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| author | Naveen N Rao <naveen@kernel.org> | 2024-10-30 10:08:48 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2024-10-31 03:00:55 +0300 |
| commit | a52f6043a2238d656ddd23ce0499cf4f12645faa (patch) | |
| tree | ebe1db9c7dd95c9e11a84bfc6b17961cc8281cdf /arch/powerpc/include/asm | |
| parent | e717754f0bb5c5347aac82232691340955735ce1 (diff) | |
| download | linux-a52f6043a2238d656ddd23ce0499cf4f12645faa.tar.xz | |
powerpc/ftrace: Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS
Add support for DYNAMIC_FTRACE_WITH_DIRECT_CALLS similar to the arm64
implementation.
ftrace direct calls allow custom trampolines to be called into directly
from function ftrace call sites, bypassing the ftrace trampoline
completely. This functionality is currently utilized by BPF trampolines
to hook into kernel function entries.
Since we have limited relative branch range, we support ftrace direct
calls through support for DYNAMIC_FTRACE_WITH_CALL_OPS. In this
approach, ftrace trampoline is not entirely bypassed. Rather, it is
re-purposed into a stub that reads direct_call field from the associated
ftrace_ops structure and branches into that, if it is not NULL. For
this, it is sufficient if we can ensure that the ftrace trampoline is
reachable from all traceable functions.
When multiple ftrace_ops are associated with a call site, we utilize a
call back to set pt_regs->orig_gpr3 that can then be tested on the
return path from the ftrace trampoline to branch into the direct caller.
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-16-hbathini@linux.ibm.com
Diffstat (limited to 'arch/powerpc/include/asm')
| -rw-r--r-- | arch/powerpc/include/asm/ftrace.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h index 1ad1328cf4e3..5eb7631355a1 100644 --- a/arch/powerpc/include/asm/ftrace.h +++ b/arch/powerpc/include/asm/ftrace.h @@ -148,6 +148,22 @@ extern unsigned int ftrace_ool_stub_text_end_count, ftrace_ool_stub_text_count, #endif void ftrace_free_init_tramp(void); unsigned long ftrace_call_adjust(unsigned long addr); + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +/* + * When an ftrace registered caller is tracing a function that is also set by a + * register_ftrace_direct() call, it needs to be differentiated in the + * ftrace_caller trampoline so that the direct call can be invoked after the + * other ftrace ops. To do this, place the direct caller in the orig_gpr3 field + * of pt_regs. This tells ftrace_caller that there's a direct caller. + */ +static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr) +{ + struct pt_regs *regs = &fregs->regs; + + regs->orig_gpr3 = addr; +} +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ #else static inline void ftrace_free_init_tramp(void) { } static inline unsigned long ftrace_call_adjust(unsigned long addr) { return addr; } |