This is a note to let you know that I've just added the patch titled
ARM: 7496/1: hw_breakpoint: don't rely on dfsr to show watchpoint access
type
to the 3.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-7496-1-hw_breakpoint-don-t-rely-on-dfsr-to-show-watchpoint-access-type.patch
and it can be found in the queue-3.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From bf8801145c01ab600f8df66e8c879ac642fa5846 Mon Sep 17 00:00:00 2001
From: Will Deacon <[email protected]>
Date: Thu, 16 Aug 2012 18:55:44 +0100
Subject: ARM: 7496/1: hw_breakpoint: don't rely on dfsr to show watchpoint
access type
From: Will Deacon <[email protected]>
commit bf8801145c01ab600f8df66e8c879ac642fa5846 upstream.
>From ARM debug architecture v7.1 onwards, a watchpoint exception causes
the DFAR to be updated with the faulting data address. However, DFSR.WnR
takes an UNKNOWN value and therefore cannot be used in general to
determine the access type that triggered the watchpoint.
This patch forbids watchpoints without an overflow handler from
specifying a specific access type (load/store). Those with overflow
handlers must be able to handle false positives potentially triggered by
a watchpoint of a different access type on the same address. For
SIGTRAP-based handlers (i.e. ptrace), this should have no impact.
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Russell King <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/arm/kernel/hw_breakpoint.c | 55 +++++++++++++++++++++++++++++-----------
1 file changed, 40 insertions(+), 15 deletions(-)
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -159,6 +159,12 @@ static int debug_arch_supported(void)
arch >= ARM_DEBUG_ARCH_V7_1;
}
+/* Can we determine the watchpoint access type from the fsr? */
+static int debug_exception_updates_fsr(void)
+{
+ return 0;
+}
+
/* Determine number of WRP registers available. */
static int get_num_wrp_resources(void)
{
@@ -619,18 +625,35 @@ int arch_validate_hwbkpt_settings(struct
info->address &= ~alignment_mask;
info->ctrl.len <<= offset;
- /*
- * Currently we rely on an overflow handler to take
- * care of single-stepping the breakpoint when it fires.
- * In the case of userspace breakpoints on a core with V7 debug,
- * we can use the mismatch feature as a poor-man's hardware
- * single-step, but this only works for per-task breakpoints.
- */
- if (!bp->overflow_handler && (arch_check_bp_in_kernelspace(bp) ||
- !core_has_mismatch_brps() || !bp->hw.bp_target)) {
- pr_warning("overflow handler required but none found\n");
- ret = -EINVAL;
+ if (!bp->overflow_handler) {
+ /*
+ * Mismatch breakpoints are required for single-stepping
+ * breakpoints.
+ */
+ if (!core_has_mismatch_brps())
+ return -EINVAL;
+
+ /* We don't allow mismatch breakpoints in kernel space. */
+ if (arch_check_bp_in_kernelspace(bp))
+ return -EPERM;
+
+ /*
+ * Per-cpu breakpoints are not supported by our stepping
+ * mechanism.
+ */
+ if (!bp->hw.bp_target)
+ return -EINVAL;
+
+ /*
+ * We only support specific access types if the fsr
+ * reports them.
+ */
+ if (!debug_exception_updates_fsr() &&
+ (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
+ info->ctrl.type == ARM_BREAKPOINT_STORE))
+ return -EINVAL;
}
+
out:
return ret;
}
@@ -706,10 +729,12 @@ static void watchpoint_handler(unsigned
goto unlock;
/* Check that the access type matches. */
- access = (fsr & ARM_FSR_ACCESS_MASK) ? HW_BREAKPOINT_W :
- HW_BREAKPOINT_R;
- if (!(access & hw_breakpoint_type(wp)))
- goto unlock;
+ if (debug_exception_updates_fsr()) {
+ access = (fsr & ARM_FSR_ACCESS_MASK) ?
+ HW_BREAKPOINT_W : HW_BREAKPOINT_R;
+ if (!(access & hw_breakpoint_type(wp)))
+ goto unlock;
+ }
/* We have a winner. */
info->trigger = addr;
Patches currently in stable-queue which might be from [email protected] are
queue-3.5/arm-7527-1-uaccess-explicitly-check-__user-pointer-when-cpu_use_domains.patch
queue-3.5/arm-7526-1-traps-send-sigill-if-get_user-fails-on-undef-handling-path.patch
queue-3.5/arm-7496-1-hw_breakpoint-don-t-rely-on-dfsr-to-show-watchpoint-access-type.patch
queue-3.5/arm-7501-1-decompressor-reset-ttbcr-for-vmsa-armv7-cores.patch
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