Support for -fpatchable-function-entry on ppc64le was added in Clang
with [1]. However, when no prefix NOPs are specified - as is the case
with CONFIG_PPC_FTRACE_OUT_OF_LINE - the first NOP is emitted at LEP,
but Clang records the Global Entry Point (GEP) unlike GCC which does
record the Local Entry Point (LEP). Issue [2] has been raised to align
Clang's behavior with GCC. As a temporary workaround to ensure ftrace
initialization works as expected with Clang, derive the LEP using
ppc_function_entry() for kernel symbols and by looking for the below
module GEP sequence for module addresses, until [2] is resolved:
ld r2, -8(r12)
add r2, r2, r12
[1] https://github.com/llvm/llvm-project/pull/151569
[2] https://github.com/llvm/llvm-project/issues/163706
Cc: Maryam Moghadas <[email protected]>
Signed-off-by: Hari Bathini <[email protected]>
---
arch/powerpc/kernel/trace/ftrace.c | 26 ++++++++++++++++++++++----
1 file changed, 22 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kernel/trace/ftrace.c
b/arch/powerpc/kernel/trace/ftrace.c
index 841d077e2825..1b2f293e7dcb 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -37,11 +37,29 @@ unsigned long ftrace_call_adjust(unsigned long addr)
if (addr >= (unsigned long)__exittext_begin && addr < (unsigned
long)__exittext_end)
return 0;
- if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) &&
- !IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
- addr += MCOUNT_INSN_SIZE;
- if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+ if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) {
+ if (!IS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)) {
addr += MCOUNT_INSN_SIZE;
+ if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
+ addr += MCOUNT_INSN_SIZE;
+ } else if (IS_ENABLED(CONFIG_CC_IS_CLANG) &&
IS_ENABLED(CONFIG_PPC64)) {
+ /*
+ * addr points to global entry point though the NOP was
emitted at local
+ * entry point due to
https://github.com/llvm/llvm-project/issues/163706
+ * Handle that here with ppc_function_entry() for
kernel symbols while
+ * adjusting module addresses in the else case, by
looking for the below
+ * module global entry point sequence:
+ * ld r2, -8(r12)
+ * add r2, r2, r12
+ */
+ if (is_kernel_text(addr) || is_kernel_inittext(addr))
+ addr = ppc_function_entry((void *)addr);
+ else if ((ppc_inst_val(ppc_inst_read((u32 *)addr)) ==
+ PPC_RAW_LD(_R2, _R12, -8)) &&
+ (ppc_inst_val(ppc_inst_read((u32 *)(addr+4)))
==
+ PPC_RAW_ADD(_R2, _R2, _R12)))
+ addr += 8;
+ }
}
return addr;
--
2.51.1
