Kernel/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2025-01-17 10:46:33 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

powerpc/64: don't refer nr_cpu_ids in asm code when it's undefined

Browse Source 
generic_secondary_common_init() calls LOAD_REG_ADDR(r7, nr_cpu_ids)
conditionally on CONFIG_SMP. However, if 'NR_CPUS == 1', kernel doesn't
use the nr_cpu_ids, and in C code, it's just:
  #if NR_CPUS == 1
  #define nr_cpu_ids
  ...

This series makes declaration of nr_cpu_ids conditional on NR_CPUS == 1,
and that reveals the issue, because compiler can't link the
LOAD_REG_ADDR(r7, nr_cpu_ids) against nonexisting symbol.

Current code looks unsafe for those who build kernel with CONFIG_SMP=y and
NR_CPUS == 1. This is weird configuration, but not disallowed.

Fix the linker error by replacing LOAD_REG_ADDR() with LOAD_REG_IMMEDIATE()
conditionally on NR_CPUS == 1.

As the following patch adds CONFIG_FORCE_NR_CPUS option that has the
similar effect on nr_cpu_ids, make the generic_secondary_common_init()
conditional on it too.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
This commit is contained in:
Yury Norov 2022-09-20 06:13:12 -07:00
parent aa47a7c215
commit 546a073d62
1 changed files with 4 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/kernel/head_64.S
View File

@ -400,8 +400,12 @@ generic_secondary_common_init:
#else
LOAD_REG_ADDR(r8, paca_ptrs) /* Load paca_ptrs pointe */
ld r8,0(r8) /* Get base vaddr of array */
#if (NR_CPUS == 1) || defined(CONFIG_FORCE_NR_CPUS)
LOAD_REG_IMMEDIATE(r7, NR_CPUS)
#else
LOAD_REG_ADDR(r7, nr_cpu_ids) /* Load nr_cpu_ids address */
lwz r7,0(r7) /* also the max paca allocated */
#endif
li r5,0 /* logical cpu id */
1:
sldi r9,r5,3 /* get paca_ptrs[] index from cpu id */