| Message ID | 1446193864-24593-4-git-send-email-huawei.libin@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
on 2015/10/30 16:31, Li Bin 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. > > Cc: <stable@vger.kernel.org> # 3.18+ > Signed-off-by: Li Bin <huawei.libin@huawei.com> Acked-by: Will Deacon <will.deacon@arm.com> https://lkml.org/lkml/2015/10/28/301 > --- > scripts/recordmcount.c | 24 +++++++++++++++++++++++- > 1 file changed, 23 insertions(+), 1 deletion(-) > > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c > index 8cc020b..698768b 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 +161,22 @@ 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; > + /* bl <_mcount> is 0x94000000 before relocation */ > + 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 > @@ -354,7 +371,12 @@ 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"; >
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 8cc020b..698768b 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 +161,22 @@ 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; + /* bl <_mcount> is 0x94000000 before relocation */ + 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 @@ -354,7 +371,12 @@ 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";
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. Cc: <stable@vger.kernel.org> # 3.18+ Signed-off-by: Li Bin <huawei.libin@huawei.com> --- scripts/recordmcount.c | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-)