Commit 4ef57b21 authored by Sami Tolvanen's avatar Sami Tolvanen Committed by Steven Rostedt (VMware)
Browse files

recordmcount: support >64k sections 

When compiling a kernel with Clang and LTO, we need to run
recordmcount on vmlinux.o with a large number of sections, which
currently fails as the program doesn't understand extended
section indexes. This change adds support for processing binaries
with >64k sections.

Link: https://lkml.kernel.org/r/20200424193046.160744-1-samitolvanen@google.com
Link: https://lore.kernel.org/lkml/CAK7LNARbZhoaA=Nnuw0=gBrkuKbr_4Ng_Ei57uafujZf7Xazgw@mail.gmail.com/



Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: default avatarMatt Helsley <mhelsley@vmware.com>
Signed-off-by: default avatarSami Tolvanen <samitolvanen@google.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent b3a9e3b9

scripts/recordmcount.h

+92 −6
Original line number Diff line number Diff line
@@ -29,6 +29,11 @@ 
#undef has_rel_mcount

#undef tot_relsize

#undef get_mcountsym

#undef find_symtab

#undef get_shnum

#undef set_shnum

#undef get_shstrndx

#undef get_symindex

#undef get_sym_str_and_relp

#undef do_func

#undef Elf_Addr
@@ -58,6 +63,11 @@ 
# define __has_rel_mcount	__has64_rel_mcount

# define has_rel_mcount		has64_rel_mcount

# define tot_relsize		tot64_relsize

# define find_symtab		find_symtab64

# define get_shnum		get_shnum64

# define set_shnum		set_shnum64

# define get_shstrndx		get_shstrndx64

# define get_symindex		get_symindex64

# define get_sym_str_and_relp	get_sym_str_and_relp_64

# define do_func		do64

# define get_mcountsym		get_mcountsym_64
@@ -91,6 +101,11 @@ 
# define __has_rel_mcount	__has32_rel_mcount

# define has_rel_mcount		has32_rel_mcount

# define tot_relsize		tot32_relsize

# define find_symtab		find_symtab32

# define get_shnum		get_shnum32

# define set_shnum		set_shnum32

# define get_shstrndx		get_shstrndx32

# define get_symindex		get_symindex32

# define get_sym_str_and_relp	get_sym_str_and_relp_32

# define do_func		do32

# define get_mcountsym		get_mcountsym_32
@@ -173,6 +188,67 @@ static int MIPS_is_fake_mcount(Elf_Rel const *rp) 
	return is_fake;

}



static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab,

				 Elf32_Word const *symtab_shndx)

{

	unsigned long offset;

	int index;



	if (sym->st_shndx != SHN_XINDEX)

		return w2(sym->st_shndx);



	offset = (unsigned long)sym - (unsigned long)symtab;

	index = offset / sizeof(*sym);



	return w(symtab_shndx[index]);

}



static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)

{

	if (shdr0 && !ehdr->e_shnum)

		return w(shdr0->sh_size);



	return w2(ehdr->e_shnum);

}



static void set_shnum(Elf_Ehdr *ehdr, Elf_Shdr *shdr0, unsigned int new_shnum)

{

	if (new_shnum >= SHN_LORESERVE) {

		ehdr->e_shnum = 0;

		shdr0->sh_size = w(new_shnum);

	} else

		ehdr->e_shnum = w2(new_shnum);

}



static int get_shstrndx(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)

{

	if (ehdr->e_shstrndx != SHN_XINDEX)

		return w2(ehdr->e_shstrndx);



	return w(shdr0->sh_link);

}



static void find_symtab(Elf_Ehdr *const ehdr, Elf_Shdr const *shdr0,

			unsigned const nhdr, Elf32_Word **symtab,

			Elf32_Word **symtab_shndx)

{

	Elf_Shdr const *relhdr;

	unsigned k;



	*symtab = NULL;

	*symtab_shndx = NULL;



	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {

		if (relhdr->sh_type == SHT_SYMTAB)

			*symtab = (void *)ehdr + relhdr->sh_offset;

		else if (relhdr->sh_type == SHT_SYMTAB_SHNDX)

			*symtab_shndx = (void *)ehdr + relhdr->sh_offset;



		if (*symtab && *symtab_shndx)

			break;

	}

}



/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */

static int append_func(Elf_Ehdr *const ehdr,

			Elf_Shdr *const shstr,
@@ -188,10 +264,12 @@ static int append_func(Elf_Ehdr *const ehdr, 
	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);

	Elf_Shdr *const shdr0 = (Elf_Shdr *)(old_shoff + (void *)ehdr);

	unsigned int const old_shnum = get_shnum(ehdr, shdr0);

	unsigned int const new_shnum = 2 + old_shnum; /* {.rel,}__mcount_loc */

	uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);

	uint_t new_e_shoff;
@@ -201,6 +279,8 @@ static int append_func(Elf_Ehdr *const ehdr, 
	t += (_align & -t);  /* word-byte align */

	new_e_shoff = t;



	set_shnum(ehdr, shdr0, new_shnum);



	/* body for new shstrtab */

	if (ulseek(sb.st_size, SEEK_SET) < 0)

		return -1;
@@ -255,7 +335,6 @@ static int append_func(Elf_Ehdr *const ehdr, 
		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)
@@ -434,6 +513,8 @@ static int find_secsym_ndx(unsigned const txtndx, 
				uint_t *const recvalp,

				unsigned int *sym_index,

				Elf_Shdr const *const symhdr,

				Elf32_Word const *symtab,

				Elf32_Word const *symtab_shndx,

				Elf_Ehdr const *const ehdr)

{

	Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
@@ -445,7 +526,7 @@ static int find_secsym_ndx(unsigned const txtndx, 
	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)

		if (txtndx == get_symindex(symp, symtab, symtab_shndx)

			/* avoid STB_WEAK */

		    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {

			/* function symbols on ARM have quirks, avoid them */
@@ -516,21 +597,23 @@ static unsigned tot_relsize(Elf_Shdr const *const shdr0, 
	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)];

	unsigned const nhdr = get_shnum(ehdr, shdr0);

	Elf_Shdr *const shstr = &shdr0[get_shstrndx(ehdr, shdr0)];

	char const *const shstrtab = (char const *)(_w(shstr->sh_offset)

		+ (void *)ehdr);



	Elf_Shdr const *relhdr;

	unsigned k;



	Elf32_Word *symtab;

	Elf32_Word *symtab_shndx;



	/* Upper bound on space: assume all relevant relocs are for mcount. */

	unsigned       totrelsz;
@@ -561,6 +644,8 @@ static int do_func(Elf_Ehdr *const ehdr, char const *const fname, 
		return -1;

	}



	find_symtab(ehdr, shdr0, nhdr, &symtab, &symtab_shndx);



	for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {

		char const *const txtname = has_rel_mcount(relhdr, shdr0,

			shstrtab, fname);
@@ -577,6 +662,7 @@ static int do_func(Elf_Ehdr *const ehdr, char const *const fname, 
			result = find_secsym_ndx(w(relhdr->sh_info), txtname,

						&recval, &recsym,

						&shdr0[symsec_sh_link],

						symtab, symtab_shndx,

						ehdr);

			if (result)

				goto out;

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