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 3.18 does not have commit
fdfeff0f9e3d ("arm64: hw_breakpoint: Handle inexact watchpoint
addresses").
- Two macros are backported (untagged_addr, sign_extend64), as they are
not present in 3.18.
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")
Cc: <stable@xxxxxxxxxxxxxxx> # 3.12.x-
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>
---
Sending this for v3.18 as it still seems active despite being EOL.
arch/arm64/include/asm/uaccess.h | 8 ++++++++
arch/arm64/kernel/hw_breakpoint.c | 3 ++-
include/linux/bitops.h | 11 +++++++++++
3 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 40d8cb5409e1..6f752728b4c1 100644
--- 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>
@@ -100,6 +101,13 @@ static inline void set_fs(mm_segment_t fs)
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
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index df1cf15377b4..8e20edfc5d13 100644
--- 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]);
@@ -688,7 +689,7 @@ 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. */
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 5d858e02997f..57351fef9088 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -171,6 +171,17 @@ static inline __s32 sign_extend32(__u32 value, int index)
return (__s32)(value << shift) >> shift;
}
+/**
+ * sign_extend64 - sign extend a 64-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<64) to sign bit
+ */
+static inline __s64 sign_extend64(__u64 value, int index)
+{
+ __u8 shift = 63 - index;
+ return (__s64)(value << shift) >> shift;
+}
+
static inline unsigned fls_long(unsigned long l)
{
if (sizeof(l) == 4)
--
2.1.4