linux-toradex.git/arch/arm64/kernel/vdso32, branch v6.4

vdso: Improve cmd_vdso_check to check all dynamic relocations

2023-03-21T20:15:34+00:00

The actual intention is that no dynamic relocation exists in the VDSO. For
this the VDSO build validates that the resulting .so file does not have any
relocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture,
which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Aside
of that ARCH_REL_TYPE_ABS is a misnomer as it checks for relative
relocations too.

However, some GNU ld ports produce unneeded R_*_NONE relocation entries. If
a port fails to determine the exact .rel[a].dyn size, the trailing zeros
become R_*_NONE relocations. E.g. ld's powerpc port recently fixed
https://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE are
generally a no-op in the dynamic loaders. So just ignore them.

Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting
.so file does not contain any R_* relocation entries except R_*_NONE.

Signed-off-by: Fangrui Song 
Signed-off-by: Thomas Gleixner 
Tested-by: Vincenzo Frascino  # for aarch64
Reviewed-by: Christophe Leroy 
Reviewed-by: Vincenzo Frascino  # for vDSO, aarch64
Acked-by: Michael Ellerman  (powerpc)
Link: https://lore.kernel.org/r/20230310190750.3323802-1-maskray@google.com

kbuild: upgrade the orphan section warning to an error if CONFIG_WERROR is set

2022-11-01T17:04:52+00:00

Andrew Cooper suggested upgrading the orphan section warning to a hard link
error. However Nathan Chancellor said outright turning the warning into an
error with no escape hatch might be too aggressive, as we have had these
warnings triggered by new compiler generated sections, and suggested turning
orphan sections into an error only if CONFIG_WERROR is set. Kees Cook echoed
and emphasized that the mandate from Linus is that we should avoid breaking
builds. It wrecks bisection, it causes problems across compiler versions, etc.

Thus upgrade the orphan section warning to a hard link error only if
CONFIG_WERROR is set.

Suggested-by: Andrew Cooper 
Suggested-by: Nathan Chancellor 
Signed-off-by: Xin Li 
Reviewed-by: Nathan Chancellor 
Tested-by: Nathan Chancellor 
Signed-off-by: Kees Cook 
Link: https://lore.kernel.org/r/20221025073023.16137-2-xin3.li@intel.com

arm64: vdso32: Add DWARF_DEBUG

2022-07-01T11:07:43+00:00

When building the 32-bit vDSO with LLVM 15 and CONFIG_DEBUG_INFO, there
are the following orphan section warnings:

  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_abbrev) is being placed in '.debug_abbrev'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_info) is being placed in '.debug_info'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_str_offsets) is being placed in '.debug_str_offsets'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_str) is being placed in '.debug_str'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_addr) is being placed in '.debug_addr'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_line) is being placed in '.debug_line'
  ld.lld: warning: arch/arm64/kernel/vdso32/note.o:(.debug_line_str) is being placed in '.debug_line_str'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_loclists) is being placed in '.debug_loclists'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_abbrev) is being placed in '.debug_abbrev'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_info) is being placed in '.debug_info'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_rnglists) is being placed in '.debug_rnglists'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_str_offsets) is being placed in '.debug_str_offsets'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_str) is being placed in '.debug_str'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_addr) is being placed in '.debug_addr'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_frame) is being placed in '.debug_frame'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_line) is being placed in '.debug_line'
  ld.lld: warning: arch/arm64/kernel/vdso32/vgettimeofday.o:(.debug_line_str) is being placed in '.debug_line_str'

These are DWARF5 sections, as that is the implicit default version for
clang-14 and newer when just '-g' is used. All DWARF sections are
handled by the DWARF_DEBUG macro from include/asm-generic/vmlinux.lds.h
so use that macro here to fix the warnings regardless of DWARF version.

Fixes: 9d4775b332e1 ("arm64: vdso32: enable orphan handling for VDSO")
Signed-off-by: Nathan Chancellor 
Reviewed-by: Nick Desaulniers 
Link: https://lore.kernel.org/r/20220630153121.1317045-3-nathan@kernel.org
Signed-off-by: Will Deacon

arm64: vdso32: Shuffle .ARM.exidx section above ELF_DETAILS

2022-07-01T11:07:43+00:00

When building the 32-bit vDSO after commit 5c4fb60816ea ("arm64: vdso32:
add ARM.exidx* sections"), ld.lld 11 fails to link:

  ld.lld: error: could not allocate headers
  ld.lld: error: unable to place section .text at file offset [0x2A0, 0xBB1]; check your linker script for overflows
  ld.lld: error: unable to place section .comment at file offset [0xBB2, 0xC8A]; check your linker script for overflows
  ld.lld: error: unable to place section .symtab at file offset [0xC8C, 0xE0B]; check your linker script for overflows
  ld.lld: error: unable to place section .strtab at file offset [0xE0C, 0xF1C]; check your linker script for overflows
  ld.lld: error: unable to place section .shstrtab at file offset [0xF1D, 0xFAA]; check your linker script for overflows
  ld.lld: error: section .ARM.exidx file range overlaps with .hash
  >>> .ARM.exidx range is [0x90, 0xCF]
  >>> .hash range is [0xB4, 0xE3]

  ld.lld: error: section .hash file range overlaps with .ARM.attributes
  >>> .hash range is [0xB4, 0xE3]
  >>> .ARM.attributes range is [0xD0, 0x10B]

  ld.lld: error: section .ARM.attributes file range overlaps with .dynsym
  >>> .ARM.attributes range is [0xD0, 0x10B]
  >>> .dynsym range is [0xE4, 0x133]

  ld.lld: error: section .ARM.exidx virtual address range overlaps with .hash
  >>> .ARM.exidx range is [0x90, 0xCF]
  >>> .hash range is [0xB4, 0xE3]

  ld.lld: error: section .ARM.exidx load address range overlaps with .hash
  >>> .ARM.exidx range is [0x90, 0xCF]
  >>> .hash range is [0xB4, 0xE3]

This was fixed in ld.lld 12 with a change to match GNU ld's semantics of
placing non-SHF_ALLOC sections after SHF_ALLOC sections.

To workaround this issue, move the .ARM.exidx section before the
.comment, .symtab, .strtab, and .shstrtab sections (ELF_DETAILS) so that
those sections remain contiguous with the .ARM.attributes section.

Fixes: 5c4fb60816ea ("arm64: vdso32: add ARM.exidx* sections")
Link: https://github.com/llvm/llvm-project/commit/ec29538af2e0886a65f479d6a533956a1c478132
Signed-off-by: Nathan Chancellor 
Link: https://lore.kernel.org/r/20220630153121.1317045-2-nathan@kernel.org
Signed-off-by: Will Deacon

arm64: vdso*: place got/plt sections in .rodata

2022-06-28T16:41:44+00:00

The vDSO will not contain absolute relocations, so place these
sections in .rodata.

Signed-off-by: Joey Gouly 
Link: https://lore.kernel.org/linux-arm-kernel/00abb0c5-6360-0004-353f-e7a88b3bd22c@arm.com/
Cc: Will Deacon 
Cc: Vincenzo Frascino 
Link: https://lore.kernel.org/r/20220628151307.35561-3-joey.gouly@arm.com
Signed-off-by: Will Deacon

arm64: vdso32: add ARM.exidx* sections

2022-06-28T16:41:44+00:00

These show up when building with clang+lld.

Signed-off-by: Joey Gouly 
Cc: Will Deacon 
Cc: Vincenzo Frascino 
Link: https://lore.kernel.org/r/20220628151307.35561-2-joey.gouly@arm.com
Signed-off-by: Will Deacon

arm64: vdso32: enable orphan handling for VDSO

2022-06-23T14:34:59+00:00

Like vmlinux, enable orphan-handling for the compat VDSO32. This can catch
subtle errors that might arise from unexpected sections being included.

Signed-off-by: Joey Gouly 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Masahiro Yamada 
Cc: Vincenzo Frascino 
Cc: Kees Cook 
Reviewed-by: Kees Cook 
Reviewed-by: Vincenzo Frascino 
Link: https://lore.kernel.org/r/20220510095834.32394-5-joey.gouly@arm.com
Signed-off-by: Will Deacon

arm64: vdso32: put ELF related sections in the linker script

2022-06-23T14:34:59+00:00

Use macros from vmlinux.lds.h to explicitly name sections that are included
in the compat VDSO32 output.

Signed-off-by: Joey Gouly 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Masahiro Yamada 
Cc: Vincenzo Frascino 
Cc: Kees Cook 
Reviewed-by: Kees Cook 
Reviewed-by: Vincenzo Frascino 
Link: https://lore.kernel.org/r/20220510095834.32394-4-joey.gouly@arm.com
Signed-off-by: Will Deacon

arm64: vdso: fix makefile dependency on vdso.so

2022-05-10T11:08:40+00:00

There is currently no dependency for vdso*-wrap.S on vdso*.so, which means that
you can get a build that uses a stale vdso*-wrap.o.

In commit a5b8ca97fbf8, the file that includes the vdso.so was moved and renamed
from arch/arm64/kernel/vdso/vdso.S to arch/arm64/kernel/vdso-wrap.S, when this
happened the Makefile was not updated to force the dependcy on vdso.so.

Fixes: a5b8ca97fbf8 ("arm64: do not descend to vdso directories twice")
Signed-off-by: Joey Gouly 
Cc: Masahiro Yamada 
Cc: Vincenzo Frascino 
Cc: Catalin Marinas 
Cc: Will Deacon 
Link: https://lore.kernel.org/r/20220510102721.50811-1-joey.gouly@arm.com
Signed-off-by: Will Deacon

Kbuild: move to -std=gnu11

2022-03-13T08:31:37+00:00

During a patch discussion, Linus brought up the option of changing
the C standard version from gnu89 to gnu99, which allows using variable
declaration inside of a for() loop. While the C99, C11 and later standards
introduce many other features, most of these are already available in
gnu89 as GNU extensions as well.

An earlier attempt to do this when gcc-5 started defaulting to
-std=gnu11 failed because at the time that caused warnings about
designated initializers with older compilers. Now that gcc-5.1 is
the minimum compiler version used for building kernels, that is no
longer a concern. Similarly, the behavior of 'inline' functions changes
between gnu89 using gnu_inline behavior and gnu11 using standard c99+
behavior, but this was taken care of by defining 'inline' to include
__attribute__((gnu_inline)) in order to allow building with clang a
while ago.

Nathan Chancellor reported a new -Wdeclaration-after-statement
warning that appears in a system header on arm, this still needs a
workaround.

The differences between gnu99, gnu11, gnu1x and gnu17 are fairly
minimal and mainly impact warnings at the -Wpedantic level that the
kernel never enables. Between these, gnu11 is the newest version
that is supported by all supported compiler versions, though it is
only the default on gcc-5, while all other supported versions of
gcc or clang default to gnu1x/gnu17.

Link: https://lore.kernel.org/lkml/CAHk-=wiyCH7xeHcmiFJ-YgXUy2Jaj7pnkdKpcovt8fYbVFW3TA@mail.gmail.com/
Link: https://github.com/ClangBuiltLinux/linux/issues/1603
Suggested-by: Linus Torvalds 
Acked-by: Marco Elver 
Acked-by: Jani Nikula 
Acked-by: David Sterba 
Tested-by: Sedat Dilek 
Reviewed-by: Alex Shi 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Miguel Ojeda 
Signed-off-by: Arnd Bergmann 
Reviewed-by: Nathan Chancellor 
Signed-off-by: Masahiro Yamada