[DTrace-devel] [PATCH 1/3] Ensure proper probe compilation context is set for trampolines

[Eugene Loh]

Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
... but if there is a user-visible difference with this patch alone, 
would it make sense to add a test?  Or, would that wait until a later patch?

On 7/2/21 2:18 PM, Kris Van Hees wrote:
> Trampolines are generated per-probe, well after the clauses have been
> compiled.  The code generation for the trampolines was not setting the
> proper probe context which could lead to obscure issues like not having
> the proper probe argument information when the trampoline is generated.
>
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>   libdtrace/dt_cc.c   | 9 ++++++---
>   libdtrace/dt_impl.h | 2 +-
>   libdtrace/dt_pid.c  | 9 +++++----
>   3 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/libdtrace/dt_cc.c b/libdtrace/dt_cc.c
> index 9c05e831..2a6904a0 100644
> --- a/libdtrace/dt_cc.c
> +++ b/libdtrace/dt_cc.c
> @@ -1560,7 +1560,7 @@ dt_compile_xlator(dt_node_t *dnp)
>   }
>   
>   void
> -dt_setcontext(dtrace_hdl_t *dtp, dtrace_probedesc_t *pdp)
> +dt_setcontext(dtrace_hdl_t *dtp, const dtrace_probedesc_t *pdp)
>   {
>   	const dtrace_pattr_t *pap;
>   	dt_probe_t *prp;
> @@ -1585,7 +1585,7 @@ dt_setcontext(dtrace_hdl_t *dtp, dtrace_probedesc_t *pdp)
>   	    isdigit(pdp->prv[strlen(pdp->prv) - 1]) &&
>   	    ((pvp = dt_provider_lookup(dtp, pdp->prv)) == NULL ||
>   	     pvp->pv_flags & DT_PROVIDER_PID) &&
> -	    dt_pid_create_probes(pdp, dtp, yypcb) != 0) {
> +	    dt_pid_create_probes((dtrace_probedesc_t *)pdp, dtp, yypcb) != 0) {
>   		longjmp(yypcb->pcb_jmpbuf, EDT_COMPILER);
>   	}
>   
> @@ -2117,7 +2117,7 @@ dt_construct(dtrace_hdl_t *dtp, dt_probe_t *prp, uint_t cflags, dt_ident_t *idp)
>   	pcb.pcb_context = DT_CTX_DPROG;
>   	pcb.pcb_token = DT_CTX_DPROG;
>   	pcb.pcb_probe = prp;
> -	pcb.pcb_pdesc = NULL;
> +	pcb.pcb_pdesc = prp->desc;
>   
>   	if ((err = setjmp(yypcb->pcb_jmpbuf)) != 0)
>   		goto out;
> @@ -2134,6 +2134,7 @@ dt_construct(dtrace_hdl_t *dtp, dt_probe_t *prp, uint_t cflags, dt_ident_t *idp)
>   	if (yypcb->pcb_pragmas != NULL)
>   		dt_idhash_iter(yypcb->pcb_pragmas, dt_idpragma, NULL);
>   
> +	dt_setcontext(dtp, yypcb->pcb_pdesc);
>   	tnp = dt_node_trampoline(prp);
>   	dt_node_type_assign(tnp, dtp->dt_ints[0].did_ctfp,
>   				 dtp->dt_ints[0].did_type);
> @@ -2164,6 +2165,8 @@ out:
>   	     ctf_write(dtp->dt_ddefs->dm_ctfp, dtp->dt_ddefs_fd) == CTF_ERR))
>   		dt_dprintf("failed to update CTF cache: %s\n", strerror(errno));
>   
> +	dt_endcontext(dtp);
> +
>   	dt_pcb_pop(dtp, err);
>   	dt_set_errno(dtp, err);
>   
> diff --git a/libdtrace/dt_impl.h b/libdtrace/dt_impl.h
> index d3e133e7..bd8d9943 100644
> --- a/libdtrace/dt_impl.h
> +++ b/libdtrace/dt_impl.h
> @@ -698,7 +698,7 @@ extern uint64_t dt_stddev(uint64_t *, uint64_t);
>   
>   extern int dt_options_load(dtrace_hdl_t *);
>   
> -extern void dt_setcontext(dtrace_hdl_t *, dtrace_probedesc_t *);
> +extern void dt_setcontext(dtrace_hdl_t *, const dtrace_probedesc_t *);
>   extern void dt_endcontext(dtrace_hdl_t *);
>   
>   extern void dt_dlib_init(dtrace_hdl_t *dtp);
> diff --git a/libdtrace/dt_pid.c b/libdtrace/dt_pid.c
> index dc710926..36e8e749 100644
> --- a/libdtrace/dt_pid.c
> +++ b/libdtrace/dt_pid.c
> @@ -504,7 +504,7 @@ dt_pid_fix_mod(dt_pid_probe_t *pp, dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp,
>   
>   static int
>   dt_pid_create_pid_probes(dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp,
> -    dt_pcb_t *pcb, dt_proc_t *dpr)
> +			 dt_pcb_t *pcb, dt_proc_t *dpr)
>   {
>   	dt_pid_probe_t pp;
>   	int ret = 0;
> @@ -685,8 +685,8 @@ dt_pid_create_usdt_probes(dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp,
>   #endif
>   
>   static pid_t
> -dt_pid_get_pid(dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp, dt_pcb_t *pcb,
> -    dt_proc_t *dpr)
> +dt_pid_get_pid(const dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp, dt_pcb_t *pcb,
> +	       dt_proc_t *dpr)
>   {
>   	pid_t pid;
>   	char *end;
> @@ -741,7 +741,8 @@ dt_pid_create_probes(dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp, dt_pcb_t *pcb)
>   		dpr = dt_proc_lookup(dtp, pid);
>   		assert(dpr != NULL);
>   
> -		if ((err = dt_pid_create_pid_probes(pdp, dtp, pcb, dpr)) == 0) {
> +		err = dt_pid_create_pid_probes(pdp, dtp, pcb, dpr);
> +		if (err == 0) {
>   			/*
>   			 * Alert other retained enablings which may match
>   			 * against the newly created probes.