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linux/scripts/recordmcount.h
Wu Zhangjin 412910cd04 ftrace/MIPS: Add module support for C version of recordmcount 
Since MIPS modules' address space differs from the core kernel space, to access
the _mcount in the core kernel, the kernel functions in modules must use long
call (-mlong-calls): load the _mcount address into one register and jump to the
address stored by the register:

 c:  3c030000        lui     v1,0x0  <-------->  b label
           c: R_MIPS_HI16  _mcount
           c: R_MIPS_NONE  *ABS*
           c: R_MIPS_NONE  *ABS*
10:  64630000        daddiu  v1,v1,0
          10: R_MIPS_LO16 _mcount
          10: R_MIPS_NONE *ABS*
          10: R_MIPS_NONE *ABS*
14:	03e0082d 	move	at,ra
18:	0060f809 	jalr	v1
label:

In the old Perl version of recordmcount, we only need to record the position of
the 1st R_MIPS_HI16 type of _mcount, and later, in ftrace_make_nop(), replace
the instruction in this position by a "b label" and in ftrace_make_call(),
replace it back.

But, the default C version of recordmcount records all of the _mcount symbols,
so, we must filter the 2nd _mcount like the Perl version of recordmcount does.

The C version of recordmcount copes with the symbols before they are linked, So
It doesn't know the type of the symbols and therefore can not filter the
symbols as the Perl version of recordmcount does. But as we can see above, the
2nd _mcount symbols of the long call alawys follows the 1st _mcount symbol of
the same long call, which means the offset from the 1st to the 2nd is fixed, it
is 0x10-0xc = 4 here, 4 is the length of the 1st load instruciton, for MIPS has
fixed length of instructions, this offset is always 4.

And as we know, the _mcount is inserted into the entry of every kernel
function, the offset between the other _mcount's is expected to be always
bigger than 4. So, to filter the 2ns _mcount symbol of the long call, we can
simply check the offset between two _mcount symbols, If it is 4, then, filter
the 2nd _mcount symbol.

To avoid touching too much code, an 'empty' function fn_is_fake_mcount() is
added for all of the archs, and the specific archs can override it via chaning
the function pointer: is_fake_mcount in do_file() with the e_machine. e.g. This
patch adds MIPS_is_fake_mcount() to override the default fn_is_fake_mcount()
pointed by is_fake_mcount.

This fn_is_fake_mcount() checks if the _mcount symbol is fake, e.g. the 2nd
_mcount symbol of the long call is fake, for there are 2 _mcount symbols mapped
to one real mcount call, so, one of them is fake and must be filtered.

This fn_is_fake_mcount() is called in sift_rel_mcount() after finding the
_mcount symbols and before adding the _mcount symbol into mrelp, so, it can
prevent the fake mcount symbol going into the last __mcount_loc table.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
LKML-Reference: <b866f0138224340a132d31861fa3f9300dee30ac.1288176026.git.wuzhangjin@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2010-10-29 19:08:55 +01:00

443 lines
13 KiB
C
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/*
* recordmcount.h
*
* This code was taken out of recordmcount.c written by
* Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved.
*
* The original code had the same algorithms for both 32bit
* and 64bit ELF files, but the code was duplicated to support
* the difference in structures that were used. This
* file creates a macro of everything that is different between
* the 64 and 32 bit code, such that by including this header
* twice we can create both sets of functions by including this
* header once with RECORD_MCOUNT_64 undefined, and again with
* it defined.
*
* This conversion to macros was done by:
* Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
*
* Licensed under the GNU General Public License, version 2 (GPLv2).
*/
#undef append_func
#undef is_fake_mcount
#undef fn_is_fake_mcount
#undef MIPS_is_fake_mcount
#undef sift_rel_mcount
#undef find_secsym_ndx
#undef __has_rel_mcount
#undef has_rel_mcount
#undef tot_relsize
#undef do_func
#undef Elf_Addr
#undef Elf_Ehdr
#undef Elf_Shdr
#undef Elf_Rel
#undef Elf_Rela
#undef Elf_Sym
#undef ELF_R_SYM
#undef Elf_r_sym
#undef ELF_R_INFO
#undef Elf_r_info
#undef ELF_ST_BIND
#undef fn_ELF_R_SYM
#undef fn_ELF_R_INFO
#undef uint_t
#undef _w
#undef _align
#undef _size
#ifdef RECORD_MCOUNT_64
# define append_func append64
# define sift_rel_mcount sift64_rel_mcount
# define find_secsym_ndx find64_secsym_ndx
# define __has_rel_mcount __has64_rel_mcount
# define has_rel_mcount has64_rel_mcount
# define tot_relsize tot64_relsize
# define do_func do64
# define is_fake_mcount is_fake_mcount64
# define fn_is_fake_mcount fn_is_fake_mcount64
# define MIPS_is_fake_mcount MIPS64_is_fake_mcount
# define Elf_Addr Elf64_Addr
# define Elf_Ehdr Elf64_Ehdr
# define Elf_Shdr Elf64_Shdr
# define Elf_Rel Elf64_Rel
# define Elf_Rela Elf64_Rela
# define Elf_Sym Elf64_Sym
# define ELF_R_SYM ELF64_R_SYM
# define Elf_r_sym Elf64_r_sym
# define ELF_R_INFO ELF64_R_INFO
# define Elf_r_info Elf64_r_info
# define ELF_ST_BIND ELF64_ST_BIND
# define fn_ELF_R_SYM fn_ELF64_R_SYM
# define fn_ELF_R_INFO fn_ELF64_R_INFO
# define uint_t uint64_t
# define _w w8
# define _align 7u
# define _size 8
#else
# define append_func append32
# define sift_rel_mcount sift32_rel_mcount
# define find_secsym_ndx find32_secsym_ndx
# define __has_rel_mcount __has32_rel_mcount
# define has_rel_mcount has32_rel_mcount
# define tot_relsize tot32_relsize
# define do_func do32
# define is_fake_mcount is_fake_mcount32
# define fn_is_fake_mcount fn_is_fake_mcount32
# define MIPS_is_fake_mcount MIPS32_is_fake_mcount
# define Elf_Addr Elf32_Addr
# define Elf_Ehdr Elf32_Ehdr
# define Elf_Shdr Elf32_Shdr
# define Elf_Rel Elf32_Rel
# define Elf_Rela Elf32_Rela
# define Elf_Sym Elf32_Sym
# define ELF_R_SYM ELF32_R_SYM
# define Elf_r_sym Elf32_r_sym
# define ELF_R_INFO ELF32_R_INFO
# define Elf_r_info Elf32_r_info
# define ELF_ST_BIND ELF32_ST_BIND
# define fn_ELF_R_SYM fn_ELF32_R_SYM
# define fn_ELF_R_INFO fn_ELF32_R_INFO
# define uint_t uint32_t
# define _w w
# define _align 3u
# define _size 4
#endif
/* Functions and pointers that do_file() may override for specific e_machine. */
static int fn_is_fake_mcount(Elf_Rel const *rp)
{
return 0;
}
static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
{
return ELF_R_SYM(_w(rp->r_info));
}
static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
{
rp->r_info = ELF_R_INFO(sym, type);
}
static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
/*
* MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
* _mcount symbol is needed for dynamic function tracer, with it, to disable
* tracing(ftrace_make_nop), the instruction in the position is replaced with
* the "b label" instruction, to enable tracing(ftrace_make_call), replace the
* instruction back. So, here, we set the 2nd one as fake and filter it.
*
* c: 3c030000 lui v1,0x0 <--> b label
* c: R_MIPS_HI16 _mcount
* c: R_MIPS_NONE *ABS*
* c: R_MIPS_NONE *ABS*
* 10: 64630000 daddiu v1,v1,0
* 10: R_MIPS_LO16 _mcount
* 10: R_MIPS_NONE *ABS*
* 10: R_MIPS_NONE *ABS*
* 14: 03e0082d move at,ra
* 18: 0060f809 jalr v1
* label:
*/
#define MIPS_FAKEMCOUNT_OFFSET 4
static int MIPS_is_fake_mcount(Elf_Rel const *rp)
{
static Elf_Addr old_r_offset;
Elf_Addr current_r_offset = _w(rp->r_offset);
int is_fake;
is_fake = old_r_offset &&
(current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
old_r_offset = current_r_offset;
return is_fake;
}
/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
static void append_func(Elf_Ehdr *const ehdr,
Elf_Shdr *const shstr,
uint_t const *const mloc0,
uint_t const *const mlocp,
Elf_Rel const *const mrel0,
Elf_Rel const *const mrelp,
unsigned int const rel_entsize,
unsigned int const symsec_sh_link)
{
/* Begin constructing output file */
Elf_Shdr mcsec;
char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
? ".rela__mcount_loc"
: ".rel__mcount_loc";
unsigned const old_shnum = w2(ehdr->e_shnum);
uint_t const old_shoff = _w(ehdr->e_shoff);
uint_t const old_shstr_sh_size = _w(shstr->sh_size);
uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
uint_t new_e_shoff;
shstr->sh_size = _w(t);
shstr->sh_offset = _w(sb.st_size);
t += sb.st_size;
t += (_align & -t); /* word-byte align */
new_e_shoff = t;
/* body for new shstrtab */
ulseek(fd_map, sb.st_size, SEEK_SET);
uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size);
uwrite(fd_map, mc_name, 1 + strlen(mc_name));
/* old(modified) Elf_Shdr table, word-byte aligned */
ulseek(fd_map, t, SEEK_SET);
t += sizeof(Elf_Shdr) * old_shnum;
uwrite(fd_map, old_shoff + (void *)ehdr,
sizeof(Elf_Shdr) * old_shnum);
/* new sections __mcount_loc and .rel__mcount_loc */
t += 2*sizeof(mcsec);
mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
+ old_shstr_sh_size);
mcsec.sh_type = w(SHT_PROGBITS);
mcsec.sh_flags = _w(SHF_ALLOC);
mcsec.sh_addr = 0;
mcsec.sh_offset = _w(t);
mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
mcsec.sh_link = 0;
mcsec.sh_info = 0;
mcsec.sh_addralign = _w(_size);
mcsec.sh_entsize = _w(_size);
uwrite(fd_map, &mcsec, sizeof(mcsec));
mcsec.sh_name = w(old_shstr_sh_size);
mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
? w(SHT_RELA)
: w(SHT_REL);
mcsec.sh_flags = 0;
mcsec.sh_addr = 0;
mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
mcsec.sh_size = _w((void *)mrelp - (void *)mrel0);
mcsec.sh_link = w(symsec_sh_link);
mcsec.sh_info = w(old_shnum);
mcsec.sh_addralign = _w(_size);
mcsec.sh_entsize = _w(rel_entsize);
uwrite(fd_map, &mcsec, sizeof(mcsec));
uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0);
uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0);
ehdr->e_shoff = _w(new_e_shoff);
ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */
ulseek(fd_map, 0, SEEK_SET);
uwrite(fd_map, ehdr, sizeof(*ehdr));
}
/*
* Look at the relocations in order to find the calls to mcount.
* Accumulate the section offsets that are found, and their relocation info,
* onto the end of the existing arrays.
*/
static uint_t *sift_rel_mcount(uint_t *mlocp,
unsigned const offbase,
Elf_Rel **const mrelpp,
Elf_Shdr const *const relhdr,
Elf_Ehdr const *const ehdr,
unsigned const recsym,
uint_t const recval,
unsigned const reltype)
{
uint_t *const mloc0 = mlocp;
Elf_Rel *mrelp = *mrelpp;
Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
+ (void *)ehdr);
unsigned const symsec_sh_link = w(relhdr->sh_link);
Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
+ (void *)ehdr);
Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
char const *const str0 = (char const *)(_w(strsec->sh_offset)
+ (void *)ehdr);
Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
+ (void *)ehdr);
unsigned rel_entsize = _w(relhdr->sh_entsize);
unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
Elf_Rel const *relp = rel0;
unsigned mcountsym = 0;
unsigned t;
for (t = nrel; t; --t) {
if (!mcountsym) {
Elf_Sym const *const symp =
&sym0[Elf_r_sym(relp)];
char const *symname = &str0[w(symp->st_name)];
if ('.' == symname[0])
++symname; /* ppc64 hack */
if (0 == strcmp((('_' == gpfx) ? "_mcount" : "mcount"),
symname))
mcountsym = Elf_r_sym(relp);
}
if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
uint_t const addend = _w(_w(relp->r_offset) - recval);
mrelp->r_offset = _w(offbase
+ ((void *)mlocp - (void *)mloc0));
Elf_r_info(mrelp, recsym, reltype);
if (sizeof(Elf_Rela) == rel_entsize) {
((Elf_Rela *)mrelp)->r_addend = addend;
*mlocp++ = 0;
} else
*mlocp++ = addend;
mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
}
relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
}
*mrelpp = mrelp;
return mlocp;
}
/*
* Find a symbol in the given section, to be used as the base for relocating
* the table of offsets of calls to mcount. A local or global symbol suffices,
* but avoid a Weak symbol because it may be overridden; the change in value
* would invalidate the relocations of the offsets of the calls to mcount.
* Often the found symbol will be the unnamed local symbol generated by
* GNU 'as' for the start of each section. For example:
* Num: Value Size Type Bind Vis Ndx Name
* 2: 00000000 0 SECTION LOCAL DEFAULT 1
*/
static unsigned find_secsym_ndx(unsigned const txtndx,
char const *const txtname,
uint_t *const recvalp,
Elf_Shdr const *const symhdr,
Elf_Ehdr const *const ehdr)
{
Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
+ (void *)ehdr);
unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
Elf_Sym const *symp;
unsigned t;
for (symp = sym0, t = nsym; t; --t, ++symp) {
unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
if (txtndx == w2(symp->st_shndx)
/* avoid STB_WEAK */
&& (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
*recvalp = _w(symp->st_value);
return symp - sym0;
}
}
fprintf(stderr, "Cannot find symbol for section %d: %s.\n",
txtndx, txtname);
fail_file();
}
/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
static char const *
__has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */
Elf_Shdr const *const shdr0,
char const *const shstrtab,
char const *const fname)
{
/* .sh_info depends on .sh_type == SHT_REL[,A] */
Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
char const *const txtname = &shstrtab[w(txthdr->sh_name)];
if (0 == strcmp("__mcount_loc", txtname)) {
fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
fname);
succeed_file();
}
if (SHT_PROGBITS != w(txthdr->sh_type) ||
!is_mcounted_section_name(txtname))
return NULL;
return txtname;
}
static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
Elf_Shdr const *const shdr0,
char const *const shstrtab,
char const *const fname)
{
if (SHT_REL != w(relhdr->sh_type) && SHT_RELA != w(relhdr->sh_type))
return NULL;
return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
}
static unsigned tot_relsize(Elf_Shdr const *const shdr0,
unsigned nhdr,
const char *const shstrtab,
const char *const fname)
{
unsigned totrelsz = 0;
Elf_Shdr const *shdrp = shdr0;
for (; nhdr; --nhdr, ++shdrp) {
if (has_rel_mcount(shdrp, shdr0, shstrtab, fname))
totrelsz += _w(shdrp->sh_size);
}
return totrelsz;
}
/* Overall supervision for Elf32 ET_REL file. */
static void
do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype)
{
Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
+ (void *)ehdr);
unsigned const nhdr = w2(ehdr->e_shnum);
Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)];
char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
+ (void *)ehdr);
Elf_Shdr const *relhdr;
unsigned k;
/* Upper bound on space: assume all relevant relocs are for mcount. */
unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
Elf_Rel *const mrel0 = umalloc(totrelsz);
Elf_Rel * mrelp = mrel0;
/* 2*sizeof(address) <= sizeof(Elf_Rel) */
uint_t *const mloc0 = umalloc(totrelsz>>1);
uint_t * mlocp = mloc0;
unsigned rel_entsize = 0;
unsigned symsec_sh_link = 0;
for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
char const *const txtname = has_rel_mcount(relhdr, shdr0,
shstrtab, fname);
if (txtname) {
uint_t recval = 0;
unsigned const recsym = find_secsym_ndx(
w(relhdr->sh_info), txtname, &recval,
&shdr0[symsec_sh_link = w(relhdr->sh_link)],
ehdr);
rel_entsize = _w(relhdr->sh_entsize);
mlocp = sift_rel_mcount(mlocp,
(void *)mlocp - (void *)mloc0, &mrelp,
relhdr, ehdr, recsym, recval, reltype);
}
}
if (mloc0 != mlocp) {
append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
rel_entsize, symsec_sh_link);
}
free(mrel0);
free(mloc0);
}
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