Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1573028 > unrolled thread

[PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

Started byHe Kuang <hekuang@huawei.com>
First post2017-02-03 12:10 +0100
Last post2017-02-07 13:20 +0100
Articles 8 — 4 participants

Back to article view | Back to linux.kernel

Contents

  [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table. He Kuang <hekuang@huawei.com> - 2017-02-03 12:10 +0100
    Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Will Deacon <will.deacon@arm.com> - 2017-02-03 14:10 +0100
      [PATCH v3] perf tools arm64: Add support for generating bpf prologue He Kuang <hekuang@huawei.com> - 2017-02-04 10:10 +0100
      Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Hekuang <hekuang@huawei.com> - 2017-02-04 10:10 +0100
        Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Will Deacon <will.deacon@arm.com> - 2017-02-06 14:10 +0100
          Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-07 02:00 +0100
            Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Will Deacon <will.deacon@arm.com> - 2017-02-07 10:30 +0100
              Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in  register table. Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-07 13:20 +0100

#1573028 — [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromHe Kuang <hekuang@huawei.com>
Date2017-02-03 12:10 +0100
Subject[PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t6JUB-QC-3@gated-at.bofh.it>
This patch changes the 'dwarfnum' to 'offset' in register table, so
the index of array becomes the dwarfnum (the index of each register
defined by DWARF) and the "offset" member means the byte-offset of the
register in (user_)pt_regs. This change makes the code consistent with
x86.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
 1 file changed, 52 insertions(+), 55 deletions(-)

diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
index d49efeb..090f36b 100644
--- a/tools/perf/arch/arm64/util/dwarf-regs.c
+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
@@ -9,72 +9,69 @@
  */
 
 #include <stddef.h>
+#include <linux/ptrace.h> /* for struct user_pt_regs */
 #include <dwarf-regs.h>
 
-struct pt_regs_dwarfnum {
+struct pt_regs_offset {
 	const char *name;
-	unsigned int dwarfnum;
+	int offset;
 };
 
-#define STR(s) #s
-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
-#define GPR_DWARFNUM_NAME(num) \
-	{.name = STR(%x##num), .dwarfnum = num}
-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
-
 /*
  * Reference:
  * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
  */
-static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
-	GPR_DWARFNUM_NAME(0),
-	GPR_DWARFNUM_NAME(1),
-	GPR_DWARFNUM_NAME(2),
-	GPR_DWARFNUM_NAME(3),
-	GPR_DWARFNUM_NAME(4),
-	GPR_DWARFNUM_NAME(5),
-	GPR_DWARFNUM_NAME(6),
-	GPR_DWARFNUM_NAME(7),
-	GPR_DWARFNUM_NAME(8),
-	GPR_DWARFNUM_NAME(9),
-	GPR_DWARFNUM_NAME(10),
-	GPR_DWARFNUM_NAME(11),
-	GPR_DWARFNUM_NAME(12),
-	GPR_DWARFNUM_NAME(13),
-	GPR_DWARFNUM_NAME(14),
-	GPR_DWARFNUM_NAME(15),
-	GPR_DWARFNUM_NAME(16),
-	GPR_DWARFNUM_NAME(17),
-	GPR_DWARFNUM_NAME(18),
-	GPR_DWARFNUM_NAME(19),
-	GPR_DWARFNUM_NAME(20),
-	GPR_DWARFNUM_NAME(21),
-	GPR_DWARFNUM_NAME(22),
-	GPR_DWARFNUM_NAME(23),
-	GPR_DWARFNUM_NAME(24),
-	GPR_DWARFNUM_NAME(25),
-	GPR_DWARFNUM_NAME(26),
-	GPR_DWARFNUM_NAME(27),
-	GPR_DWARFNUM_NAME(28),
-	GPR_DWARFNUM_NAME(29),
-	REG_DWARFNUM_NAME("%lr", 30),
-	REG_DWARFNUM_NAME("%sp", 31),
-	REG_DWARFNUM_END,
-};
+#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
+			.offset = offsetof(struct user_pt_regs, regs[num])}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+#define GPR_OFFSET_NAME(r) \
+	{.name = "%x" #r, .offset = offsetof(struct user_pt_regs, regs[r])}
 
-/**
- * get_arch_regstr() - lookup register name from it's DWARF register number
- * @n:	the DWARF register number
- *
- * get_arch_regstr() returns the name of the register in struct
- * regdwarfnum_table from it's DWARF register number. If the register is not
- * found in the table, this returns NULL;
+/* This table is for reverse searching for the offset or register
+ * names in aarch64_regstr_tbl[].
  */
+static const struct pt_regs_offset regoffset_table[] = {
+	GPR_OFFSET_NAME(0),
+	GPR_OFFSET_NAME(1),
+	GPR_OFFSET_NAME(2),
+	GPR_OFFSET_NAME(3),
+	GPR_OFFSET_NAME(4),
+	GPR_OFFSET_NAME(5),
+	GPR_OFFSET_NAME(6),
+	GPR_OFFSET_NAME(7),
+	GPR_OFFSET_NAME(8),
+	GPR_OFFSET_NAME(9),
+	GPR_OFFSET_NAME(10),
+	GPR_OFFSET_NAME(11),
+	GPR_OFFSET_NAME(12),
+	GPR_OFFSET_NAME(13),
+	GPR_OFFSET_NAME(14),
+	GPR_OFFSET_NAME(15),
+	GPR_OFFSET_NAME(16),
+	GPR_OFFSET_NAME(17),
+	GPR_OFFSET_NAME(18),
+	GPR_OFFSET_NAME(19),
+	GPR_OFFSET_NAME(20),
+	GPR_OFFSET_NAME(21),
+	GPR_OFFSET_NAME(22),
+	GPR_OFFSET_NAME(23),
+	GPR_OFFSET_NAME(24),
+	GPR_OFFSET_NAME(25),
+	GPR_OFFSET_NAME(26),
+	GPR_OFFSET_NAME(27),
+	GPR_OFFSET_NAME(28),
+	GPR_OFFSET_NAME(29),
+	REG_OFFSET_NAME(lr, 30),
+	REG_OFFSET_NAME(sp, 31),
+	REG_OFFSET_END,
+};
+
+/* Minus 1 for the ending REG_OFFSET_END */
+#define ARCH_MAX_REGS ((sizeof(regoffset_table) /		\
+			sizeof(regoffset_table[0])) - 1)
+
+/* Return architecture dependent register string (for kprobe-tracer) */
 const char *get_arch_regstr(unsigned int n)
 {
-	const struct pt_regs_dwarfnum *roff;
-	for (roff = regdwarfnum_table; roff->name != NULL; roff++)
-		if (roff->dwarfnum == n)
-			return roff->name;
-	return NULL;
+	return (n < ARCH_MAX_REGS) ? regoffset_table[n].name : NULL;
 }
-- 
1.8.5.2

[toc] | [next] | [standalone]

#1573073 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromWill Deacon <will.deacon@arm.com>
Date2017-02-03 14:10 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t6LMK-1Zp-15@gated-at.bofh.it>
In reply to#1573028
On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
> This patch changes the 'dwarfnum' to 'offset' in register table, so
> the index of array becomes the dwarfnum (the index of each register
> defined by DWARF) and the "offset" member means the byte-offset of the
> register in (user_)pt_regs. This change makes the code consistent with
> x86.
> 
> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: He Kuang <hekuang@huawei.com>
> ---
>  tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
>  1 file changed, 52 insertions(+), 55 deletions(-)

Thanks for splitting this up. Comment below.

> diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
> index d49efeb..090f36b 100644
> --- a/tools/perf/arch/arm64/util/dwarf-regs.c
> +++ b/tools/perf/arch/arm64/util/dwarf-regs.c
> @@ -9,72 +9,69 @@
>   */
>  
>  #include <stddef.h>
> +#include <linux/ptrace.h> /* for struct user_pt_regs */
>  #include <dwarf-regs.h>
>  
> -struct pt_regs_dwarfnum {
> +struct pt_regs_offset {
>  	const char *name;
> -	unsigned int dwarfnum;
> +	int offset;
>  };
>  
> -#define STR(s) #s
> -#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
> -#define GPR_DWARFNUM_NAME(num) \
> -	{.name = STR(%x##num), .dwarfnum = num}
> -#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
> -
>  /*
>   * Reference:
>   * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
>   */
> -static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
> -	GPR_DWARFNUM_NAME(0),
> -	GPR_DWARFNUM_NAME(1),
> -	GPR_DWARFNUM_NAME(2),
> -	GPR_DWARFNUM_NAME(3),
> -	GPR_DWARFNUM_NAME(4),
> -	GPR_DWARFNUM_NAME(5),
> -	GPR_DWARFNUM_NAME(6),
> -	GPR_DWARFNUM_NAME(7),
> -	GPR_DWARFNUM_NAME(8),
> -	GPR_DWARFNUM_NAME(9),
> -	GPR_DWARFNUM_NAME(10),
> -	GPR_DWARFNUM_NAME(11),
> -	GPR_DWARFNUM_NAME(12),
> -	GPR_DWARFNUM_NAME(13),
> -	GPR_DWARFNUM_NAME(14),
> -	GPR_DWARFNUM_NAME(15),
> -	GPR_DWARFNUM_NAME(16),
> -	GPR_DWARFNUM_NAME(17),
> -	GPR_DWARFNUM_NAME(18),
> -	GPR_DWARFNUM_NAME(19),
> -	GPR_DWARFNUM_NAME(20),
> -	GPR_DWARFNUM_NAME(21),
> -	GPR_DWARFNUM_NAME(22),
> -	GPR_DWARFNUM_NAME(23),
> -	GPR_DWARFNUM_NAME(24),
> -	GPR_DWARFNUM_NAME(25),
> -	GPR_DWARFNUM_NAME(26),
> -	GPR_DWARFNUM_NAME(27),
> -	GPR_DWARFNUM_NAME(28),
> -	GPR_DWARFNUM_NAME(29),
> -	REG_DWARFNUM_NAME("%lr", 30),
> -	REG_DWARFNUM_NAME("%sp", 31),
> -	REG_DWARFNUM_END,
> -};
> +#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
> +			.offset = offsetof(struct user_pt_regs, regs[num])}

Whilst this works in practice, this is undefined behaviour for "sp", since
you'll go off the end of the regs array.

I still think you're better off sticking with the dwarfnum, then just having
a dwarfnum2offset macro that multiplies by the size of a register.

Will

[toc] | [prev] | [next] | [standalone]

#1573626 — [PATCH v3] perf tools arm64: Add support for generating bpf prologue

FromHe Kuang <hekuang@huawei.com>
Date2017-02-04 10:10 +0100
Subject[PATCH v3] perf tools arm64: Add support for generating bpf prologue
Message-ID<t74w1-6J8-9@gated-at.bofh.it>
In reply to#1573073
Since HAVE_KPROBES can be enabled in arm64, this patch introduces
regs_query_register_offset() to convert register name to offset for
arm64, so the BPF prologue feature is ready to use.

Signed-off-by: He Kuang <hekuang@huawei.com>
---
 tools/perf/arch/arm64/Makefile          |  1 +
 tools/perf/arch/arm64/util/dwarf-regs.c | 30 +++++++++++++++++++++++-------
 2 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
index 18b1351..eebe1ec 100644
--- a/tools/perf/arch/arm64/Makefile
+++ b/tools/perf/arch/arm64/Makefile
@@ -2,3 +2,4 @@ ifndef NO_DWARF
 PERF_HAVE_DWARF_REGS := 1
 endif
 PERF_HAVE_JITDUMP := 1
+PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET := 1
diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
index d49efeb..f2b49bf 100644
--- a/tools/perf/arch/arm64/util/dwarf-regs.c
+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
@@ -10,17 +10,22 @@
 
 #include <stddef.h>
 #include <dwarf-regs.h>
+#include <linux/ptrace.h> /* for struct user_pt_regs */
+#include "util.h"
 
 struct pt_regs_dwarfnum {
 	const char *name;
 	unsigned int dwarfnum;
+	unsigned int ptregs_offset;
 };
 
-#define STR(s) #s
-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
-#define GPR_DWARFNUM_NAME(num) \
-	{.name = STR(%x##num), .dwarfnum = num}
-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
+#define REG_DWARFNUM_NAME(r, num)					\
+		{.name = STR(%)STR(r), .dwarfnum = num,			\
+		.ptregs_offset = offsetof(struct user_pt_regs, r)}
+#define GPR_DWARFNUM_NAME(num)						\
+		{.name = STR(%x##num), .dwarfnum = num,		\
+		.ptregs_offset = offsetof(struct user_pt_regs, regs[num])}
+#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0, .ptregs_offset = 0}
 
 /*
  * Reference:
@@ -57,8 +62,9 @@ struct pt_regs_dwarfnum {
 	GPR_DWARFNUM_NAME(27),
 	GPR_DWARFNUM_NAME(28),
 	GPR_DWARFNUM_NAME(29),
-	REG_DWARFNUM_NAME("%lr", 30),
-	REG_DWARFNUM_NAME("%sp", 31),
+	{.name = "%lr", .dwarfnum = 30,
+	 .ptregs_offset = offsetof(struct user_pt_regs, regs[30])},
+	REG_DWARFNUM_NAME(sp, 31),
 	REG_DWARFNUM_END,
 };
 
@@ -78,3 +84,13 @@ const char *get_arch_regstr(unsigned int n)
 			return roff->name;
 	return NULL;
 }
+
+int regs_query_register_offset(const char *name)
+{
+	const struct pt_regs_dwarfnum *roff;
+
+	for (roff = regdwarfnum_table; roff->name != NULL; roff++)
+		if (!strcmp(roff->name, name))
+			return roff->ptregs_offset;
+	return -EINVAL;
+}
-- 
1.8.5.2

[toc] | [prev] | [next] | [standalone]

#1573629 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromHekuang <hekuang@huawei.com>
Date2017-02-04 10:10 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t74w1-6J8-11@gated-at.bofh.it>
In reply to#1573073
hi

在 2017/2/3 21:00, Will Deacon 写道:
> On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
>> This patch changes the 'dwarfnum' to 'offset' in register table, so
>> the index of array becomes the dwarfnum (the index of each register
>> defined by DWARF) and the "offset" member means the byte-offset of the
>> register in (user_)pt_regs. This change makes the code consistent with
>> x86.
>>
>> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
>> Signed-off-by: He Kuang <hekuang@huawei.com>
>> ---
>>   tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
>>   1 file changed, 52 insertions(+), 55 deletions(-)
> Thanks for splitting this up. Comment below.
>
>> diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
>> index d49efeb..090f36b 100644
>> --- a/tools/perf/arch/arm64/util/dwarf-regs.c
>> +++ b/tools/perf/arch/arm64/util/dwarf-regs.c
>> @@ -9,72 +9,69 @@
>>    */
>>   
>>   #include <stddef.h>
>> +#include <linux/ptrace.h> /* for struct user_pt_regs */
>>   #include <dwarf-regs.h>
>>   
>> -struct pt_regs_dwarfnum {
>> +struct pt_regs_offset {
>>   	const char *name;
>> -	unsigned int dwarfnum;
>> +	int offset;
>>   };
>>   
>> -#define STR(s) #s
>> -#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
>> -#define GPR_DWARFNUM_NAME(num) \
>> -	{.name = STR(%x##num), .dwarfnum = num}
>> -#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
>> -
>>   /*
>>    * Reference:
>>    * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
>>    */
>> -static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
>> -	GPR_DWARFNUM_NAME(0),
>> -	GPR_DWARFNUM_NAME(1),
>> -	GPR_DWARFNUM_NAME(2),
>> -	GPR_DWARFNUM_NAME(3),
>> -	GPR_DWARFNUM_NAME(4),
>> -	GPR_DWARFNUM_NAME(5),
>> -	GPR_DWARFNUM_NAME(6),
>> -	GPR_DWARFNUM_NAME(7),
>> -	GPR_DWARFNUM_NAME(8),
>> -	GPR_DWARFNUM_NAME(9),
>> -	GPR_DWARFNUM_NAME(10),
>> -	GPR_DWARFNUM_NAME(11),
>> -	GPR_DWARFNUM_NAME(12),
>> -	GPR_DWARFNUM_NAME(13),
>> -	GPR_DWARFNUM_NAME(14),
>> -	GPR_DWARFNUM_NAME(15),
>> -	GPR_DWARFNUM_NAME(16),
>> -	GPR_DWARFNUM_NAME(17),
>> -	GPR_DWARFNUM_NAME(18),
>> -	GPR_DWARFNUM_NAME(19),
>> -	GPR_DWARFNUM_NAME(20),
>> -	GPR_DWARFNUM_NAME(21),
>> -	GPR_DWARFNUM_NAME(22),
>> -	GPR_DWARFNUM_NAME(23),
>> -	GPR_DWARFNUM_NAME(24),
>> -	GPR_DWARFNUM_NAME(25),
>> -	GPR_DWARFNUM_NAME(26),
>> -	GPR_DWARFNUM_NAME(27),
>> -	GPR_DWARFNUM_NAME(28),
>> -	GPR_DWARFNUM_NAME(29),
>> -	REG_DWARFNUM_NAME("%lr", 30),
>> -	REG_DWARFNUM_NAME("%sp", 31),
>> -	REG_DWARFNUM_END,
>> -};
>> +#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
>> +			.offset = offsetof(struct user_pt_regs, regs[num])}
> Whilst this works in practice, this is undefined behaviour for "sp", since
> you'll go off the end of the regs array.

It's not undefined behaviour here,
struct user_pt_regs {
         __u64           regs[31];
         __u64           sp;
         __u64           pc;
         __u64           pstate;
};
user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct.
>
> I still think you're better off sticking with the dwarfnum, then just having
> a dwarfnum2offset macro that multiplies by the size of a register.
>
> Will
I think add a ptregs_offset field is more suitable and makes the code 
indepent
to struct user_pt_regs layout, for example if the structure changed to this:

struct user_pt_regs {
         __u64           sp;
         __u64           pc;
         __u64           pstate;
         __u64           regs[31];
};

The multiply result will be incorrect.
Patch updated and the change is similar to commit "4679bccaa308"
  (perf tools powerpc: Add support for generating bpf prologue)

Please review, thanks.

[toc] | [prev] | [next] | [standalone]

#1574659 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromWill Deacon <will.deacon@arm.com>
Date2017-02-06 14:10 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t7Rdo-5m6-13@gated-at.bofh.it>
In reply to#1573629
On Sat, Feb 04, 2017 at 05:03:20PM +0800, Hekuang wrote:
> hi
> 
> 在 2017/2/3 21:00, Will Deacon 写道:
> >On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
> >>This patch changes the 'dwarfnum' to 'offset' in register table, so
> >>the index of array becomes the dwarfnum (the index of each register
> >>defined by DWARF) and the "offset" member means the byte-offset of the
> >>register in (user_)pt_regs. This change makes the code consistent with
> >>x86.
> >>
> >>Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> >>Signed-off-by: He Kuang <hekuang@huawei.com>
> >>---
> >>  tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
> >>  1 file changed, 52 insertions(+), 55 deletions(-)
> >Thanks for splitting this up. Comment below.
> >
> >>diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
> >>index d49efeb..090f36b 100644
> >>--- a/tools/perf/arch/arm64/util/dwarf-regs.c
> >>+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
> >>@@ -9,72 +9,69 @@
> >>   */
> >>  #include <stddef.h>
> >>+#include <linux/ptrace.h> /* for struct user_pt_regs */
> >>  #include <dwarf-regs.h>
> >>-struct pt_regs_dwarfnum {
> >>+struct pt_regs_offset {
> >>  	const char *name;
> >>-	unsigned int dwarfnum;
> >>+	int offset;
> >>  };
> >>-#define STR(s) #s
> >>-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
> >>-#define GPR_DWARFNUM_NAME(num) \
> >>-	{.name = STR(%x##num), .dwarfnum = num}
> >>-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
> >>-
> >>  /*
> >>   * Reference:
> >>   * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
> >>   */
> >>-static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
> >>-	GPR_DWARFNUM_NAME(0),
> >>-	GPR_DWARFNUM_NAME(1),
> >>-	GPR_DWARFNUM_NAME(2),
> >>-	GPR_DWARFNUM_NAME(3),
> >>-	GPR_DWARFNUM_NAME(4),
> >>-	GPR_DWARFNUM_NAME(5),
> >>-	GPR_DWARFNUM_NAME(6),
> >>-	GPR_DWARFNUM_NAME(7),
> >>-	GPR_DWARFNUM_NAME(8),
> >>-	GPR_DWARFNUM_NAME(9),
> >>-	GPR_DWARFNUM_NAME(10),
> >>-	GPR_DWARFNUM_NAME(11),
> >>-	GPR_DWARFNUM_NAME(12),
> >>-	GPR_DWARFNUM_NAME(13),
> >>-	GPR_DWARFNUM_NAME(14),
> >>-	GPR_DWARFNUM_NAME(15),
> >>-	GPR_DWARFNUM_NAME(16),
> >>-	GPR_DWARFNUM_NAME(17),
> >>-	GPR_DWARFNUM_NAME(18),
> >>-	GPR_DWARFNUM_NAME(19),
> >>-	GPR_DWARFNUM_NAME(20),
> >>-	GPR_DWARFNUM_NAME(21),
> >>-	GPR_DWARFNUM_NAME(22),
> >>-	GPR_DWARFNUM_NAME(23),
> >>-	GPR_DWARFNUM_NAME(24),
> >>-	GPR_DWARFNUM_NAME(25),
> >>-	GPR_DWARFNUM_NAME(26),
> >>-	GPR_DWARFNUM_NAME(27),
> >>-	GPR_DWARFNUM_NAME(28),
> >>-	GPR_DWARFNUM_NAME(29),
> >>-	REG_DWARFNUM_NAME("%lr", 30),
> >>-	REG_DWARFNUM_NAME("%sp", 31),
> >>-	REG_DWARFNUM_END,
> >>-};
> >>+#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
> >>+			.offset = offsetof(struct user_pt_regs, regs[num])}
> >Whilst this works in practice, this is undefined behaviour for "sp", since
> >you'll go off the end of the regs array.
> 
> It's not undefined behaviour here,
> struct user_pt_regs {
>         __u64           regs[31];
>         __u64           sp;
>         __u64           pc;
>         __u64           pstate;
> };
> user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct.

I think it's undefined from the C standard perspective.

> >
> >I still think you're better off sticking with the dwarfnum, then just having
> >a dwarfnum2offset macro that multiplies by the size of a register.
> >
> >Will
> I think add a ptregs_offset field is more suitable and makes the code
> indepent
> to struct user_pt_regs layout, for example if the structure changed to this:
> 
> struct user_pt_regs {
>         __u64           sp;
>         __u64           pc;
>         __u64           pstate;
>         __u64           regs[31];
> };

We won't reorder a uapi structure because that would binary compatibility.

Just send a patch using the dwarfnum as the index for the offset calculation,
like I've been saying since you posted the first version.

Will

[toc] | [prev] | [next] | [standalone]

#1575296 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromMasami Hiramatsu <mhiramat@kernel.org>
Date2017-02-07 02:00 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t82it-3XP-17@gated-at.bofh.it>
In reply to#1574659
On Mon, 6 Feb 2017 13:02:29 +0000
Will Deacon <will.deacon@arm.com> wrote:

> On Sat, Feb 04, 2017 at 05:03:20PM +0800, Hekuang wrote:
> > hi
> > 
> > 在 2017/2/3 21:00, Will Deacon 写道:
> > >On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
> > >>This patch changes the 'dwarfnum' to 'offset' in register table, so
> > >>the index of array becomes the dwarfnum (the index of each register
> > >>defined by DWARF) and the "offset" member means the byte-offset of the
> > >>register in (user_)pt_regs. This change makes the code consistent with
> > >>x86.
> > >>
> > >>Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> > >>Signed-off-by: He Kuang <hekuang@huawei.com>
> > >>---
> > >>  tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
> > >>  1 file changed, 52 insertions(+), 55 deletions(-)
> > >Thanks for splitting this up. Comment below.
> > >
> > >>diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
> > >>index d49efeb..090f36b 100644
> > >>--- a/tools/perf/arch/arm64/util/dwarf-regs.c
> > >>+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
> > >>@@ -9,72 +9,69 @@
> > >>   */
> > >>  #include <stddef.h>
> > >>+#include <linux/ptrace.h> /* for struct user_pt_regs */
> > >>  #include <dwarf-regs.h>
> > >>-struct pt_regs_dwarfnum {
> > >>+struct pt_regs_offset {
> > >>  	const char *name;
> > >>-	unsigned int dwarfnum;
> > >>+	int offset;
> > >>  };
> > >>-#define STR(s) #s
> > >>-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
> > >>-#define GPR_DWARFNUM_NAME(num) \
> > >>-	{.name = STR(%x##num), .dwarfnum = num}
> > >>-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
> > >>-
> > >>  /*
> > >>   * Reference:
> > >>   * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
> > >>   */
> > >>-static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
> > >>-	GPR_DWARFNUM_NAME(0),
> > >>-	GPR_DWARFNUM_NAME(1),
> > >>-	GPR_DWARFNUM_NAME(2),
> > >>-	GPR_DWARFNUM_NAME(3),
> > >>-	GPR_DWARFNUM_NAME(4),
> > >>-	GPR_DWARFNUM_NAME(5),
> > >>-	GPR_DWARFNUM_NAME(6),
> > >>-	GPR_DWARFNUM_NAME(7),
> > >>-	GPR_DWARFNUM_NAME(8),
> > >>-	GPR_DWARFNUM_NAME(9),
> > >>-	GPR_DWARFNUM_NAME(10),
> > >>-	GPR_DWARFNUM_NAME(11),
> > >>-	GPR_DWARFNUM_NAME(12),
> > >>-	GPR_DWARFNUM_NAME(13),
> > >>-	GPR_DWARFNUM_NAME(14),
> > >>-	GPR_DWARFNUM_NAME(15),
> > >>-	GPR_DWARFNUM_NAME(16),
> > >>-	GPR_DWARFNUM_NAME(17),
> > >>-	GPR_DWARFNUM_NAME(18),
> > >>-	GPR_DWARFNUM_NAME(19),
> > >>-	GPR_DWARFNUM_NAME(20),
> > >>-	GPR_DWARFNUM_NAME(21),
> > >>-	GPR_DWARFNUM_NAME(22),
> > >>-	GPR_DWARFNUM_NAME(23),
> > >>-	GPR_DWARFNUM_NAME(24),
> > >>-	GPR_DWARFNUM_NAME(25),
> > >>-	GPR_DWARFNUM_NAME(26),
> > >>-	GPR_DWARFNUM_NAME(27),
> > >>-	GPR_DWARFNUM_NAME(28),
> > >>-	GPR_DWARFNUM_NAME(29),
> > >>-	REG_DWARFNUM_NAME("%lr", 30),
> > >>-	REG_DWARFNUM_NAME("%sp", 31),
> > >>-	REG_DWARFNUM_END,
> > >>-};
> > >>+#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
> > >>+			.offset = offsetof(struct user_pt_regs, regs[num])}
> > >Whilst this works in practice, this is undefined behaviour for "sp", since
> > >you'll go off the end of the regs array.
> > 
> > It's not undefined behaviour here,
> > struct user_pt_regs {
> >         __u64           regs[31];
> >         __u64           sp;
> >         __u64           pc;
> >         __u64           pstate;
> > };
> > user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct.
> 
> I think it's undefined from the C standard perspective.

Actually, this '%sp' is used for kprobes/uprobes dynamic events, which only 
depend on how regs_query_register_offset()@arch/arm64/kernel/ptrace.c is implemented.
And also, since perf-probe uses debuginfo, it can find out the base register.

So we don't need to care the C standard in this file :)

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

[toc] | [prev] | [next] | [standalone]

#1575510 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromWill Deacon <will.deacon@arm.com>
Date2017-02-07 10:30 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t8ag3-Zm-37@gated-at.bofh.it>
In reply to#1575296
On Tue, Feb 07, 2017 at 09:54:51AM +0900, Masami Hiramatsu wrote:
> On Mon, 6 Feb 2017 13:02:29 +0000
> Will Deacon <will.deacon@arm.com> wrote:
> 
> > On Sat, Feb 04, 2017 at 05:03:20PM +0800, Hekuang wrote:
> > > hi
> > > 
> > > 在 2017/2/3 21:00, Will Deacon 写道:
> > > >On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
> > > >>This patch changes the 'dwarfnum' to 'offset' in register table, so
> > > >>the index of array becomes the dwarfnum (the index of each register
> > > >>defined by DWARF) and the "offset" member means the byte-offset of the
> > > >>register in (user_)pt_regs. This change makes the code consistent with
> > > >>x86.
> > > >>
> > > >>Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> > > >>Signed-off-by: He Kuang <hekuang@huawei.com>
> > > >>---
> > > >>  tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
> > > >>  1 file changed, 52 insertions(+), 55 deletions(-)
> > > >Thanks for splitting this up. Comment below.
> > > >
> > > >>diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
> > > >>index d49efeb..090f36b 100644
> > > >>--- a/tools/perf/arch/arm64/util/dwarf-regs.c
> > > >>+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
> > > >>@@ -9,72 +9,69 @@
> > > >>   */
> > > >>  #include <stddef.h>
> > > >>+#include <linux/ptrace.h> /* for struct user_pt_regs */
> > > >>  #include <dwarf-regs.h>
> > > >>-struct pt_regs_dwarfnum {
> > > >>+struct pt_regs_offset {
> > > >>  	const char *name;
> > > >>-	unsigned int dwarfnum;
> > > >>+	int offset;
> > > >>  };
> > > >>-#define STR(s) #s
> > > >>-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
> > > >>-#define GPR_DWARFNUM_NAME(num) \
> > > >>-	{.name = STR(%x##num), .dwarfnum = num}
> > > >>-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
> > > >>-
> > > >>  /*
> > > >>   * Reference:
> > > >>   * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
> > > >>   */
> > > >>-static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
> > > >>-	GPR_DWARFNUM_NAME(0),
> > > >>-	GPR_DWARFNUM_NAME(1),
> > > >>-	GPR_DWARFNUM_NAME(2),
> > > >>-	GPR_DWARFNUM_NAME(3),
> > > >>-	GPR_DWARFNUM_NAME(4),
> > > >>-	GPR_DWARFNUM_NAME(5),
> > > >>-	GPR_DWARFNUM_NAME(6),
> > > >>-	GPR_DWARFNUM_NAME(7),
> > > >>-	GPR_DWARFNUM_NAME(8),
> > > >>-	GPR_DWARFNUM_NAME(9),
> > > >>-	GPR_DWARFNUM_NAME(10),
> > > >>-	GPR_DWARFNUM_NAME(11),
> > > >>-	GPR_DWARFNUM_NAME(12),
> > > >>-	GPR_DWARFNUM_NAME(13),
> > > >>-	GPR_DWARFNUM_NAME(14),
> > > >>-	GPR_DWARFNUM_NAME(15),
> > > >>-	GPR_DWARFNUM_NAME(16),
> > > >>-	GPR_DWARFNUM_NAME(17),
> > > >>-	GPR_DWARFNUM_NAME(18),
> > > >>-	GPR_DWARFNUM_NAME(19),
> > > >>-	GPR_DWARFNUM_NAME(20),
> > > >>-	GPR_DWARFNUM_NAME(21),
> > > >>-	GPR_DWARFNUM_NAME(22),
> > > >>-	GPR_DWARFNUM_NAME(23),
> > > >>-	GPR_DWARFNUM_NAME(24),
> > > >>-	GPR_DWARFNUM_NAME(25),
> > > >>-	GPR_DWARFNUM_NAME(26),
> > > >>-	GPR_DWARFNUM_NAME(27),
> > > >>-	GPR_DWARFNUM_NAME(28),
> > > >>-	GPR_DWARFNUM_NAME(29),
> > > >>-	REG_DWARFNUM_NAME("%lr", 30),
> > > >>-	REG_DWARFNUM_NAME("%sp", 31),
> > > >>-	REG_DWARFNUM_END,
> > > >>-};
> > > >>+#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
> > > >>+			.offset = offsetof(struct user_pt_regs, regs[num])}
> > > >Whilst this works in practice, this is undefined behaviour for "sp", since
> > > >you'll go off the end of the regs array.
> > > 
> > > It's not undefined behaviour here,
> > > struct user_pt_regs {
> > >         __u64           regs[31];
> > >         __u64           sp;
> > >         __u64           pc;
> > >         __u64           pstate;
> > > };
> > > user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct.
> > 
> > I think it's undefined from the C standard perspective.
> 
> Actually, this '%sp' is used for kprobes/uprobes dynamic events, which only 
> depend on how regs_query_register_offset()@arch/arm64/kernel/ptrace.c is implemented.
> And also, since perf-probe uses debuginfo, it can find out the base register.
> 
> So we don't need to care the C standard in this file :)

Up to the perf tool maintainers really, but I expect it will irritate
anybody running UBSAN and it's really not difficult to fix.

Will

[toc] | [prev] | [next] | [standalone]

#1575614 — Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.

FromMasami Hiramatsu <mhiramat@kernel.org>
Date2017-02-07 13:20 +0100
SubjectRe: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table.
Message-ID<t8cUx-2IN-11@gated-at.bofh.it>
In reply to#1575510
On Tue, 7 Feb 2017 09:20:03 +0000
Will Deacon <will.deacon@arm.com> wrote:

> On Tue, Feb 07, 2017 at 09:54:51AM +0900, Masami Hiramatsu wrote:
> > On Mon, 6 Feb 2017 13:02:29 +0000
> > Will Deacon <will.deacon@arm.com> wrote:
> > 
> > > On Sat, Feb 04, 2017 at 05:03:20PM +0800, Hekuang wrote:
> > > > hi
> > > > 
> > > > 在 2017/2/3 21:00, Will Deacon 写道:
> > > > >On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote:
> > > > >>This patch changes the 'dwarfnum' to 'offset' in register table, so
> > > > >>the index of array becomes the dwarfnum (the index of each register
> > > > >>defined by DWARF) and the "offset" member means the byte-offset of the
> > > > >>register in (user_)pt_regs. This change makes the code consistent with
> > > > >>x86.
> > > > >>
> > > > >>Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> > > > >>Signed-off-by: He Kuang <hekuang@huawei.com>
> > > > >>---
> > > > >>  tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++----------------
> > > > >>  1 file changed, 52 insertions(+), 55 deletions(-)
> > > > >Thanks for splitting this up. Comment below.
> > > > >
> > > > >>diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c
> > > > >>index d49efeb..090f36b 100644
> > > > >>--- a/tools/perf/arch/arm64/util/dwarf-regs.c
> > > > >>+++ b/tools/perf/arch/arm64/util/dwarf-regs.c
> > > > >>@@ -9,72 +9,69 @@
> > > > >>   */
> > > > >>  #include <stddef.h>
> > > > >>+#include <linux/ptrace.h> /* for struct user_pt_regs */
> > > > >>  #include <dwarf-regs.h>
> > > > >>-struct pt_regs_dwarfnum {
> > > > >>+struct pt_regs_offset {
> > > > >>  	const char *name;
> > > > >>-	unsigned int dwarfnum;
> > > > >>+	int offset;
> > > > >>  };
> > > > >>-#define STR(s) #s
> > > > >>-#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num}
> > > > >>-#define GPR_DWARFNUM_NAME(num) \
> > > > >>-	{.name = STR(%x##num), .dwarfnum = num}
> > > > >>-#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0}
> > > > >>-
> > > > >>  /*
> > > > >>   * Reference:
> > > > >>   * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf
> > > > >>   */
> > > > >>-static const struct pt_regs_dwarfnum regdwarfnum_table[] = {
> > > > >>-	GPR_DWARFNUM_NAME(0),
> > > > >>-	GPR_DWARFNUM_NAME(1),
> > > > >>-	GPR_DWARFNUM_NAME(2),
> > > > >>-	GPR_DWARFNUM_NAME(3),
> > > > >>-	GPR_DWARFNUM_NAME(4),
> > > > >>-	GPR_DWARFNUM_NAME(5),
> > > > >>-	GPR_DWARFNUM_NAME(6),
> > > > >>-	GPR_DWARFNUM_NAME(7),
> > > > >>-	GPR_DWARFNUM_NAME(8),
> > > > >>-	GPR_DWARFNUM_NAME(9),
> > > > >>-	GPR_DWARFNUM_NAME(10),
> > > > >>-	GPR_DWARFNUM_NAME(11),
> > > > >>-	GPR_DWARFNUM_NAME(12),
> > > > >>-	GPR_DWARFNUM_NAME(13),
> > > > >>-	GPR_DWARFNUM_NAME(14),
> > > > >>-	GPR_DWARFNUM_NAME(15),
> > > > >>-	GPR_DWARFNUM_NAME(16),
> > > > >>-	GPR_DWARFNUM_NAME(17),
> > > > >>-	GPR_DWARFNUM_NAME(18),
> > > > >>-	GPR_DWARFNUM_NAME(19),
> > > > >>-	GPR_DWARFNUM_NAME(20),
> > > > >>-	GPR_DWARFNUM_NAME(21),
> > > > >>-	GPR_DWARFNUM_NAME(22),
> > > > >>-	GPR_DWARFNUM_NAME(23),
> > > > >>-	GPR_DWARFNUM_NAME(24),
> > > > >>-	GPR_DWARFNUM_NAME(25),
> > > > >>-	GPR_DWARFNUM_NAME(26),
> > > > >>-	GPR_DWARFNUM_NAME(27),
> > > > >>-	GPR_DWARFNUM_NAME(28),
> > > > >>-	GPR_DWARFNUM_NAME(29),
> > > > >>-	REG_DWARFNUM_NAME("%lr", 30),
> > > > >>-	REG_DWARFNUM_NAME("%sp", 31),
> > > > >>-	REG_DWARFNUM_END,
> > > > >>-};
> > > > >>+#define REG_OFFSET_NAME(r, num) {.name = "%" #r,			\
> > > > >>+			.offset = offsetof(struct user_pt_regs, regs[num])}
> > > > >Whilst this works in practice, this is undefined behaviour for "sp", since
> > > > >you'll go off the end of the regs array.
> > > > 
> > > > It's not undefined behaviour here,
> > > > struct user_pt_regs {
> > > >         __u64           regs[31];
> > > >         __u64           sp;
> > > >         __u64           pc;
> > > >         __u64           pstate;
> > > > };
> > > > user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct.
> > > 
> > > I think it's undefined from the C standard perspective.
> > 
> > Actually, this '%sp' is used for kprobes/uprobes dynamic events, which only 
> > depend on how regs_query_register_offset()@arch/arm64/kernel/ptrace.c is implemented.
> > And also, since perf-probe uses debuginfo, it can find out the base register.
> > 
> > So we don't need to care the C standard in this file :)
> 
> Up to the perf tool maintainers really, but I expect it will irritate
> anybody running UBSAN and it's really not difficult to fix.

Hmm, sorry, I'm not sure, what the point UBSAN user be irriteted?
And what is that related to this story?

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web