From: Yury Norov yury.norov@gmail.com
[ Upstream commit 546a073d628111e3338af689938407e77d5dc38f ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/head_64.S | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S index 9019f1395d39..be6e94f203c1 100644 --- a/arch/powerpc/kernel/head_64.S +++ b/arch/powerpc/kernel/head_64.S @@ -395,8 +395,12 @@ 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 */