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Commit 008d7a91 authored by Rusty Russell's avatar Rusty Russell Committed by Anton Blanchard
Browse files

powerpc: modules: implement stubs for ELFv2 ABI. 



ELFv2 doesn't use function descriptors, because it doesn't need to
load a new r2 when calling into a function.  On the other hand, you're
supposed to use a local entry point for R_PPC_REL24 branches.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 5c729a11

arch/powerpc/kernel/module_64.c

+61 −12
Original line number Diff line number Diff line
@@ -43,8 +43,58 @@ 


#if defined(_CALL_ELF) && _CALL_ELF == 2

#define R2_STACK_OFFSET 24



/* An address is simply the address of the function. */

typedef unsigned long func_desc_t;



static func_desc_t func_desc(unsigned long addr)

{

	return addr;

}

static unsigned long func_addr(unsigned long addr)

{

	return addr;

}

static unsigned long stub_func_addr(func_desc_t func)

{

	return func;

}



/* PowerPC64 specific values for the Elf64_Sym st_other field.  */

#define STO_PPC64_LOCAL_BIT	5

#define STO_PPC64_LOCAL_MASK	(7 << STO_PPC64_LOCAL_BIT)

#define PPC64_LOCAL_ENTRY_OFFSET(other)					\

 (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)



static unsigned int local_entry_offset(const Elf64_Sym *sym)

{

	/* sym->st_other indicates offset to local entry point

	 * (otherwise it will assume r12 is the address of the start

	 * of function and try to derive r2 from it). */

	return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);

}

#else

#define R2_STACK_OFFSET 40



/* An address is address of the OPD entry, which contains address of fn. */

typedef struct ppc64_opd_entry func_desc_t;



static func_desc_t func_desc(unsigned long addr)

{

	return *(struct ppc64_opd_entry *)addr;

}

static unsigned long func_addr(unsigned long addr)

{

	return func_desc(addr).funcaddr;

}

static unsigned long stub_func_addr(func_desc_t func)

{

	return func.funcaddr;

}

static unsigned int local_entry_offset(const Elf64_Sym *sym)

{

	return 0;

}

#endif



/* Like PPC32, we need little trampolines to do > 24-bit jumps (into
@@ -56,7 +106,7 @@ struct ppc64_stub_entry 
	u32 jump[7];

	u32 unused;

	/* Data for the above code */

	struct ppc64_opd_entry opd;

	func_desc_t funcdata;

};



/*
@@ -225,7 +275,7 @@ static Elf64_Sym *find_dot_toc(Elf64_Shdr *sechdrs, 


	for (i = 1; i < numsyms; i++) {

		if (syms[i].st_shndx == SHN_UNDEF

		    && strcmp(strtab + syms[i].st_name, ".TOC.") == 0)

		    && strcmp(strtab + syms[i].st_name, "TOC.") == 0)

			return &syms[i];

	}

	return NULL;
@@ -295,7 +345,7 @@ static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me) 
/* Patch stub to reference function and correct r2 value. */

static inline int create_stub(Elf64_Shdr *sechdrs,

			      struct ppc64_stub_entry *entry,

			      struct ppc64_opd_entry *opd,

			      unsigned long addr,

			      struct module *me)

{

	long reladdr;
@@ -313,33 +363,31 @@ static inline int create_stub(Elf64_Shdr *sechdrs, 


	entry->jump[0] |= PPC_HA(reladdr);

	entry->jump[1] |= PPC_LO(reladdr);

	entry->opd.funcaddr = opd->funcaddr;

	entry->opd.r2 = opd->r2;

	entry->funcdata = func_desc(addr);

	return 1;

}



/* Create stub to jump to function described in this OPD: we need the

/* Create stub to jump to function described in this OPD/ptr: we need the

   stub to set up the TOC ptr (r2) for the function. */

static unsigned long stub_for_addr(Elf64_Shdr *sechdrs,

				   unsigned long opdaddr,

				   unsigned long addr,

				   struct module *me)

{

	struct ppc64_stub_entry *stubs;

	struct ppc64_opd_entry *opd = (void *)opdaddr;

	unsigned int i, num_stubs;



	num_stubs = sechdrs[me->arch.stubs_section].sh_size / sizeof(*stubs);



	/* Find this stub, or if that fails, the next avail. entry */

	stubs = (void *)sechdrs[me->arch.stubs_section].sh_addr;

	for (i = 0; stubs[i].opd.funcaddr; i++) {

	for (i = 0; stub_func_addr(stubs[i].funcdata); i++) {

		BUG_ON(i >= num_stubs);



		if (stubs[i].opd.funcaddr == opd->funcaddr)

		if (stub_func_addr(stubs[i].funcdata) == func_addr(addr))

			return (unsigned long)&stubs[i];

	}



	if (!create_stub(sechdrs, &stubs[i], opd, me))

	if (!create_stub(sechdrs, &stubs[i], addr, me))

		return 0;



	return (unsigned long)&stubs[i];
@@ -480,7 +528,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, 
					return -ENOENT;

				if (!restore_r2((u32 *)location + 1, me))

					return -ENOEXEC;

			}

			} else

				value += local_entry_offset(sym);



			/* Convert value to relative */

			value -= (unsigned long)location;