Commit 136cd345 authored by Michael Ellerman's avatar Michael Ellerman

powerpc/module: Only try to generate the ftrace_caller() stub once

Currently we generate the module stub for ftrace_caller() at the bottom
of apply_relocate_add(). However apply_relocate_add() is potentially
called more than once per module, which means we will try to generate
the ftrace_caller() stub multiple times.

Although the current code deals with that correctly, ie. it only
generates a stub the first time, it would be clearer to only try to
generate the stub once.

Note also on first reading it may appear that we generate a different
stub for each section that requires relocation, but that is not the
case. The code in stub_for_addr() that searches for an existing stub
uses sechdrs[me->arch.stubs_section], ie. the single stub section for
this module.

A cleaner approach is to only generate the ftrace_caller() stub once,
from module_finalize(). Although the original code didn't check to see
if the stub was actually generated correctly, it seems prudent to add a
check, so do that. And an additional benefit is we can clean the ifdefs
up a little.

Finally we must propagate the const'ness of some of the pointers passed
to module_finalize(), but that is also an improvement.
Reviewed-by: default avatarBalbir Singh <bsingharora@gmail.com>
Reviewed-by: default avatarTorsten Duwe <duwe@suse.de>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent a5cab83c
......@@ -82,6 +82,15 @@ bool is_module_trampoline(u32 *insns);
int module_trampoline_target(struct module *mod, u32 *trampoline,
unsigned long *target);
#ifdef CONFIG_DYNAMIC_FTRACE
int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs);
#else
static inline int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
{
return 0;
}
#endif
struct exception_table_entry;
void sort_ex_table(struct exception_table_entry *start,
struct exception_table_entry *finish);
......
......@@ -47,6 +47,11 @@ int module_finalize(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs, struct module *me)
{
const Elf_Shdr *sect;
int rc;
rc = module_finalize_ftrace(me, sechdrs);
if (rc)
return rc;
/* Apply feature fixups */
sect = find_section(hdr, sechdrs, "__ftr_fixup");
......
......@@ -181,7 +181,7 @@ static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
/* Set up a trampoline in the PLT to bounce us to the distant function */
static uint32_t do_plt_call(void *location,
Elf32_Addr val,
Elf32_Shdr *sechdrs,
const Elf32_Shdr *sechdrs,
struct module *mod)
{
struct ppc_plt_entry *entry;
......@@ -294,11 +294,19 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
return -ENOEXEC;
}
}
return 0;
}
#ifdef CONFIG_DYNAMIC_FTRACE
module->arch.tramp =
do_plt_call(module->core_layout.base,
int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
{
module->arch.tramp = do_plt_call(module->core_layout.base,
(unsigned long)ftrace_caller,
sechdrs, module);
#endif
if (!module->arch.tramp)
return -ENOENT;
return 0;
}
#endif
......@@ -413,7 +413,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
/* r2 is the TOC pointer: it actually points 0x8000 into the TOC (this
gives the value maximum span in an instruction which uses a signed
offset) */
static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me)
static inline unsigned long my_r2(const Elf64_Shdr *sechdrs, struct module *me)
{
return sechdrs[me->arch.toc_section].sh_addr + 0x8000;
}
......@@ -426,7 +426,7 @@ static inline unsigned long my_r2(Elf64_Shdr *sechdrs, struct module *me)
#define PPC_HA(v) PPC_HI ((v) + 0x8000)
/* Patch stub to reference function and correct r2 value. */
static inline int create_stub(Elf64_Shdr *sechdrs,
static inline int create_stub(const Elf64_Shdr *sechdrs,
struct ppc64_stub_entry *entry,
unsigned long addr,
struct module *me)
......@@ -452,7 +452,7 @@ static inline int create_stub(Elf64_Shdr *sechdrs,
/* 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,
static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
unsigned long addr,
struct module *me)
{
......@@ -693,12 +693,18 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
}
}
return 0;
}
#ifdef CONFIG_DYNAMIC_FTRACE
me->arch.toc = my_r2(sechdrs, me);
me->arch.tramp = stub_for_addr(sechdrs,
(unsigned long)ftrace_caller,
me);
#endif
int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
{
mod->arch.toc = my_r2(sechdrs, mod);
mod->arch.tramp = stub_for_addr(sechdrs, (unsigned long)ftrace_caller, mod);
if (!mod->arch.tramp)
return -ENOENT;
return 0;
}
#endif
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