diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2023-04-08 12:17:51 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2023-04-20 12:59:21 +1000 |
| commit | 7e3a68be42e10f5fa5890e97afc0afd992355bc3 (patch) | |
| tree | 98c6a0b7b0f14f3ecff9df3e3ff2397d06fee033 /arch/powerpc/platforms/Kconfig.cputype | |
| parent | 4e991e3c16a350d1eeffc100ce3fb25292596d03 (diff) | |
powerpc/64: vmlinux support building with PCREL addresing
PC-Relative or PCREL addressing is an extension to the ELF ABI which
uses Power ISA v3.1 PC-relative instructions to calculate addresses,
rather than the traditional TOC scheme.
Add an option to build vmlinux using pcrel addressing. Modules continue
to use TOC addressing.
- TOC address helpers and r2 are poisoned with -1 when running vmlinux.
r2 could be used for something useful once things are ironed out.
- Assembly must call C functions with @notoc annotation, or the linker
complains aobut a missing nop after the call. This is done with the
CFUNC macro introduced earlier.
- Boot: with the exception of prom_init, the execution branches to the
kernel virtual address early in boot, before any addresses are
generated, which ensures 34-bit pcrel addressing does not miss the
high PAGE_OFFSET bits. TOC relative addressing has a similar
requirement. prom_init does not go to the virtual address and its
addresses should not carry over to the post-prom kernel.
- Ftrace trampolines are converted from TOC addressing to pcrel
addressing, including module ftrace trampolines that currently use the
kernel TOC to find ftrace target functions.
- BPF function prologue and function calling generation are converted
from TOC to pcrel.
- copypage_64.S has an interesting problem, prefixed instructions have
alignment restrictions so the linker can add padding, which makes the
assembler treat the difference between two local labels as
non-constant even if alignment is arranged so padding is not required.
This may need toolchain help to solve nicely, for now move the prefix
instruction out of the alternate patch section to work around it.
This reduces kernel text size by about 6%.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230408021752.862660-6-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/platforms/Kconfig.cputype')
| -rw-r--r-- | arch/powerpc/platforms/Kconfig.cputype | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index 1ff0d2818da6..45fd975ef521 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype @@ -181,6 +181,7 @@ config POWER10_CPU depends on PPC_BOOK3S_64 select ARCH_HAS_FAST_MULTIPLIER select PPC_HAVE_PREFIXED_SUPPORT + select PPC_HAVE_PCREL_SUPPORT config E5500_CPU bool "Freescale e5500" @@ -471,6 +472,20 @@ config PPC_KERNEL_PREFIXED Kernel support for prefixed instructions in applications and guests is not affected by this option. +config PPC_KERNEL_PCREL + depends on PPC_HAVE_PCREL_SUPPORT + depends on PPC_HAVE_PREFIXED_SUPPORT + depends on CC_HAS_PCREL + default n + select PPC_KERNEL_PREFIXED + bool "Build Kernel with PC-Relative addressing model" + help + POWER10 and later CPUs support pc relative addressing. Recent + compilers have support for an ELF ABI extension for a pc relative + ABI. + + This option builds the kernel with the pc relative ABI model. + config PPC_KUEP bool "Kernel Userspace Execution Prevention" if !40x default y if !40x @@ -510,6 +525,9 @@ config PPC_HAVE_PMU_SUPPORT config PPC_HAVE_PREFIXED_SUPPORT bool +config PPC_HAVE_PCREL_SUPPORT + bool + config PMU_SYSFS bool "Create PMU SPRs sysfs file" default n |