[DTrace-devel] [PATCH] WIP Implement builtin variables

[Kris Van Hees]

This one isn't quite ready yet for review - feel free to look at it but please
know that it is still a work-in-progress.

On Mon, May 18, 2020 at 10:44:06AM -0700, Kris Van Hees wrote:
> Variables that are currently implemented:
> 
> 	arg0 .. arg9
> 	curthread
> 	pid
> 	tid
> 	uid
> 	gid
> 
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> ---
>  bpf/Build         |  2 +-
>  bpf/get_bvar.c    | 46 +++++++++++++++++++++++++++++++++++++++++++---
>  libdtrace/dt_cg.c |  6 +++++-
>  3 files changed, 49 insertions(+), 5 deletions(-)
> 
> diff --git a/bpf/Build b/bpf/Build
> index b24b71e0..bc77dcf3 100644
> --- a/bpf/Build
> +++ b/bpf/Build
> @@ -12,7 +12,7 @@ $(objdir)/include/.dir.stamp:
>  	@touch $(objdir)/include/.dir.stamp
>  
>  BPFLIBS += bpf_dlib
> -bpf_dlib_CPPFLAGS = -Ilibdtrace -I$(objdir)/include
> +bpf_dlib_CPPFLAGS = -Ilibdtrace -Iinclude -I$(objdir)/include
>  bpf_dlib_TARGET = dlibs/bpf_dlib
>  bpf_dlib_DIR := $(current-dir)
>  bpf_dlib_SRCDEPS = $(objdir)/include/.dir.stamp
> diff --git a/bpf/get_bvar.c b/bpf/get_bvar.c
> index 6b0b354a..4891b144 100644
> --- a/bpf/get_bvar.c
> +++ b/bpf/get_bvar.c
> @@ -5,13 +5,53 @@
>  #include <linux/bpf.h>
>  #include <stdint.h>
>  #include <bpf-helpers.h>
> +#include <dtrace/dif_defines.h>
> +#include <dt_bpf_ctx.h>
>  
>  #ifndef noinline
>  # define noinline	__attribute__((noinline))
>  #endif
>  
> -noinline uint64_t dt_get_bvar(uint32_t id)
> +noinline uint64_t dt_get_bvar(struct dt_bpf_context *dctx, uint32_t id)
>  {
> -	/* Not implemented yet. */
> -	return (uint64_t)-1;
> +	switch (id) {
> +	case DIF_VAR_EPID:
> +		return dctx->epid;
> +	case DIF_VAR_ARG0: case DIF_VAR_ARG1: case DIF_VAR_ARG2:
> +	case DIF_VAR_ARG3: case DIF_VAR_ARG4: case DIF_VAR_ARG5:
> +	case DIF_VAR_ARG6: case DIF_VAR_ARG7: case DIF_VAR_ARG8:
> +	case DIF_VAR_ARG9:
> +		return dctx->argv[id - DIF_VAR_ARG0];
> +	case DIF_VAR_CURTHREAD:
> +		return bpf_get_current_task();
> +	case DIF_VAR_TIMESTAMP:
> +		return bpf_ktime_get_ns();
> +	case DIF_VAR_PID: {
> +		uint64_t	val = bpf_get_current_pid_tgid();
> +
> +		return val >> 32;
> +	}
> +	case DIF_VAR_TID: {
> +		uint64_t	val = bpf_get_current_pid_tgid();
> +
> +		return val & 0x00000000ffffffffUL;
> +	}
> +	case DIF_VAR_UID: {
> +		uint64_t	val = bpf_get_current_uid_gid();
> +
> +		return val & 0x00000000ffffffffUL;
> +	}
> +	case DIF_VAR_GID: {
> +		uint64_t	val = bpf_get_current_uid_gid();
> +
> +		return val >> 32;
> +	}
> +	default:
> +		/* Not implemented yet. */
> +#if 1
> +		return (uint64_t)-1;
> +#else
> +		return (uint64_t)id;
> +#endif
> +	}
>  }
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index 3e8adf86..e5d3ac73 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
> @@ -895,7 +895,11 @@ dt_cg_load_var(dt_node_t *dst, dt_irlist_t *dlp, dt_regset_t *drp)
>  		if (dt_regset_xalloc_args(drp) == -1)
>  			longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
>  		if (idp->di_id < DIF_VAR_OTHER_UBASE) {	/* built-in var */
> -			instr = BPF_MOV_IMM(BPF_REG_1, idp->di_id);
> +			instr = BPF_LOAD(BPF_DW, BPF_REG_1,
> +					 BPF_REG_FP, DT_STK_DCTX);
> +			dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE,
> +					 instr));
> +			instr = BPF_MOV_IMM(BPF_REG_2, idp->di_id);
>  			dt_irlist_append(dlp, dt_cg_node_alloc(DT_LBL_NONE,
>  					 instr));
>  			idp = dt_dlib_get_func(yypcb->pcb_hdl, "dt_get_bvar");
> -- 
> 2.26.0
> 
> 
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