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powerpc/kprobes: Use ftrace to determine if a probe is at function entry

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Rather than hard-coding the offset into a function to be used to
determine if a kprobe is at function entry, use ftrace_location() to
determine the ftrace location within the function and categorize all
instructions till that offset to be function entry.

For functions that cannot be traced, we fall back to using a fixed
offset of 8 (two instructions) to categorize a probe as being at
function entry for 64-bit elfv2, unless we are using pcrel.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-3-hbathini@linux.ibm.com
This commit is contained in:
Naveen N Rao 2024-10-30 12:38:35 +05:30 committed by Michael Ellerman
parent 0b9846529e
commit be87d713ea
1 changed files with 8 additions and 10 deletions
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18
arch/powerpc/kernel/kprobes.c
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@ -105,24 +105,22 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
return addr;
}
static bool arch_kprobe_on_func_entry(unsigned long offset)
static bool arch_kprobe_on_func_entry(unsigned long addr, unsigned long offset)
{
#ifdef CONFIG_PPC64_ELF_ABI_V2
#ifdef CONFIG_KPROBES_ON_FTRACE
return offset <= 16;
#else
return offset <= 8;
#endif
#else
unsigned long ip = ftrace_location(addr);
if (ip)
return offset <= (ip - addr);
if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && !IS_ENABLED(CONFIG_PPC_KERNEL_PCREL))
return offset <= 8;
return !offset;
#endif
}
/* XXX try and fold the magic of kprobe_lookup_name() in this */
kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
bool *on_func_entry)
{
*on_func_entry = arch_kprobe_on_func_entry(offset);
*on_func_entry = arch_kprobe_on_func_entry(addr, offset);
return (kprobe_opcode_t *)(addr + offset);
}