Re: [PATCH v6 3/7] ftrace: Add arm64 support to recordmcount

[AKASHI Takahiro]

On 03/13/2014 09:38 PM, Will Deacon wrote:
> On Thu, Mar 13, 2014 at 10:13:46AM +0000, AKASHI Takahiro wrote:
> > Recordmcount utility under scripts is run, after compiling each object,
> > to find out all the locations of calling _mcount() and put them into
> > specific seciton named __mcount_loc.
> > Then linker collects all such information into a table in the kernel image
> > (between __start_mcount_loc and __stop_mcount_loc) for later use by ftrace.
> >
> > This patch adds arm64 specific definitions to identify such locations.
> > There are two types of implementation, C and Perl. On arm64, only C version
> > is used to build the kernel now that CONFIG_HAVE_C_RECORDMCOUNT is on.
> > But Perl version is also maintained.
> >
> > This patch also contains a workaround just in case where a header file,
> > elf.h, on host machine doesn't have definitions of EM_AARCH64 nor
> > R_AARCH64_ABS64. Without them, compiling C version of recordmcount will
> > fail.
>
> [...]
>
> > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> > index 9c22317..047c8cd 100644
> > --- a/scripts/recordmcount.c
> > +++ b/scripts/recordmcount.c
> > @@ -40,6 +40,11 @@
> >   #define R_METAG_NONE                     3
> >   #endif
> >
> > +#ifndef EM_AARCH64
> > +#define EM_AARCH64	183
> > +#define R_AARCH64_ABS64	257
> > +#endif
> > +
> >   static int fd_map;	/* File descriptor for file being modified. */
> >   static int mmap_failed; /* Boolean flag. */
> >   static void *ehdr_curr; /* current ElfXX_Ehdr *  for resource cleanup */
> > @@ -347,6 +352,10 @@ do_file(char const *const fname)
> >   	case EM_ARM:	 reltype = R_ARM_ABS32;
> >   			 altmcount = "__gnu_mcount_nc";
> >   			 break;
> > +	case EM_AARCH64:
> > +			 reltype = R_AARCH64_ABS64;
> > +			 altmcount = "_mcount";
>
> Shouldn't you be setting gpfx = '_' instead of overriding altmcount like
> this?

Yep. Fix it.

> > +			 break;
> >   	case EM_IA_64:	 reltype = R_IA64_IMM64;   gpfx = '_'; break;
> >   	case EM_METAG:	 reltype = R_METAG_ADDR32;
> >   			 altmcount = "_mcount_wrapper";
> > diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> > index 91280b8..397b6b8 100755
> > --- a/scripts/recordmcount.pl
> > +++ b/scripts/recordmcount.pl
> > @@ -279,6 +279,11 @@ if ($arch eq "x86_64") {
> >       $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_ARM_(CALL|PC24|THM_CALL)" .
> >   			"\\s+(__gnu_mcount_nc|mcount)\$";
> >
> > +} elsif ($arch eq "arm64") {
> > +    $alignment = 3;
> > +    $section_type = '%progbits';
> > +    $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_AARCH64_CALL26\\s+_mcount\$";
>
> What about "mcount" (i.e. no underscore)?

I don't think it works since such regex doesn't match to "CALL26   _mcount".

Thanks,
-Takahiro AKASHI

> Will
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