[DTrace-devel] [PATCH 6/6] Add support for pid function "-" with absolute offset
Kris Van Hees
kris.van.hees at oracle.com
Thu Jan 9 19:12:02 UTC 2025
A first early comment. You are changing the existing implementation of this
quite a bit so I am still tracing through it a bit to understand it all :)
Good stuff though.
On Fri, Dec 20, 2024 at 05:27:16PM -0500, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
>
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> ---
> include/dtrace/pid.h | 1 +
> libdtrace/dt_pid.c | 75 +++++++++++++-----
> libdtrace/dt_prov_uprobe.c | 2 +-
> test/unittest/pid/tst.dash.r | 1 +
> test/unittest/pid/tst.dash.sh | 118 ++++++++++++++++++++++++++++
> test/unittest/usdt/tst.pidprobes.sh | 18 ++++-
> 6 files changed, 192 insertions(+), 23 deletions(-)
> create mode 100644 test/unittest/pid/tst.dash.r
> create mode 100755 test/unittest/pid/tst.dash.sh
>
> diff --git a/include/dtrace/pid.h b/include/dtrace/pid.h
> index c53e60047..ad0aad9d8 100644
> --- a/include/dtrace/pid.h
> +++ b/include/dtrace/pid.h
> @@ -47,6 +47,7 @@ typedef struct pid_probespec {
> /*
> * Fields below this point do not apply to underlying probes.
> */
> + int pps_absoff; /* use "-" for overlying probe function */
Why use this? All you do with it is record that func is "-", and then later
in the pid provider, you actually use that to force the function name in the
probe description to be "-". But that function name in the probe desc is (in
the pid provider) already coming from pps_fun, and the code was already
assigning func to pps_fun, so it would be "-" anyway. So the pps_absoff seems
to serve no purpose, and you could just rely on pps_fun being "-" when needed.
> pid_t pps_pid; /* task PID */
> uint64_t pps_nameoff; /* offset to use for name */
> } pid_probespec_t;
> diff --git a/libdtrace/dt_pid.c b/libdtrace/dt_pid.c
> index b8bbb0396..dae499422 100644
> --- a/libdtrace/dt_pid.c
> +++ b/libdtrace/dt_pid.c
> @@ -155,7 +155,6 @@ dt_pid_per_sym(dt_pid_probe_t *pp, const GElf_Sym *symp, const char *func)
> uint_t nmatches = 0;
> ulong_t sz;
> int glob, rc = 0;
> - int isdash = strcmp("-", func) == 0;
> pid_t pid;
>
> /*
> @@ -182,8 +181,50 @@ dt_pid_per_sym(dt_pid_probe_t *pp, const GElf_Sym *symp, const char *func)
> psp->pps_fun = (char *) func;
> psp->pps_nameoff = 0;
> psp->pps_off = symp->st_value - pp->dpp_vaddr;
> + psp->pps_absoff = 0;
>
> - if (!isdash && gmatch("return", pp->dpp_name)) {
> + /*
> + * The special function "-" means the probe name is an absolute
> + * virtual address.
> + */
> + if (strcmp("-", func) == 0) {
> + char *end;
> + GElf_Sym sym;
> +
> + off = strtoull(pp->dpp_name, &end, 16);
> + if (*end != '\0') {
> + rc = dt_pid_error(dtp, pcb, dpr, D_PROC_NAME,
> + "'%s' is an invalid probe name",
> + pp->dpp_name);
> + goto out;
> + }
> +
> + psp->pps_absoff = 1;
> + psp->pps_nameoff = off;
> +
> + if (dt_Plookup_by_addr(dtp, pid, off, (const char **)&psp->pps_fun, &sym)) {
> + rc = dt_pid_error(dtp, pcb, dpr, D_PROC_NAME,
> + "failed to lookup 0x%lx in module '%s'", off, pp->dpp_mod);
> + if (psp->pps_fun != func && psp->pps_fun != NULL)
> + free(psp->pps_fun);
> + goto out;
> + }
> +
> + psp->pps_prb = (char*)pp->dpp_name; // make sure dt_prov_uprobe uses it
> + psp->pps_off = off - sym.st_value; // make sure dt_prov_uprobe uses it // dump this
> + psp->pps_off = off - pp->dpp_vaddr; // make sure dt_prov_uprobe uses it
> +
> + if (dt_pid_create_one_probe(pp->dpp_pr, dtp, psp, DTPPT_OFFSETS) < 0)
> + rc = dt_pid_error(dtp, pcb, dpr, D_PROC_CREATEFAIL,
> + "failed to create probes at '%s+0x%llx': %s",
> + func, (unsigned long long)off, dtrace_errmsg(dtp, dtrace_errno(dtp)));
> + else
> + pp->dpp_nmatches++;
> + free(psp->pps_fun);
> + goto out;
> + }
> +
> + if (gmatch("return", pp->dpp_name)) {
> if (dt_pid_create_one_probe(pp->dpp_pr, dtp, psp, DTPPT_RETURN) < 0) {
> rc = dt_pid_error(
> dtp, pcb, dpr, D_PROC_CREATEFAIL,
> @@ -195,7 +236,7 @@ dt_pid_per_sym(dt_pid_probe_t *pp, const GElf_Sym *symp, const char *func)
> nmatches++;
> }
>
> - if (!isdash && gmatch("entry", pp->dpp_name)) {
> + if (gmatch("entry", pp->dpp_name)) {
> if (dt_pid_create_one_probe(pp->dpp_pr, dtp, psp, DTPPT_ENTRY) < 0) {
> rc = dt_pid_error(
> dtp, pcb, dpr, D_PROC_CREATEFAIL,
> @@ -240,7 +281,7 @@ dt_pid_per_sym(dt_pid_probe_t *pp, const GElf_Sym *symp, const char *func)
> }
>
> nmatches++;
> - } else if (glob && !isdash) {
> + } else if (glob) {
> #if defined(__amd64)
> /*
> * We need to step through the instructions to find their
> @@ -449,31 +490,26 @@ dt_pid_per_mod(void *arg, const prmap_t *pmp, const char *obj)
> else
> pp->dpp_obj++;
>
> + /*
> + * If it is the special function "-", cut to dt_pid_per_sym() now.
> + */
> + if (strcmp("-", pp->dpp_func) == 0)
> + return dt_pid_per_sym(pp, &sym, pp->dpp_func);
> +
> /*
> * If pp->dpp_func contains any globbing meta-characters, we need
> * to iterate over the symbol table and compare each function name
> * against the pattern.
> */
> if (!strisglob(pp->dpp_func)) {
> - /*
> - * If we fail to lookup the symbol, try interpreting the
> - * function as the special "-" function that indicates that the
> - * probe name should be interpreted as a absolute virtual
> - * address. If that fails and we were matching a specific
> + /* If we are matching a specific
> * function in a specific module, report the error, otherwise
> * just fail silently in the hopes that some other object will
> * contain the desired symbol.
> */
> if (dt_Pxlookup_by_name(dtp, pid, pp->dpp_lmid, obj,
> pp->dpp_func, &sym, NULL) != 0) {
> - if (strcmp("-", pp->dpp_func) == 0) {
> - sym.st_name = 0;
> - sym.st_info =
> - GELF_ST_INFO(STB_LOCAL, STT_FUNC);
> - sym.st_other = 0;
> - sym.st_value = 0;
> - sym.st_size = Pelf64(pp->dpp_pr) ? -1ULL : -1U;
> - } else if (!strisglob(pp->dpp_mod)) {
> + if (!strisglob(pp->dpp_mod)) {
> return dt_pid_error(
> dtp, pcb, dpr, D_PROC_FUNC,
> "failed to lookup '%s' in module '%s'",
> @@ -647,9 +683,10 @@ dt_pid_create_pid_probes_proc(dtrace_probedesc_t *pdp, dtrace_hdl_t *dtp,
> if (strcmp(pp.dpp_func, "-") == 0) {
> const prmap_t *aout, *pmp;
>
> - if (pdp->mod[0] == '\0') {
> - pp.dpp_mod = pdp->mod;
> + if (strcmp(pp.dpp_mod, "*") == 0) {
> + /* Tolerate two glob cases: "" and "*". */
> pdp->mod = "a.out";
> + pp.dpp_mod = pdp->mod;
> } else if (strisglob(pp.dpp_mod) ||
> (aout = dt_Pname_to_map(dtp, pid, "a.out")) == NULL ||
> (pmp = dt_Pname_to_map(dtp, pid, pp.dpp_mod)) == NULL ||
> diff --git a/libdtrace/dt_prov_uprobe.c b/libdtrace/dt_prov_uprobe.c
> index acf1c914f..ae4b262ac 100644
> --- a/libdtrace/dt_prov_uprobe.c
> +++ b/libdtrace/dt_prov_uprobe.c
> @@ -735,7 +735,7 @@ static int provide_probe(dtrace_hdl_t *dtp, const pid_probespec_t *psp,
> pd.id = DTRACE_IDNONE;
> pd.prv = prv;
> pd.mod = psp->pps_mod;
> - pd.fun = psp->pps_fun;
> + pd.fun = psp->pps_absoff ? "-" : psp->pps_fun;
> pd.prb = prb;
>
> /* Get (or create) the provider for the PID of the probe. */
> diff --git a/test/unittest/pid/tst.dash.r b/test/unittest/pid/tst.dash.r
> new file mode 100644
> index 000000000..2e9ba477f
> --- /dev/null
> +++ b/test/unittest/pid/tst.dash.r
> @@ -0,0 +1 @@
> +success
> diff --git a/test/unittest/pid/tst.dash.sh b/test/unittest/pid/tst.dash.sh
> new file mode 100755
> index 000000000..996b79f4f
> --- /dev/null
> +++ b/test/unittest/pid/tst.dash.sh
> @@ -0,0 +1,118 @@
> +#!/bin/bash
> +#
> +# Oracle Linux DTrace.
> +# Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
> +# Licensed under the Universal Permissive License v 1.0 as shown at
> +# http://oss.oracle.com/licenses/upl.
> +#
> +
> +dtrace=$1
> +
> +DIRNAME=$tmpdir/pid-dash.$$.$RANDOM
> +mkdir $DIRNAME
> +cd $DIRNAME
> +
> +# Make trigger program.
> +
> +cat << EOF > main.c
> +int foo0(int i) {
> + int j, k;
> +
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> +
> + return i;
> +}
> +int foo1(int i) {
> + int j, k;
> +
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> +
> + return i;
> +}
> +int foo2(int i) {
> + int j, k;
> +
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> + j = i ^ 1; k = j ^ 1; i = k ^ 1;
> +
> + return i;
> +}
> +int main(int c, char **v) {
> + int i = 0;
> +
> + i = foo0(i) ^ i;
> + i = foo1(i) ^ i;
> + i = foo2(i) ^ i;
> +
> + return i;
> +}
> +EOF
> +
> +gcc main.c
> +if [ $? -ne 0 ]; then
> + echo ERROR compile
> + exit 1
> +fi
> +
> +# Loop over functions in the program.
> +
> +for func in foo0 foo1 foo2 main; do
> + # For each function, get the absolute and relative
> + # (to the function) address of some instruction in
> + # the function.
> + read ABS REL <<< `objdump -d a.out | awk '
> + # Look for the function.
> + /^[0-9a-f]* <'$func'>:$/ {
> +
> + # Get the first instruction and note the base address of the function.
> + getline; sub(":", ""); base = strtonum("0x"$1);
> +
> + # Get the next instruction.
> + getline;
> +
> + # Get the next instruction. Note its PC.
> + getline; sub(":", ""); pc = strtonum("0x"$1);
> +
> + # Print the address, both absolute and relative.
> + printf("%x %x\n", pc, pc - base);
> + exit(0);
> + }'`
> +
> + # Write the expected output to the compare file.
> + echo got $ABS $func:$REL >> dtrace.exp
> + echo got $ABS "-":$ABS >> dtrace.exp
> +
> + # Write the actual dtrace output to the output file.
> + # Specify the pid probe with both relative and absolute
> + # forms.
> + for probe in $func:$REL "-:$ABS"; do
> + $dtrace -c ./a.out -o dtrace.out -qn '
> + pid$target:a.out:'$probe'
> + { printf("got %x %s:%s", uregs[R_PC], probefunc,
> + probename); }'
> + if [ $? -ne 0 ]; then
> + echo ERROR: dtrace
> + cat dtrace.out
> + exit 1
> + fi
> + done
> +done
> +
> +# Check results.
> +
> +if ! diff -q dtrace.exp dtrace.out; then
> + echo ERROR:
> + echo "==== expected"
> + cat dtrace.exp
> + echo "==== actual"
> + cat dtrace.out
> + exit 1
> +fi
> +
> +echo success
> +exit 0
> diff --git a/test/unittest/usdt/tst.pidprobes.sh b/test/unittest/usdt/tst.pidprobes.sh
> index 54444d49b..e3e4e2043 100755
> --- a/test/unittest/usdt/tst.pidprobes.sh
> +++ b/test/unittest/usdt/tst.pidprobes.sh
> @@ -121,7 +121,13 @@ fi
> pcs=`awk '{print strtonum("0x"$1)}' disasm_foo.txt`
> pc0=`echo $pcs | awk '{print $1}'`
>
> -# Run dtrace.
> +# Construct D script: add a pid$pid::-:$absoff probe for each PC in foo.
> +
> +for pc in $pcs; do
> + printf 'p*d$target::-:%x,\n' $pc >> pidprobes.d
> +done
> +
> +# Construct D script: add a glob for all pid and USDT pyramid probes in foo.
>
> cat >> pidprobes.d <<'EOF'
> p*d$target::foo:
> @@ -130,6 +136,8 @@ p*d$target::foo:
> }
> EOF
>
> +# Construct D script: add a glob for all USDT pyramid probes, dumping args.
> +
> if [[ -n $usdt ]]; then
> echo 'pyramid$target::foo: {' >> pidprobes.d
>
> @@ -141,6 +149,8 @@ if [[ -n $usdt ]]; then
> echo '}' >> pidprobes.d
> fi
>
> +# Run dtrace.
> +
> $dtrace $dt_flags -q -c ./main -o dtrace.out -s pidprobes.d > main.out2
> if [ $? -ne 0 ]; then
> echo "failed to run dtrace" >&2
> @@ -286,14 +296,16 @@ fi
> # - a blank line
> # - pid entry
> # - pid return
> -# - pid offset
> +# - pid offset (relative -- that is, pid$pid:main:foo:$reloff)
> +# - pid offset (absolute -- that is, pid$pid:main:-:$absoff)
> # - two USDT probes (ignore is-enabled probes)
>
> echo > dtrace.out.expected
> -printf "$pid pid$pid:main:foo:entry %x\n" $pc0 >> dtrace.out.expected
> +printf "$pid pid$pid:main:foo:entry %x\n" $pc0 >> dtrace.out.expected
> echo "$pid pid$pid:main:foo:return $pc_return" >> dtrace.out.expected
> for pc in $pcs; do
> printf "$pid pid$pid:main:foo:%x %x\n" $(($pc - $pc0)) $pc >> dtrace.out.expected
> + printf "$pid pid$pid:main:-:%x %x\n" $pc $pc >> dtrace.out.expected
> done
> echo $usdt_pcs | awk '{printf("'$pid' pyramid'$pid':main:foo:entry %x\n", $1);}' >> dtrace.out.expected
> echo $usdt_pcs | awk '{printf("'$pid' pyramid'$pid':main:foo:entry %x\n", $2);}' >> dtrace.out.expected
> --
> 2.43.5
>
>
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