4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kristina Martsenko <kristina.martsenko@xxxxxxx>
commit 7dcd9dd8cebe9fa626af7e2358d03a37041a70fb upstream.
This backport has a few small differences from the upstream commit:
- The address tag is removed in watchpoint_handler() instead of
get_distance_from_watchpoint(), because 4.4 does not have commit
fdfeff0f9e3d ("arm64: hw_breakpoint: Handle inexact watchpoint
addresses").
- A macro is backported (untagged_addr), as it is not present in 4.4.
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@xxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/uaccess.h | 8 ++++++++
arch/arm64/kernel/hw_breakpoint.c | 3 ++-
2 files changed, 10 insertions(+), 1 deletion(-)
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -21,6 +21,7 @@
/*
* User space memory access functions
*/
+#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/thread_info.h>
@@ -103,6 +104,13 @@ static inline void set_fs(mm_segment_t f
flag; \
})
+/*
+ * 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)
+
#define access_ok(type, addr, size) __range_ok(addr, size)
#define user_addr_max get_fs
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -35,6 +35,7 @@
#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]);
@@ -690,7 +691,7 @@ static int watchpoint_handler(unsigned l
/* 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. */