[PULL 08/14] linux-user/mips: sync k0 TLS for EF_MIPS_MACH_OCTEON userlands

[Helge Deller <deller@kernel.org>]

From: James Hilliard <james.hilliard1@gmail.com>

Cavium Octeon userspace is not following a generic MIPS Linux TLS
ABI rule here. Older Octeon glibc uses the k0 register as the fast
thread pointer, while newer Octeon2 and Octeon3 glibc variants use
the normal rdhwr $29 path.

linux-user already updates CP0_UserLocal for cpu_set_tls() and
TARGET_NR_set_thread_area, but it does not keep gpr[26]
synchronized. That leaves EF_MIPS_MACH_OCTEON userlands able to
complete set_thread_area() and still reach pthread startup or
pthread_self() with a stale k0 value.

Use the existing MIPS ELF machine flags from linux-user/elfload.c and
mirror CP0_UserLocal into gpr[26] only for EF_MIPS_MACH_OCTEON.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>
---
 linux-user/elfload.c         | 3 +++
 linux-user/mips/target_cpu.h | 5 +++++
 linux-user/qemu.h            | 1 +
 linux-user/syscall.c         | 2 +-
 4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 59b543f740..0e757787d2 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1476,6 +1476,9 @@ static void load_elf_image(const char *image_name, const ImageSource *src,
     /* Usual start for brk is after all sections of the main executable. */
     info->brk = TARGET_PAGE_ALIGN(hiaddr + load_bias);
     info->elf_flags = ehdr->e_flags;
+#ifdef TARGET_MIPS
+    info->use_k0_tls = (ehdr->e_flags & EF_MIPS_MACH) == EF_MIPS_MACH_OCTEON;
+#endif
 
     prot_exec = PROT_EXEC;
 #ifdef TARGET_AARCH64
diff --git a/linux-user/mips/target_cpu.h b/linux-user/mips/target_cpu.h
index c375616c55..2bbd0a81c5 100644
--- a/linux-user/mips/target_cpu.h
+++ b/linux-user/mips/target_cpu.h
@@ -35,7 +35,12 @@ static inline void cpu_clone_regs_parent(CPUMIPSState *env, unsigned flags)
 
 static inline void cpu_set_tls(CPUMIPSState *env, target_ulong newtls)
 {
+    TaskState *ts = get_task_state(env_cpu(env));
+
     env->active_tc.CP0_UserLocal = newtls;
+    if (ts->info->use_k0_tls) {
+        env->active_tc.gpr[26] = newtls;
+    }
 }
 
 static inline abi_ulong get_sp_from_cpustate(CPUMIPSState *state)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index cfe5f45fc4..7f98fb2607 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -65,6 +65,7 @@ struct image_info {
         uint32_t        note_flags;
 
 #ifdef TARGET_MIPS
+        bool            use_k0_tls;
         int             fp_abi;
         int             interp_fp_abi;
 #endif
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f4b74ad350..8e96cc26db 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -13216,7 +13216,7 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
 #ifdef TARGET_NR_set_thread_area
     case TARGET_NR_set_thread_area:
 #if defined(TARGET_MIPS)
-      cpu_env->active_tc.CP0_UserLocal = arg1;
+      cpu_set_tls(cpu_env, arg1);
       return 0;
 #elif defined(TARGET_I386) && defined(TARGET_ABI32)
       return do_set_thread_area(cpu_env, arg1);
-- 
2.53.0