Messages in this thread Patch in this message | | | From | Bhupesh Sharma <> | Subject | [PATCH 2/2] perf/arm64: Allow per-task kernel breakpoints | Date | Tue, 4 Feb 2020 03:56:24 +0530 |
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commit 478fcb2cdb23 ("arm64: Debugging support") disallowed per-task kernel breakpoints on arm64 since these would have potentially complicated the stepping code.
However, we now have several use-cases (for e.g. perf) which require per-task address execution h/w breakpoint to be exercised/set on arm64:
For e.g. we can set address execution h/w breakpoints, using the format prescribed by 'perf-list' command: mem:<addr>[/len][:access] [Hardware breakpoint]
Without this patch, currently 'perf stat -e' reports that per-task address execution h/w breakpoints are 'not supported' on arm64. See below:
$ TEST_FUNC="vfs_read" $ ADDR=0x`cat /proc/kallsyms | grep -P "\\s$TEST_FUNC\$" | cut -f1 -d' '` $ perf stat -e mem:$ADDR:x -x';' -- cat /proc/cpuinfo > /dev/null
<not supported>;;mem:0xffff00001031dd68:x;0;100.00;;
After this patch, this use-case can be supported:
$ TEST_FUNC="vfs_read" $ ADDR=0x`cat /proc/kallsyms | grep -P "\\s$TEST_FUNC\$" | cut -f1 -d' '` $ perf stat -e mem:$ADDR:x -x';' -- cat /proc/cpuinfo > /dev/null
5;;mem:0xfffffe0010361d20:x;912200;100.00;;
Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> --- arch/arm64/kernel/hw_breakpoint.c | 7 ------- 1 file changed, 7 deletions(-)
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c index 0b727edf4104..c28f04e02845 100644 --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -562,13 +562,6 @@ int hw_breakpoint_arch_parse(struct perf_event *bp, hw->address &= ~alignment_mask; hw->ctrl.len <<= offset; - /* - * Disallow per-task kernel breakpoints since these would - * complicate the stepping code. - */ - if (hw->ctrl.privilege == AARCH64_BREAKPOINT_EL1 && bp->hw.target) - return -EINVAL; - return 0; } -- 2.7.4
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