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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: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2014-03-19 10:42:22 +10:30 committed by Anton Blanchard
parent 5c729a115e
commit 008d7a914e
1 changed files with 61 additions and 12 deletions
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73
arch/powerpc/kernel/module_64.c
View File

@ -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;