[DTrace-devel] [PATCH] Store probe id in the trampoline
Kris Van Hees
kris.van.hees at oracle.com
Mon Mar 29 19:50:00 PDT 2021
On Mon, Mar 29, 2021 at 10:16:48PM -0400, Eugene Loh wrote:
> Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
> though
>
> On 3/29/21 1:28 PM, Kris Van Hees wrote:
> > The probe id (PRID) is associated with the probe and is therefore unique
> > for every final BPF program that is attached to a probe. It will have
> > the same value for all clauses associated with thst probe and it is
> > therefore no necessary to store it in the DTrace machine state (DMST) in
> > every clause.
>
> no -> not?
>
> thst?
>
> Also, while this commit message makes sense at this point, isn't it
> about to become obsolete with the PID patch?
No, because it actually affects all probe programs, regardless of the
provider involved. The PID provider will implement an override for this
mechanism for its specific case, but other providers still benefit from this.
> And FWIW, most of the refactoring in this patch is unrelated to the patch.
It is related because the introduction of an emite call caused the other
emit* calls to be changed to have the BPF_* macros line up.
> > Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> > ---
> > libdtrace/dt_cg.c | 49 +++++++++++++++++++++++------------------------
> > 1 file changed, 24 insertions(+), 25 deletions(-)
> >
> > diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> > index d606925a..f55d58f6 100644
> > --- a/libdtrace/dt_cg.c
> > +++ b/libdtrace/dt_cg.c
> > @@ -49,6 +49,7 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
> > dt_irlist_t *dlp = &pcb->pcb_ir;
> > dt_ident_t *mem = dt_dlib_get_map(dtp, "mem");
> > dt_ident_t *state = dt_dlib_get_map(dtp, "state");
> > + dt_ident_t *prid = dt_dlib_get_var(pcb->pcb_hdl, "PRID");
> > uint_t lbl_exit = pcb->pcb_exitlbl;
> >
> > assert(mem != NULL);
> > @@ -67,8 +68,8 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
> > * // mov %r8, %r1
> > * dctx.ctx = ctx; // stdw [%fp + DCTX_FP(DCTX_CTX)], %r8
> > */
> > - emit(dlp, BPF_MOV_REG(BPF_REG_8, BPF_REG_1));
> > - emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_CTX), BPF_REG_8));
> > + emit(dlp, BPF_MOV_REG(BPF_REG_8, BPF_REG_1));
> > + emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_CTX), BPF_REG_8));
> >
> > /*
> > * key = DT_STATE_ACTIVITY;// stw [%fp + DCTX_FP(DCTX_ACT)],
> > @@ -87,15 +88,15 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
> > *
> > * dctx.act = rc; // stdw [%fp + DCTX_FP(DCTX_ACT)], %r0
> > */
> > - emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_FP, DCTX_FP(DCTX_ACT), DT_STATE_ACTIVITY));
> > + emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_FP, DCTX_FP(DCTX_ACT), DT_STATE_ACTIVITY));
> > dt_cg_xsetx(dlp, state, DT_LBL_NONE, BPF_REG_1, state->di_id);
> > - emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
> > - emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DCTX_FP(DCTX_ACT)));
> > - emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
> > - emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, lbl_exit));
> > - emit(dlp, BPF_LOAD(BPF_W, BPF_REG_1, BPF_REG_0, 0));
> > - emit(dlp, BPF_BRANCH_IMM(BPF_JNE, BPF_REG_1, act, lbl_exit));
> > - emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_ACT), BPF_REG_0));
> > + emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
> > + emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DCTX_FP(DCTX_ACT)));
> > + emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
> > + emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, lbl_exit));
> > + emit(dlp, BPF_LOAD(BPF_W, BPF_REG_1, BPF_REG_0, 0));
> > + emit(dlp, BPF_BRANCH_IMM(BPF_JNE, BPF_REG_1, act, lbl_exit));
> > + emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_ACT), BPF_REG_0));
> >
> > /*
> > * key = 0; // stw [%fp + DCTX_FP(DCTX_MST)], 0
> > @@ -112,15 +113,17 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
> > * // (%r7 = pointer to dt_mstate_t)
> > * // mov %r7, %r0
> > * dctx.mst = rc; // stdw [%fp + DCTX_FP(DCTX_MST)], %r7
> > + * dctx.mst->prid = PRID; // stw [%r7 + DMST_PRID], PRID
> > */
> > - emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_FP, DCTX_FP(DCTX_MST), 0));
> > + emit(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_FP, DCTX_FP(DCTX_MST), 0));
> > dt_cg_xsetx(dlp, mem, DT_LBL_NONE, BPF_REG_1, mem->di_id);
> > - emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
> > - emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DCTX_FP(DCTX_MST)));
> > - emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
> > - emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, lbl_exit));
> > - emit(dlp, BPF_MOV_REG(BPF_REG_7, BPF_REG_0));
> > - emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_MST), BPF_REG_7));
> > + emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_FP));
> > + emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, DCTX_FP(DCTX_MST)));
> > + emit(dlp, BPF_CALL_HELPER(BPF_FUNC_map_lookup_elem));
> > + emit(dlp, BPF_BRANCH_IMM(BPF_JEQ, BPF_REG_0, 0, lbl_exit));
> > + emit(dlp, BPF_MOV_REG(BPF_REG_7, BPF_REG_0));
> > + emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_MST), BPF_REG_7));
> > + emite(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_7, DMST_PRID, -1), prid);
> >
> > /*
> > * buf = rc + roundup(sizeof(dt_mstate_t), 8);
> > @@ -132,10 +135,10 @@ dt_cg_tramp_prologue_act(dt_pcb_t *pcb, dt_activity_t act)
> > * // (%r0 = pointer to buffer space)
> > * dctx.buf = buf; // stdw [%fp + DCTX_FP(DCTX_BUF)], %r0
> > */
> > - emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, roundup(sizeof(dt_mstate_t), 8)));
> > - emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_0, 0, 0));
> > - emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8));
> > - emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_BUF), BPF_REG_0));
> > + emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, roundup(sizeof(dt_mstate_t), 8)));
> > + emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_0, 0, 0));
> > + emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 8));
> > + emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DCTX_FP(DCTX_BUF), BPF_REG_0));
> >
> > if (dt_idhash_datasize(dtp->dt_aggs) > 0) {
> > dt_ident_t *aggs = dt_dlib_get_map(dtp, "aggs");
> > @@ -420,11 +423,9 @@ dt_cg_prologue(dt_pcb_t *pcb, dt_node_t *pred)
> > {
> > dt_irlist_t *dlp = &pcb->pcb_ir;
> > dt_ident_t *epid = dt_dlib_get_var(pcb->pcb_hdl, "EPID");
> > - dt_ident_t *prid = dt_dlib_get_var(pcb->pcb_hdl, "PRID");
> > dt_ident_t *clid = dt_dlib_get_var(pcb->pcb_hdl, "CLID");
> >
> > assert(epid != NULL);
> > - assert(prid != NULL);
> > assert(clid != NULL);
> >
> > /*
> > @@ -451,7 +452,6 @@ dt_cg_prologue(dt_pcb_t *pcb, dt_node_t *pred)
> > * // stdw [%r0 + DMST_FAULT], 0
> > * dctx->mst->tstamp = 0; // stdw [%r0 + DMST_TSTAMP], 0
> > * dctx->mst->epid = EPID; // stw [%r0 + DMST_EPID], EPID
> > - * dctx->mst->prid = PRID; // stw [%r0 + DMST_PRID], PRID
> > * dctx->mst->clid = CLID; // stw [%r0 + DMST_CLID], CLID
> > * *((uint32_t *)&buf[0]) = EPID;
> > * // stw [%r9 + 0], EPID
> > @@ -460,7 +460,6 @@ dt_cg_prologue(dt_pcb_t *pcb, dt_node_t *pred)
> > emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_0, DMST_FAULT, 0));
> > emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_0, DMST_TSTAMP, 0));
> > emite(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_0, DMST_EPID, -1), epid);
> > - emite(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_0, DMST_PRID, -1), prid);
> > emite(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_0, DMST_CLID, -1), clid);
> > emite(dlp, BPF_STORE_IMM(BPF_W, BPF_REG_9, 0, -1), epid);
> >
>
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