[PATCH v2] perf: libdw support for powerpc [ping]

[Paolo Bonzini]

On 01/06/2017 12:24, Paolo Bonzini wrote:
> Porting PPC to libdw only needs an architecture-specific hook to move
> the register state from perf to libdw.
> 
> The ARM and x86 architectures already use libdw, and it is useful to
> have as much common code for the unwinder as possible.  Mark Wielaard
> has contributed a frame-based unwinder to libdw, so that unwinding works
> even for binaries that do not have CFI information.  In addition,
> libunwind is always preferred to libdw by the build machinery so this
> cannot introduce regressions on machines that have both libunwind and
> libdw installed.
> 
> Cc: acme at kernel.org
> Cc: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> Cc: Ravi Bangoria <ravi.bangoria at linux.vnet.ibm.com>
> Cc: linuxppc-dev at lists.ozlabs.org
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
> 	v1->v2: fix for 4.11->4.12 changes

Ravi, Naveen, any reviews?

Thanks,

Paolo

> 
>  tools/perf/Makefile.config                  |  2 +-
>  tools/perf/arch/powerpc/util/Build          |  2 +
>  tools/perf/arch/powerpc/util/unwind-libdw.c | 73 +++++++++++++++++++++++++++++
>  3 files changed, 76 insertions(+), 1 deletion(-)
>  create mode 100644 tools/perf/arch/powerpc/util/unwind-libdw.c
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 8354d04b392f..e7b04a729417 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -61,7 +61,7 @@ endif
>  # Disable it on all other architectures in case libdw unwind
>  # support is detected in system. Add supported architectures
>  # to the check.
> -ifneq ($(ARCH),$(filter $(ARCH),x86 arm))
> +ifneq ($(ARCH),$(filter $(ARCH),x86 arm powerpc))
>    NO_LIBDW_DWARF_UNWIND := 1
>  endif
>  
> diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
> index 90ad64b231cd..2e6595310420 100644
> --- a/tools/perf/arch/powerpc/util/Build
> +++ b/tools/perf/arch/powerpc/util/Build
> @@ -5,4 +5,6 @@ libperf-y += perf_regs.o
>  
>  libperf-$(CONFIG_DWARF) += dwarf-regs.o
>  libperf-$(CONFIG_DWARF) += skip-callchain-idx.o
> +
>  libperf-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
> +libperf-$(CONFIG_LIBDW_DWARF_UNWIND) += unwind-libdw.o
> diff --git a/tools/perf/arch/powerpc/util/unwind-libdw.c b/tools/perf/arch/powerpc/util/unwind-libdw.c
> new file mode 100644
> index 000000000000..3a24b3c43273
> --- /dev/null
> +++ b/tools/perf/arch/powerpc/util/unwind-libdw.c
> @@ -0,0 +1,73 @@
> +#include <elfutils/libdwfl.h>
> +#include "../../util/unwind-libdw.h"
> +#include "../../util/perf_regs.h"
> +#include "../../util/event.h"
> +
> +/* See backends/ppc_initreg.c and backends/ppc_regs.c in elfutils.  */
> +static const int special_regs[3][2] = {
> +	{ 65, PERF_REG_POWERPC_LINK },
> +	{ 101, PERF_REG_POWERPC_XER },
> +	{ 109, PERF_REG_POWERPC_CTR },
> +};
> +
> +bool libdw__arch_set_initial_registers(Dwfl_Thread *thread, void *arg)
> +{
> +	struct unwind_info *ui = arg;
> +	struct regs_dump *user_regs = &ui->sample->user_regs;
> +	Dwarf_Word dwarf_regs[32], dwarf_nip;
> +	size_t i;
> +
> +#define REG(r) ({						\
> +	Dwarf_Word val = 0;					\
> +	perf_reg_value(&val, user_regs, PERF_REG_POWERPC_##r);	\
> +	val;							\
> +})
> +
> +	dwarf_regs[0]  = REG(R0);
> +	dwarf_regs[1]  = REG(R1);
> +	dwarf_regs[2]  = REG(R2);
> +	dwarf_regs[3]  = REG(R3);
> +	dwarf_regs[4]  = REG(R4);
> +	dwarf_regs[5]  = REG(R5);
> +	dwarf_regs[6]  = REG(R6);
> +	dwarf_regs[7]  = REG(R7);
> +	dwarf_regs[8]  = REG(R8);
> +	dwarf_regs[9]  = REG(R9);
> +	dwarf_regs[10] = REG(R10);
> +	dwarf_regs[11] = REG(R11);
> +	dwarf_regs[12] = REG(R12);
> +	dwarf_regs[13] = REG(R13);
> +	dwarf_regs[14] = REG(R14);
> +	dwarf_regs[15] = REG(R15);
> +	dwarf_regs[16] = REG(R16);
> +	dwarf_regs[17] = REG(R17);
> +	dwarf_regs[18] = REG(R18);
> +	dwarf_regs[19] = REG(R19);
> +	dwarf_regs[20] = REG(R20);
> +	dwarf_regs[21] = REG(R21);
> +	dwarf_regs[22] = REG(R22);
> +	dwarf_regs[23] = REG(R23);
> +	dwarf_regs[24] = REG(R24);
> +	dwarf_regs[25] = REG(R25);
> +	dwarf_regs[26] = REG(R26);
> +	dwarf_regs[27] = REG(R27);
> +	dwarf_regs[28] = REG(R28);
> +	dwarf_regs[29] = REG(R29);
> +	dwarf_regs[30] = REG(R30);
> +	dwarf_regs[31] = REG(R31);
> +	if (!dwfl_thread_state_registers(thread, 0, 32, dwarf_regs))
> +		return false;
> +
> +	dwarf_nip = REG(NIP);
> +	dwfl_thread_state_register_pc(thread, dwarf_nip);
> +	for (i = 0; i < ARRAY_SIZE(special_regs); i++) {
> +		Dwarf_Word val = 0;
> +		perf_reg_value(&val, user_regs, special_regs[i][1]);
> +		if (!dwfl_thread_state_registers(thread,
> +						 special_regs[i][0], 1,
> +						 &val))
> +			return false;
> +	}
> +
> +	return true;
> +}
>