From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit 8cfaf106918a8c13abb24c641556172afbb9545c ]
In cpufeatures_process_feature(), if a provided CPU feature is unknown and enable_unknown is false, we erroneously print that the feature is being enabled and return true, even though no feature has been enabled, and may also set feature bits based on the last entry in the match table.
Fix this so that we only set feature bits from the match table if we have actually enabled a feature from that table, and when failing to enable an unknown feature, always print the "not enabling" message and return false.
Coincidentally, some older gccs (<GCC 7), when invoked with -fsanitize-coverage=trace-pc, cause a spurious uninitialised variable warning in this function:
arch/powerpc/kernel/dt_cpu_ftrs.c: In function ‘cpufeatures_process_feature’: arch/powerpc/kernel/dt_cpu_ftrs.c:686:7: warning: ‘m’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (m->cpu_ftr_bit_mask)
An upcoming patch will enable support for kcov, which requires this option. This patch avoids the warning.
Fixes: 5a61ef74f269 ("powerpc/64s: Support new device tree binding for discovering CPU features") Reported-by: Segher Boessenkool segher@kernel.crashing.org Signed-off-by: Michael Ellerman mpe@ellerman.id.au [ajd: add commit message] Signed-off-by: Andrew Donnellan andrew.donnellan@au1.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/dt_cpu_ftrs.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c index c6f41907f0d7..a4b31e17492d 100644 --- a/arch/powerpc/kernel/dt_cpu_ftrs.c +++ b/arch/powerpc/kernel/dt_cpu_ftrs.c @@ -666,8 +666,10 @@ static bool __init cpufeatures_process_feature(struct dt_cpu_feature *f) m = &dt_cpu_feature_match_table[i]; if (!strcmp(f->name, m->name)) { known = true; - if (m->enable(f)) + if (m->enable(f)) { + cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask; break; + }
pr_info("not enabling: %s (disabled or unsupported by kernel)\n", f->name); @@ -675,17 +677,12 @@ static bool __init cpufeatures_process_feature(struct dt_cpu_feature *f) } }
- if (!known && enable_unknown) { - if (!feat_try_enable_unknown(f)) { - pr_info("not enabling: %s (unknown and unsupported by kernel)\n", - f->name); - return false; - } + if (!known && (!enable_unknown || !feat_try_enable_unknown(f))) { + pr_info("not enabling: %s (unknown and unsupported by kernel)\n", + f->name); + return false; }
- if (m->cpu_ftr_bit_mask) - cur_cpu_spec->cpu_features |= m->cpu_ftr_bit_mask; - if (known) pr_debug("enabling: %s\n", f->name); else