On 09/05/2016 06:03 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> The patch below was submitted to be applied to the 4.7-stable tree.
>
> I fail to see how this patch meets the stable kernel rules as found at
> Documentation/stable_kernel_rules.txt.
>
> I could be totally wrong, and if so, please respond to
> <stable@xxxxxxxxxxxxxxx> and let me know why this patch should be
> applied. Otherwise, it is now dropped from my patch queues, never to be
> seen again.
Hi Greg,
We are about to switch to new version of GNU tools (gcc 6.x based) which
unfortunately has a non compatible ABI change - as described in the patch.
Some of our customers are going to stick with older kernels and thus this helps
them upgrade to newer tools with their existing baseline kernels.
Thx,
-Vineet
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
> From 840c054fd0efb048df6fceb0c46385ec5b66dfe6 Mon Sep 17 00:00:00 2001
> From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
> Date: Wed, 10 Aug 2016 14:10:57 -0700
> Subject: [PATCH] ARC: Support syscall ABI v4
>
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>
> diff --git a/arch/arc/include/uapi/asm/elf.h b/arch/arc/include/uapi/asm/elf.h
> index 0f99ac8fcbb2..0037a587320d 100644
> --- 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 b5db9e7fd649..be1972bd2729 100644
> --- a/arch/arc/kernel/process.c
> +++ b/arch/arc/kernel/process.c
> @@ -199,7 +199,7 @@ int elf_check_arch(const struct elf32_hdr *x)
> }
>
> 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 a946400a86d0..f52a0d0dc462 100644
> --- a/arch/arc/kernel/setup.c
> +++ b/arch/arc/kernel/setup.c
> @@ -291,8 +291,10 @@ 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;
> }
>
>
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html