runtime: get per-process random number from auxv for hash table

Decode AT_RANDOM, AT_HWCAP, and AT_PLATFORM.
This CL only make use of AT_RANDOM, but future CLs will make use of the others.

R=dave, rsc
CC=golang-dev
https://golang.org/cl/5978051

diff --git a/src/pkg/runtime/asm_arm.s b/src/pkg/runtime/asm_arm.s
index 1ba3500496580eb9f213dc109fe92db0a70646bc..1d98a6841e8983237395f02aade6da4f54155c80 100644 (file)
--- a/src/pkg/runtime/asm_arm.s
+++ b/src/pkg/runtime/asm_arm.s
@@ -375,16 +375,6 @@ TEXT runtime·getcallersp(SB),7,$-4
 TEXT runtime·emptyfunc(SB),0,$0
        RET
 
-// int64 runtime·cputicks(), so really
-// void runtime·cputicks(int64 *ticks)
-// stubbed: return int64(0)
-TEXT runtime·cputicks(SB),7,$0
-       MOVW    0(FP), R1
-       MOVW    $0, R0
-       MOVW    R0, 0(R1)
-       MOVW    R0, 4(R1)
-       RET
-
 TEXT runtime·abort(SB),7,$-4
        MOVW    $0, R0
        MOVW    (R0), R1

diff --git a/src/pkg/runtime/rt0_linux_arm.s b/src/pkg/runtime/rt0_linux_arm.s
index 54ea860dc1c89defa8fdfdb0ce2698badbb953f2..a648160cf7112481c451f6e8c4c300934c56de34 100644 (file)
--- a/src/pkg/runtime/rt0_linux_arm.s
+++ b/src/pkg/runtime/rt0_linux_arm.s
@@ -37,6 +37,10 @@ TEXT _rt0_arm_linux(SB),7,$-4
        MOVW    $174, R7 // sys_sigaction
        SWI     $0 // restore signal handler
        ADD     $32, R13
+
+       SUB     $4, R13 // fake a stack frame for runtime·setup_auxv
+       BL      runtime·setup_auxv(SB)
+       ADD     $4, R13
        B       _rt0_arm(SB)
 
 TEXT bad_abi<>(SB),7,$-4

diff --git a/src/pkg/runtime/signal_linux_arm.c b/src/pkg/runtime/signal_linux_arm.c
index d1da4b0ea23d8e9c128a57db8991e45acfe73149..d20af688bda1e010fe09f5dd8c4d6ba1a41c1cc7 100644 (file)
--- a/src/pkg/runtime/signal_linux_arm.c
+++ b/src/pkg/runtime/signal_linux_arm.c
@@ -141,3 +141,60 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
        sa.sa_handler = fn;
        runtime·rt_sigaction(i, &sa, nil, 8);
 }
+
+#define AT_NULL                0
+#define AT_PLATFORM    15 // introduced in at least 2.6.11
+#define AT_HWCAP       16 // introduced in at least 2.6.11
+#define AT_RANDOM      25 // introduced in 2.6.29
+static uint32 runtime·randomNumber;
+uint32 runtime·hwcap;
+uint8 runtime·armArch = 6; // we default to ARMv6
+
+#pragma textflag 7
+void
+runtime·setup_auxv(int32 argc, void *argv_list)
+{
+       byte **argv = &argv_list;
+       byte **envp;
+       uint32 *auxv;
+       uint32 t;
+
+       // skip envp to get to ELF auxiliary vector.
+       for(envp = &argv[argc+1]; *envp != nil; envp++)
+               ;
+       envp++;
+       
+       for(auxv=(uint32*)envp; auxv[0] != AT_NULL; auxv += 2) {
+               switch(auxv[0]) {
+               case AT_RANDOM: // kernel provided 16-byte worth of random data
+                       if(auxv[1])
+                               runtime·randomNumber = *(uint32*)(auxv[1] + 4);
+                       break;
+               case AT_PLATFORM: // v5l, v6l, v7l
+                       if(auxv[1]) {
+                               t = *(uint8*)(auxv[1]+1);
+                               if(t >= '5' && t <= '7')
+                                       runtime·armArch = t - '0';
+                       }
+                       break;
+               case AT_HWCAP: // CPU capability bit flags
+                       runtime·hwcap = auxv[1];
+                       break;
+               }
+       }
+}
+
+#pragma textflag 7
+int64
+runtime·cputicks() {
+       // copied from runtime.c:/^fastrand1
+       uint32 x;
+
+       x = runtime·randomNumber;
+       x += x;
+       if(x & 0x80000000L)
+               x ^= 0x88888eefUL;
+       runtime·randomNumber = x;
+
+       return ((int64)x) << 32 | x;
+}