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Date: Thu, 21 Mar 2013 21:49:08 +0000
From: Russell King - ARM Linux <linux@....linux.org.uk>
To: Kevin Hilman <khilman@...aro.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>,
linux-kernel@...r.kernel.org,
Paul McKenney <paulmck@...ux.vnet.ibm.com>,
linux-arm-kernel@...ts.infradead.org,
linaro-kernel@...ts.linaro.org,
Mats Liljegren <mats.liljegren@...a.com>
Subject: Re: [PATCH 1/4] ARM: context tracking: add exception support
On Wed, Mar 20, 2013 at 05:01:58PM -0700, Kevin Hilman wrote:
> Add ARM support for the context tracking subsystem by instrumenting
> exception entry/exit points.
>
> Special thanks to Mats Liljegren for testing, collaboration and adding
> support for exceptions/faults that were missing in early test versions.
Not sure all of these are a good idea or are correct...
> @@ -405,7 +406,9 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
> unsigned int instr;
> siginfo_t info;
> void __user *pc;
> + enum ctx_state prev_state;
>
> + prev_state = exception_enter();
> pc = (void __user *)instruction_pointer(regs);
>
> if (processor_mode(regs) == SVC_MODE) {
> @@ -433,8 +436,10 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
> goto die_sig;
> }
>
> - if (call_undef_hook(regs, instr) == 0)
> + if (call_undef_hook(regs, instr) == 0) {
> + exception_exit(prev_state);
> return;
> + }
>
> die_sig:
> #ifdef CONFIG_DEBUG_USER
> @@ -451,12 +456,17 @@ die_sig:
> info.si_addr = pc;
>
> arm_notify_die("Oops - undefined instruction", regs, &info, 0, 6);
> + exception_exit(prev_state);
So, FP emulation and VFP support happens via a separate path. Does this
also need to be instrumented?
> }
>
> asmlinkage void do_unexp_fiq (struct pt_regs *regs)
> {
> + enum ctx_state prev_state;
> +
> + prev_state = exception_enter();
> printk("Hmm. Unexpected FIQ received, but trying to continue\n");
> printk("You may have a hardware problem...\n");
> + exception_exit(prev_state);
Not a good idea. If we get here chances are things are really broken.
> }
>
> /*
> @@ -467,6 +477,9 @@ asmlinkage void do_unexp_fiq (struct pt_regs *regs)
> */
> asmlinkage void bad_mode(struct pt_regs *regs, int reason)
> {
> + enum ctx_state prev_state;
> +
> + prev_state = exception_enter();
> console_verbose();
>
> printk(KERN_CRIT "Bad mode in %s handler detected\n", handler[reason]);
Same here. If we get here, we're probably about to die a horrid death.
> @@ -746,7 +759,9 @@ baddataabort(int code, unsigned long instr, struct pt_regs *regs)
> {
> unsigned long addr = instruction_pointer(regs);
> siginfo_t info;
> + enum ctx_state prev_state;
>
> + prev_state = exception_enter();
> #ifdef CONFIG_DEBUG_USER
> if (user_debug & UDBG_BADABORT) {
> printk(KERN_ERR "[%d] %s: bad data abort: code %d instr 0x%08lx\n",
> @@ -762,6 +777,7 @@ baddataabort(int code, unsigned long instr, struct pt_regs *regs)
> info.si_addr = (void __user *)addr;
>
> arm_notify_die("unknown data abort code", regs, &info, instr, 0);
> + exception_exit(prev_state);
> }
>
> void __readwrite_bug(const char *fn)
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index 5dbf13f..759b70d 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -19,6 +19,7 @@
> #include <linux/sched.h>
> #include <linux/highmem.h>
> #include <linux/perf_event.h>
> +#include <linux/context_tracking.h>
>
> #include <asm/exception.h>
> #include <asm/pgtable.h>
> @@ -424,9 +425,15 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
> pgd_t *pgd, *pgd_k;
> pud_t *pud, *pud_k;
> pmd_t *pmd, *pmd_k;
> -
> - if (addr < TASK_SIZE)
> - return do_page_fault(addr, fsr, regs);
> + enum ctx_state prev_state;
> +
> + prev_state = exception_enter();
> + if (addr < TASK_SIZE) {
> + int ret;
> + ret = do_page_fault(addr, fsr, regs);
> + exception_exit(prev_state);
> + return ret;
> + }
>
> if (user_mode(regs))
> goto bad_area;
> @@ -472,10 +479,12 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
> goto bad_area;
>
> copy_pmd(pmd, pmd_k);
> + exception_exit(prev_state);
> return 0;
>
> bad_area:
> do_bad_area(addr, fsr, regs);
> + exception_exit(prev_state);
> return 0;
> }
> #else /* CONFIG_MMU */
> @@ -494,7 +503,12 @@ do_translation_fault(unsigned long addr, unsigned int fsr,
> static int
> do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> {
> + enum ctx_state prev_state;
> +
> + prev_state = exception_enter();
> do_bad_area(addr, fsr, regs);
> + exception_exit(prev_state);
> +
> return 0;
> }
>
> @@ -542,9 +556,11 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> {
> const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
> struct siginfo info;
> + enum ctx_state prev_state;
>
> + prev_state = exception_enter();
> if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
> - return;
> + goto out;
>
> printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
> inf->name, fsr, addr);
> @@ -554,6 +570,8 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
> info.si_code = inf->code;
> info.si_addr = (void __user *)addr;
> arm_notify_die("", regs, &info, fsr, 0);
> +out:
> + exception_exit(prev_state);
> }
>
> void __init
> @@ -574,9 +592,11 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
> {
> const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
> struct siginfo info;
> + enum ctx_state prev_state;
>
> + prev_state = exception_enter();
> if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
> - return;
> + goto out;
>
> printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
> inf->name, ifsr, addr);
> @@ -586,6 +606,8 @@ do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
> info.si_code = inf->code;
> info.si_addr = (void __user *)addr;
> arm_notify_die("", regs, &info, ifsr, 0);
> +out:
> + exception_exit(prev_state);
> }
>
> #ifndef CONFIG_ARM_LPAE
What is the reason for putting all this in the individual functions
and not in the prefetch/data abort handlers -
do_PrefetchAbort()/do_DataAbort()?
--
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