linux.git/arch/s390/kernel/vmlinux.lds.S, branch v5.19

s390: remove .fixup section

2022-03-07T23:33:01+00:00

The only user is gone. Remove the section.

Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/boot: allocate amode31 section in decompressor

2021-10-04T07:49:37+00:00

The memory for amode31 section is allocated from the decompressed
kernel. Instead, allocate that memory from the decompressor. This
is a prerequisite to allow initialization of the virtual memory
before the decompressed kernel takes over.

Reviewed-by: Heiko Carstens 
Signed-off-by: Alexander Gordeev 
Signed-off-by: Vasily Gorbik

s390: fix typo in linker script

2021-08-25T09:03:34+00:00

Rename amod31 to amode31 like it was supposed to be.

Fixes: c78d0c7484f0 ("s390: rename dma section to amode31")
Signed-off-by: Heiko Carstens

s390: rename dma section to amode31

2021-08-05T12:10:53+00:00

The dma section name is confusing, since the code which resides within
that section has nothing to do with direct memory access.  Instead the
limitation is that the code has to run in 31 bit addressing mode, and
therefore has to reside below 2GB.  So the name was chosen since
ZONE_DMA is the same region.

To reduce confusion rename the section to amode31, which hopefully
describes better what this is about.

Note: this will also change vmcoreinfo strings
- SDMA=... gets renamed to SAMODE31=...
- EDMA=... gets renamed to EAMODE31=...

Acked-by: Vasily Gorbik 
Reviewed-by: Alexander Egorenkov 
Signed-off-by: Heiko Carstens

s390/ftrace: implement hotpatching

2021-08-03T12:31:40+00:00

s390 allows hotpatching the mask of a conditional jump instruction.
Make use of this feature in order to avoid the expensive stop_machine()
call.

The new trampolines are split in 3 stages:

- A first stage is a 6-byte relative conditional long branch located at
  each function's entry point. Its offset always points to the second
  stage for the corresponding function, and its mask is either all 0s
  (ftrace off) or all 1s (ftrace on). The code for flipping the mask is
  borrowed from ftrace_{enable,disable}_ftrace_graph_caller. After
  flipping, ftrace_arch_code_modify_post_process() syncs with all the
  other CPUs by sending SIGPs.

- Second stages for vmlinux are stored in a separate part of the .text
  section reserved by the linker script, and in dynamically allocated
  memory for modules. This prevents the icache pollution. The total
  size of second stages is about 1.5% of that of the kernel image.

  Putting second stages in the .bss section is possible and decreases
  the size of the non-compressed vmlinux, but splits the kernel 1:1
  mapping, which is a bad tradeoff.

  Each second stage contains a call to the third stage, a pointer to
  the part of the intercepted function right after the first stage, and
  a pointer to an interceptor function (e.g. ftrace_caller).

  Second stages are 8-byte aligned for the future direct calls
  implementation.

- There are only two copies of the third stage: in the .text section
  for vmlinux and in dynamically allocated memory for modules. It can be
  an expoline, which is relatively large, so inlining it into each
  second stage is prohibitively expensive.

As a result of this organization, phoronix-test-suite with ftrace off
does not show any performance degradation.

Suggested-by: Sven Schnelle 
Suggested-by: Vasily Gorbik 
Co-developed-by: Heiko Carstens 
Signed-off-by: Ilya Leoshkevich 
Link: https://lore.kernel.org/r/20210728212546.128248-3-iii@linux.ibm.com
Signed-off-by: Heiko Carstens

s390/boot: move dma sections from decompressor to decompressed kernel

2021-07-27T07:39:17+00:00

This change simplifies the task of making the decompressor relocatable.

The decompressor's image contains special DMA sections between _sdma and
_edma. This DMA segment is loaded at boot as part of the decompressor and
then simply handed over to the decompressed kernel. The decompressor itself
never uses it in any way. The primary reason for this is the need to keep
the aforementioned DMA segment below 2GB which is required by architecture,
and because the decompressor is always loaded at a fixed low physical
address, it is guaranteed that the DMA region will not cross the 2GB
memory limit. If the DMA region had been placed in the decompressed kernel,
then KASLR would make this guarantee impossible to fulfill or it would
be restricted to the first 2GB of memory address space.

This commit moves all DMA sections between _sdma and _edma from
the decompressor's image to the decompressed kernel's image. The complete
DMA region is placed in the init section of the decompressed kernel and
immediately relocated below 2GB at start-up before it is needed by other
parts of the decompressed kernel. The relocation of the DMA region happens
even if the decompressed kernel is already located below 2GB in order
to keep the first implementation simple. The relocation should not have
any noticeable impact on boot time because the DMA segment is only a couple
of pages.

After relocating the DMA sections, the kernel has to fix all references
which point into it. In order to automate this, place all variables
pointing into the DMA sections in a special .dma.refs section. All such
variables must be defined using the new __dma_ref macro. Only variables
containing addresses within the DMA sections must be placed in the new
.dma.refs section.

Furthermore, move the initialization of control registers from
the decompressor to the decompressed kernel because some control registers
reference tables that must be placed in the DMA data section to
guarantee that their addresses are below 2G. Because the decompressed
kernel relocates the DMA sections at startup, the content of control
registers CR2, CR5 and CR15 must be updated with new addresses after
the relocation. The decompressed kernel initializes all control registers
early at boot and then updates the content of CR2, CR5 and CR15
as soon as the DMA relocation has occurred. This practically reverts
the commit a80313ff91ab ("s390/kernel: introduce .dma sections").

Signed-off-by: Alexander Egorenkov 
Acked-by: Heiko Carstens 
Signed-off-by: Heiko Carstens

s390/mm: use invalid asce instead of kernel asce

2020-11-23T11:01:12+00:00

Create a region 3 page table which contains only invalid entries, and
use that via "s390_invalid_asce" instead of the kernel ASCE whenever
there is either
- no user address space available, e.g. during early startup
- as an intermediate ASCE when address spaces are switched

This makes sure that user space accesses in such situations are
guaranteed to fail.

Reviewed-by: Sven Schnelle 
Reviewed-by: Alexander Gordeev 
Signed-off-by: Heiko Carstens

vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG

2020-09-01T07:50:35+00:00

The .comment section doesn't belong in STABS_DEBUG. Split it out into a
new macro named ELF_DETAILS. This will gain other non-debug sections
that need to be accounted for when linking with --orphan-handling=warn.

Signed-off-by: Kees Cook 
Signed-off-by: Ingo Molnar 
Cc: linux-arch@vger.kernel.org
Link: https://lore.kernel.org/r/20200821194310.3089815-5-keescook@chromium.org

vmlinux.lds.h: Replace RW_DATA_SECTION with RW_DATA

2019-11-04T14:57:41+00:00

Rename RW_DATA_SECTION to RW_DATA. (Calling this a "section" is a lie,
since it's multiple sections and section flags cannot be applied to
the macro.)

Signed-off-by: Kees Cook 
Signed-off-by: Borislav Petkov 
Acked-by: Heiko Carstens  # s390
Acked-by: Geert Uytterhoeven  # m68k
Cc: Andy Lutomirski 
Cc: Arnd Bergmann 
Cc: Dave Hansen 
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Rick Edgecombe 
Cc: Segher Boessenkool 
Cc: Will Deacon 
Cc: x86-ml 
Cc: Yoshinori Sato 
Link: https://lkml.kernel.org/r/20191029211351.13243-14-keescook@chromium.org

vmlinux.lds.h: Replace RO_DATA_SECTION with RO_DATA

2019-11-04T14:56:16+00:00

Finish renaming RO_DATA_SECTION to RO_DATA. (Calling this a "section"
is a lie, since it's multiple sections and section flags cannot be
applied to the macro.)

Signed-off-by: Kees Cook 
Signed-off-by: Borislav Petkov 
Acked-by: Heiko Carstens  # s390
Acked-by: Geert Uytterhoeven  # m68k
Cc: Andy Lutomirski 
Cc: Arnd Bergmann 
Cc: Dave Hansen 
Cc: linux-alpha@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Rick Edgecombe 
Cc: Segher Boessenkool 
Cc: Will Deacon 
Cc: x86-ml 
Cc: Yoshinori Sato 
Link: https://lkml.kernel.org/r/20191029211351.13243-13-keescook@chromium.org