Re: [PATCH v4 2/2] perf probe: add sdt probes arguments into the uprobe cmd string

From: Arnaldo Carvalho de Melo
Date: Fri Dec 09 2016 - 10:14:45 EST

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Em Wed, Dec 07, 2016 at 12:26:10PM +0900, Masami Hiramatsu escreveu:
> Hello Alexis,
>
> On Sat, 26 Nov 2016 01:58:03 +0100
> Alexis Berlemont <alexis.berlemont@xxxxxxxxx> wrote:
>
> > An sdt probe can be associated with arguments but they were not passed
> > to the user probe tracing interface (uprobe_events); this patch adapts
> > the sdt argument descriptors according to the uprobe input format.
>
> Great!

Yeah, good to see work in this area!

I applied the first patch, with Masami's ack, waiting for his concerns
on this one to be addressed, ok?

- Arnaldo

> >
> > As the uprobe parser does not support scaled address mode, perf will
> > skip arguments which cannot be adapted to the uprobe format.
>
> OK, it seems that skipping argument is a good idea :)
> I just tried to support fixed-number arguments in probe events,
> but skipping it is better with older kernel.
>
> I have some comments.
>
> > Here are the results:
> >
> > $ perf buildid-cache -v --add test_sdt
> > $ perf probe -x test_sdt sdt_libfoo:table_frob
> > $ perf probe -x test_sdt sdt_libfoo:table_diddle
> > $ perf record -e sdt_libfoo:table_frob -e sdt_libfoo:table_diddle test_sdt
> > $ perf script
> > test_sdt ... 666.255678: sdt_libfoo:table_frob: (4004d7) arg0=0 arg1=0
> > test_sdt ... 666.255683: sdt_libfoo:table_diddle: (40051a) arg0=0 arg1=0
> > test_sdt ... 666.255686: sdt_libfoo:table_frob: (4004d7) arg0=1 arg1=2
> > test_sdt ... 666.255689: sdt_libfoo:table_diddle: (40051a) arg0=3 arg1=4
> > test_sdt ... 666.255692: sdt_libfoo:table_frob: (4004d7) arg0=2 arg1=4
> > test_sdt ... 666.255694: sdt_libfoo:table_diddle: (40051a) arg0=6 arg1=8
>
> We'd better start with arg1, since sdt.h and original Dtrace SDT starts
> arguments from arg1 (I'm not sure why) and dtrace/systemtap scripts
> call it "arg1".
>
> >
> > Signed-off-by: Alexis Berlemont <alexis.berlemont@xxxxxxxxx>
> > ---
> > tools/perf/arch/x86/util/perf_regs.c | 18 ++++
> > tools/perf/util/perf_regs.c | 4 +
> > tools/perf/util/perf_regs.h | 13 +++
> > tools/perf/util/probe-file.c | 169 ++++++++++++++++++++++++++++++++++-
> > 4 files changed, 200 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/arch/x86/util/perf_regs.c b/tools/perf/arch/x86/util/perf_regs.c
> > index c5db14f..52a1e65 100644
> > --- a/tools/perf/arch/x86/util/perf_regs.c
> > +++ b/tools/perf/arch/x86/util/perf_regs.c
> > @@ -26,3 +26,21 @@ const struct sample_reg sample_reg_masks[] = {
> > #endif
> > SMPL_REG_END
> > };
> > +
> > +const struct sdt_name_reg sdt_reg_renamings[] = {
> > + SDT_NAME_REG(eax, ax),
> > + SDT_NAME_REG(rax, ax),
> > + SDT_NAME_REG(ebx, bx),
> > + SDT_NAME_REG(rbx, bx),
> > + SDT_NAME_REG(ecx, cx),
> > + SDT_NAME_REG(rcx, cx),
> > + SDT_NAME_REG(edx, dx),
> > + SDT_NAME_REG(rdx, dx),
> > + SDT_NAME_REG(esi, si),
> > + SDT_NAME_REG(rsi, si),
> > + SDT_NAME_REG(edi, di),
> > + SDT_NAME_REG(rdi, di),
> > + SDT_NAME_REG(ebp, bp),
> > + SDT_NAME_REG(rbp, bp),
> > + SDT_NAME_REG_END,
> > +};
>
> It is not enough, rNN registers also have to take care, since
> gcc adds 'd', 'w' or 'b'suffixes for those registers to indicate
> its size. e.g. r15d means r15 register with 32 lower bits.
> What we need is just cut them off, since probe event uses
> length modifiers (like :u32)
>
> > diff --git a/tools/perf/util/perf_regs.c b/tools/perf/util/perf_regs.c
> > index c4023f2..1c21150 100644
> > --- a/tools/perf/util/perf_regs.c
> > +++ b/tools/perf/util/perf_regs.c
> > @@ -6,6 +6,10 @@ const struct sample_reg __weak sample_reg_masks[] = {
> > SMPL_REG_END
> > };
> >
> > +const struct sdt_name_reg __weak sdt_reg_renamings[] = {
> > + SDT_NAME_REG_END,
> > +};
> > +
> > #ifdef HAVE_PERF_REGS_SUPPORT
> > int perf_reg_value(u64 *valp, struct regs_dump *regs, int id)
> > {
> > diff --git a/tools/perf/util/perf_regs.h b/tools/perf/util/perf_regs.h
> > index 679d6e4..41815ca 100644
> > --- a/tools/perf/util/perf_regs.h
> > +++ b/tools/perf/util/perf_regs.h
> > @@ -15,6 +15,19 @@ struct sample_reg {
> >
> > extern const struct sample_reg sample_reg_masks[];
> >
> > +struct sdt_name_reg {
> > + const char *sdt_name;
> > + const char *uprobe_name;
> > +};
> > +#define SDT_NAME_REG(n, m) {.sdt_name = "%" #n, .uprobe_name = "%" #m}
> > +#define SDT_NAME_REG_END {.sdt_name = NULL, .uprobe_name = NULL}
> > +
> > +/*
> > + * The table sdt_reg_renamings is used for adjusting gcc/gas-generated
> > + * registers before filling the uprobe tracer interface.
> > + */
> > +extern const struct sdt_name_reg sdt_reg_renamings[];
> > +
> > #ifdef HAVE_PERF_REGS_SUPPORT
> > #include <perf_regs.h>
> >
> > diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
> > index 436b647..75033c7 100644
> > --- a/tools/perf/util/probe-file.c
> > +++ b/tools/perf/util/probe-file.c
> > @@ -27,6 +27,7 @@
> > #include "probe-event.h"
> > #include "probe-file.h"
> > #include "session.h"
> > +#include "perf_regs.h"
> >
> > #define MAX_CMDLEN 256
> >
> > @@ -687,6 +688,165 @@ static unsigned long long sdt_note__get_addr(struct sdt_note *note)
> > : (unsigned long long)note->addr.a64[0];
> > }
> >
> > +static const char * const type_to_suffix[] = {
> > + ":s64", "", "", "", ":s32", "", ":s16", ":s8",
> > + "", ":u8", ":u16", "", ":u32", "", "", "", ":u64"
> > +};
> > +
> > +static int synthesize_sdt_probe_arg(struct strbuf *buf, int i, const char *arg)
> > +{
> > + const struct sdt_name_reg *rnames;
> > + char *tmp, *desc = strdup(arg);
> > + const char *prefix = "", *suffix = "";
> > + int ret = -1;
> > +
> > + if (desc == NULL) {
> > + pr_debug4("Allocation error\n");
> > + return ret;
> > + }
> > +
> > + tmp = strchr(desc, '@');
> > + if (tmp) {
> > + long type_idx;
> > + /*
> > + * Isolate the string number and convert it into a
> > + * binary value; this will be an index to get suffix
> > + * of the uprobe name (defining the type)
> > + */
> > + tmp[0] = '\0';
> > + type_idx = strtol(desc, NULL, 10);
> > + if (type_idx == LONG_MIN ||
> > + type_idx == LONG_MAX) {
> > + pr_debug4("Failed to get sdt type\n");
> > + goto error;
> > + }
>
> You must ensure 0 <= type_idx + 8 <= 16 here.
>
> > + suffix = type_to_suffix[type_idx + 8];
> > + /* Get rid of the sdt prefix which is now useless */
> > + tmp++;
> > + memmove(desc, tmp, strlen(tmp) + 1);
> > + }
> > +
> > + /*
> > + * The uprobe tracer format does not support all the
> > + * addressing modes (notably: in x86 the scaled mode); so, we
> > + * detect ',' characters, if there is just one, there is no
> > + * use converting the sdt arg into a uprobe one.
> > + */
> > + if (strchr(desc, ',')) {
> > + pr_debug4("SDT argument format not supported\n");
>
> Please print 'desc' by %s too.
>
> > + goto out;
> > + }
> > +
> > + /*
> > + * If the argument addressing mode is indirect, we must check
> > + * a few things...
> > + */
> > + tmp = strchr(desc, '(');
> > + if (tmp) {
> > + int j;
> > +
> > + /*
> > + * ...if the addressing mode is indirect with a
> > + * positive offset (ex.: "1608(%ax)"), we need to add
> > + * a '+' prefix so as to be compliant with uprobe
> > + * format.
> > + */
> > + if (desc[0] != '+' && desc[0] != '-')
> > + prefix = "+";
> > +
> > + /*
> > + * ...or if the addressing mode is indirect with a symbol
> > + * as offset, the argument will not be supported by
> > + * the uprobe tracer format; so, let's skip this one.
> > + */
> > + for (j = 0; j < tmp - desc; j++) {
> > + if (desc[j] != '+' && desc[j] != '-' &&
> > + !isdigit(desc[j]))
> > + goto out;
> > + }
> > + }
> > +
> > + /*
> > + * The uprobe parser does not support all gas register names;
> > + * so, we have to replace them (ex. for x86_64: %rax -> %ax);
> > + * the loop below performs all the needed renamings if needed.
> > + */
> > + for (rnames = sdt_reg_renamings; rnames->sdt_name != NULL; rnames++) {
> > + char *new_desc, *sdt_name;
> > + size_t prefix_len, uprobe_len, mid_ofs, desc_len;
> > +
> > + sdt_name = strstr(desc, rnames->sdt_name);
> > + if (sdt_name == NULL)
> > + continue;
>
> It is better to search '%' from the desc and parse it.
> And here, we also find fixed numbers which starts with '$',
> since that is not supported yet.
>
> For example, with your patch, I still see some entries which have fixed num.
>
> $ perf buildid-cache --add /usr/lib64/libglib-2.0.so
> $ grep \$[0-9] ~/.debug/usr/lib64/libglib-2.0.so.0.5000.2/fda1ca4181ba7135d41bf3cfadc813a432f31066/probes | tail -n 2
> p:sdt_glib/mem__realloc /usr/lib64/libglib-2.0.so.0.5000.2:0x4f670 arg0=%ax:u64 arg1=%bx:u64 arg2=%bp:u32 arg3=$0:s32
> p:sdt_glib/mem__realloc /usr/lib64/libglib-2.0.so.0.5000.2:0x4f75d arg0=%ax:u64 arg1=%bp:u64 arg2=%bx:u32 arg3=$1:s32
>
> These arguments should be skipped.
>
> Thank you,
>
> > +
> > + new_desc = zalloc(strlen(desc) + 1 +
> > + strlen(rnames->uprobe_name) -
> > + strlen(rnames->sdt_name));
> > + if (new_desc == NULL)
> > + goto error;
> > +
> > + prefix_len = sdt_name - desc;
> > + if (prefix_len != 0)
> > + memcpy(new_desc, desc, prefix_len);
> > +
> > + uprobe_len = strlen(rnames->uprobe_name);
> > + memcpy(new_desc + prefix_len, rnames->uprobe_name, uprobe_len);
> > +
> > + mid_ofs = prefix_len + strlen(rnames->sdt_name);
> > + desc_len = strlen(desc);
> > + if (mid_ofs < desc_len)
> > + memcpy(new_desc + prefix_len + uprobe_len,
> > + desc + mid_ofs, desc_len - mid_ofs);
> > +
> > + free(desc);
> > + desc = new_desc;
> > + }
> > +
> > + if (strbuf_addf(buf, " arg%d=%s%s%s", i, prefix, desc, suffix) < 0)
> > + goto error;
> > +
> > +out:
> > + ret = 0;
> > +error:
> > + free(desc);
> > + return ret;
> > +}
> > +
> > +static char *synthesize_sdt_probe_command(struct sdt_note *note,
> > + const char *pathname,
> > + const char *sdtgrp)
> > +{
> > + struct strbuf buf;
> > + char *ret = NULL, **args;
> > + int i, args_count;
> > +
> > + if (strbuf_init(&buf, 32) < 0)
> > + return NULL;
> > +
> > + if (strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
> > + sdtgrp, note->name, pathname,
> > + sdt_note__get_addr(note)) < 0)
> > + goto error;
> > +
> > + if (!note->args)
> > + goto out;
> > +
> > + if (note->args) {
> > + args = argv_split(note->args, &args_count);
> > +
> > + for (i = 0; i < args_count; ++i) {
> > + if (synthesize_sdt_probe_arg(&buf, i, args[i]) < 0)
> > + goto error;
> > + }
> > + }
> > +
> > +out:
> > + ret = strbuf_detach(&buf, NULL);
> > +error:
> > + strbuf_release(&buf);
> > + return ret;
> > +}
> > +
> > int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
> > {
> > struct probe_cache_entry *entry = NULL;
> > @@ -723,11 +883,12 @@ int probe_cache__scan_sdt(struct probe_cache *pcache, const char *pathname)
> > entry->pev.group = strdup(sdtgrp);
> > list_add_tail(&entry->node, &pcache->entries);
> > }
> > - ret = asprintf(&buf, "p:%s/%s %s:0x%llx",
> > - sdtgrp, note->name, pathname,
> > - sdt_note__get_addr(note));
> > - if (ret < 0)
> > + buf = synthesize_sdt_probe_command(note, pathname, sdtgrp);
> > + if (!buf) {
> > + ret = -ENOMEM;
> > break;
> > + }
> > +
> > strlist__add(entry->tevlist, buf);
> > free(buf);
> > entry = NULL;
> > --
> > 2.10.2
> >
>
>
> --
> Masami Hiramatsu <mhiramat@xxxxxxxxxx>

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