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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>
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@ -12,6 +12,8 @@
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#include <asm/types.h>
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#include <asm/ppc-opcode.h>
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#include <linux/string.h>
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#include <linux/kallsyms.h>
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/* Flags for create_branch:
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* "b" == create_branch(addr, target, 0);
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@ -99,6 +101,45 @@ static inline unsigned long ppc_global_function_entry(void *func)
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#endif
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}
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/*
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* Wrapper around kallsyms_lookup() to return function entry address:
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* - For ABIv1, we lookup the dot variant.
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* - For ABIv2, we return the local entry point.
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*/
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static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
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{
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unsigned long addr;
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#ifdef PPC64_ELF_ABI_v1
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/* check for dot variant */
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char dot_name[1 + KSYM_NAME_LEN];
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bool dot_appended = false;
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if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
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return 0;
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if (name[0] != '.') {
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dot_name[0] = '.';
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dot_name[1] = '\0';
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strlcat(dot_name, name, sizeof(dot_name));
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dot_appended = true;
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} else {
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dot_name[0] = '\0';
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strlcat(dot_name, name, sizeof(dot_name));
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}
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addr = kallsyms_lookup_name(dot_name);
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if (!addr && dot_appended)
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/* Let's try the original non-dot symbol lookup */
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addr = kallsyms_lookup_name(name);
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#elif defined(PPC64_ELF_ABI_v2)
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addr = kallsyms_lookup_name(name);
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if (addr)
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addr = ppc_function_entry((void *)addr);
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#else
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addr = kallsyms_lookup_name(name);
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#endif
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return addr;
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}
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#ifdef CONFIG_PPC64
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/*
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* Some instruction encodings commonly used in dynamic ftracing
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@ -243,10 +243,10 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
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/*
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* 2. branch to optimized_callback() and emulate_step()
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*/
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op_callback_addr = kprobe_lookup_name("optimized_callback", 0);
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emulate_step_addr = kprobe_lookup_name("emulate_step", 0);
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op_callback_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("optimized_callback");
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emulate_step_addr = (kprobe_opcode_t *)ppc_kallsyms_lookup_name("emulate_step");
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if (!op_callback_addr || !emulate_step_addr) {
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WARN(1, "kprobe_lookup_name() failed\n");
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WARN(1, "Unable to lookup optimized_callback()/emulate_step()\n");
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goto error;
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}
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