user/sven/linux.git/scripts/kallsyms.c, branch v4.14.117

scripts/kallsyms: filter arm64's __efistub_ symbols

2019-01-13T09:01:06Z

commit 1212f7a16af492d59304ba3abccbcc5b5e41423e upstream. On arm64, the EFI stub and the kernel proper are essentially the same binary, although the EFI stub executes at a different virtual address as the kernel. For this reason, the EFI stub is restricted in the symbols it can link to, which is ensured by prefixing all EFI stub symbols with __efistub_ (and emitting __efistub_ prefixed aliases for routines that may be shared between the core kernel and the stub) These symbols are leaking into kallsyms, polluting the namespace, so let's filter them explicitly. Signed-off-by: Ard Biesheuvel Signed-off-by: Will Deacon Cc: Nick Desaulniers Signed-off-by: Greg Kroah-Hartman

scripts/kallsyms.c: ignore symbol type 'n'

2017-10-13T23:18:32Z

gcc on aarch64 may emit synbols of type 'n' if the kernel is built with '-frecord-gcc-switches'. In most cases, those symbols are reported with nm as 000000000000000e n $d and with objdump as 0000000000000000 l d .GCC.command.line 0000000000000000 .GCC.command.line 000000000000000e l .GCC.command.line 0000000000000000 $d Those symbols are detected in is_arm_mapping_symbol() and ignored. However, if "--prefix-symbols=" is configured as well, the situation is different. For example, in efi/libstub, arm64 images are built with '--prefix-alloc-sections=.init --prefix-symbols=__efistub_'. In combination with '-frecord-gcc-switches', the symbols are now reported by nm as: 000000000000000e n __efistub_$d and by objdump as: 0000000000000000 l d .GCC.command.line 0000000000000000 .GCC.command.line 000000000000000e l .GCC.command.line 0000000000000000 __efistub_$d Those symbols are no longer ignored and included in the base address calculation. This results in a base address of 000000000000000e, which in turn causes kallsyms to abort with kallsyms failure: relative symbol value 0xffffff900800a000 out of range in relative mode The problem is seen in little endian arm64 builds with CONFIG_EFI enabled and with '-frecord-gcc-switches' set in KCFLAGS. Explicitly ignore symbols of type 'n' since those are clearly debug symbols. Link: http://lkml.kernel.org/r/1507136063-3139-1-git-send-email-linux@roeck-us.net Signed-off-by: Guenter Roeck Acked-by: Ard Biesheuvel Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kbuild: modversions: add infrastructure for emitting relative CRCs

2017-02-03T16:28:25Z

This add the kbuild infrastructure that will allow architectures to emit vmlinux symbol CRCs as 32-bit offsets to another location in the kernel where the actual value is stored. This works around problems with CRCs being mistaken for relocatable symbols on kernels that self relocate at runtime (i.e., powerpc with CONFIG_RELOCATABLE=y) For the kbuild side of things, this comes down to the following: - introducing a Kconfig symbol MODULE_REL_CRCS - adding a -R switch to genksyms to instruct it to emit the CRC symbols as references into the .rodata section - making modpost distinguish such references from absolute CRC symbols by the section index (SHN_ABS) - making kallsyms disregard non-absolute symbols with a __crc_ prefix Signed-off-by: Ard Biesheuvel Signed-off-by: Linus Torvalds

scripts/kallsyms: remove last remnants of --page-offset option

2016-12-11T11:46:15Z

The implementation of the --page-offset kallsyms command line option has been removed, so remove it from the usage string as well. Signed-off-by: Ard Biesheuvel Signed-off-by: Michal Marek

ARM: 8553/1: kallsyms: remove --page-offset command line option

2016-04-07T20:57:16Z

The --page-offset command line option was only used for ARM, to filter symbol addresses below CONFIG_PAGE_OFFSET. This is no longer needed, so remove the functionality altogether. Acked-by: Nicolas Pitre Acked-by: Chris Brandt Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King

ARM: 8555/1: kallsyms: ignore ARM mode switching veneers

2016-04-07T20:57:15Z

On ARM, the linker may emit veneers to deal with relative branch instructions that appear too far away from their targets. Since the second kallsyms pass results in an increase of the kernel size, it may result in additional veneers to be emitted, potentially affecting the output of kallsyms itself if these symbols are visible to it, and for that reason, symbols whose names end in '_veneer' are ignored explicitly. However, when building Thumb2 kernels, such veneers are named differently if they also incur a mode switch, and since they are not filtered by kallsyms, they may cause the build to fail. So filter symbols whose names end in '_from_arm' or '_from_thumb' as well. Tested-by: Arnd Bergmann Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King

kallsyms: add support for relative offsets in kallsyms address table

2016-03-15T23:55:16Z

Similar to how relative extables are implemented, it is possible to emit the kallsyms table in such a way that it contains offsets relative to some anchor point in the kernel image rather than absolute addresses. On 64-bit architectures, it cuts the size of the kallsyms address table in half, since offsets between kernel symbols can typically be expressed in 32 bits. This saves several hundreds of kilobytes of permanent .rodata on average. In addition, the kallsyms address table is no longer subject to dynamic relocation when CONFIG_RELOCATABLE is in effect, so the relocation work done after decompression now doesn't have to do relocation updates for all these values. This saves up to 24 bytes (i.e., the size of a ELF64 RELA relocation table entry) per value, which easily adds up to a couple of megabytes of uncompressed __init data on ppc64 or arm64. Even if these relocation entries typically compress well, the combined size reduction of 2.8 MB uncompressed for a ppc64_defconfig build (of which 2.4 MB is __init data) results in a ~500 KB space saving in the compressed image. Since it is useful for some architectures (like x86) to retain the ability to emit absolute values as well, this patch also adds support for capturing both absolute and relative values when KALLSYMS_ABSOLUTE_PERCPU is in effect, by emitting absolute per-cpu addresses as positive 32-bit values, and addresses relative to the lowest encountered relative symbol as negative values, which are subtracted from the runtime address of this base symbol to produce the actual address. Support for the above is enabled by default for all architectures except IA-64 and Tile-GX, whose symbols are too far apart to capture in this manner. Signed-off-by: Ard Biesheuvel Tested-by: Guenter Roeck Reviewed-by: Kees Cook Tested-by: Kees Cook Cc: Heiko Carstens Cc: Michael Ellerman Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Benjamin Herrenschmidt Cc: Michal Marek Cc: Rusty Russell Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kallsyms: don't overload absolute symbol type for percpu symbols

2016-03-15T23:55:16Z

Commit c6bda7c988a5 ("kallsyms: fix percpu vars on x86-64 with relocation") overloaded the 'A' (absolute) symbol type to signify that a symbol is not subject to dynamic relocation. However, the original A type does not imply that at all, and depending on the version of the toolchain, many A type symbols are emitted that are in fact relative to the kernel text, i.e., if the kernel is relocated at runtime, these symbols should be updated as well. For instance, on sparc32, the following symbols are emitted as absolute (kindly provided by Guenter Roeck): f035a420 A _etext f03d9000 A _sdata f03de8c4 A jiffies f03f8860 A _edata f03fc000 A __init_begin f041bdc8 A __init_text_end f0423000 A __bss_start f0423000 A __init_end f044457d A __bss_stop f044457d A _end On x86_64, similar behavior can be observed: ffffffff81a00000 A __end_rodata_hpage_align ffffffff81b19000 A __vvar_page ffffffff81d3d000 A _end Even if only a couple of them pass the symbol range check that results in them to be taken into account for the final kallsyms symbol table, it is obvious that 'A' does not mean the symbol does not need to be updated at relocation time, and overloading its meaning to signify that is perhaps not a good idea. So instead, add a new percpu_absolute member to struct sym_entry, and when --absolute-percpu is in effect, use it to record symbols whose addresses should be emitted as final values rather than values that still require relocation at runtime. That way, we can drop the check against the 'A' type. Signed-off-by: Ard Biesheuvel Tested-by: Guenter Roeck Reviewed-by: Kees Cook Tested-by: Kees Cook Cc: Heiko Carstens Cc: Michael Ellerman Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Benjamin Herrenschmidt Cc: Michal Marek Acked-by: Rusty Russell Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Kbuild: kallsyms: drop special handling of pre-3.0 GCC symbols

2015-04-07T11:04:51Z

Since we have required at least GCC v3.2 for some time now, we can drop the special handling of the 'gcc[0-9]_compiled.' label which is not emitted anymore since GCC v3.0. Signed-off-by: Ard Biesheuvel Signed-off-by: Michal Marek

Kbuild: kallsyms: ignore veneers emitted by the ARM linker

2015-04-07T11:04:50Z

When linking large kernels on ARM, the linker will insert veneers (i.e., PLT like stubs) when function symbols are out of reach for the ordinary relative branch/branch-and-link instructions. However, due to the fact that the kallsyms region sits in .rodata, which is between .text and .init.text, additional veneers may be emitted in the second pass due to the fact that the size of the kallsyms region itself has pushed the .init.text section further apart, requiring even more veneers. So ignore the veneers when generating the symbol table. Veneers have no corresponding source code, and they will not turn up in backtraces anyway. This patch also lightly refactors the symbol_valid() function to use a local 'sym_name' rather than the obfuscated 'sym + 1' and 'sym + offset' Signed-off-by: Ard Biesheuvel Signed-off-by: Michal Marek