On Wed, 28 Oct 2015 16:04:05 +0800
Li Bin <huawei.li...@huawei.com> wrote:
> By now, the recordmcount only records the function that in
> following sections:
> .text/.ref.text/.sched.text/.spinlock.text/.irqentry.text/
> .kprobes.text/.text.unlikely
>
> For the function that not in these sections, the call mcount
> will be in place and not be replaced when kernel boot up. And
> it will bring performance overhead, such as do_mem_abort (in
> .exception.text section). This patch make the call mcount to
> nop for this case in recordmcount.
I can take this in my tree with an Ack from the ARM64 maintainers.
-- Steve
>
> Signed-off-by: Li Bin <huawei.li...@huawei.com>
> ---
> scripts/recordmcount.c | 23 ++++++++++++++++++++++-
> 1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> index 3d1984e..f697226 100644
> --- a/scripts/recordmcount.c
> +++ b/scripts/recordmcount.c
> @@ -42,6 +42,7 @@
>
> #ifndef EM_AARCH64
> #define EM_AARCH64 183
> +#define R_AARCH64_NONE 0
> #define R_AARCH64_ABS64 257
> #endif
>
> @@ -160,6 +161,21 @@ static int make_nop_x86(void *map, size_t const offset)
> return 0;
> }
>
> +static unsigned char ideal_nop4_arm64[4] = {0x1f, 0x20, 0x03, 0xd5};
> +static int make_nop_arm64(void *map, size_t const offset)
> +{
> + uint32_t *ptr;
> +
> + ptr = map + offset;
> + if (*ptr != 0x94000000)
> + return -1;
> +
> + /* Convert to nop */
> + ulseek(fd_map, offset, SEEK_SET);
> + uwrite(fd_map, ideal_nop, 4);
> + return 0;
> +}
> +
> /*
> * Get the whole file as a programming convenience in order to avoid
> * malloc+lseek+read+free of many pieces. If successful, then mmap
> @@ -353,7 +369,12 @@ do_file(char const *const fname)
> altmcount = "__gnu_mcount_nc";
> break;
> case EM_AARCH64:
> - reltype = R_AARCH64_ABS64; gpfx = '_'; break;
> + reltype = R_AARCH64_ABS64;
> + make_nop = make_nop_arm64;
> + rel_type_nop = R_AARCH64_NONE;
> + ideal_nop = ideal_nop4_arm64;
> + gpfx = '_';
> + break;
> case EM_IA_64: reltype = R_IA64_IMM64; gpfx = '_'; break;
> case EM_METAG: reltype = R_METAG_ADDR32;
> altmcount = "_mcount_wrapper";
--
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