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arm64: hw_breakpoint: fix watchpoint matching for tagged pointers

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commit 7dcd9dd8cebe9fa626af7e2358d03a37041a70fb upstream.

This backport has a small difference from the upstream commit:
 - The address tag is removed in watchpoint_handler() instead of
   get_distance_from_watchpoint(), because 4.9 does not have commit
   fdfeff0f9e3d ("arm64: hw_breakpoint: Handle inexact watchpoint
   addresses").

Original patch description:

When we take a watchpoint exception, the address that triggered the
watchpoint is found in FAR_EL1. We compare it to the address of each
configured watchpoint to see which one was hit.

The configured watchpoint addresses are untagged, while the address in
FAR_EL1 will have an address tag if the data access was done using a
tagged address. The tag needs to be removed to compare the address to
the watchpoints.

Currently we don't remove it, and as a result can report the wrong
watchpoint as being hit (specifically, always either the highest TTBR0
watchpoint or lowest TTBR1 watchpoint). This patch removes the tag.

Fixes: d50240a5f6ce ("arm64: mm: permit use of tagged pointers at EL0")
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kristina Martsenko 2017-06-06 20:14:09 +01:00 committed by Greg Kroah-Hartman
parent 791d94ef40
commit 1d61ccb5ac
2 changed files with 5 additions and 4 deletions
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6
arch/arm64/include/asm/uaccess.h
View File

@ -105,9 +105,9 @@ static inline void set_fs(mm_segment_t fs)
})
/*
* When dealing with data aborts or instruction traps we may end up with
* a tagged userland pointer. Clear the tag to get a sane pointer to pass
* on to access_ok(), for instance.
* When dealing with data aborts, watchpoints, or instruction traps we may end
* up with a tagged userland pointer. Clear the tag to get a sane pointer to
* pass on to access_ok(), for instance.
*/
#define untagged_addr(addr) sign_extend64(addr, 55)

3
arch/arm64/kernel/hw_breakpoint.c
View File

@ -36,6 +36,7 @@
#include <asm/traps.h>
#include <asm/cputype.h>
#include <asm/system_misc.h>
#include <asm/uaccess.h>
/* Breakpoint currently in use for each BRP. */
static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
@ -696,7 +697,7 @@ static int watchpoint_handler(unsigned long addr, unsigned int esr,
/* Check if the watchpoint value matches. */
val = read_wb_reg(AARCH64_DBG_REG_WVR, i);
if (val != (addr & ~alignment_mask))
if (val != (untagged_addr(addr) & ~alignment_mask))
goto unlock;
/* Possible match, check the byte address select to confirm. */