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powerpc64/ftrace: Implement support for ftrace_regs_caller()

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With -mprofile-kernel, we always save the full register state in
ftrace_caller(). While this works, this is inefficient if we're not
interested in the register state, such as when we're using the function
tracer.

Rename the existing ftrace_caller() as ftrace_regs_caller() and provide
a simpler implementation for ftrace_caller() that is used when registers
are not required to be saved.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao
2018-04-19 12:34:09 +05:30
committed by Michael Ellerman
parent 9ef4042364
commit ae30cc05be
5 changed files with 262 additions and 26 deletions
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28
arch/powerpc/kernel/module_64.c
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@@ -280,6 +280,10 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
#ifdef CONFIG_DYNAMIC_FTRACE
/* make the trampoline to the ftrace_caller */
relocs++;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
/* an additional one for ftrace_regs_caller */
relocs++;
#endif
#endif
pr_debug("Looks like a total of %lu stubs, max\n", relocs);
@@ -765,7 +769,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
* via the paca (in r13). The target (ftrace_caller()) is responsible for
* saving and restoring the toc before returning.
*/
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
struct module *me, unsigned long addr)
{
struct ppc64_stub_entry *entry;
unsigned int i, num_stubs;
@@ -792,9 +797,10 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
memcpy(entry->jump, stub_insns, sizeof(stub_insns));
/* Stub uses address relative to kernel toc (from the paca) */
reladdr = (unsigned long)ftrace_caller - kernel_toc_addr();
reladdr = addr - kernel_toc_addr();
if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
pr_err("%s: Address of ftrace_caller out of range of kernel_toc.\n", me->name);
pr_err("%s: Address of %ps out of range of kernel_toc.\n",
me->name, (void *)addr);
return 0;
}
@@ -802,22 +808,30 @@ static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module
entry->jump[2] |= PPC_LO(reladdr);
/* Eventhough we don't use funcdata in the stub, it's needed elsewhere. */
entry->funcdata = func_desc((unsigned long)ftrace_caller);
entry->funcdata = func_desc(addr);
entry->magic = STUB_MAGIC;
return (unsigned long)entry;
}
#else
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs, struct module *me)
static unsigned long create_ftrace_stub(const Elf64_Shdr *sechdrs,
struct module *me, unsigned long addr)
{
return stub_for_addr(sechdrs, (unsigned long)ftrace_caller, me);
return stub_for_addr(sechdrs, addr, me);
}
#endif
int module_finalize_ftrace(struct module *mod, const Elf_Shdr *sechdrs)
{
mod->arch.toc = my_r2(sechdrs, mod);
mod->arch.tramp = create_ftrace_stub(sechdrs, mod);
mod->arch.tramp = create_ftrace_stub(sechdrs, mod,
(unsigned long)ftrace_caller);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
mod->arch.tramp_regs = create_ftrace_stub(sechdrs, mod,
(unsigned long)ftrace_regs_caller);
if (!mod->arch.tramp_regs)
return -ENOENT;
#endif
if (!mod->arch.tramp)
return -ENOENT;