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linux/scripts/recordmcount.h

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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* 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.
*/
#undef append_func
#undef is_fake_mcount
#undef fn_is_fake_mcount
#undef MIPS_is_fake_mcount
#undef mcount_adjust
#undef sift_rel_mcount
#undef nop_mcount
#undef find_secsym_ndx
#undef __has_rel_mcount
#undef has_rel_mcount
#undef tot_relsize
#undef get_mcountsym
#undef get_sym_str_and_relp
#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 ELF_ST_TYPE
#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 nop_mcount nop_mcount_64
# 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 get_sym_str_and_relp get_sym_str_and_relp_64
# define do_func do64
# define get_mcountsym get_mcountsym_64
# 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 mcount_adjust mcount_adjust_64
# 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 ELF_ST_TYPE ELF64_ST_TYPE
# 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 nop_mcount nop_mcount_32
# 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 get_sym_str_and_relp get_sym_str_and_relp_32
# define do_func do32
# define get_mcountsym get_mcountsym_32
# 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 mcount_adjust mcount_adjust_32
# 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 ELF_ST_TYPE ELF32_ST_TYPE
# 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 = _w(ELF_R_INFO(sym, type));
}
static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
static int mcount_adjust = 0;
/*
* 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)0;
Elf_Addr current_r_offset = _w(rp->r_offset);
int is_fake;
is_fake = (old_r_offset != ~(Elf_Addr)0) &&
(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));
}
static unsigned get_mcountsym(Elf_Sym const *const sym0,
Elf_Rel const *relp,
char const *const str0)
{
unsigned mcountsym = 0;
Elf_Sym const *const symp =
&sym0[Elf_r_sym(relp)];
char const *symname = &str0[w(symp->st_name)];
char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
char const *fentry = "__fentry__";
if (symname[0] == '.')
++symname; /* ppc64 hack */
if (strcmp(mcount, symname) == 0 ||
(altmcount && strcmp(altmcount, symname) == 0) ||
(strcmp(fentry, symname) == 0))
mcountsym = Elf_r_sym(relp);
return mcountsym;
}
static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
Elf_Ehdr const *const ehdr,
Elf_Sym const **sym0,
char const **str0,
Elf_Rel const **relp)
{
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_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
+ (void *)ehdr);
*sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
+ (void *)ehdr);
*str0 = (char const *)(_w(strsec->sh_offset)
+ (void *)ehdr);
*relp = rel0;
}
/*
* 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_Sym const *sym0;
char const *str0;
Elf_Rel const *relp;
unsigned rel_entsize = _w(relhdr->sh_entsize);
unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
unsigned mcountsym = 0;
unsigned t;
get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
for (t = nrel; t; --t) {
if (!mcountsym)
mcountsym = get_mcountsym(sym0, relp, str0);
if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
uint_t const addend =
_w(_w(relp->r_offset) - recval + mcount_adjust);
mrelp->r_offset = _w(offbase
+ ((void *)mlocp - (void *)mloc0));
Elf_r_info(mrelp, recsym, reltype);
if (rel_entsize == sizeof(Elf_Rela)) {
((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;
}
/*
* Read the relocation table again, but this time its called on sections
* that are not going to be traced. The mcount calls here will be converted
* into nops.
*/
static void nop_mcount(Elf_Shdr const *const relhdr,
Elf_Ehdr const *const ehdr,
const char *const txtname)
{
Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
+ (void *)ehdr);
Elf_Sym const *sym0;
char const *str0;
Elf_Rel const *relp;
Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)];
unsigned rel_entsize = _w(relhdr->sh_entsize);
unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
unsigned mcountsym = 0;
unsigned t;
int once = 0;
get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
for (t = nrel; t; --t) {
int ret = -1;
if (!mcountsym)
mcountsym = get_mcountsym(sym0, relp, str0);
if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
if (make_nop)
ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset));
if (warn_on_notrace_sect && !once) {
printf("Section %s has mcount callers being ignored\n",
txtname);
once = 1;
/* just warn? */
if (!make_nop)
return;
}
}
/*
* If we successfully removed the mcount, mark the relocation
* as a nop (don't do anything with it).
*/
if (!ret) {
Elf_Rel rel;
rel = *(Elf_Rel *)relp;
Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET);
uwrite(fd_map, &rel, sizeof(rel));
}
relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
}
}
/*
* 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)) {
/* function symbols on ARM have quirks, avoid them */
if (w2(ehdr->e_machine) == EM_ARM
&& ELF_ST_TYPE(symp->st_info) == STT_FUNC)
continue;
*recvalp = _w(symp->st_value);
return symp - sym0;
}
}
fprintf(stderr, "Cannot find symbol for section %u: %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 (strcmp("__mcount_loc", txtname) == 0) {
fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
fname);
succeed_file();
}
if (w(txthdr->sh_type) != SHT_PROGBITS ||
!(_w(txthdr->sh_flags) & SHF_EXECINSTR))
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 (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
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;
char const *txtname;
for (; nhdr; --nhdr, ++shdrp) {
txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
if (txtname && is_mcounted_section_name(txtname))
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 && is_mcounted_section_name(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);
} else if (txtname && (warn_on_notrace_sect || make_nop)) {
/*
* This section is ignored by ftrace, but still
* has mcount calls. Convert them to nops now.
*/
nop_mcount(relhdr, ehdr, txtname);
}
}
if (mloc0 != mlocp) {
append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
rel_entsize, symsec_sh_link);
}
free(mrel0);
free(mloc0);
}
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