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[PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation

Sathvika Vasireddy posted 16 patches 3 years, 7 months ago
There is a newer version of this series
[PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Sathvika Vasireddy 3 years, 7 months ago 
This patch enables objtool --mcount on powerpc, and
adds implementation specific to powerpc.

Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
---
 arch/powerpc/Kconfig                          |  1 +
 tools/objtool/arch/powerpc/decode.c           | 22 +++++++++++++++++++
 tools/objtool/arch/powerpc/include/arch/elf.h |  2 ++
 3 files changed, 25 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index dc05cd23c233..6be2e68fa9eb 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -238,6 +238,7 @@ config PPC
 	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
 	select HAVE_OPTPROBES
 	select HAVE_OBJTOOL			if PPC32 || MPROFILE_KERNEL
+	select HAVE_OBJTOOL_MCOUNT		if HAVE_OBJTOOL
 	select HAVE_PERF_EVENTS
 	select HAVE_PERF_EVENTS_NMI		if PPC64
 	select HAVE_PERF_REGS
diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
index 8b6a14680da7..b71c265ed503 100644
--- a/tools/objtool/arch/powerpc/decode.c
+++ b/tools/objtool/arch/powerpc/decode.c
@@ -9,6 +9,14 @@
 #include <objtool/builtin.h>
 #include <objtool/endianness.h>
 
+bool arch_ftrace_match(char *name)
+{
+	if (!strcmp(name, "_mcount"))
+		return true;
+
+	return false;
+}
+
 unsigned long arch_dest_reloc_offset(int addend)
 {
 	return addend;
@@ -41,12 +49,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
 			    struct list_head *ops_list)
 {
 	u32 insn;
+	unsigned int opcode;
 
 	*immediate = 0;
 	insn = bswap_if_needed(file->elf, *(u32 *)(sec->data->d_buf + offset));
 	*len = 4;
 	*type = INSN_OTHER;
 
+	opcode = insn >> 26;
+
+	switch (opcode) {
+	case 18: /* bl */
+		if ((insn & 3) == 1) {
+			*type = INSN_CALL;
+			*immediate = insn & 0x3fffffc;
+			if (*immediate & 0x2000000)
+				*immediate -= 0x4000000;
+		}
+		break;
+	}
+
 	return 0;
 }
 
diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
index 3c8ebb7d2a6b..73f9ae172fe5 100644
--- a/tools/objtool/arch/powerpc/include/arch/elf.h
+++ b/tools/objtool/arch/powerpc/include/arch/elf.h
@@ -4,5 +4,7 @@
 #define _OBJTOOL_ARCH_ELF
 
 #define R_NONE R_PPC_NONE
+#define R_ABS64 R_PPC64_ADDR64
+#define R_ABS32 R_PPC_ADDR32
 
 #endif /* _OBJTOOL_ARCH_ELF */
-- 
2.31.1
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Christophe Leroy 3 years, 7 months ago 

Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :
> This patch enables objtool --mcount on powerpc, and
> adds implementation specific to powerpc.
> 
> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
> ---
>   arch/powerpc/Kconfig                          |  1 +
>   tools/objtool/arch/powerpc/decode.c           | 22 +++++++++++++++++++
>   tools/objtool/arch/powerpc/include/arch/elf.h |  2 ++
>   3 files changed, 25 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index dc05cd23c233..6be2e68fa9eb 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -238,6 +238,7 @@ config PPC
>   	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>   	select HAVE_OPTPROBES
>   	select HAVE_OBJTOOL			if PPC32 || MPROFILE_KERNEL
> +	select HAVE_OBJTOOL_MCOUNT		if HAVE_OBJTOOL
>   	select HAVE_PERF_EVENTS
>   	select HAVE_PERF_EVENTS_NMI		if PPC64
>   	select HAVE_PERF_REGS
> diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
> index 8b6a14680da7..b71c265ed503 100644
> --- a/tools/objtool/arch/powerpc/decode.c
> +++ b/tools/objtool/arch/powerpc/decode.c
> @@ -9,6 +9,14 @@
>   #include <objtool/builtin.h>
>   #include <objtool/endianness.h>
>   
> +bool arch_ftrace_match(char *name)
> +{
> +	if (!strcmp(name, "_mcount"))
> +		return true;
> +
> +	return false;
> +}
> +
>   unsigned long arch_dest_reloc_offset(int addend)
>   {
>   	return addend;
> @@ -41,12 +49,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
>   			    struct list_head *ops_list)
>   {
>   	u32 insn;
> +	unsigned int opcode;
>   
>   	*immediate = 0;
>   	insn = bswap_if_needed(file->elf, *(u32 *)(sec->data->d_buf + offset));
>   	*len = 4;
>   	*type = INSN_OTHER;
>   
> +	opcode = insn >> 26;
> +
> +	switch (opcode) {
> +	case 18: /* bl */

case 18 is more than 'bl', it includes also 'b'.
In both cases, the calculation of *immediate is the same.

It would therefore be more correct to perform the calculation and setup 
of *immediate outside the 'if ((insn & 3) == 1)', that would avoid 
unnecessary churn the day we add support for branches without link.

> +		if ((insn & 3) == 1) {
> +			*type = INSN_CALL;
> +			*immediate = insn & 0x3fffffc;
> +			if (*immediate & 0x2000000)
> +				*immediate -= 0x4000000;
> +		}
> +		break;
> +	}
> +
>   	return 0;
>   }
>   
> diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
> index 3c8ebb7d2a6b..73f9ae172fe5 100644
> --- a/tools/objtool/arch/powerpc/include/arch/elf.h
> +++ b/tools/objtool/arch/powerpc/include/arch/elf.h
> @@ -4,5 +4,7 @@
>   #define _OBJTOOL_ARCH_ELF
>   
>   #define R_NONE R_PPC_NONE
> +#define R_ABS64 R_PPC64_ADDR64
> +#define R_ABS32 R_PPC_ADDR32
>   
>   #endif /* _OBJTOOL_ARCH_ELF */
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Segher Boessenkool 3 years, 7 months ago 
On Wed, Aug 31, 2022 at 12:50:07PM +0000, Christophe Leroy wrote:
> Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :
> > +	opcode = insn >> 26;
> > +
> > +	switch (opcode) {
> > +	case 18: /* bl */
> 
> case 18 is more than 'bl', it includes also 'b'.
> In both cases, the calculation of *immediate is the same.

It also is "ba" and "bla", sometimes written as "b[l][a]".

> It would therefore be more correct to perform the calculation and setup 
> of *immediate outside the 'if ((insn & 3) == 1)', that would avoid 
> unnecessary churn the day we add support for branches without link.
> 
> > +		if ((insn & 3) == 1) {
> > +			*type = INSN_CALL;
> > +			*immediate = insn & 0x3fffffc;
> > +			if (*immediate & 0x2000000)
> > +				*immediate -= 0x4000000;
> > +		}
> > +		break;
> > +	}

Does this handle AA=1 correctly at all?  That is valid both with and
without relocations, just like AA=0.  Same for AA=1 LK=0 btw.

If you only handle AA=0, the code should explicitly test for that.


Segher
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Naveen N. Rao 3 years, 7 months ago 
Segher Boessenkool wrote:
> On Wed, Aug 31, 2022 at 12:50:07PM +0000, Christophe Leroy wrote:
>> Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :
>> > +	opcode = insn >> 26;
>> > +
>> > +	switch (opcode) {
>> > +	case 18: /* bl */
>> 
>> case 18 is more than 'bl', it includes also 'b'.
>> In both cases, the calculation of *immediate is the same.
> 
> It also is "ba" and "bla", sometimes written as "b[l][a]".
> 
>> It would therefore be more correct to perform the calculation and setup 
>> of *immediate outside the 'if ((insn & 3) == 1)', that would avoid 
>> unnecessary churn the day we add support for branches without link.

Yeah, and probably move the comments around:

+	case 18: /* b[l][a] */
+		if ((insn & 3) == 1) { /* bl */

>> 
>> > +		if ((insn & 3) == 1) {
>> > +			*type = INSN_CALL;
>> > +			*immediate = insn & 0x3fffffc;
>> > +			if (*immediate & 0x2000000)
>> > +				*immediate -= 0x4000000;
>> > +		}
>> > +		break;
>> > +	}
> 
> Does this handle AA=1 correctly at all?  That is valid both with and
> without relocations, just like AA=0.  Same for AA=1 LK=0 btw.
> 
> If you only handle AA=0, the code should explicitly test for that.

The code does test for AA=0 LK=1 with the if statement there?


- Naveen
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Segher Boessenkool 3 years, 7 months ago 
Hi!

On Mon, Sep 05, 2022 at 04:15:07PM +0530, Naveen N. Rao wrote:
> Segher Boessenkool wrote:
> >>> +		if ((insn & 3) == 1) {
> >>> +			*type = INSN_CALL;
> >>> +			*immediate = insn & 0x3fffffc;
> >>> +			if (*immediate & 0x2000000)
> >>> +				*immediate -= 0x4000000;
> >>> +		}
> >>> +		break;
> >>> +	}
> >
> >Does this handle AA=1 correctly at all?  That is valid both with and
> >without relocations, just like AA=0.  Same for AA=1 LK=0 btw.
> >
> >If you only handle AA=0, the code should explicitly test for that.
> 
> The code does test for AA=0 LK=1 with the if statement there?

Yes, but that is not what I said :-)

It may be fine to not *handle* AA=1 at all, but the code should at least
scream bloody murder when it encounters it anyway :-)


Segher
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Christophe Leroy 3 years, 7 months ago 

Le 05/09/2022 à 22:43, Segher Boessenkool a écrit :
> Hi!
> 
> On Mon, Sep 05, 2022 at 04:15:07PM +0530, Naveen N. Rao wrote:
>> Segher Boessenkool wrote:
>>>>> +		if ((insn & 3) == 1) {
>>>>> +			*type = INSN_CALL;
>>>>> +			*immediate = insn & 0x3fffffc;
>>>>> +			if (*immediate & 0x2000000)
>>>>> +				*immediate -= 0x4000000;
>>>>> +		}
>>>>> +		break;
>>>>> +	}
>>>
>>> Does this handle AA=1 correctly at all?  That is valid both with and
>>> without relocations, just like AA=0.  Same for AA=1 LK=0 btw.
>>>
>>> If you only handle AA=0, the code should explicitly test for that.
>>
>> The code does test for AA=0 LK=1 with the if statement there?
> 
> Yes, but that is not what I said :-)
> 
> It may be fine to not *handle* AA=1 at all, but the code should at least
> scream bloody murder when it encounters it anyway :-)
> 


By the way, I proposed a cleanup patch that handles it, see 
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/ebe11b73d1015a17034a2c4bedf093fa57f5d29f.1662032631.git.christophe.leroy@csgroup.eu/

Christophe
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
Posted by Christophe Leroy 3 years, 7 months ago 

Le 29/08/2022 à 07:52, Sathvika Vasireddy a écrit :
> This patch enables objtool --mcount on powerpc, and
> adds implementation specific to powerpc.
> 
> Signed-off-by: Sathvika Vasireddy <sv@linux.ibm.com>
> ---
>   arch/powerpc/Kconfig                          |  1 +
>   tools/objtool/arch/powerpc/decode.c           | 22 +++++++++++++++++++
>   tools/objtool/arch/powerpc/include/arch/elf.h |  2 ++
>   3 files changed, 25 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index dc05cd23c233..6be2e68fa9eb 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -238,6 +238,7 @@ config PPC
>   	select HAVE_NMI				if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
>   	select HAVE_OPTPROBES
>   	select HAVE_OBJTOOL			if PPC32 || MPROFILE_KERNEL
> +	select HAVE_OBJTOOL_MCOUNT		if HAVE_OBJTOOL
>   	select HAVE_PERF_EVENTS
>   	select HAVE_PERF_EVENTS_NMI		if PPC64
>   	select HAVE_PERF_REGS
> diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
> index 8b6a14680da7..b71c265ed503 100644
> --- a/tools/objtool/arch/powerpc/decode.c
> +++ b/tools/objtool/arch/powerpc/decode.c
> @@ -9,6 +9,14 @@
>   #include <objtool/builtin.h>
>   #include <objtool/endianness.h>
>   
> +bool arch_ftrace_match(char *name)
> +{
> +	if (!strcmp(name, "_mcount"))
> +		return true;
> +
> +	return false;

Same as for x86, could be:

	return !strcmp(name, "_mcount");




Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>




> +}
> +
>   unsigned long arch_dest_reloc_offset(int addend)
>   {
>   	return addend;
> @@ -41,12 +49,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
>   			    struct list_head *ops_list)
>   {
>   	u32 insn;
> +	unsigned int opcode;
>   
>   	*immediate = 0;
>   	insn = bswap_if_needed(file->elf, *(u32 *)(sec->data->d_buf + offset));
>   	*len = 4;
>   	*type = INSN_OTHER;
>   
> +	opcode = insn >> 26;
> +
> +	switch (opcode) {
> +	case 18: /* bl */
> +		if ((insn & 3) == 1) {
> +			*type = INSN_CALL;
> +			*immediate = insn & 0x3fffffc;
> +			if (*immediate & 0x2000000)
> +				*immediate -= 0x4000000;
> +		}
> +		break;
> +	}
> +
>   	return 0;
>   }
>   
> diff --git a/tools/objtool/arch/powerpc/include/arch/elf.h b/tools/objtool/arch/powerpc/include/arch/elf.h
> index 3c8ebb7d2a6b..73f9ae172fe5 100644
> --- a/tools/objtool/arch/powerpc/include/arch/elf.h
> +++ b/tools/objtool/arch/powerpc/include/arch/elf.h
> @@ -4,5 +4,7 @@
>   #define _OBJTOOL_ARCH_ELF
>   
>   #define R_NONE R_PPC_NONE
> +#define R_ABS64 R_PPC64_ADDR64
> +#define R_ABS32 R_PPC_ADDR32
>   
>   #endif /* _OBJTOOL_ARCH_ELF */

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