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Date: Mon, 31 Aug 2015 17:43:28 -0300
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Wang Nan <wangnan0@...wei.com>
Cc: mingo@...nel.org, ast@...mgrid.com, linux-kernel@...r.kernel.org,
lizefan@...wei.com, pi3orama@....com,
He Kuang <hekuang@...wei.com>,
Brendan Gregg <brendan.d.gregg@...il.com>,
Daniel Borkmann <daniel@...earbox.net>,
David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
Kaixu Xia <xiakaixu@...wei.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Namhyung Kim <namhyung@...nel.org>,
Paul Mackerras <paulus@...ba.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 23/31] perf tools: Introduce arch_get_reg_info() for x86
Em Sat, Aug 29, 2015 at 04:21:57AM +0000, Wang Nan escreveu:
> From: He Kuang <hekuang@...wei.com>
>
> arch_get_reg_info() is a helper function which converts register name
> like "%rax" to offset of a register in 'struct pt_regs', which is
> required by BPF prologue generator.
Is this something like:
/* Query offset/name of register from its name/offset */
extern int regs_query_register_offset(const char *name);
in ptrace? Can't we reuse that name and even code?
Was this that was done and only a rename was made?
- Arnaldo
> This patch replaces original string table by a 'struct reg_info' table,
> which records offset of registers according to its name.
>
> For x86, since there are two sub-archs (x86_32 and x86_64) but we can
> only get pt_regs for the arch we are currently on, this patch fills
> offset with '-1' for another sub-arch. This introduces a limitation to
> perf prologue that, we are unable to generate prologue on a x86_32
> compiled perf for BPF programs targeted on x86_64 kernel. This
> limitation is acceptable, because this is a very rare usecase.
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Signed-off-by: He Kuang <hekuang@...wei.com>
> Cc: Alexei Starovoitov <ast@...mgrid.com>
> Cc: Brendan Gregg <brendan.d.gregg@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: David Ahern <dsahern@...il.com>
> Cc: He Kuang <hekuang@...wei.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kaixu Xia <xiakaixu@...wei.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Link: http://lkml.kernel.org/n/1436445342-1402-34-git-send-email-wangnan0@huawei.com
> ---
> tools/perf/arch/x86/Makefile | 1 +
> tools/perf/arch/x86/util/Build | 2 +
> tools/perf/arch/x86/util/dwarf-regs.c | 104 ++++++++++++++++++++++++----------
> 3 files changed, 78 insertions(+), 29 deletions(-)
>
> diff --git a/tools/perf/arch/x86/Makefile b/tools/perf/arch/x86/Makefile
> index 21322e0..a84a6f6f 100644
> --- a/tools/perf/arch/x86/Makefile
> +++ b/tools/perf/arch/x86/Makefile
> @@ -2,3 +2,4 @@ ifndef NO_DWARF
> PERF_HAVE_DWARF_REGS := 1
> endif
> HAVE_KVM_STAT_SUPPORT := 1
> +PERF_HAVE_ARCH_GET_REG_INFO := 1
> diff --git a/tools/perf/arch/x86/util/Build b/tools/perf/arch/x86/util/Build
> index 2c55e1b..09429f6 100644
> --- a/tools/perf/arch/x86/util/Build
> +++ b/tools/perf/arch/x86/util/Build
> @@ -3,6 +3,8 @@ libperf-y += tsc.o
> libperf-y += pmu.o
> libperf-y += kvm-stat.o
>
> +# BPF_PROLOGUE also need dwarf-regs.o. However, if CONFIG_BPF_PROLOGUE
> +# is true, CONFIG_DWARF must true.
> libperf-$(CONFIG_DWARF) += dwarf-regs.o
>
> libperf-$(CONFIG_LIBUNWIND) += unwind-libunwind.o
> diff --git a/tools/perf/arch/x86/util/dwarf-regs.c b/tools/perf/arch/x86/util/dwarf-regs.c
> index be22dd4..9928caf 100644
> --- a/tools/perf/arch/x86/util/dwarf-regs.c
> +++ b/tools/perf/arch/x86/util/dwarf-regs.c
> @@ -22,44 +22,67 @@
>
> #include <stddef.h>
> #include <dwarf-regs.h>
> +#include <string.h>
> +#include <linux/ptrace.h>
> +#include <linux/kernel.h> /* for offsetof */
> +#include <util/bpf-loader.h>
> +
> +struct reg_info {
> + const char *name; /* Reg string in debuginfo */
> + int offset; /* Reg offset in struct pt_regs */
> +};
>
> /*
> * Generic dwarf analysis helpers
> */
> -
> +/*
> + * x86_64 compiling can't access pt_regs for x86_32, so fill offset
> + * with -1.
> + */
> +#ifdef __x86_64__
> +# define REG_INFO(n, f) { .name = n, .offset = -1, }
> +#else
> +# define REG_INFO(n, f) { .name = n, .offset = offsetof(struct pt_regs, f), }
> +#endif
> #define X86_32_MAX_REGS 8
> -const char *x86_32_regs_table[X86_32_MAX_REGS] = {
> - "%ax",
> - "%cx",
> - "%dx",
> - "%bx",
> - "$stack", /* Stack address instead of %sp */
> - "%bp",
> - "%si",
> - "%di",
> +
> +struct reg_info x86_32_regs_table[X86_32_MAX_REGS] = {
> + REG_INFO("%ax", eax),
> + REG_INFO("%cx", ecx),
> + REG_INFO("%dx", edx),
> + REG_INFO("%bx", ebx),
> + REG_INFO("$stack", esp), /* Stack address instead of %sp */
> + REG_INFO("%bp", ebp),
> + REG_INFO("%si", esi),
> + REG_INFO("%di", edi),
> };
>
> +#undef REG_INFO
> +#ifdef __x86_64__
> +# define REG_INFO(n, f) { .name = n, .offset = offsetof(struct pt_regs, f), }
> +#else
> +# define REG_INFO(n, f) { .name = n, .offset = -1, }
> +#endif
> #define X86_64_MAX_REGS 16
> -const char *x86_64_regs_table[X86_64_MAX_REGS] = {
> - "%ax",
> - "%dx",
> - "%cx",
> - "%bx",
> - "%si",
> - "%di",
> - "%bp",
> - "%sp",
> - "%r8",
> - "%r9",
> - "%r10",
> - "%r11",
> - "%r12",
> - "%r13",
> - "%r14",
> - "%r15",
> +struct reg_info x86_64_regs_table[X86_64_MAX_REGS] = {
> + REG_INFO("%ax", rax),
> + REG_INFO("%dx", rdx),
> + REG_INFO("%cx", rcx),
> + REG_INFO("%bx", rbx),
> + REG_INFO("%si", rsi),
> + REG_INFO("%di", rdi),
> + REG_INFO("%bp", rbp),
> + REG_INFO("%sp", rsp),
> + REG_INFO("%r8", r8),
> + REG_INFO("%r9", r9),
> + REG_INFO("%r10", r10),
> + REG_INFO("%r11", r11),
> + REG_INFO("%r12", r12),
> + REG_INFO("%r13", r13),
> + REG_INFO("%r14", r14),
> + REG_INFO("%r15", r15),
> };
>
> -/* TODO: switching by dwarf address size */
> #ifdef __x86_64__
> #define ARCH_MAX_REGS X86_64_MAX_REGS
> #define arch_regs_table x86_64_regs_table
> @@ -71,5 +94,28 @@ const char *x86_64_regs_table[X86_64_MAX_REGS] = {
> /* Return architecture dependent register string (for kprobe-tracer) */
> const char *get_arch_regstr(unsigned int n)
> {
> - return (n <= ARCH_MAX_REGS) ? arch_regs_table[n] : NULL;
> + return (n <= ARCH_MAX_REGS) ? arch_regs_table[n].name : NULL;
> }
> +
> +#ifdef HAVE_BPF_PROLOGUE
> +int arch_get_reg_info(const char *name, int *offset)
> +{
> + int i;
> + struct reg_info *info;
> +
> + if (!name || !offset)
> + return -1;
> +
> + for (i = 0; i < ARCH_MAX_REGS; i++) {
> + info = &arch_regs_table[i];
> + if (strcmp(info->name, name) == 0) {
> + if (info->offset < 0)
> + return -1;
> + *offset = info->offset;
> + return 0;
> + }
> + }
> +
> + return -1;
> +}
> +#endif
> --
> 2.1.0
--
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