2 files changed, 57 insertions, 4 deletions

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index 2d32b9ced20a..f2f32eee2c5b 100644
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -325,8 +325,10 @@ do_file(char const *const fname)
                 }
                 if (EM_S390 == w2(ehdr->e_machine))
                         reltype = R_390_32;
-                if (EM_MIPS == w2(ehdr->e_machine))
+                if (EM_MIPS == w2(ehdr->e_machine)) {
                         reltype = R_MIPS_32;
+                        is_fake_mcount32 = MIPS32_is_fake_mcount;
+                }
                 do32(ehdr, fname, reltype);
         } break;
         case ELFCLASS64: {
@@ -343,6 +345,7 @@ do_file(char const *const fname)
                         reltype = R_MIPS_64;
                         Elf64_r_sym = MIPS64_r_sym;
                         Elf64_r_info = MIPS64_r_info;
+                        is_fake_mcount64 = MIPS64_is_fake_mcount;
                 }
                 do64(ghdr, fname, reltype);
         } break;
diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index 190fd18dc853..58e933a20544 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -19,12 +19,16 @@
  * Licensed under the GNU General Public License, version 2 (GPLv2).
  */
 #undef append_func
+#undef is_fake_mcount
+#undef fn_is_fake_mcount
+#undef MIPS_is_fake_mcount
 #undef sift_rel_mcount
 #undef find_secsym_ndx
 #undef __has_rel_mcount
 #undef has_rel_mcount
 #undef tot_relsize
 #undef do_func
+#undef Elf_Addr
 #undef Elf_Ehdr
 #undef Elf_Shdr
 #undef Elf_Rel
@@ -50,6 +54,10 @@
 # define has_rel_mcount         has64_rel_mcount
 # define tot_relsize            tot64_relsize
 # define do_func                do64
+# define is_fake_mcount         is_fake_mcount64
+# define fn_is_fake_mcount      fn_is_fake_mcount64
+# define MIPS_is_fake_mcount    MIPS64_is_fake_mcount
+# define Elf_Addr               Elf64_Addr
 # define Elf_Ehdr               Elf64_Ehdr
 # define Elf_Shdr               Elf64_Shdr
 # define Elf_Rel                Elf64_Rel
@@ -74,6 +82,10 @@
 # define has_rel_mcount         has32_rel_mcount
 # define tot_relsize            tot32_relsize
 # define do_func                do32
+# define is_fake_mcount         is_fake_mcount32
+# define fn_is_fake_mcount      fn_is_fake_mcount32
+# define MIPS_is_fake_mcount    MIPS32_is_fake_mcount
+# define Elf_Addr               Elf32_Addr
 # define Elf_Ehdr               Elf32_Ehdr
 # define Elf_Shdr               Elf32_Shdr
 # define Elf_Rel                Elf32_Rel
@@ -92,7 +104,13 @@
 # define _size                  4
 #endif
 
-/* Functions and pointers that 64-bit EM_MIPS can override. */
+/* Functions and pointers that do_file() may override for specific e_machine. */
+static int fn_is_fake_mcount(Elf_Rel const *rp)
+{
+        return 0;
+}
+static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
+
 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
 {
         return ELF_R_SYM(_w(rp->r_info));
@@ -105,6 +123,39 @@ static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
 }
 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
 
+/*
+ * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
+ * _mcount symbol is needed for dynamic function tracer, with it, to disable
+ * tracing(ftrace_make_nop), the instruction in the position is replaced with
+ * the "b label" instruction, to enable tracing(ftrace_make_call), replace the
+ * instruction back. So, here, we set the 2nd one as fake and filter it.
+ *
+ * c:   3c030000        lui     v1,0x0          <-->    b       label
+ *              c: R_MIPS_HI16  _mcount
+ *              c: R_MIPS_NONE  *ABS*
+ *              c: R_MIPS_NONE  *ABS*
+ * 10:  64630000        daddiu  v1,v1,0
+ *              10: R_MIPS_LO16 _mcount
+ *              10: R_MIPS_NONE *ABS*
+ *              10: R_MIPS_NONE *ABS*
+ * 14:  03e0082d        move    at,ra
+ * 18:  0060f809        jalr    v1
+ * label:
+ */
+#define MIPS_FAKEMCOUNT_OFFSET  4
+
+static int MIPS_is_fake_mcount(Elf_Rel const *rp)
+{
+        static Elf_Addr old_r_offset;
+        Elf_Addr current_r_offset = _w(rp->r_offset);
+        int is_fake;
+
+        is_fake = old_r_offset &&
+                (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
+        old_r_offset = current_r_offset;
+
+        return is_fake;
+}
 
 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
 static void append_func(Elf_Ehdr *const ehdr,
@@ -183,7 +234,6 @@ static void append_func(Elf_Ehdr *const ehdr,
         uwrite(fd_map, ehdr, sizeof(*ehdr));
 }
 
-
 /*
  * Look at the relocations in order to find the calls to mcount.
  * Accumulate the section offsets that are found, and their relocation info,
@@ -233,7 +283,7 @@ static uint_t *sift_rel_mcount(uint_t *mlocp,
                                 mcountsym = Elf_r_sym(relp);
                 }
 
-                if (mcountsym == Elf_r_sym(relp)) {
+                if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
                         uint_t const addend = _w(_w(relp->r_offset) - recval);
 
                         mrelp->r_offset = _w(offbase