From: Will Deacon Date: Fri, 6 Jul 2012 14:43:03 +0000 (+0100) Subject: ARM: 7445/1: mm: update CONTEXTIDR register to contain PID of current process X-Git-Tag: next-20120724~113^2^5~8 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=575320d62;p=karo-tx-linux.git ARM: 7445/1: mm: update CONTEXTIDR register to contain PID of current process This patch introduces a new Kconfig option which, when enabled, causes the kernel to write the PID of the current task into the PROCID field of the CONTEXTIDR on context switch. This is useful when analysing hardware trace, since writes to this register can be configured to emit an event into the trace stream. The thread notifier for writing the PID is deliberately kept separate from the ASID-writing code so that we can support newer processors using LPAE, where the ASID is stored in TTBR0. As such, the switch_mm code is updated to perform a read-modify-write sequence to ensure that we don't clobber the PID on CPUs using the classic 2-level page tables. Signed-off-by: Will Deacon Signed-off-by: Russell King --- diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 01a134141216..521e15bc6401 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -369,4 +369,13 @@ config ARM_KPROBES_TEST help Perform tests of kprobes API and instruction set simulation. +config PID_IN_CONTEXTIDR + bool "Write the current PID to the CONTEXTIDR register" + depends on CPU_COPY_V6 + help + Enabling this option causes the kernel to write the current PID to + the PROCID field of the CONTEXTIDR register, at the expense of some + additional instructions during context switch. Say Y here only if you + are planning to use hardware trace tools with this kernel. + endmenu diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 806cc4f63516..119bc52ab93e 100644 --- a/arch/arm/mm/context.c +++ b/arch/arm/mm/context.c @@ -14,6 +14,7 @@ #include #include +#include #include static DEFINE_RAW_SPINLOCK(cpu_asid_lock); @@ -48,6 +49,40 @@ void cpu_set_reserved_ttbr0(void) } #endif +#ifdef CONFIG_PID_IN_CONTEXTIDR +static int contextidr_notifier(struct notifier_block *unused, unsigned long cmd, + void *t) +{ + u32 contextidr; + pid_t pid; + struct thread_info *thread = t; + + if (cmd != THREAD_NOTIFY_SWITCH) + return NOTIFY_DONE; + + pid = task_pid_nr(thread->task) << ASID_BITS; + asm volatile( + " mrc p15, 0, %0, c13, c0, 1\n" + " bfi %1, %0, #0, %2\n" + " mcr p15, 0, %1, c13, c0, 1\n" + : "=r" (contextidr), "+r" (pid) + : "I" (ASID_BITS)); + isb(); + + return NOTIFY_OK; +} + +static struct notifier_block contextidr_notifier_block = { + .notifier_call = contextidr_notifier, +}; + +static int __init contextidr_notifier_init(void) +{ + return thread_register_notifier(&contextidr_notifier_block); +} +arch_initcall(contextidr_notifier_init); +#endif + /* * We fork()ed a process, and we need a new context for the child * to run in. diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S index 5900cd520e84..86b8b480634f 100644 --- a/arch/arm/mm/proc-v6.S +++ b/arch/arm/mm/proc-v6.S @@ -107,6 +107,12 @@ ENTRY(cpu_v6_switch_mm) mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB mcr p15, 0, r2, c7, c10, 4 @ drain write buffer mcr p15, 0, r0, c2, c0, 0 @ set TTB 0 +#ifdef CONFIG_PID_IN_CONTEXTIDR + mrc p15, 0, r2, c13, c0, 1 @ read current context ID + bic r2, r2, #0xff @ extract the PID + and r1, r1, #0xff + orr r1, r1, r2 @ insert into new context ID +#endif mcr p15, 0, r1, c13, c0, 1 @ set context ID #endif mov pc, lr diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S index 42ac069c8012..fd045e706390 100644 --- a/arch/arm/mm/proc-v7-2level.S +++ b/arch/arm/mm/proc-v7-2level.S @@ -46,6 +46,11 @@ ENTRY(cpu_v7_switch_mm) #ifdef CONFIG_ARM_ERRATA_430973 mcr p15, 0, r2, c7, c5, 6 @ flush BTAC/BTB #endif +#ifdef CONFIG_PID_IN_CONTEXTIDR + mrc p15, 0, r2, c13, c0, 1 @ read current context ID + lsr r2, r2, #8 @ extract the PID + bfi r1, r2, #8, #24 @ insert into new context ID +#endif #ifdef CONFIG_ARM_ERRATA_754322 dsb #endif