[DTrace-devel] [PATCH 59/61] Add disassembly for aggregation variables

[Kris Van Hees]

On Fri, Jul 08, 2022 at 10:45:43AM -0400, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>

... queued for dev

> ---
>  libdtrace/dt_dis.c                  | 19 +++++++++++++++++++
>  test/unittest/disasm/tst.ann-agg.r  |  3 +++
>  test/unittest/disasm/tst.ann-agg.sh | 22 ++++++++++++++++++++++
>  3 files changed, 44 insertions(+)
>  create mode 100644 test/unittest/disasm/tst.ann-agg.r
>  create mode 100755 test/unittest/disasm/tst.ann-agg.sh
> 
> diff --git a/libdtrace/dt_dis.c b/libdtrace/dt_dis.c
> index 98fcd20e..8af6a246 100644
> --- a/libdtrace/dt_dis.c
> +++ b/libdtrace/dt_dis.c
> @@ -355,6 +355,25 @@ dt_dis_bpf_args(const dtrace_difo_t *dp, const char *fn,
>  		snprintf(buf, len, "%s",
>  			 dt_dis_varname_id(dp, in->imm, DIFV_SCOPE_GLOBAL, addr));
>  		return buf;
> +	} else if (strcmp(fn, "dt_get_agg") == 0) {
> +		/*
> +		 * If the immediately preceding instruction is a 16-byte
> +		 * instruction, back up to streamline instruction counting.
> +		 */
> +		if (in[-2].code == (BPF_LD | BPF_DW | BPF_IMM) &&
> +		    in[-1].code == 0)
> +			in--;
> +
> +		/*
> +		 * We know that the previous six instructions exist and
> +		 * move the variable id to a register in the first instruction
> +		 * of that seqeuence (because we wrote the code generator to
> +		 * emit the instructions in this exact order.)
> +		 */
> +		in -= 6;
> +		snprintf(buf, len, "@%s",
> +			 dt_dis_varname_id(dp, in->imm, DIFV_SCOPE_GLOBAL, addr));
> +		return buf;
>  	} else if (strcmp(fn, "dt_get_tvar") == 0) {
>  		/*
>  		 * We know that the previous three instructions exist and
> diff --git a/test/unittest/disasm/tst.ann-agg.r b/test/unittest/disasm/tst.ann-agg.r
> new file mode 100644
> index 00000000..c14f6464
> --- /dev/null
> +++ b/test/unittest/disasm/tst.ann-agg.r
> @@ -0,0 +1,3 @@
> +85 0 1 0000 ffffffff    call dt_get_agg               ! @myvar_agg
> +85 0 1 0000 ffffffff    call dt_get_agg               ! @myvar_agg_3keys
> +85 0 1 0000 ffffffff    call dt_get_agg               ! @myvar_agg_min
> diff --git a/test/unittest/disasm/tst.ann-agg.sh b/test/unittest/disasm/tst.ann-agg.sh
> new file mode 100755
> index 00000000..3f8e74a4
> --- /dev/null
> +++ b/test/unittest/disasm/tst.ann-agg.sh
> @@ -0,0 +1,22 @@
> +#!/bin/bash
> +#
> +# Oracle Linux DTrace.
> +# Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
> +# Licensed under the Universal Permissive License v 1.0 as shown at
> +# http://oss.oracle.com/licenses/upl.
> +#
> +
> +dtrace=$1
> +
> +$dtrace $dt_flags -Sen '
> +BEGIN
> +{
> +	myvar_global = 0xdeadbeef;
> +	@myvar_agg = quantize(myvar_global);
> +	@myvar_agg_3keys[1, 2, "hi"] = sum(myvar_global);
> +	@myvar_agg_min = min(myvar_global);
> +	exit(0);
> +}
> +' 2>&1 | awk '/ call dt_get_agg/ { sub(/^[^:]+: /, ""); print; }'
> +
> +exit $?
> -- 
> 2.18.4
> 
> 
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