 12:20:30PM -0800, H.J. Lu 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: typo: signle -> single > > 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: Ah-ha! Okay, thanks for this detail. > > [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. Okay, I'm convinced. If we ever DO need it, it seems the solution would be to make the regular .note 8 byte aligned... Thanks for the extra details! -Kees -- Kees Cook ^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2020-01-30 22:09 UTC | newest] Thread overview: 12+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2020-01-24 18:18 [PATCH 0/2] x86: Discard .note.gnu.property sections H.J. Lu 2020-01-24 18:18 ` [PATCH 1/2] x86: Discard .note.gnu.property sections in vDSO H.J. Lu 2020-01-24 18:18 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux H.J. Lu 2020-01-27 23:34 ` Kees Cook 2020-01-30 17:51 ` H.J. Lu 2020-01-30 19:51 ` Kees Cook 2020-01-30 20:04 ` H.J. Lu 2020-01-30 20:08 ` Kees Cook 2020-01-30 20:20 ` H.J. Lu 2020-01-30 20:48 ` [PATCH] Discard .note.gnu.property sections in generic NOTES H.J. Lu 2020-01-30 22:09 ` Kees Cook 2020-01-30 22:06 ` [PATCH 2/2] x86: Discard .note.gnu.property sections in vmlinux Kees Cook
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