[PATCH v2 2/9] LoongArch/ftrace: Add recordmcount support

[Qing Zhang]

Recordmcount utility under scripts is run, after compiling each object,
to find out all the locations of calling _mcount() and put them into
specific seciton named __mcount_loc.
Then linker collects all such information into a table in the kernel image
(between __start_mcount_loc and __stop_mcount_loc) for later use by ftrace.

This patch adds loongarch specific definitions to identify such locations.
On loongarch, only C version is used to build the kernel now that
CONFIG_HAVE_C_RECORDMCOUNT is on.

Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
---
 arch/loongarch/Kconfig |  2 ++
 scripts/recordmcount.c | 23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 703a2c3a8e0d..4d13bac368ed 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -80,10 +80,12 @@ config LOONGARCH
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_CONTEXT_TRACKING_USER
+	select HAVE_C_RECORDMCOUNT
 	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_EXIT_THREAD
 	select HAVE_FAST_GUP
+	select HAVE_FTRACE_MCOUNT_RECORD
         select HAVE_FUNCTION_GRAPH_TRACER
         select HAVE_FUNCTION_TRACER
 	select HAVE_GENERIC_VDSO
diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index cce12e1971d8..ae42f9c5dc42 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -38,6 +38,13 @@
 #define R_AARCH64_ABS64	257
 #endif
 
+#ifndef EM_LOONGARCH
+#define EM_LOONGARCH		258
+#define R_LARCH_64		2
+#define R_LARCH_MARK_LA			20
+#define R_LARCH_SOP_PUSH_PLT_PCREL	29
+#endif
+
 #define R_ARM_PC24		1
 #define R_ARM_THM_CALL		10
 #define R_ARM_CALL		28
@@ -441,6 +448,17 @@ static int arm64_is_fake_mcount(Elf64_Rel const *rp)
 	return ELF64_R_TYPE(w8(rp->r_info)) != R_AARCH64_CALL26;
 }
 
+static int LARCH64_is_fake_mcount(Elf64_Rel const *rp)
+{
+	switch (ELF64_R_TYPE(w(rp->r_info))) {
+	case R_LARCH_MARK_LA:
+	case R_LARCH_SOP_PUSH_PLT_PCREL:
+		return 0;
+	}
+
+	return 1;
+}
+
 /* 64-bit EM_MIPS has weird ELF64_Rela.r_info.
  * http://techpubs.sgi.com/library/manuals/4000/007-4658-001/pdf/007-4658-001.pdf
  * We interpret Table 29 Relocation Operation (Elf64_Rel, Elf64_Rela) [p.40]
@@ -558,6 +576,7 @@ static int do_file(char const *const fname)
 		break;
 	case EM_IA_64:	reltype = R_IA64_IMM64; break;
 	case EM_MIPS:	/* reltype: e_class    */ break;
+	case EM_LOONGARCH:	/* reltype: e_class    */ break;
 	case EM_PPC:	reltype = R_PPC_ADDR32; break;
 	case EM_PPC64:	reltype = R_PPC64_ADDR64; break;
 	case EM_S390:	/* reltype: e_class    */ break;
@@ -610,6 +629,10 @@ static int do_file(char const *const fname)
 			Elf64_r_info = MIPS64_r_info;
 			is_fake_mcount64 = MIPS64_is_fake_mcount;
 		}
+		if (w2(ghdr->e_machine) == EM_LOONGARCH) {
+			reltype = R_LARCH_64;
+			is_fake_mcount64 = LARCH64_is_fake_mcount;
+		}
 		if (do64(ghdr, fname, reltype) < 0)
 			goto out;
 		break;
-- 
2.20.1