Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
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 & 0x3fc;
> + if (*immediate & 0x200)
> + *immediate -= 0x400;
> + }
> + 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.le...@csgroup.eu/
Christophe
Re: [PATCH v2 16/16] objtool/powerpc: Add --mcount specific implementation
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 & 0x3fc;
> >>> + if (*immediate & 0x200)
> >>> + *immediate -= 0x400;
> >>> + }
> >>> + 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
Segher Boessenkool wrote:
On Wed, Aug 31, 2022 at 12:50:07PM +, 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 & 0x3fc;
> + if (*immediate & 0x200)
> + *immediate -= 0x400;
> + }
> + 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
On Wed, Aug 31, 2022 at 12:50:07PM +, 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 & 0x3fc;
> > + if (*immediate & 0x200)
> > + *immediate -= 0x400;
> > + }
> > + 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
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
> ---
> 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
> #include
>
> +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 & 0x3fc;
> + if (*immediate & 0x200)
> + *immediate -= 0x400;
> + }
> + 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
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
> ---
> 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
> #include
>
> +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
> +}
> +
> 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 & 0x3fc;
> + if (*immediate & 0x200)
> + *immediate -= 0x400;
> + }
> + 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 */
