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linux/scripts/recordmcount.h
Matt Helsley c97fea2625 recordmcount: Remove redundant cleanup() calls 
Redundant cleanup calls were introduced when transitioning from
the old error/success handling via setjmp/longjmp -- the longjmp
ensured the cleanup() call only happened once but replacing
the success_file()/fail_file() calls with cleanup() meant that
multiple cleanup() calls can happen as we return from function
calls.

In do_file(), looking just before and after the "goto out" jumps we
can see that multiple cleanups() are being performed. We remove
cleanup() calls from the nested functions because it makes the code
easier to review -- the resources being cleaned up are generally
allocated and initialized in the callers so freeing them there
makes more sense.

Other redundant cleanup() calls:

mmap_file() is only called from do_file() and, if mmap_file() fails,
then we goto out and do cleanup() there too.

write_file() is only called from do_file() and do_file()
calls cleanup() unconditionally after returning from write_file()
therefore the cleanup() calls in write_file() are not necessary.

find_secsym_ndx(), called from do_func()'s for-loop, when we are
cleaning up here it's obvious that we break out of the loop and
do another cleanup().

__has_rel_mcount() is called from two parts of do_func()
and calls cleanup(). In theory we move them into do_func(), however
these in turn prove redundant so another simplification step
removes them as well.

Link: http://lkml.kernel.org/r/de197e17fc5426623a847ea7cf3a1560a7402a4b.1564596289.git.mhelsley@vmware.com

Signed-off-by: Matt Helsley <mhelsley@vmware.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2019-08-31 12:19:40 -04:00

610 lines
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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 int 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 */
if (ulseek(sb.st_size, SEEK_SET) < 0)
return -1;
if (uwrite(old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size) < 0)
return -1;
if (uwrite(mc_name, 1 + strlen(mc_name)) < 0)
return -1;
/* old(modified) Elf_Shdr table, word-byte aligned */
if (ulseek(t, SEEK_SET) < 0)
return -1;
t += sizeof(Elf_Shdr) * old_shnum;
if (uwrite(old_shoff + (void *)ehdr,
sizeof(Elf_Shdr) * old_shnum) < 0)
return -1;
/* 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);
if (uwrite(&mcsec, sizeof(mcsec)) < 0)
return -1;
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);
if (uwrite(&mcsec, sizeof(mcsec)) < 0)
return -1;
if (uwrite(mloc0, (void *)mlocp - (void *)mloc0) < 0)
return -1;
if (uwrite(mrel0, (void *)mrelp - (void *)mrel0) < 0)
return -1;
ehdr->e_shoff = _w(new_e_shoff);
ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */
if (ulseek(0, SEEK_SET) < 0)
return -1;
if (uwrite(ehdr, sizeof(*ehdr)) < 0)
return -1;
return 0;
}
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 && 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 int 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 (ret < 0)
return -1;
}
if (warn_on_notrace_sect && !once) {
printf("Section %s has mcount callers being ignored\n",
txtname);
once = 1;
/* just warn? */
if (!make_nop)
return 0;
}
}
/*
* 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);
if (ulseek((void *)relp - (void *)ehdr, SEEK_SET) < 0)
return -1;
if (uwrite(&rel, sizeof(rel)) < 0)
return -1;
}
relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
}
return 0;
}
/*
* 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 int find_secsym_ndx(unsigned const txtndx,
char const *const txtname,
uint_t *const recvalp,
unsigned int *sym_index,
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);
*sym_index = symp - sym0;
return 0;
}
}
fprintf(stderr, "Cannot find symbol for section %u: %s.\n",
txtndx, txtname);
return -1;
}
/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */
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);
return already_has_rel_mcount;
}
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 == already_has_rel_mcount) {
totrelsz = 0;
break;
}
if (txtname && is_mcounted_section_name(txtname))
totrelsz += _w(shdrp->sh_size);
}
return totrelsz;
}
/* Overall supervision for Elf32 ET_REL file. */
static int 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 totrelsz;
Elf_Rel * mrel0;
Elf_Rel * mrelp;
uint_t * mloc0;
uint_t * mlocp;
unsigned rel_entsize = 0;
unsigned symsec_sh_link = 0;
int result = 0;
totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
if (totrelsz == 0)
return 0;
mrel0 = umalloc(totrelsz);
mrelp = mrel0;
if (!mrel0)
return -1;
/* 2*sizeof(address) <= sizeof(Elf_Rel) */
mloc0 = umalloc(totrelsz>>1);
mlocp = mloc0;
if (!mloc0) {
free(mrel0);
return -1;
}
for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
char const *const txtname = has_rel_mcount(relhdr, shdr0,
shstrtab, fname);
if (txtname == already_has_rel_mcount) {
result = 0;
file_updated = 0;
goto out; /* Nothing to be done; don't append! */
}
if (txtname && is_mcounted_section_name(txtname)) {
unsigned int recsym;
uint_t recval = 0;
symsec_sh_link = w(relhdr->sh_link);
result = find_secsym_ndx(w(relhdr->sh_info), txtname,
&recval, &recsym,
&shdr0[symsec_sh_link],
ehdr);
if (result)
goto out;
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.
*/
if (nop_mcount(relhdr, ehdr, txtname) < 0) {
result = -1;
goto out;
}
}
}
if (!result && mloc0 != mlocp)
result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
rel_entsize, symsec_sh_link);
out:
free(mrel0);
free(mloc0);
return result;
}
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