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SubjectRe: [RESEND PATCH] ARM: kdump: Add vmcore_elf64_check_arch
On Sat, May 03, 2014 at 02:44:46PM +0100, Liu Hua wrote:
> Hi Will or Russell,

Hello,

> With CONFIG_LPAE=y, memory in 32-bit ARM systems can exceed
> 4G. So if we use kdump in such systems. The capture kernel
> should parse 64-bit elf header(parse_crash_elf64_headers).
>
> And this process can not pass because ARM linux only provides
> zero vmcore_elf64_check_arch function by commit 4b3bf7aef.
>
> This patch adds check functions related to elf64 header.

[...]

> diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c
> index d0d1e83..452086a 100644
> --- a/arch/arm/kernel/elf.c
> +++ b/arch/arm/kernel/elf.c
> @@ -38,6 +38,39 @@ int elf_check_arch(const struct elf32_hdr *x)
> }
> EXPORT_SYMBOL(elf_check_arch);
>
> +int elf_check_arch_64(const struct elf64_hdr *x)
> +{
> + unsigned int eflags;
> +
> + /* Make sure it's an ARM executable */
> + if (x->e_machine != EM_ARM)
> + return 0;
> +
> + /* Make sure the entry address is reasonable */
> + if (x->e_entry & 1) {
> + if (!(elf_hwcap & HWCAP_THUMB))
> + return 0;
> + } else if (x->e_entry & 3)
> + return 0;
> +
> + eflags = x->e_flags;
> + if ((eflags & EF_ARM_EABI_MASK) == EF_ARM_EABI_UNKNOWN) {
> + unsigned int flt_fmt;
> +
> + /* APCS26 is only allowed if the CPU supports it */
> + if ((eflags & EF_ARM_APCS_26) && !(elf_hwcap & HWCAP_26BIT))
> + return 0;
> +
> + flt_fmt = eflags & (EF_ARM_VFP_FLOAT | EF_ARM_SOFT_FLOAT);
> +
> + /* VFP requires the supporting code */
> + if (flt_fmt == EF_ARM_VFP_FLOAT && !(elf_hwcap & HWCAP_VFP))
> + return 0;
> + }
> + return 1;
> +}
> +EXPORT_SYMBOL(elf_check_arch_64);

This function looks identical to elf_check_arch. Why do we need to duplicate
that code? You could use some pre-processor magic to make the core part of
the functions agnostic to header type.

In fact, if elf_check_arch could handle both header types then the generic
definition of vmcore_elf64_check_arch in include/linux/crash_dump.h would
work out of the box.

Will


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