[Sanitizer] Add MIPS vfork interception

[wzssyqa]

Summary

https://github.com/google/sanitizers/issues/925
claims that vfork can have better performance than fork, and
bionic is using vfork.

Let's support it for MIPS.

Tested on Debian's mipsel (mipsel-linux-gnu) and
mips64el (mips64el-linux-gnu) ports.

Test fails on MIPSr6 due to another problem:
https://github.com/llvm/llvm-project/issues/64974

[MaskRay]

If test/asan/TestCases/Linux/vfork.cpp passes now, adjust its REQUIRES to use the modern // REQUIRES: target={{....|mips64}}.*

[MaskRay]

Add https://github.com/google/sanitizers/issues/925 to the descriotion.

[brad]

compiler-rt/lib/asan/asan_interceptors_vfork.S

13

As this is already in alphabetical order it would be good if you could move your addition above riscv64.

[wzssyqa]

This patch depends on https://reviews.llvm.org/D158491.

[MaskRay]

compiler-rt/lib/asan/asan_interceptors.h

123

Just ignore clang-format warning, and don't add indentation, to decrease the amount of unrelated changes.

compiler-rt/test/asan/TestCases/Linux/vfork.cpp

4

Can you name the mips platforms that you have tested?

[wzssyqa]

compiler-rt/test/asan/TestCases/Linux/vfork.cpp

4

Can you name the mips platforms that you have tested?

I tested it on Debian mipsel-linux-gnu and mips64el-linux-gnuabi64.

Should I add this info into the code, or commit msg?

compiler-rt/lib/asan/asan_interceptors.h

 # define ASAN_INTERCEPT_TRYJOIN 0
 #endif
 
-#if SANITIZER_LINUX &&                                                \
-    (defined(__arm__) || defined(__aarch64__) || defined(__i386__) || \
-     defined(__x86_64__) || SANITIZER_RISCV64 || SANITIZER_LOONGARCH64)
+#if SANITIZER_LINUX &&                                                    \
+    (defined(__arm__) || defined(__aarch64__) || defined(__i386__) ||     \
+     defined(__x86_64__) || SANITIZER_RISCV64 || SANITIZER_LOONGARCH64 || \
+     defined(__mips))
 # define ASAN_INTERCEPT_VFORK 1
 #else
 # define ASAN_INTERCEPT_VFORK 0

compiler-rt/lib/asan/asan_interceptors_vfork.S

 #include "sanitizer_common/sanitizer_common_interceptors_vfork_arm.inc.S"
 #include "sanitizer_common/sanitizer_common_interceptors_vfork_i386.inc.S"
 #include "sanitizer_common/sanitizer_common_interceptors_vfork_loongarch64.inc.S"
+#include "sanitizer_common/sanitizer_common_interceptors_vfork_mips.inc.S"
 #include "sanitizer_common/sanitizer_common_interceptors_vfork_riscv64.inc.S"
 #include "sanitizer_common/sanitizer_common_interceptors_vfork_x86_64.inc.S"
 #endif

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors_vfork_mips.inc.S

+#if defined(__mips) && defined(__linux__)
+
+#if defined(__mips64)
+# define ADDI daddiu
+# define ADDU DADDU
+# define ST sd
+# define LD ld
+# define LA dla
+# define GOT_DISP got_disp
+#else
+# define ADDI addiu
+# define ADDU addu
+# define ST sw
+# define LD lw
+# define LA la
+# define GOT_DISP got
+#endif
+
+// MEMOEY USAGE:
+// SP[0]: ra; SP[8]: gp
+// SPILL[0]: ra; SPILL[8]: s8
+
+#include "sanitizer_common/sanitizer_asm.h"
+
+ASM_HIDDEN(COMMON_INTERCEPTOR_SPILL_AREA)
+
+.comm _ZN14__interception10real_vforkE,__SIZEOF_POINTER__,__SIZEOF_POINTER__
+.globl ASM_WRAPPER_NAME(vfork)
+ASM_TYPE_FUNCTION(ASM_WRAPPER_NAME(vfork))
+ASM_WRAPPER_NAME(vfork):
+        ADDI  $sp, $sp, -16
+        ST  $ra, 0($sp)
+#if __mips_isa_rev < 6
+  // __interceptor_trampoline_vfork call us by `b`, so the t9 contains the
+  // address of __interceptor_trampoline_vfork instead of __interceptor_vfork.
+#  if defined(__mips64)
+  // Compute $gp
+  lui $gp, %hi(%neg(%gp_rel(__interceptor_trampoline_vfork)))
+  ADDU  $gp, $gp, $t9
+  ADDI  $gp, $gp, %lo(%neg(%gp_rel(__interceptor_trampoline_vfork)))
+#  else
+  .set  noreorder
+  #nal FIXME: nal is not supported by llvm yet. So use bltzal now.
+  # It is used to get the value of PC.
+  bltzal  $0, .L_exit
+  nop
+  addiu $t9, $ra, 4
+  .cpload $t9
+  .set  reorder
+#  endif
+#endif
+
+#if __mips_isa_rev >= 6
+        balc  COMMON_INTERCEPTOR_SPILL_AREA
+#else
+  LD  $t9, %GOT_DISP(COMMON_INTERCEPTOR_SPILL_AREA)($gp)
+        ST  $gp, 8($sp)
+        jalr  $t9
+
+        LD  $gp, 8($sp)
+  // save s8, and move gp to s0, so that we can always known our gp.
+  // we didn't it earlier, due to that we need COMMON_INTERCEPTOR_SPILL_AREA,
+  // which can keep data cross vfork call.
+        ST  $s8, 8($v0)
+        MOVE  $s8, $gp
+#endif
+        // restore previous values from stack
+        LD  $ra, 0($sp)
+        // adjust stack
+        ADDI  $sp, $sp, 16
+        // Save ra in the off-stack spill area.
+        ST  $ra, 0($v0)
+
+        // Call real vfork. This may return twice. User code that runs between the first and the second return
+        // may clobber the stack frame of the interceptor; that's why it does not have a frame.
+  // do *NOT* use s8, since it is not set by MIPSr6.
+  LD  $t9, %GOT_DISP(_ZN14__interception10real_vforkE)($gp)
+  LD  $t9, 0($t9)
+        jalr  $t9
+
+        // adjust stack
+        ADDI  $sp, $sp, -16
+        // store v0 by adjusted stack
+        sd  $v0, 8($sp)
+        // jump to exit label if v0 is 0 => child process
+        beqz  $v0, .L_exit
+
+        // v0 != 0 => parent process. Clear stack shadow.
+        ADDI  $a0, $sp, 16
+#if __mips_isa_rev >= 6
+        balc  COMMON_INTERCEPTOR_HANDLE_VFORK
+#else
+  // here, s8 has the value of gp
+        LD  $t9, %GOT_DISP(COMMON_INTERCEPTOR_HANDLE_VFORK)($s8)
+  jalr  $t9
+#endif
+
+.L_exit:
+#if __mips_isa_rev >= 6
+        balc  COMMON_INTERCEPTOR_SPILL_AREA
+#else
+  // here, s8 has the value of gp
+  LD  $t9, %GOT_DISP(COMMON_INTERCEPTOR_SPILL_AREA)($s8)
+        jalr  $t9
+
+        LD  $s8, 8($v0)
+#endif
+        // Restore ra
+        LD  $ra, 0($v0)
+        // the return value of vfork
+        LD  $v0, 8($sp)
+        ADDI  $sp, $sp, 16
+        jr  $ra
+ASM_SIZE(vfork)
+
+ASM_INTERCEPTOR_TRAMPOLINE(vfork)
+ASM_TRAMPOLINE_ALIAS(vfork, vfork)
+
+#endif

compiler-rt/test/asan/TestCases/Linux/vfork.cpp

 // https://github.com/google/sanitizers/issues/925
 // RUN: %clang_asan -O0 %s -o %t && %run %t 2>&1
 
-// REQUIRES: aarch64-target-arch || x86_64-target-arch || i386-target-arch || arm-target-arch || riscv64-target-arch || loongarch64-target-arch
+// REQUIRES: target={{(aarch64|arm|i386|loongarch64|mips.*|riscv64|x86_64)-.*}}
 
 #include <assert.h>
 #include <sys/types.h>