linux-toradex.git/include/linux/linkage.h, branch v5.12-rc6

x86/entry: Emit a symbol for register restoring thunk

2021-01-14T16:18:25+00:00

Arnd found a randconfig that produces the warning:

arch/x86/entry/thunk_64.o: warning: objtool: missing symbol for insn at
offset 0x3e

when building with LLVM_IAS=1 (Clang's integrated assembler). Josh
notes:

With the LLVM assembler not generating section symbols, objtool has no
way to reference this code when it generates ORC unwinder entries,
because this code is outside of any ELF function.

The limitation now being imposed by objtool is that all code must be
contained in an ELF symbol. And .L symbols don't create such symbols.

So basically, you can use an .L symbol *inside* a function or a code
segment, you just can't use the .L symbol to contain the code using a
SYM_*_START/END annotation pair.

Fangrui notes that this optimization is helpful for reducing image size
when compiling with -ffunction-sections and -fdata-sections. I have
observed on the order of tens of thousands of symbols for the kernel
images built with those flags.

A patch has been authored against GNU binutils to match this behavior
of not generating unused section symbols ([1]), so this will
also become a problem for users of GNU binutils once they upgrade to 2.36.

Omit the .L prefix on a label so that the assembler will emit an entry
into the symbol table for the label, with STB_LOCAL binding. This
enables objtool to generate proper unwind info here with LLVM_IAS=1 or
GNU binutils 2.36+.

[ bp: Massage commit message. ]

Reported-by: Arnd Bergmann
Suggested-by: Josh Poimboeuf
Suggested-by: Borislav Petkov
Suggested-by: Mark Brown
Signed-off-by: Nick Desaulniers
Signed-off-by: Borislav Petkov
Acked-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Link: https://lkml.kernel.org/r/20210112194625.4181814-1-ndesaulniers@google.com
Link: https://github.com/ClangBuiltLinux/linux/issues/1209
Link: https://reviews.llvm.org/D93783
Link: https://sourceware.org/binutils/docs/as/Symbol-Names.html
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1408485ce69f844dcd7ded093a8 [1]

treewide: Convert macro and uses of section(foo) to section("foo")

2020-10-25T21:51:49+00:00

Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

    https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Miguel Ojeda 
Signed-off-by: Linus Torvalds

x86/asm: Provide a Kconfig symbol for disabling old assembly annotations

2020-04-18T15:43:09+00:00

As x86 was converted to use the modern SYM_ annotations for assembly,
ifdefs were added to remove the generic definitions of the old style
annotations on x86. Rather than collect a list of architectures in the
ifdefs as more architectures are converted over, provide a Kconfig
symbol for this and update x86 to use it.

Signed-off-by: Mark Brown 
Signed-off-by: Borislav Petkov 
Acked-by: Jiri Slaby 
Link: https://lkml.kernel.org/r/20200416182402.6206-1-broonie@kernel.org

x86/asm: Replace WEAK uses by SYM_INNER_LABEL_ALIGN

2019-10-18T10:13:35+00:00

Use the new SYM_INNER_LABEL_ALIGN for WEAK entries in the middle of x86
assembly functions.

And make sure WEAK is not defined for x86 anymore as these were the last
users.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Cc: Andrey Ryabinin 
Cc: Boris Ostrovsky 
Cc: Herbert Xu 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Josh Poimboeuf 
Cc: linux-arch@vger.kernel.org
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: "Rafael J. Wysocki" 
Cc: "Steven Rostedt (VMware)" 
Cc: Thomas Gleixner 
Cc: x86-ml 
Link: https://lkml.kernel.org/r/20191011115108.12392-29-jslaby@suse.cz

x86/asm/32: Change all ENTRY+ENDPROC to SYM_FUNC_*

2019-10-18T10:03:43+00:00

These are all functions which are invoked from elsewhere, so annotate
them as global using the new SYM_FUNC_START and their ENDPROC's by
SYM_FUNC_END.

Now, ENTRY/ENDPROC can be forced to be undefined on X86, so do so.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Cc: Allison Randal 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: Andy Shevchenko 
Cc: Ard Biesheuvel 
Cc: Bill Metzenthen 
Cc: Boris Ostrovsky 
Cc: Darren Hart 
Cc: "David S. Miller" 
Cc: Greg Kroah-Hartman 
Cc: Herbert Xu 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: linux-arch@vger.kernel.org
Cc: linux-crypto@vger.kernel.org
Cc: linux-efi 
Cc: linux-efi@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: Mark Rutland 
Cc: Matt Fleming 
Cc: Pavel Machek 
Cc: platform-driver-x86@vger.kernel.org
Cc: "Rafael J. Wysocki" 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: x86-ml 
Link: https://lkml.kernel.org/r/20191011115108.12392-28-jslaby@suse.cz

x86/asm/32: Change all ENTRY+END to SYM_CODE_*

2019-10-18T10:00:43+00:00

Change all assembly code which is marked using END (and not ENDPROC) to
appropriate new markings SYM_CODE_START and SYM_CODE_END.

And since the last user of END on X86 is gone now, make sure that END is
not defined there.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: Boris Ostrovsky 
Cc: Herbert Xu 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Josh Poimboeuf 
Cc: linux-arch@vger.kernel.org
Cc: Mark Rutland 
Cc: Peter Zijlstra 
Cc: "Rafael J. Wysocki" 
Cc: "Steven Rostedt (VMware)" 
Cc: Thomas Gleixner 
Cc: x86-ml 
Link: https://lkml.kernel.org/r/20191011115108.12392-27-jslaby@suse.cz

x86/asm: Change all ENTRY+ENDPROC to SYM_FUNC_*

2019-10-18T09:58:33+00:00

These are all functions which are invoked from elsewhere, so annotate
them as global using the new SYM_FUNC_START and their ENDPROC's by
SYM_FUNC_END.

Make sure ENTRY/ENDPROC is not defined on X86_64, given these were the
last users.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Reviewed-by: Rafael J. Wysocki  [hibernate]
Reviewed-by: Boris Ostrovsky  [xen bits]
Acked-by: Herbert Xu  [crypto]
Cc: Allison Randal 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: Andy Shevchenko 
Cc: Ard Biesheuvel 
Cc: Armijn Hemel 
Cc: Cao jin 
Cc: Darren Hart 
Cc: Dave Hansen 
Cc: "David S. Miller" 
Cc: Enrico Weigelt 
Cc: Greg Kroah-Hartman 
Cc: Herbert Xu 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Jim Mattson 
Cc: Joerg Roedel 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Kate Stewart 
Cc: "Kirill A. Shutemov" 
Cc: kvm ML 
Cc: Len Brown 
Cc: linux-arch@vger.kernel.org
Cc: linux-crypto@vger.kernel.org
Cc: linux-efi 
Cc: linux-efi@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: Mark Rutland 
Cc: Matt Fleming 
Cc: Paolo Bonzini 
Cc: Pavel Machek 
Cc: Peter Zijlstra 
Cc: platform-driver-x86@vger.kernel.org
Cc: "Radim Krčmář" 
Cc: Sean Christopherson 
Cc: Stefano Stabellini 
Cc: "Steven Rostedt (VMware)" 
Cc: Thomas Gleixner 
Cc: Vitaly Kuznetsov 
Cc: Wanpeng Li 
Cc: Wei Huang 
Cc: x86-ml 
Cc: xen-devel@lists.xenproject.org
Cc: Xiaoyao Li 
Link: https://lkml.kernel.org/r/20191011115108.12392-25-jslaby@suse.cz

x86/asm: Remove the last GLOBAL user and remove the macro

2019-10-18T09:29:50+00:00

Convert the remaining 32bit users and remove the GLOBAL macro finally.
In particular, this means to use SYM_ENTRY for the singlestepping hack
region.

Exclude the global definition of GLOBAL from x86 too.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Cc: Andrew Morton 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: linux-arch@vger.kernel.org
Cc: Mark Rutland 
Cc: "Rafael J. Wysocki" 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: x86-ml 
Link: https://lkml.kernel.org/r/20191011115108.12392-20-jslaby@suse.cz

linkage: Introduce new macros for assembler symbols

2019-10-18T07:48:11+00:00

Introduce new C macros for annotations of functions and data in
assembly. There is a long-standing mess in macros like ENTRY, END,
ENDPROC and similar. They are used in different manners and sometimes
incorrectly.

So introduce macros with clear use to annotate assembly as follows:

a) Support macros for the ones below
   SYM_T_FUNC -- type used by assembler to mark functions
   SYM_T_OBJECT -- type used by assembler to mark data
   SYM_T_NONE -- type used by assembler to mark entries of unknown type

   They are defined as STT_FUNC, STT_OBJECT, and STT_NOTYPE
   respectively. According to the gas manual, this is the most portable
   way. I am not sure about other assemblers, so this can be switched
   back to %function and %object if this turns into a problem.
   Architectures can also override them by something like ", @function"
   if they need.

   SYM_A_ALIGN, SYM_A_NONE -- align the symbol?
   SYM_L_GLOBAL, SYM_L_WEAK, SYM_L_LOCAL -- linkage of symbols

b) Mostly internal annotations, used by the ones below
   SYM_ENTRY -- use only if you have to (for non-paired symbols)
   SYM_START -- use only if you have to (for paired symbols)
   SYM_END -- use only if you have to (for paired symbols)

c) Annotations for code
   SYM_INNER_LABEL_ALIGN -- only for labels in the middle of code
   SYM_INNER_LABEL -- only for labels in the middle of code

   SYM_FUNC_START_LOCAL_ALIAS -- use where there are two local names for
	one function
   SYM_FUNC_START_ALIAS -- use where there are two global names for one
	function
   SYM_FUNC_END_ALIAS -- the end of LOCAL_ALIASed or ALIASed function

   SYM_FUNC_START -- use for global functions
   SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment
   SYM_FUNC_START_LOCAL -- use for local functions
   SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o
	alignment
   SYM_FUNC_START_WEAK -- use for weak functions
   SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment
   SYM_FUNC_END -- the end of SYM_FUNC_START_LOCAL, SYM_FUNC_START,
	SYM_FUNC_START_WEAK, ...

   For functions with special (non-C) calling conventions:
   SYM_CODE_START -- use for non-C (special) functions
   SYM_CODE_START_NOALIGN -- use for non-C (special) functions, w/o
	alignment
   SYM_CODE_START_LOCAL -- use for local non-C (special) functions
   SYM_CODE_START_LOCAL_NOALIGN -- use for local non-C (special)
	functions, w/o alignment
   SYM_CODE_END -- the end of SYM_CODE_START_LOCAL or SYM_CODE_START

d) For data
   SYM_DATA_START -- global data symbol
   SYM_DATA_START_LOCAL -- local data symbol
   SYM_DATA_END -- the end of the SYM_DATA_START symbol
   SYM_DATA_END_LABEL -- the labeled end of SYM_DATA_START symbol
   SYM_DATA -- start+end wrapper around simple global data
   SYM_DATA_LOCAL -- start+end wrapper around simple local data

==========

The macros allow to pair starts and ends of functions and mark functions
correctly in the output ELF objects.

All users of the old macros in x86 are converted to use these in further
patches.

Signed-off-by: Jiri Slaby 
Signed-off-by: Borislav Petkov 
Acked-by: Rafael J. Wysocki 
Cc: Andrew Morton 
Cc: Andrey Ryabinin 
Cc: Boris Ostrovsky 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Len Brown 
Cc: Linus Torvalds 
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: Mark Rutland 
Cc: Pavel Machek 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: x86-ml 
Cc: xen-devel@lists.xenproject.org
Link: https://lkml.kernel.org/r/20191011115108.12392-2-jslaby@suse.cz

linkage: add generic GLOBAL() macro

2018-11-30T13:29:04+00:00

Declaring a global symbol in assembly is tedious, error-prone, and
painful to read. While ENTRY() exists, this is supposed to be used for
function entry points, and this affects alignment in a potentially
undesireable manner.

Instead, let's add a generic GLOBAL() macro for this, as x86 added
locally in commit:

  95695547a7db44b8 ("x86: asm linkage - introduce GLOBAL macro")

... thus allowing us to use this more freely in the kernel.

Signed-off-by: Mark Rutland 
Cc: AKASHI Takahiro 
Cc: Ard Biesheuvel 
Cc: Catalin Marinas 
Cc: Torsten Duwe 
Cc: Will Deacon 
Signed-off-by: Will Deacon