ARC/NPTL: clone to set TP if CLONE_SETTLS

Typically kernel would set the TP register of newly created thread in
clone syscall with CLONE_SETTLS.

However this implies that:
* kernel knows of the exact TP register (which is already different for
  ARCompact and ARCv2) and is a detail which becomes part of the ABI
* kernel also needs to handle the unlikely but possible case of !TLS
  userspace (e.g. Android libc) case where TP reg is not reserved and
  thus need not be mucked with (using ELF personality based detection)

It is better to confine this detail to userspace runtime and set TP reg
right after clone syscall returns.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

diff --git a/libc/sysdeps/linux/arc/clone.S b/libc/sysdeps/linux/arc/clone.S
index db5000c..3c1388e 100644 (file)
--- a/libc/sysdeps/linux/arc/clone.S
+++ b/libc/sysdeps/linux/arc/clone.S
@@ -29,6 +29,7 @@
 
 #define CLONE_VM               0x00000100
 #define CLONE_THREAD           0x00010000
+#define CLONE_SETTLS           0x00080000
 #define CLONE_THREAD_N_VM      (CLONE_THREAD | CLONE_VM)
 
 ENTRY(clone)
@@ -42,6 +43,7 @@ ENTRY(clone)
        mov     r10, r0         ; @fn
        mov     r11, r3         ; @args
        mov     r12, r2         ; @clone_flags
+       mov     r9,  r5         ; @tls
 
        ; adjust libc args for syscall
 
@@ -57,6 +59,14 @@ ENTRY(clone)
        jnz     [blink]         ; Parent returns
 
        ; ----- child starts here ---------
+
+#if defined(__UCLIBC_HAS_TLS__)
+       ; Setup TP register (since kernel doesn't do that)
+       and.f   0, r12, CLONE_SETTLS
+       bz      .Lnext_clone_quirk
+       SET_TP  r9
+
+.Lnext_clone_quirk:
 #ifdef RESET_PID
        mov_s   r2, CLONE_THREAD_N_VM
        and_s   r2, r2, r12
@@ -70,7 +80,7 @@ ENTRY(clone)
 
 .Lgo_thread:
 #endif
-
+#endif
        ; child jumps off to @fn with @arg as argument, and returns here
        jl.d    [r10]
        mov     r0, r11