Revert "[MIPS] Support FR=0 emulation on FR=1 64-bit FP registers"

This reverts commit 40d9e7bf842423e328cda58e21ff5fc0cbab5c8a.

Bug: http://b/22045439
Change-Id: Ia9c56f65d35e404332a462f46460335cef39f0a4

3 files changed, 6 insertions, 153 deletions

diff --git a/linker/linker.cpp b/linker/linker.cpp
index bb8b22d7f..e147a131c 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -2816,12 +2816,6 @@ bool soinfo::prelink_image() {
     }
   }
 
-#if defined(__mips__) && !defined(__LP64__)
-  if (!mips_check_and_adjust_fp_modes()) {
-    return false;
-  }
-#endif
-
   DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
         reinterpret_cast<void*>(base), strtab_, symtab_);
 
diff --git a/linker/linker.h b/linker/linker.h
index 6f425e02e..6042cb844 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -250,9 +250,7 @@ struct soinfo {
   bool mips_relocate_got(const VersionTracker& version_tracker,
                          const soinfo_list_t& global_group,
                          const soinfo_list_t& local_group);
-#if !defined(__LP64__)
-  bool mips_check_and_adjust_fp_modes();
-#endif
+
 #endif
   size_t ref_count_;
  public:
diff --git a/linker/linker_mips.cpp b/linker/linker_mips.cpp
index 75ea29042..a7a4bc064 100644
--- a/linker/linker_mips.cpp
+++ b/linker/linker_mips.cpp
@@ -26,21 +26,8 @@
  * SUCH DAMAGE.
  */
 
-#if !defined(__LP64__) && __mips_isa_rev >= 5
-#include <sys/prctl.h>
-#if defined(PR_SET_FP_MODE)
-#error "remove following defs when avail in Android's kernel headers"
-#else
-#define PR_SET_FP_MODE 45
-#define PR_GET_FP_MODE 46
-#define PR_FP_MODE_FR  (1 << 0)
-#define PR_FP_MODE_FRE (1 << 1)
-#endif
-#endif
-
 #include "linker.h"
 #include "linker_debug.h"
-#include "linker_phdr.h"
 #include "linker_relocs.h"
 #include "linker_reloc_iterators.h"
 #include "linker_sleb128.h"
@@ -75,7 +62,7 @@ bool soinfo::relocate(const VersionTracker& version_tracker,
     ElfW(Addr) sym_addr = 0;
     const char* sym_name = nullptr;
 
-    DEBUG("Processing '%s' relocation at index %zd", get_realpath(), idx);
+    DEBUG("Processing '%s' relocation at index %zd", get_soname(), idx);
     if (type == R_GENERIC_NONE) {
       continue;
     }
@@ -97,8 +84,7 @@ bool soinfo::relocate(const VersionTracker& version_tracker,
 
       if (s == nullptr) {
         // mips does not support relocation with weak-undefined symbols
-        DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...",
-               sym_name, get_realpath());
+        DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, get_soname());
         return false;
       } else {
         // We got a definition.
@@ -185,22 +171,20 @@ bool soinfo::mips_relocate_got(const VersionTracker& version_tracker,
       }
     } else if (st_visibility == STV_PROTECTED) {
       if (local_sym->st_value == 0) {
-        DL_ERR("%s: invalid symbol \"%s\" (PROTECTED/UNDEFINED) ",
-               get_realpath(), sym_name);
+        DL_ERR("%s: invalid symbol \"%s\" (PROTECTED/UNDEFINED) ", get_soname(), sym_name);
         return false;
       }
       s = local_sym;
       lsi = this;
     } else {
-      DL_ERR("%s: invalid symbol \"%s\" visibility: 0x%x",
-             get_realpath(), sym_name, st_visibility);
+      DL_ERR("%s: invalid symbol \"%s\" visibility: 0x%x", get_soname(), sym_name, st_visibility);
       return false;
     }
 
     if (s == nullptr) {
       // We only allow an undefined symbol if this is a weak reference.
       if (ELF_ST_BIND(local_sym->st_info) != STB_WEAK) {
-        DL_ERR("%s: cannot locate \"%s\"...", get_realpath(), sym_name);
+        DL_ERR("%s: cannot locate \"%s\"...", get_soname(), sym_name);
         return false;
       }
       *got = 0;
@@ -214,126 +198,3 @@ bool soinfo::mips_relocate_got(const VersionTracker& version_tracker,
   return true;
 }
 
-#if !defined(__LP64__)
-
-// Checks for mips32's various floating point abis.
-// (Mips64 Android has a single floating point abi and doesn't need any checks)
-
-// Linux kernel has declarations similar to the following
-//   in <linux>/arch/mips/include/asm/elf.h,
-// but that non-uapi internal header file will never be imported
-// into bionic's kernel headers.
-
-#define PT_MIPS_ABIFLAGS  0x70000003	// is .MIPS.abiflags segment
-
-struct mips_elf_abiflags_v0 {
-  uint16_t version;  // version of this structure
-  uint8_t  isa_level, isa_rev, gpr_size, cpr1_size, cpr2_size;
-  uint8_t  fp_abi;  // mips32 ABI variants for floating point
-  uint16_t isa_ext, ases, flags1, flags2;
-};
-
-// Bits of flags1:
-#define MIPS_AFL_FLAGS1_ODDSPREG 1  // Uses odd-numbered single-prec fp regs
-
-// Some values of fp_abi:        via compiler flag:
-#define MIPS_ABI_FP_DOUBLE 1  // -mdouble-float
-#define MIPS_ABI_FP_XX     5  // -mfpxx
-#define MIPS_ABI_FP_64A    7  // -mips32r* -mfp64 -mno-odd-spreg
-
-#if __mips_isa_rev >= 5
-static bool mips_fre_mode_on = false;  // have set FRE=1 mode for process
-#endif
-
-bool soinfo::mips_check_and_adjust_fp_modes() {
-  mips_elf_abiflags_v0* abiflags = nullptr;
-  int mips_fpabi;
-
-  // Find soinfo's optional .MIPS.abiflags segment
-  for (size_t i = 0; i<phnum; ++i) {
-    const ElfW(Phdr)& ph = phdr[i];
-    if (ph.p_type == PT_MIPS_ABIFLAGS) {
-      if (ph.p_filesz < sizeof (mips_elf_abiflags_v0)) {
-        DL_ERR("Corrupt PT_MIPS_ABIFLAGS header found \"%s\"", get_realpath());
-        return false;
-      }
-      abiflags = reinterpret_cast<mips_elf_abiflags_v0*>(ph.p_vaddr + load_bias);
-      break;
-    }
-  }
-
-  // FP ABI-variant compatibility checks for MIPS o32 ABI
-  if (abiflags == nullptr) {
-    // Old compiles lack the new abiflags section.
-    // These compilers used -mfp32 -mdouble-float -modd-spreg defaults,
-    //   ie FP32 aka DOUBLE, using odd-numbered single-prec regs
-    mips_fpabi = MIPS_ABI_FP_DOUBLE;
-  } else {
-    mips_fpabi = abiflags->fp_abi;
-    if ( (abiflags->flags1 & MIPS_AFL_FLAGS1_ODDSPREG)
-         && (mips_fpabi == MIPS_ABI_FP_XX ||
-             mips_fpabi == MIPS_ABI_FP_64A   ) ) {
-      // Android supports fewer cases than Linux
-      DL_ERR("Unsupported odd-single-prec FloatPt reg uses in \"%s\"",
-             get_realpath());
-      return false;
-    }
-  }
-  if (!(mips_fpabi == MIPS_ABI_FP_DOUBLE ||
-#if __mips_isa_rev >= 5
-        mips_fpabi == MIPS_ABI_FP_64A    ||
-#endif
-        mips_fpabi == MIPS_ABI_FP_XX       )) {
-    DL_ERR("Unsupported MIPS32 FloatPt ABI %d found in \"%s\"",
-           mips_fpabi, get_realpath());
-    return false;
-  }
-
-#if __mips_isa_rev >= 5
-  // Adjust process's FR Emulation mode, if needed
-  //
-  // On Mips R5 & R6, Android runs continuously in FR=1 64bit-fpreg mode.
-  // NDK mips32 apps compiled with old compilers generate FP32 code
-  //   which expects FR=0 32-bit fp registers.
-  // NDK mips32 apps compiled with newer compilers generate modeless
-  //   FPXX code which runs on both FR=0 and FR=1 modes.
-  // Android itself is compiled in FP64A which requires FR=1 mode.
-  // FP32, FPXX, and FP64A all interlink okay, without dynamic FR mode
-  //   changes during calls.  For details, see
-  //   http://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking
-  // Processes containing FR32 FR=0 code are run via kernel software assist,
-  //   which maps all odd-numbered single-precision reg refs onto the
-  //   upper half of the paired even-numbered double-precision reg.
-  // FRE=1 triggers traps to the kernel's emulator on every single-precision
-  //   fp op (for both odd and even-numbered registers).
-  // Turning on FRE=1 traps is done at most once per process, simultanously
-  //   for all threads of that process, when dlopen discovers FP32 code.
-  // The kernel repacks threads' registers when FRE mode is turn on or off.
-  //   These asynchronous adjustments are wrong if any thread was executing
-  //   FPXX code using odd-numbered single-precision regs.
-  // Current Android compilers default to the -mno-oddspreg option,
-  //   and this requirement is checked by Android's dlopen.
-  //   So FRE can always be safely turned on for FP32, anytime.
-  // Deferred enhancement: Allow loading of odd-spreg FPXX modules.
-
-  if (mips_fpabi == MIPS_ABI_FP_DOUBLE && !mips_fre_mode_on) {
-    // Turn on FRE mode, which emulates mode-sensitive FR=0 code on FR=1
-    //   register files, by trapping to kernel on refs to single-precision regs
-    if (prctl(PR_SET_FP_MODE, PR_FP_MODE_FR|PR_FP_MODE_FRE)) {
-      DL_ERR("Kernel or cpu failed to set FRE mode required for running \"%s\"",
-             get_realpath());
-      return false;
-    }
-    DL_WARN("Using FRE=1 mode to run \"%s\"", get_realpath());
-    mips_fre_mode_on = true;  // Avoid future redundant mode-switch calls
-    // FRE mode is never turned back off.
-    // Deferred enhancement:
-    //   Reset FRE mode when dlclose() removes all FP32 modules
-  }
-#else
-  // Android runs continuously in FR=0 32bit-fpreg mode.
-#endif  // __mips_isa_rev
-  return true;
-}
-
-#endif  // __LP64___