| Message ID | 1476786468-2173-4-git-send-email-james.morse@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Oct 18, 2016 at 11:27:48AM +0100, James Morse wrote: > The suspend/resume path in kernel/sleep.S, as used by cpu-idle, does not > save/restore PSTATE. As a result of this cpufeatures that were detected > and have bits in PSTATE get lost when we resume from idle. > > UAO gets set appropriately on the next context switch. PAN will be > re-enabled next time we return from user-space, but on a preemptible > kernel we may run work accessing user space before this point. > > Add code to re-enable theses two features in __cpu_suspend_exit(). > We re-use uao_thread_switch() passing current. > > Signed-off-by: James Morse <james.morse@arm.com> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > > --- > This patch applies to linux-stable v4.7.8, but with some fuzz... > but 'git am' rejects it. > > asm/exec.h is my best guess at the appropriate header file. Contradictions > welcome. uaccess.h ? It is a shame you have to export uao_thread_switch() (see below for a possible solution) but I agree that prevents useless code duplication and that this needs fixing. > arch/arm64/include/asm/exec.h | 3 +++ > arch/arm64/kernel/process.c | 3 ++- > arch/arm64/kernel/suspend.c | 11 +++++++++++ > 3 files changed, 16 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/exec.h b/arch/arm64/include/asm/exec.h > index db0563c23482..f7865dd9d868 100644 > --- a/arch/arm64/include/asm/exec.h > +++ b/arch/arm64/include/asm/exec.h > @@ -18,6 +18,9 @@ > #ifndef __ASM_EXEC_H > #define __ASM_EXEC_H > > +#include <linux/sched.h> > + > extern unsigned long arch_align_stack(unsigned long sp); > +void uao_thread_switch(struct task_struct *next); > > #endif /* __ASM_EXEC_H */ > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 27b2f1387df4..4f186c56c5eb 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -49,6 +49,7 @@ > #include <asm/alternative.h> > #include <asm/compat.h> > #include <asm/cacheflush.h> > +#include <asm/exec.h> > #include <asm/fpsimd.h> > #include <asm/mmu_context.h> > #include <asm/processor.h> > @@ -301,7 +302,7 @@ static void tls_thread_switch(struct task_struct *next) > } > > /* Restore the UAO state depending on next's addr_limit */ > -static void uao_thread_switch(struct task_struct *next) > +void uao_thread_switch(struct task_struct *next) > { > if (IS_ENABLED(CONFIG_ARM64_UAO)) { > if (task_thread_info(next)->addr_limit == KERNEL_DS) > diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c > index ad734142070d..bb0cd787a9d3 100644 > --- a/arch/arm64/kernel/suspend.c > +++ b/arch/arm64/kernel/suspend.c > @@ -1,8 +1,11 @@ > #include <linux/ftrace.h> > #include <linux/percpu.h> > #include <linux/slab.h> > +#include <asm/alternative.h> > #include <asm/cacheflush.h> > +#include <asm/cpufeature.h> > #include <asm/debug-monitors.h> > +#include <asm/exec.h> > #include <asm/pgtable.h> > #include <asm/memory.h> > #include <asm/mmu_context.h> > @@ -50,6 +53,14 @@ void notrace __cpu_suspend_exit(void) > set_my_cpu_offset(per_cpu_offset(cpu)); > > /* > + * PSTATE was not saved over suspend/resume, re-enable any detected > + * features that might not have been set correctly. > + */ > + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, > + CONFIG_ARM64_PAN)); > + uao_thread_switch(current); set_fs(get_fs()); would do (?), but that's horrendous to say the least, maybe you can refactor the code in asm/uaccess.h to achieve the same goal (ie you factor out the code setting UAO from set_fs() in a separate inline that you can also reuse in uao_thread_switch() and here). Other than that: Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > + > + /* > * Restore HW breakpoint registers to sane values > * before debug exceptions are possibly reenabled > * through local_dbg_restore. > -- > 2.8.0.rc3 >
diff --git a/arch/arm64/include/asm/exec.h b/arch/arm64/include/asm/exec.h index db0563c23482..f7865dd9d868 100644 --- a/arch/arm64/include/asm/exec.h +++ b/arch/arm64/include/asm/exec.h @@ -18,6 +18,9 @@ #ifndef __ASM_EXEC_H #define __ASM_EXEC_H +#include <linux/sched.h> + extern unsigned long arch_align_stack(unsigned long sp); +void uao_thread_switch(struct task_struct *next); #endif /* __ASM_EXEC_H */ diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 27b2f1387df4..4f186c56c5eb 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -49,6 +49,7 @@ #include <asm/alternative.h> #include <asm/compat.h> #include <asm/cacheflush.h> +#include <asm/exec.h> #include <asm/fpsimd.h> #include <asm/mmu_context.h> #include <asm/processor.h> @@ -301,7 +302,7 @@ static void tls_thread_switch(struct task_struct *next) } /* Restore the UAO state depending on next's addr_limit */ -static void uao_thread_switch(struct task_struct *next) +void uao_thread_switch(struct task_struct *next) { if (IS_ENABLED(CONFIG_ARM64_UAO)) { if (task_thread_info(next)->addr_limit == KERNEL_DS) diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c index ad734142070d..bb0cd787a9d3 100644 --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -1,8 +1,11 @@ #include <linux/ftrace.h> #include <linux/percpu.h> #include <linux/slab.h> +#include <asm/alternative.h> #include <asm/cacheflush.h> +#include <asm/cpufeature.h> #include <asm/debug-monitors.h> +#include <asm/exec.h> #include <asm/pgtable.h> #include <asm/memory.h> #include <asm/mmu_context.h> @@ -50,6 +53,14 @@ void notrace __cpu_suspend_exit(void) set_my_cpu_offset(per_cpu_offset(cpu)); /* + * PSTATE was not saved over suspend/resume, re-enable any detected + * features that might not have been set correctly. + */ + asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, + CONFIG_ARM64_PAN)); + uao_thread_switch(current); + + /* * Restore HW breakpoint registers to sane values * before debug exceptions are possibly reenabled * through local_dbg_restore.
The suspend/resume path in kernel/sleep.S, as used by cpu-idle, does not save/restore PSTATE. As a result of this cpufeatures that were detected and have bits in PSTATE get lost when we resume from idle. UAO gets set appropriately on the next context switch. PAN will be re-enabled next time we return from user-space, but on a preemptible kernel we may run work accessing user space before this point. Add code to re-enable theses two features in __cpu_suspend_exit(). We re-use uao_thread_switch() passing current. Signed-off-by: James Morse <james.morse@arm.com> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> --- This patch applies to linux-stable v4.7.8, but with some fuzz... but 'git am' rejects it. asm/exec.h is my best guess at the appropriate header file. Contradictions welcome. arch/arm64/include/asm/exec.h | 3 +++ arch/arm64/kernel/process.c | 3 ++- arch/arm64/kernel/suspend.c | 11 +++++++++++ 3 files changed, 16 insertions(+), 1 deletion(-)