Re: [PATCH v2 17/31] perf dwarf-regs: Pass ELF flags to get_dwarf_regstr

From: Ian Rogers
Date: Mon Oct 07 2024 - 11:07:20 EST

On Mon, Oct 7, 2024 at 1:09 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> On Sat, 5 Oct 2024 12:55:27 -0700
> Ian Rogers <irogers@xxxxxxxxxx> wrote:
>
> > Pass a flags value as architectures like csky need the flags to
> > determine the ABI variant.
> >
>
> Same here. I need some examples of this chaneg.

The code here was already using the ELF machine, so dwarf-regs.c
functions would already support cross building. There is the addition
of ELF flags as on csky the registers change depending on the ABI
version in the ELF flags.

Thanks,
Ian

> > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> > ---
> > tools/perf/util/dwarf-regs.c | 3 ++-
> > tools/perf/util/include/dwarf-regs.h | 11 ++++++-----
> > tools/perf/util/probe-finder.c | 13 +++++++------
> > tools/perf/util/probe-finder.h | 3 ++-
> > 4 files changed, 17 insertions(+), 13 deletions(-)
> >
> > diff --git a/tools/perf/util/dwarf-regs.c b/tools/perf/util/dwarf-regs.c
> > index 1321387f6948..86b3ef638fbb 100644
> > --- a/tools/perf/util/dwarf-regs.c
> > +++ b/tools/perf/util/dwarf-regs.c
> > @@ -29,7 +29,8 @@
> > #define __get_dwarf_regstr(tbl, n) (((n) < ARRAY_SIZE(tbl)) ? (tbl)[(n)] : NULL)
> >
> > /* Return architecture dependent register string (for kprobe-tracer) */
> > -const char *get_dwarf_regstr(unsigned int n, unsigned int machine)
> > +const char *get_dwarf_regstr(unsigned int n, unsigned int machine,
> > + unsigned int flags __maybe_unused)
> > {
> > switch (machine) {
> > case EM_NONE: /* Generic arch - use host arch */
> > diff --git a/tools/perf/util/include/dwarf-regs.h b/tools/perf/util/include/dwarf-regs.h
> > index ee0a734564c7..925525405e2d 100644
> > --- a/tools/perf/util/include/dwarf-regs.h
> > +++ b/tools/perf/util/include/dwarf-regs.h
> > @@ -80,12 +80,13 @@
> >
> > #ifdef HAVE_LIBDW_SUPPORT
> > const char *get_arch_regstr(unsigned int n);
> > -/*
> > - * get_dwarf_regstr - Returns ftrace register string from DWARF regnum
> > - * n: DWARF register number
> > - * machine: ELF machine signature (EM_*)
> > +/**
> > + * get_dwarf_regstr() - Returns ftrace register string from DWARF regnum.
> > + * @n: DWARF register number.
> > + * @machine: ELF machine signature (EM_*).
> > + * @flags: ELF flags for things like ABI differences.
> > */
> > -const char *get_dwarf_regstr(unsigned int n, unsigned int machine);
> > +const char *get_dwarf_regstr(unsigned int n, unsigned int machine, unsigned int flags);
> >
> > int get_arch_regnum(const char *name);
> > /*
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index 8019d232f515..29eaa9beca86 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -56,7 +56,7 @@ static struct probe_trace_arg_ref *alloc_trace_arg_ref(long offs)
> > */
> > static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
> > Dwarf_Op *fb_ops, Dwarf_Die *sp_die,
> > - unsigned int machine,
> > + const struct probe_finder *pf,
> > struct probe_trace_arg *tvar)
> > {
> > Dwarf_Attribute attr;
> > @@ -166,7 +166,7 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
> > if (!tvar)
> > return ret2;
> >
> > - regs = get_dwarf_regstr(regn, machine);
> > + regs = get_dwarf_regstr(regn, pf->e_machine, pf->e_flags);
> > if (!regs) {
> > /* This should be a bug in DWARF or this tool */
> > pr_warning("Mapping for the register number %u "
> > @@ -451,7 +451,7 @@ static int convert_variable(Dwarf_Die *vr_die, struct probe_finder *pf)
> > dwarf_diename(vr_die));
> >
> > ret = convert_variable_location(vr_die, pf->addr, pf->fb_ops,
> > - &pf->sp_die, pf->machine, pf->tvar);
> > + &pf->sp_die, pf, pf->tvar);
> > if (ret == -ENOENT && pf->skip_empty_arg)
> > /* This can be found in other place. skip it */
> > return 0;
> > @@ -1134,7 +1134,8 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
> > if (gelf_getehdr(elf, &ehdr) == NULL)
> > return -EINVAL;
> >
> > - pf->machine = ehdr.e_machine;
> > + pf->e_machine = ehdr.e_machine;
> > + pf->e_flags = ehdr.e_flags;
> >
> > do {
> > GElf_Shdr shdr;
> > @@ -1171,7 +1172,7 @@ static int copy_variables_cb(Dwarf_Die *die_mem, void *data)
> > (tag == DW_TAG_variable && vf->vars)) {
> > if (convert_variable_location(die_mem, vf->pf->addr,
> > vf->pf->fb_ops, &pf->sp_die,
> > - pf->machine, NULL) == 0) {
> > + pf, /*tvar=*/NULL) == 0) {
> > vf->args[vf->nargs].var = (char *)dwarf_diename(die_mem);
> > if (vf->args[vf->nargs].var == NULL) {
> > vf->ret = -ENOMEM;
> > @@ -1403,7 +1404,7 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
> > tag == DW_TAG_variable) {
> > ret = convert_variable_location(die_mem, af->pf.addr,
> > af->pf.fb_ops, &af->pf.sp_die,
> > - af->pf.machine, NULL);
> > + &af->pf, /*tvar=*/NULL);
> > if (ret == 0 || ret == -ERANGE) {
> > int ret2;
> > bool externs = !af->child;
> > diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
> > index b9a5afca4cc1..71e21cb4492a 100644
> > --- a/tools/perf/util/probe-finder.h
> > +++ b/tools/perf/util/probe-finder.h
> > @@ -68,7 +68,8 @@ struct probe_finder {
> > /* Call Frame Information from .debug_frame */
> > Dwarf_CFI *cfi_dbg;
> > Dwarf_Op *fb_ops; /* Frame base attribute */
> > - unsigned int machine; /* Target machine arch */
> > + unsigned int e_machine; /* ELF target machine arch */
> > + unsigned int e_flags; /* ELF target machine flags */
> > struct perf_probe_arg *pvar; /* Current target variable */
> > struct probe_trace_arg *tvar; /* Current result variable */
> > bool skip_empty_arg; /* Skip non-exist args */
> > --
> > 2.47.0.rc0.187.ge670bccf7e-goog
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>