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powerpc: Introduce a new helper to obtain function entry points 

kprobe_lookup_name() is specific to the kprobe subsystem and may not always
return the function entry point (in a subsequent patch for KPROBES_ON_FTRACE).
For looking up function entry points, introduce a separate helper and use it
in optprobes.c

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 2017-04-19 18:22:27 +05:30 committed by Michael Ellerman
parent ead514d5fb
commit 1b32cd1715
2 changed files with 44 additions and 3 deletions
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41
arch/powerpc/include/asm/code-patching.h
View File

@ -12,6 +12,8 @@
#include <asm/types.h>
#include <asm/ppc-opcode.h>
#include <linux/string.h>
#include <linux/kallsyms.h>
/* Flags for create_branch:
* "b" == create_branch(addr, target, 0);
@ -99,6 +101,45 @@ static inline unsigned long ppc_global_function_entry(void *func)
#endif
}
/*
* Wrapper around kallsyms_lookup() to return function entry address:
* - For ABIv1, we lookup the dot variant.
* - For ABIv2, we return the local entry point.
*/
static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
{
unsigned long addr;
#ifdef PPC64_ELF_ABI_v1
/* check for dot variant */
char dot_name[1 + KSYM_NAME_LEN];
bool dot_appended = false;
if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
return 0;
if (name[0] != '.') {
dot_name[0] = '.';
dot_name[1] = '\0';
strlcat(dot_name, name, sizeof(dot_name));
dot_appended = true;
} else {
dot_name[0] = '\0';
strlcat(dot_name, name, sizeof(dot_name));
}
addr = kallsyms_lookup_name(dot_name);
if (!addr && dot_appended)
/* Let's try the original non-dot symbol lookup */
addr = kallsyms_lookup_name(name);
#elif defined(PPC64_ELF_ABI_v2)
addr = kallsyms_lookup_name(name);
if (addr)
addr = ppc_function_entry((void *)addr);
#else
addr = kallsyms_lookup_name(name);
#endif
return addr;
}
#ifdef CONFIG_PPC64
/*
* Some instruction encodings commonly used in dynamic ftracing

6
arch/powerpc/kernel/optprobes.c
View File

@ -243,10 +243,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
/*
* 2. branch to optimized_callback() and emulate_step()
*/
op_callback_addr = kprobe_lookup_name("optimized_callback", 0);
emulate_step_addr = kprobe_lookup_name("emulate_step", 0);
op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");
emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step");
if (!op_callback_addr || !emulate_step_addr) {
WARN(1, "kprobe_lookup_name() failed\n");
WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
goto error;
}