| Message ID | 12fbfb3099623ae8044f48983bfa58321495cf79.1504281470.git.joabreu@synopsys.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] arc: Re-enable MMU upon die() | expand |
Oops, the commit title is now a little bit odd. Let me rephrase and send a new version. On 01-09-2017 17:00, Jose Abreu wrote: > I recently came upon a scenario where I would get a double fault > after a machine check error. It turns out that for Ksymbol lookup > to work with modules we need to have MMU enabled because module > address is mapped in the cached space. > > This patch re-enables the MMU before start printing the stacktrace > making stacktracing of modules work upon a fatal exception. > > Signed-off-by: Jose Abreu <joabreu@synopsys.com> > Cc: Vineet Gupta <vgupta@synopsys.com> > Cc: Alexey Brodkin <abrodkin@synopsys.com> > > Changes from v1: > - Moved MMU re-enable to machine check exception handler > --- > arch/arc/kernel/traps.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c > index ff83e78..d92f161 100644 > --- a/arch/arc/kernel/traps.c > +++ b/arch/arc/kernel/traps.c > @@ -19,6 +19,8 @@ > #include <linux/ptrace.h> > #include <linux/kprobes.h> > #include <linux/kgdb.h> > +#include <asm/arcregs.h> > +#include <asm/mmu.h> > #include <asm/setup.h> > #include <asm/unaligned.h> > #include <asm/kprobes.h> > @@ -103,6 +105,9 @@ int do_misaligned_access(unsigned long address, struct pt_regs *regs, > */ > void do_machine_check_fault(unsigned long address, struct pt_regs *regs) > { > + /* MMU must be enabled for Ksymbol lookup in modules */ > + write_aux_reg(ARC_REG_PID, MMU_ENABLE | read_aux_reg(ARC_REG_PID)); > + > die("Machine Check Exception", regs, address); > } >
On 09/01/2017 09:01 AM, Jose Abreu wrote: > Oops, the commit title is now a little bit odd. Let me rephrase > and send a new version. Don't worry - I'll fix it up here ! Thx, -Vineet > > On 01-09-2017 17:00, Jose Abreu wrote: >> I recently came upon a scenario where I would get a double fault >> after a machine check error. It turns out that for Ksymbol lookup >> to work with modules we need to have MMU enabled because module >> address is mapped in the cached space. >> >> This patch re-enables the MMU before start printing the stacktrace >> making stacktracing of modules work upon a fatal exception. >> >> Signed-off-by: Jose Abreu <joabreu@synopsys.com> >> Cc: Vineet Gupta <vgupta@synopsys.com> >> Cc: Alexey Brodkin <abrodkin@synopsys.com> >> >> Changes from v1: >> - Moved MMU re-enable to machine check exception handler >> --- >> arch/arc/kernel/traps.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c >> index ff83e78..d92f161 100644 >> --- a/arch/arc/kernel/traps.c >> +++ b/arch/arc/kernel/traps.c >> @@ -19,6 +19,8 @@ >> #include <linux/ptrace.h> >> #include <linux/kprobes.h> >> #include <linux/kgdb.h> >> +#include <asm/arcregs.h> >> +#include <asm/mmu.h> >> #include <asm/setup.h> >> #include <asm/unaligned.h> >> #include <asm/kprobes.h> >> @@ -103,6 +105,9 @@ int do_misaligned_access(unsigned long address, struct pt_regs *regs, >> */ >> void do_machine_check_fault(unsigned long address, struct pt_regs *regs) >> { >> + /* MMU must be enabled for Ksymbol lookup in modules */ >> + write_aux_reg(ARC_REG_PID, MMU_ENABLE | read_aux_reg(ARC_REG_PID)); >> + >> die("Machine Check Exception", regs, address); >> } >> >
diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c index ff83e78..d92f161 100644 --- a/arch/arc/kernel/traps.c +++ b/arch/arc/kernel/traps.c @@ -19,6 +19,8 @@ #include <linux/ptrace.h> #include <linux/kprobes.h> #include <linux/kgdb.h> +#include <asm/arcregs.h> +#include <asm/mmu.h> #include <asm/setup.h> #include <asm/unaligned.h> #include <asm/kprobes.h> @@ -103,6 +105,9 @@ int do_misaligned_access(unsigned long address, struct pt_regs *regs, */ void do_machine_check_fault(unsigned long address, struct pt_regs *regs) { + /* MMU must be enabled for Ksymbol lookup in modules */ + write_aux_reg(ARC_REG_PID, MMU_ENABLE | read_aux_reg(ARC_REG_PID)); + die("Machine Check Exception", regs, address); }
I recently came upon a scenario where I would get a double fault after a machine check error. It turns out that for Ksymbol lookup to work with modules we need to have MMU enabled because module address is mapped in the cached space. This patch re-enables the MMU before start printing the stacktrace making stacktracing of modules work upon a fatal exception. Signed-off-by: Jose Abreu <joabreu@synopsys.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Alexey Brodkin <abrodkin@synopsys.com> Changes from v1: - Moved MMU re-enable to machine check exception handler --- arch/arc/kernel/traps.c | 5 +++++ 1 file changed, 5 insertions(+)