[v6,0/1] riscv: Allow to downgrade paging mode from the command line

Message

Alexandre Ghiti Feb. 23, 2023, 8:24 a.m. UTC

This new version gets rid of the limitation that prevented KASAN kernels         
to use the newly introduced parameters.                                          
                                                                                 
While looking into KASLR, I fell onto commit aacd149b6238 ("arm64: head:         
avoid relocating the kernel twice for KASLR"): it allows to use the fdt          
functions very early in the boot process with KASAN enabled by simply            
compiling a new version of those functions without instrumentation.              
                                                                                 
I had to change the handling of the command line parsing to make the             
code self-contained in kernel/pi/cmd_early.c to avoid calling too many           
__pi prefixed functions from outside this file.                                  
                                                                                 
I'll use this approach like arm64 to handle the extraction of the random         
seedi from the device tree for KASLR. 

base-commit-tag: riscv-for-linus-6.2-rc8

v6:
- Fix llvm warning by forward declaring set_satp_mode_from_cmdline

v5:                                                                              
- Handle null command line, Thanks Björn!                                        
- Add RB/TB from Björn                                                           
                                                                                 
v4:                                                                              
- Introduce pi/ for KASAN to work                                                
                                                                                 
v3:                                                                              
- Massage commit log to make no4lvl clearer, as asked by Conor                   
- Add a note to kernel-parameters.txt regarding the impossibility to use         
  those parameters when KASAN is enabled, as suggested by Conor                  
- Add RB from Björn                                                              
                                                                                 
v2:                                                                              
- Honor CMDLINE_EXTEND and CMDLINE_FORCE as noticed by Björn

Alexandre Ghiti (1):
  riscv: Allow to downgrade paging mode from the command line

 .../admin-guide/kernel-parameters.txt         |  5 +-
 arch/riscv/kernel/Makefile                    |  2 +
 arch/riscv/kernel/pi/Makefile                 | 34 ++++++++++
 arch/riscv/kernel/pi/cmdline_early.c          | 62 +++++++++++++++++++
 arch/riscv/lib/memcpy.S                       |  2 +
 arch/riscv/lib/memmove.S                      |  2 +
 arch/riscv/mm/init.c                          | 36 +++++++++--
 7 files changed, 136 insertions(+), 7 deletions(-)
 create mode 100644 arch/riscv/kernel/pi/Makefile
 create mode 100644 arch/riscv/kernel/pi/cmdline_early.c