From: Daniel Thompson daniel.thompson@linaro.org
[ Upstream commit ab8ad279ceac4fc78ae4dcf1a26326e05695e537 ]
flush_icache_range() contains a bodge to avoid issuing IPIs when the kgdb trap handler is running because issuing IPIs is unsafe (and not needed) in this execution context. However the current test, based on kgdb_connected is flawed: it both over-matches and under-matches.
The over match occurs because kgdb_connected is set when gdb attaches to the stub and remains set during normal running. This is relatively harmelss because in almost all cases irq_disabled() will be false.
The under match is more serious. When kdb is used instead of kgdb to access the debugger then kgdb_connected is not set in all the places that the debug core updates sw breakpoints (and hence flushes the icache). This can lead to deadlock.
Fix by replacing the ad-hoc check with the proper kgdb macro. This also allows us to drop the #ifdef wrapper.
Fixes: 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache for kernel mappings") Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Reviewed-by: Douglas Anderson dianders@chromium.org Link: https://lore.kernel.org/r/20200504170518.2959478-1-daniel.thompson@linaro.or... Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/cacheflush.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h index e6cca3d4acf7..ce50c1f1f1ea 100644 --- a/arch/arm64/include/asm/cacheflush.h +++ b/arch/arm64/include/asm/cacheflush.h @@ -79,7 +79,7 @@ static inline void flush_icache_range(unsigned long start, unsigned long end) * IPI all online CPUs so that they undergo a context synchronization * event and are forced to refetch the new instructions. */ -#ifdef CONFIG_KGDB + /* * KGDB performs cache maintenance with interrupts disabled, so we * will deadlock trying to IPI the secondary CPUs. In theory, we can @@ -89,9 +89,9 @@ static inline void flush_icache_range(unsigned long start, unsigned long end) * the patching operation, so we don't need extra IPIs here anyway. * In which case, add a KGDB-specific bodge and return early. */ - if (kgdb_connected && irqs_disabled()) + if (in_dbg_master()) return; -#endif + kick_all_cpus_sync(); }