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From: Kris Van Hees <kris.van.hees@oracle.com>
To: Alan Maguire <alan.maguire@oracle.com>
Cc: dtrace@lists.linux.dev, dtrace-devel@oss.oracle.com
Subject: Re: [DTrace-devel] [PATCH v3 1/7] cg: move get_member() to dt_cg.c
Date: Mon, 21 Jul 2025 16:37:47 -0400	[thread overview]
Message-ID: <aH6lG8uF2/mwsC7c@oracle.com> (raw)
In-Reply-To: <20250709140948.15090-2-alan.maguire@oracle.com>

On Wed, Jul 09, 2025 at 03:09:42PM +0100, Alan Maguire via DTrace-devel wrote:
> It will be used by both dt_prov_ip.c and dt_prov_tcp.c.
> 
> Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
> Reviewed-by: Eugene Loh <eugene.loh@oracle.com>

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

... albeit a newer version that is a collaboration of Alan and I to improve
    (what is now called) dt_cg_tramp_get_member()

> ---
>  libdtrace/dt_cg.c      | 39 ++++++++++++++++++++++++++++++++++++
>  libdtrace/dt_cg.h      |  2 ++
>  libdtrace/dt_prov_ip.c | 45 ++++--------------------------------------
>  3 files changed, 45 insertions(+), 41 deletions(-)
> 
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index bd0763d6..d6fc8259 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
> @@ -1901,6 +1901,45 @@ dt_cg_ctf_offsetof(const char *structname, const char *membername,
>  	return (ctm.ctm_offset / NBBY);
>  }
>  
> +/*
> + * Retrieve the value of a member in a given struct.
> + *
> + * Entry:
> + *	reg = TYPE *ptr
> + *
> + * Return:
> + *	%r0 = ptr->member
> + * Clobbers:
> + *	%r1 .. %r5
> + */
> +int
> +dt_cg_get_member(dt_pcb_t *pcb, const char *name, int reg,
> +		 const char *member)
> +{
> +	dtrace_hdl_t		*dtp = pcb->pcb_hdl;
> +	dt_irlist_t		*dlp = &pcb->pcb_ir;
> +	dtrace_typeinfo_t	tt;
> +	ctf_membinfo_t		ctm;
> +	size_t			size;
> +	uint_t			ldop;
> +
> +	if (dtrace_lookup_by_type(dtp, DTRACE_OBJ_KMODS, name, &tt) == -1 ||
> +	    ctf_member_info(tt.dtt_ctfp, tt.dtt_type, member, &ctm) == CTF_ERR)
> +		return -1;
> +
> +	ldop = dt_cg_ldsize(NULL, tt.dtt_ctfp, ctm.ctm_type, &size);
> +
> +	emit(dlp, BPF_MOV_REG(BPF_REG_3, reg));
> +	emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, ctm.ctm_offset / NBBY));
> +	emit(dlp, BPF_MOV_IMM(BPF_REG_2, size));
> +	emit(dlp, BPF_MOV_REG(BPF_REG_1, BPF_REG_FP));
> +	emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, DT_TRAMP_SP_BASE));
> +	emit(dlp, BPF_CALL_HELPER(dtp->dt_bpfhelper[BPF_FUNC_probe_read_kernel]));
> +	emit(dlp, BPF_LOAD(ldop, BPF_REG_0, BPF_REG_FP, DT_TRAMP_SP_BASE));
> +
> +	return 0;
> +}
> +
>  static void
>  dt_cg_act_breakpoint(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
>  {
> diff --git a/libdtrace/dt_cg.h b/libdtrace/dt_cg.h
> index 81b79399..36f587d3 100644
> --- a/libdtrace/dt_cg.h
> +++ b/libdtrace/dt_cg.h
> @@ -44,6 +44,8 @@ extern void dt_cg_tramp_epilogue_advance(dt_pcb_t *pcb, dt_activity_t act);
>  extern void dt_cg_tramp_error(dt_pcb_t *pcb);
>  extern int dt_cg_ctf_offsetof(const char *structname, const char *membername,
>  			      size_t *sizep, int relaxed);
> +extern int dt_cg_get_member(dt_pcb_t *pcb, const char *name, int reg,
> +			    const char *member);
>  extern uint_t dt_cg_ldsize(dt_node_t *dnp, ctf_file_t *ctfp, ctf_id_t type,
>  			 ssize_t *ret_size);
>  extern uint_t bpf_ldst_size(ssize_t size, int store);
> diff --git a/libdtrace/dt_prov_ip.c b/libdtrace/dt_prov_ip.c
> index c4a3a6e2..37f91e3d 100644
> --- a/libdtrace/dt_prov_ip.c
> +++ b/libdtrace/dt_prov_ip.c
> @@ -62,43 +62,6 @@ static int populate(dtrace_hdl_t *dtp)
>  			       probe_args, probes);
>  }
>  
> -/*
> - * Retrieve the value of a member in a given struct.
> - *
> - * Entry:
> - *	reg = TYPE *ptr
> - *
> - * Return:
> - *	%r0 = ptr->member
> - * Clobbers:
> - *	%r1 .. %r5
> - */
> -static int get_member(dt_pcb_t *pcb, const char *name, int reg,
> -		      const char *member) {
> -	dtrace_hdl_t		*dtp = pcb->pcb_hdl;
> -	dt_irlist_t		*dlp = &pcb->pcb_ir;
> -	dtrace_typeinfo_t	tt;
> -	ctf_membinfo_t		ctm;
> -	size_t			size;
> -	uint_t			ldop;
> -
> -	if (dtrace_lookup_by_type(dtp, DTRACE_OBJ_KMODS, name, &tt) == -1 ||
> -	    ctf_member_info(tt.dtt_ctfp, tt.dtt_type, member, &ctm) == CTF_ERR)
> -		return -1;
> -
> -	ldop = dt_cg_ldsize(NULL, tt.dtt_ctfp, ctm.ctm_type, &size);
> -
> -	emit(dlp, BPF_MOV_REG(BPF_REG_3, reg));
> -	emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, ctm.ctm_offset / NBBY));
> -	emit(dlp, BPF_MOV_IMM(BPF_REG_2, size));
> -	emit(dlp, BPF_MOV_REG(BPF_REG_1, BPF_REG_FP));
> -	emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, DT_TRAMP_SP_BASE));
> -	emit(dlp, BPF_CALL_HELPER(dtp->dt_bpfhelper[BPF_FUNC_probe_read_kernel]));
> -	emit(dlp, BPF_LOAD(ldop, BPF_REG_0, BPF_REG_FP, DT_TRAMP_SP_BASE));
> -
> -	return 0;
> -}
> -
>  /*
>   * Generate a BPF trampoline for a SDT probe.
>   *
> @@ -142,7 +105,7 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
>  
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(0), BPF_REG_6));
>  
> -	get_member(pcb, "struct sk_buff", BPF_REG_6, "sk");
> +	dt_cg_get_member(pcb, "struct sk_buff", BPF_REG_6, "sk");
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(1), BPF_REG_0));
>  
>  	/*
> @@ -150,11 +113,11 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
>  	 *	skb_network_header(skb)	=	(include/linux/ip.h)
>  	 *	skb->head + skb->network_header	(include/linux/skbuff.h)
>  	 */
> -	get_member(pcb, "struct sk_buff", BPF_REG_6, "head");
> +	dt_cg_get_member(pcb, "struct sk_buff", BPF_REG_6, "head");
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(2), BPF_REG_0));
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(4), BPF_REG_0));
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(5), BPF_REG_0));
> -	get_member(pcb, "struct sk_buff", BPF_REG_6, "network_header");
> +	dt_cg_get_member(pcb, "struct sk_buff", BPF_REG_6, "network_header");
>  	emit(dlp, BPF_XADD_REG(BPF_DW, BPF_REG_7, DMST_ARG(2), BPF_REG_0));
>  	emit(dlp, BPF_XADD_REG(BPF_DW, BPF_REG_7, DMST_ARG(4), BPF_REG_0));
>  	emit(dlp, BPF_XADD_REG(BPF_DW, BPF_REG_7, DMST_ARG(5), BPF_REG_0));
> @@ -168,7 +131,7 @@ static int trampoline(dt_pcb_t *pcb, uint_t exitlbl)
>  	else
>  		emit(dlp, BPF_STORE_IMM(BPF_DW, BPF_REG_7, DMST_ARG(5), 0));
>  
> -	get_member(pcb, "struct sk_buff", BPF_REG_6, "dev");
> +	dt_cg_get_member(pcb, "struct sk_buff", BPF_REG_6, "dev");
>  	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_7, DMST_ARG(3), BPF_REG_0));
>  
>  	return 0;
> -- 
> 2.39.3
> 
> 
> _______________________________________________
> DTrace-devel mailing list
> DTrace-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/dtrace-devel

  reply	other threads:[~2025-07-21 20:38 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-07-09 14:09 [PATCH v3 0/7] DTrace TCP provider Alan Maguire
2025-07-09 14:09 ` [PATCH v3 1/7] cg: move get_member() to dt_cg.c Alan Maguire
2025-07-21 20:37   ` Kris Van Hees [this message]
2025-07-09 14:09 ` [PATCH v3 2/7] cg: bump number of TSLOTS to 6 Alan Maguire
2025-07-21 20:39   ` [DTrace-devel] " Kris Van Hees
2025-07-09 14:09 ` [PATCH v3 3/7] test/operators: extend ternary tests to cover inet_ntoa*()s Alan Maguire
2025-07-09 14:09 ` [PATCH v3 4/7] providers: move network-generic definitions to net.d Alan Maguire
2025-07-09 14:09 ` [PATCH v3 5/7] tcp: new provider Alan Maguire
2025-07-09 14:09 ` [PATCH v3 6/7] dlibs: sync ip.d, net.d and tcp.d Alan Maguire
2025-07-09 14:09 ` [PATCH v3 7/7] unittest/tcp: update test.x Alan Maguire

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