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Date: Fri, 5 Apr 2013 18:06:00 +1100
From: Michael Ellerman <michael@...erman.id.au>
To: Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
Cc: benh@...nel.crashing.org, michaele@....ibm.com,
Steve Munroe <sjmunroe@...ibm.com>,
linux-kernel@...r.kernel.org, paulus@...ba.org,
Ryan Arnold <ryanarn@...ibm.com>,
linuxppc-dev@...ts.ozlabs.org, akpm@...ux-foundation.org,
vda.linux@...glemail.com, viro@...iv.linux.org.uk
Subject: Re: [PATCH] powerpc: Add HWCAP2 aux entry
Hi guys,
Added some folks to CC, blame scripts/get_maintainer.pl.
Comment below ..
On Tue, Apr 02, 2013 at 02:22:05PM -0700, Nishanth Aravamudan wrote:
> From: Michael Neuling <michael.neuling@....ibm.com>
>
> We are currently out of free bits in AT_HWCAP. With POWER8, we have
> several hardware features that we need to advertise. Tested on POWER and
> x86.
>
> Signed-off-by: Michael Neuling <michael.neuling@....ibm.com>
> Signed-off-by: Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
>
> diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
> index fb3245e..ccadad6 100644
> --- a/arch/powerpc/include/asm/cputable.h
> +++ b/arch/powerpc/include/asm/cputable.h
> @@ -52,6 +52,7 @@ struct cpu_spec {
> char *cpu_name;
> unsigned long cpu_features; /* Kernel features */
> unsigned int cpu_user_features; /* Userland features */
> + unsigned int cpu_user_features2; /* Userland features v2 */
> unsigned int mmu_features; /* MMU features */
>
> /* cache line sizes */
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index ac9790f..cc0655a 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -61,6 +61,7 @@ typedef elf_vrregset_t elf_fpxregset_t;
> instruction set this cpu supports. This could be done in userspace,
> but it's not easy, and we've already done it here. */
> # define ELF_HWCAP (cur_cpu_spec->cpu_user_features)
> +# define ELF_HWCAP2 (cur_cpu_spec->cpu_user_features2)
>
> /* This yields a string that ld.so will use to load implementation
> specific libraries for optimization. This is more specific in
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 3939829..51adc23 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -140,6 +140,13 @@ static int padzero(unsigned long elf_bss)
> #define ELF_BASE_PLATFORM NULL
> #endif
>
> +/*
> + * Most archs don't need this
> + */
> +#ifndef ELF_HWCAP2
> +#define ELF_HWCAP2 (0)
> +#endif
> +
> static int
> create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
> unsigned long load_addr, unsigned long interp_load_addr)
> @@ -240,6 +247,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
> NEW_AUX_ENT(AT_EGID, from_kgid_munged(cred->user_ns, cred->egid));
> NEW_AUX_ENT(AT_SECURE, security_bprm_secureexec(bprm));
> NEW_AUX_ENT(AT_RANDOM, (elf_addr_t)(unsigned long)u_rand_bytes);
> + NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2);
Wouldn't it be safer to not emit AT_HWCAP2 unless it is defined by the arch?
That way the change would only impact powerpc.
cheers
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 9c13e02..0b553d3 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -469,6 +469,13 @@ error_kill:
> #endif
>
> /*
> + * Most archs don't need this
> + */
> +#ifndef ELF_HWCAP2
> +#define ELF_HWCAP2 (0)
> +#endif
> +
> +/*
> * present useful information to the program by shovelling it onto the new
> * process's stack
> */
> @@ -483,7 +490,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
> size_t platform_len = 0, len;
> char *k_platform, *k_base_platform;
> char __user *u_platform, *u_base_platform, *p;
> - long hwcap;
> int loop;
> int nr; /* reset for each csp adjustment */
>
> @@ -502,8 +508,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
> return -EFAULT;
> #endif
>
> - hwcap = ELF_HWCAP;
> -
> /*
> * If this architecture has a platform capability string, copy it
> * to userspace. In some cases (Sparc), this info is impossible
> @@ -617,7 +621,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
>
> nr = 0;
> csp -= DLINFO_ITEMS * 2 * sizeof(unsigned long);
> - NEW_AUX_ENT(AT_HWCAP, hwcap);
> + NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP);
> + NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2);
> NEW_AUX_ENT(AT_PAGESZ, PAGE_SIZE);
> NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC);
> NEW_AUX_ENT(AT_PHDR, exec_params->ph_addr);
> diff --git a/include/uapi/linux/auxvec.h b/include/uapi/linux/auxvec.h
> index 61594d5..835c065 100644
> --- a/include/uapi/linux/auxvec.h
> +++ b/include/uapi/linux/auxvec.h
> @@ -28,6 +28,7 @@
> #define AT_BASE_PLATFORM 24 /* string identifying real platform, may
> * differ from AT_PLATFORM. */
> #define AT_RANDOM 25 /* address of 16 random bytes */
> +#define AT_HWCAP2 26 /* extension of AT_HWCAP */
>
> #define AT_EXECFN 31 /* filename of program */
>
>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@...ts.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
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