ARC: Support syscall ABI v4

[ Upstream commit 840c054fd0efb048df6fceb0c46385ec5b66dfe6 ]

The syscall ABI includes the gcc functional calling ABI since a syscall
implies userland caller and kernel callee.

The current gcc ABI (v3) for ARCv2 ISA required 64-bit data be passed in
even-odd register pairs, (potentially punching reg holes when passing such
values as args). This was partly driven by the fact that the double-word
LDD/STD instructions in ARCv2 expect the register alignment and thus gcc
forcing this avoids extra MOV at the cost of a few unused register (which we
have plenty anyways).

This however was rejected as part of upstreaming gcc port to HS. So the new
ABI v4 doesn't enforce the even-odd reg restriction.

Do note that for ARCompact ISA builds v3 and v4 are practically the same in
terms of gcc code generation.

In terms of change management, we infer the new ABI if gcc 6.x onwards
is used for building the kernel.

This also needs a stable backport to enable older kernels to work with
new tools/user-space

Cc: <stable@vger.kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/arch/arc/include/uapi/asm/elf.h b/arch/arc/include/uapi/asm/elf.h
index 0f99ac8fcbb23f051753c4fb8e551a0e13541394..0037a587320d51c4262e7c3b7b504a8dafb34ddc 100644 (file)
--- a/arch/arc/include/uapi/asm/elf.h
+++ b/arch/arc/include/uapi/asm/elf.h
@@ -13,8 +13,15 @@
 
 /* Machine specific ELF Hdr flags */
 #define EF_ARC_OSABI_MSK       0x00000f00
-#define EF_ARC_OSABI_ORIG      0x00000000   /* MUST be zero for back-compat */
-#define EF_ARC_OSABI_CURRENT   0x00000300   /* v3 (no legacy syscalls) */
+
+#define EF_ARC_OSABI_V3                0x00000300   /* v3 (no legacy syscalls) */
+#define EF_ARC_OSABI_V4                0x00000400   /* v4 (64bit data any reg align) */
+
+#if __GNUC__ < 6
+#define EF_ARC_OSABI_CURRENT   EF_ARC_OSABI_V3
+#else
+#define EF_ARC_OSABI_CURRENT   EF_ARC_OSABI_V4
+#endif
 
 typedef unsigned long elf_greg_t;
 typedef unsigned long elf_fpregset_t;

diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index e095c557afdddc3aefce744c97d5d7bb20a6f2e6..72d3990799d5d3ace403d21e59692cf128313319 100644 (file)
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -201,7 +201,7 @@ int elf_check_arch(const struct elf32_hdr *x)
                return 0;
 
        eflags = x->e_flags;
-       if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
+       if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
                pr_err("ABI mismatch - you need newer toolchain\n");
                force_sigsegv(SIGSEGV, current);
                return 0;

diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 1d167c6df8caae8a48d59b2aa08539e9f20b51d6..321a4b67bfa0eea5168ad65bab35601bb2793349 100644 (file)
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -237,8 +237,10 @@ static char *arc_extn_mumbojumbo(int cpu_id, char *buf, int len)
                               cpu->dccm.base_addr, TO_KB(cpu->dccm.sz),
                               cpu->iccm.base_addr, TO_KB(cpu->iccm.sz));
 
-       n += scnprintf(buf + n, len - n,
-                      "OS ABI [v3]\t: no-legacy-syscalls\n");
+       n += scnprintf(buf + n, len - n, "OS ABI [v%d]\t: %s\n",
+                       EF_ARC_OSABI_CURRENT >> 8,
+                       EF_ARC_OSABI_CURRENT == EF_ARC_OSABI_V3 ?
+                       "no-legacy-syscalls" : "64-bit data any register aligned");
 
        return buf;
 }