[DTrace-devel] [PATCH 3/7 v2] Add support for indexed built-in variables lookup

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>

On 5/27/22 22:37, Kris Van Hees via DTrace-devel wrote:
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>   bpf/get_bvar.c     | 7 ++++++-
>   libdtrace/dt_cg.c  | 1 +
>   libdtrace/dt_dis.c | 9 +++++----
>   3 files changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/bpf/get_bvar.c b/bpf/get_bvar.c
> index 0da4b35a..4ff9b695 100644
> --- a/bpf/get_bvar.c
> +++ b/bpf/get_bvar.c
> @@ -33,7 +33,7 @@ extern uint64_t BOOTTM;
>   		-1; \
>   	})
>   
> -noinline uint64_t dt_get_bvar(const dt_dctx_t *dctx, uint32_t id)
> +noinline uint64_t dt_get_bvar(const dt_dctx_t *dctx, uint32_t id, uint32_t idx)
>   {
>   	dt_mstate_t	*mst = dctx->mst;
>   
> @@ -54,6 +54,11 @@ noinline uint64_t dt_get_bvar(const dt_dctx_t *dctx, uint32_t id)
>   	case DIF_VAR_ARG6: case DIF_VAR_ARG7: case DIF_VAR_ARG8:
>   	case DIF_VAR_ARG9:
>   		return mst->argv[id - DIF_VAR_ARG0];
> +	case DIF_VAR_ARGS:
> +		if (idx >= sizeof(mst->argv) / sizeof(mst->argv[0]))
> +			return error(dctx, DTRACEFLT_ILLOP, 0);
> +
> +		return mst->argv[idx];
>   	case DIF_VAR_STACKDEPTH:
>   	case DIF_VAR_USTACKDEPTH: {
>   		uint32_t bufsiz = (uint32_t) (uint64_t) (&STKSIZ);
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index 50afa413..7d15849d 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
> @@ -2232,6 +2232,7 @@ dt_cg_load_var(dt_node_t *dst, dt_irlist_t *dlp, dt_regset_t *drp)
>   
>   	emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_1, BPF_REG_FP, DT_STK_DCTX));
>   	emit(dlp, BPF_MOV_IMM(BPF_REG_2, idp->di_id));
> +	emit(dlp, BPF_MOV_IMM(BPF_REG_3, 0));
>   	idp = dt_dlib_get_func(yypcb->pcb_hdl, "dt_get_bvar");
>   	assert(idp != NULL);
>   	dt_regset_xalloc(drp, BPF_REG_0);
> diff --git a/libdtrace/dt_dis.c b/libdtrace/dt_dis.c
> index 58c02fd5..75438985 100644
> --- a/libdtrace/dt_dis.c
> +++ b/libdtrace/dt_dis.c
> @@ -346,11 +346,12 @@ dt_dis_bpf_args(const dtrace_difo_t *dp, const char *fn,
>   {
>   	if (strcmp(fn, "dt_get_bvar") == 0) {
>   		/*
> -		 * We know that the previous instruction exists and moves
> -		 * the variable id to a register (because we wrote the code
> -		 * generator to emit the instructions in this exact order.)
> +		 * We know that the previous two instructions exist and move
> +		 * the variable id to a register in the first instruction of
> +		 * that sequence (because we wrote the code generator to emit
> +		 * the instructions in this exact order.)
>   		 */
> -		in--;
> +		in -= 2;
>   		snprintf(buf, len, "%s",
>   			 dt_dis_varname_id(dp, in->imm, DIFV_SCOPE_GLOBAL, addr));
>   		return buf;