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Consolidate bpf_get_stack()-call code generation for stack and ustack()
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Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>
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@euloh @kvanhees
euloh authored and kvanhees committed Jan 31, 2024
1 parent bb73572 commit b0810a4
Showing 1 changed file with 80 additions and 62 deletions.
142 changes: 80 additions & 62 deletions libdtrace/dt_cg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2558,34 +2558,83 @@ dt_cg_stack_arg(dtrace_hdl_t *dtp, dt_node_t *dnp, dtrace_actkind_t kind)
return DTRACE_USTACK_ARG(nframes, strsize);
}

static void
dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
/*
* Call the bpf_get_stack() helper function.
*
* dnp->dn_arg has optional, integer-constant sizing information.
*
* If reg>=0, reg is a register holding the output pointer.
* If reg<0, we write the stack to the output buffer in %r9.
*
* These cases treat "off" differently:
* - reg>=0: "off" tracks how far the pointer in "reg" has
* been advanced, both at function entry and return
*
* - reg<0: "off" is basically just a local variable since
* offsets with the %r9 buffer are managed by
* dt_rec_add()
*
* The "kind" argument is either DTRACEACT_STACK or DTRACEACT_USTACK.
*/
static int
dt_cg_act_stack_sub(dt_pcb_t *pcb, dt_node_t *dnp, int reg, int off, dtrace_actkind_t kind)
{
dtrace_hdl_t *dtp = pcb->pcb_hdl;
dt_irlist_t *dlp = &pcb->pcb_ir;
dt_regset_t *drp = pcb->pcb_regs;
uint64_t arg;
int nframes;
int skip = 0;
uint_t off;
int nframes, stacksize, prefsz, align = sizeof(uint64_t);
uint_t lbl_valid = dt_irlist_label(dlp);

arg = dt_cg_stack_arg(dtp, dnp, DTRACEACT_STACK);
/* Get sizing information from dnp->dn_arg. */
arg = dt_cg_stack_arg(dtp, dnp, kind);
prefsz = kind == DTRACEACT_USTACK ? sizeof(uint64_t) : 0;
nframes = DTRACE_USTACK_NFRAMES(arg);
stacksize = nframes * sizeof(uint64_t);

/* Reserve space in the output buffer. */
off = dt_rec_add(dtp, dt_cg_fill_gap, DTRACEACT_STACK,
sizeof(uint64_t) * nframes, sizeof(uint64_t),
NULL, nframes);
/* Handle alignment and reserve space in the output buffer. */
if (reg >= 0) {
uint_t nextoff;
nextoff = (off + (align - 1)) & ~(align - 1);
if (off < nextoff)
emit(dlp, BPF_ALU64_IMM(BPF_ADD, reg, nextoff - off));
off = nextoff + prefsz + stacksize;
} else {
off = dt_rec_add(dtp, dt_cg_fill_gap,
kind,
prefsz + stacksize, align, NULL, arg);
}

/* Now call bpf_get_stack(ctx, buf, size, flags). */
/* Write the tgid. */
if (kind == DTRACEACT_USTACK) {
if (dt_regset_xalloc_args(drp) == -1)
longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
dt_regset_xalloc(drp, BPF_REG_0);
emit(dlp, BPF_CALL_HELPER(BPF_FUNC_get_current_pid_tgid));
dt_regset_free_args(drp);
emit(dlp, BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffffffff));
if (reg >= 0)
emit(dlp, BPF_STORE(BPF_DW, reg, 0, BPF_REG_0));
else
emit(dlp, BPF_STORE(BPF_DW, BPF_REG_9, off, BPF_REG_0));
dt_regset_free(drp, BPF_REG_0);
}

/* Call bpf_get_stack(ctx, buf, size, flags). */
if (dt_regset_xalloc_args(drp) == -1)
longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
dt_cg_access_dctx(BPF_REG_1, dlp, drp, DCTX_CTX);
emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_9));
emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, off));
emit(dlp, BPF_MOV_IMM(BPF_REG_3, sizeof(uint64_t) * nframes));
emit(dlp, BPF_MOV_IMM(BPF_REG_4, skip & BPF_F_SKIP_FIELD_MASK));
if (reg >= 0) {
emit(dlp, BPF_MOV_REG(BPF_REG_2, reg));
if (prefsz)
emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, prefsz));
} else {
emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_9));
emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, off + prefsz));
}
emit(dlp, BPF_MOV_IMM(BPF_REG_3, stacksize));
emit(dlp, BPF_MOV_IMM(BPF_REG_4, (0 & BPF_F_SKIP_FIELD_MASK)
| (kind == DTRACEACT_USTACK ? BPF_F_USER_STACK : 0)));
dt_regset_xalloc(drp, BPF_REG_0);
emit(dlp, BPF_CALL_HELPER(BPF_FUNC_get_stack));
dt_regset_free_args(drp);
Expand All @@ -2594,6 +2643,18 @@ dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
dt_cg_probe_error(pcb, DTRACEFLT_BADSTACK, DT_ISIMM, 0);
emitl(dlp, lbl_valid,
BPF_NOP());

/* Finish. */
if (reg >= 0)
emit(dlp, BPF_ALU64_IMM(BPF_ADD, reg, prefsz + stacksize));

return off;
}

static void
dt_cg_act_stack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
{
dt_cg_act_stack_sub(pcb, dnp, -1, 0, kind);
}

static void
Expand Down Expand Up @@ -2748,51 +2809,6 @@ dt_cg_act_trunc(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
dt_cg_store_val(pcb, trunc, DTRACEACT_LIBACT, NULL, DT_ACT_TRUNC);
}

static void
dt_cg_act_ustack(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
{
dt_irlist_t *dlp = &pcb->pcb_ir;
dt_regset_t *drp = pcb->pcb_regs;
dtrace_hdl_t *dtp = pcb->pcb_hdl;
uint64_t arg;
int nframes, stacksize;
int skip = 0;
uint_t off;
uint_t lbl_valid = dt_irlist_label(dlp);

arg = dt_cg_stack_arg(dtp, dnp, DTRACEACT_USTACK);
nframes = DTRACE_USTACK_NFRAMES(arg);
stacksize = nframes * sizeof(uint64_t);

/* Reserve space in the output buffer. */
off = dt_rec_add(pcb->pcb_hdl, dt_cg_fill_gap, DTRACEACT_USTACK,
8 + stacksize, 8, NULL, arg);

if (dt_regset_xalloc_args(drp) == -1)
longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
dt_regset_xalloc(drp, BPF_REG_0);

/* Write the tgid. */
emit(dlp, BPF_CALL_HELPER(BPF_FUNC_get_current_pid_tgid));
emit(dlp, BPF_ALU64_IMM(BPF_AND, BPF_REG_0, 0xffffffff));
emit(dlp, BPF_STORE(BPF_DW, BPF_REG_9, off, BPF_REG_0));

/* Now call bpf_get_stack(ctx, buf, size, flags). */
dt_cg_access_dctx(BPF_REG_1, dlp, drp, DCTX_CTX);
emit(dlp, BPF_MOV_REG(BPF_REG_2, BPF_REG_9));
emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, off + 8));
emit(dlp, BPF_MOV_IMM(BPF_REG_3, stacksize));
emit(dlp, BPF_MOV_IMM(BPF_REG_4, (skip & BPF_F_SKIP_FIELD_MASK)
| BPF_F_USER_STACK));
emit(dlp, BPF_CALL_HELPER(BPF_FUNC_get_stack));
dt_regset_free_args(drp);
emit(dlp, BPF_BRANCH_IMM(BPF_JSGE, BPF_REG_0, 0, lbl_valid));
dt_regset_free(drp, BPF_REG_0);
dt_cg_probe_error(pcb, DTRACEFLT_BADSTACK, DT_ISIMM, 0);
emitl(dlp, lbl_valid,
BPF_NOP());
}

static void
dt_cg_act_print(dt_pcb_t *pcb, dt_node_t *dnp, dtrace_actkind_t kind)
{
Expand Down Expand Up @@ -2852,7 +2868,8 @@ static const dt_cg_actdesc_t _dt_cg_actions[DT_ACT_MAX] = {
DTRACEACT_PRINTF },
[DT_ACT_IDX(DT_ACT_TRACE)] = { &dt_cg_act_trace, },
[DT_ACT_IDX(DT_ACT_TRACEMEM)] = { &dt_cg_act_tracemem, },
[DT_ACT_IDX(DT_ACT_STACK)] = { &dt_cg_act_stack, },
[DT_ACT_IDX(DT_ACT_STACK)] = { &dt_cg_act_stack,
DTRACEACT_STACK },
[DT_ACT_IDX(DT_ACT_STOP)] = { &dt_cg_act_stop,
DTRACEACT_STOP },
[DT_ACT_IDX(DT_ACT_BREAKPOINT)] = { &dt_cg_act_breakpoint,
Expand All @@ -2869,7 +2886,8 @@ static const dt_cg_actdesc_t _dt_cg_actions[DT_ACT_MAX] = {
DTRACEACT_CHILL },
[DT_ACT_IDX(DT_ACT_EXIT)] = { &dt_cg_act_exit,
DTRACEACT_EXIT },
[DT_ACT_IDX(DT_ACT_USTACK)] = { &dt_cg_act_ustack, },
[DT_ACT_IDX(DT_ACT_USTACK)] = { &dt_cg_act_stack,
DTRACEACT_USTACK },
[DT_ACT_IDX(DT_ACT_PRINTA)] = { &dt_cg_act_printa, },
[DT_ACT_IDX(DT_ACT_RAISE)] = { &dt_cg_act_raise,
DTRACEACT_RAISE },
Expand Down

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