linux-stable.git/arch/riscv/Makefile.postlink, branch linux-rolling-stable

kbuild: Create intermediate vmlinux build with relocations preserved

2025-03-16T15:29:50+00:00

The imperative paradigm used to build vmlinux, extract some info from it
or perform some checks on it, and subsequently modify it again goes
against the declarative paradigm that is usually employed for defining
make rules.

In particular, the Makefile.postlink files that consume their input via
an output rule result in some dodgy logic in the decompressor makefiles
for RISC-V and x86, given that the vmlinux.relocs input file needed to
generate the arch-specific relocation tables may not exist or be out of
date, but cannot be constructed using the ordinary Make dependency based
rules, because the info needs to be extracted while vmlinux is in its
ephemeral, non-stripped form.

So instead, for architectures that require the static relocations that
are emitted into vmlinux when passing --emit-relocs to the linker, and
are subsequently stripped out again, introduce an intermediate vmlinux
target called vmlinux.unstripped, and organize the reset of the build
logic accordingly:

- vmlinux.unstripped is created only once, and not updated again
- build rules under arch/*/boot can depend on vmlinux.unstripped without
  running the risk of the data disappearing or being out of date
- the final vmlinux generated by the build is not bloated with static
  relocations that are never needed again after the build completes.

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Masahiro Yamada

kbuild: Strip runtime const RELA sections correctly

2025-01-31T19:28:05+00:00

Due to the fact that runtime const ELF sections are named without a
leading period or double underscore, the RSTRIP logic that removes the
static RELA sections from vmlinux fails to identify them. This results
in a situation like below, where some sections that were supposed to get
removed are left behind.

  [Nr] Name                              Type            Address          Off     Size   ES Flg Lk Inf Al

  [58] runtime_shift_d_hash_shift        PROGBITS        ffffffff83500f50 2900f50 000014 00   A  0   0  1
  [59] .relaruntime_shift_d_hash_shift   RELA            0000000000000000 55b6f00 000078 18   I 70  58  8
  [60] runtime_ptr_dentry_hashtable      PROGBITS        ffffffff83500f68 2900f68 000014 00   A  0   0  1
  [61] .relaruntime_ptr_dentry_hashtable RELA            0000000000000000 55b6f78 000078 18   I 70  60  8
  [62] runtime_ptr_USER_PTR_MAX          PROGBITS        ffffffff83500f80 2900f80 000238 00   A  0   0  1
  [63] .relaruntime_ptr_USER_PTR_MAX     RELA            0000000000000000 55b6ff0 000d50 18   I 70  62  8

So tweak the match expression to strip all sections starting with .rel.
While at it, consolidate the logic used by RISC-V, s390 and x86 into a
single shared Makefile library command.

Link: https://lore.kernel.org/all/CAHk-=wjk3ynjomNvFN8jf9A1k=qSc=JFF591W00uXj-qqNUxPQ@mail.gmail.com/
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Charlie Jenkins 
Tested-by: Charlie Jenkins 
Tested-by: Alexander Gordeev 
Signed-off-by: Masahiro Yamada

kbuild: remove ARCH_POSTLINK from module builds

2023-10-28T12:10:08+00:00

The '%.ko' rule in arch/*/Makefile.postlink does nothing but call the
'true' command.

Remove the unneeded code.

Signed-off-by: Masahiro Yamada 
Reviewed-by: Nicolas Schier

riscv: Use --emit-relocs in order to move .rela.dyn in init

2023-04-19T14:46:33+00:00

To circumvent an issue where placing the relocations inside the init
sections produces empty relocations, use --emit-relocs. But to avoid
carrying those relocations in vmlinux, use an intermediate
vmlinux.relocs file which is a copy of vmlinux *before* stripping its
relocations.

Suggested-by: Björn Töpel 
Suggested-by: Nick Desaulniers 
Signed-off-by: Alexandre Ghiti 
Link: https://lore.kernel.org/r/20230329045329.64565-7-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt

riscv: Check relocations at compile time

2023-04-19T14:46:32+00:00

Relocating kernel at runtime is done very early in the boot process, so
it is not convenient to check for relocations there and react in case a
relocation was not expected.

There exists a script in scripts/ that extracts the relocations from
vmlinux that is then used at postlink to check the relocations.

Signed-off-by: Alexandre Ghiti 
Reviewed-by: Anup Patel 
Link: https://lore.kernel.org/r/20230329045329.64565-6-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt