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authorWill Deacon <will.deacon@arm.com>2010-11-25 12:01:54 +0000
committerWill Deacon <will.deacon@arm.com>2010-12-06 11:55:56 +0000
commit6ee33c2712fcdff2568d9bbadb25c8e5a7c36212 (patch)
tree94c2510ccdd1cb2843897422746b67adf6ba1cd5
parent7d99331e4793b52d488e911876ef11d843c6c8c9 (diff)
downloadblackbird-op-linux-6ee33c2712fcdff2568d9bbadb25c8e5a7c36212.tar.gz
blackbird-op-linux-6ee33c2712fcdff2568d9bbadb25c8e5a7c36212.zip
ARM: hw_breakpoint: correct and simplify alignment fixup code
The current hw_breakpoint code tries to fix up the alignment of breakpoints so that we can make use of sparse byte-address-select bits in the control register and give the illusion that we can set breakpoints on unaligned addresses. Although this works on v6 cores, v7 forbids this behaviour, instead requiring breakpoints to be set on aligned addresses and have contiguous byte-address-select ranges depending on the instruction set in use. For ARM the only supported size is 4 bytes, whilst Thumb-2 also permits 2 byte breakpoints (watchpoints can be of 1, 2, 4 or 8 bytes long). This patch simplifies the alignment fixup code so that we require addresses to be aligned to the size of the corresponding breakpoint. This allows us to handle the common case of breaking on a half-word aligned Thumb-2 instruction and also allows us to set byte watchpoints on arbitrary addresses. Signed-off-by: Will Deacon <will.deacon@arm.com>
-rw-r--r--arch/arm/kernel/hw_breakpoint.c57
1 files changed, 31 insertions, 26 deletions
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 515a3c44c118..d37ed3501e57 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -537,6 +537,17 @@ static int arch_build_bp_info(struct perf_event *bp)
return -EINVAL;
}
+ /*
+ * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
+ * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
+ * by the hardware and must be aligned to the appropriate number of
+ * bytes.
+ */
+ if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
+ info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
+ info->ctrl.len != ARM_BREAKPOINT_LEN_4)
+ return -EINVAL;
+
/* Address */
info->address = bp->attr.bp_addr;
@@ -561,7 +572,7 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
int ret = 0;
- u32 bytelen, max_len, offset, alignment_mask = 0x3;
+ u32 offset, alignment_mask = 0x3;
/* Build the arch_hw_breakpoint. */
ret = arch_build_bp_info(bp);
@@ -571,32 +582,27 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
/* Check address alignment. */
if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
alignment_mask = 0x7;
- if (info->address & alignment_mask) {
- /*
- * Try to fix the alignment. This may result in a length
- * that is too large, so we must check for that.
- */
- bytelen = get_hbp_len(info->ctrl.len);
- max_len = info->ctrl.type == ARM_BREAKPOINT_EXECUTE ? 4 :
- max_watchpoint_len;
-
- if (max_len >= 8)
- offset = info->address & 0x7;
- else
- offset = info->address & 0x3;
-
- if (bytelen > (1 << ((max_len - (offset + 1)) >> 1))) {
- ret = -EFBIG;
- goto out;
- }
-
- info->ctrl.len <<= offset;
- info->address &= ~offset;
-
- pr_debug("breakpoint alignment fixup: length = 0x%x, "
- "address = 0x%x\n", info->ctrl.len, info->address);
+ offset = info->address & alignment_mask;
+ switch (offset) {
+ case 0:
+ /* Aligned */
+ break;
+ case 1:
+ /* Allow single byte watchpoint. */
+ if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
+ break;
+ case 2:
+ /* Allow halfword watchpoints and breakpoints. */
+ if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
+ break;
+ default:
+ ret = -EINVAL;
+ goto out;
}
+ 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.
@@ -607,7 +613,6 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
(arch_check_bp_in_kernelspace(bp) || !core_has_mismatch_bps()),
"overflow handler required but none found")) {
ret = -EINVAL;
- goto out;
}
out:
return ret;
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