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SubjectRe: [PATCH] powerpc: Fix kernel-jump address for ppc64 wrapper boot
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Le 04/06/2021 à 11:22, He Ying a écrit :
> From "64-bit PowerPC ELF Application Binary Interface Supplement 1.9",
> we know that the value of a function pointer in a language like C is
> the address of the function descriptor and the first doubleword
> of the function descriptor contains the address of the entry point
> of the function.
>
> So, when we want to jump to an address (e.g. addr) to execute for
> PPC-elf64abi, we should assign the address of addr *NOT* addr itself
> to the function pointer or system will jump to the wrong address.
>
> Link: https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#FUNC-DES
> Signed-off-by: He Ying <heying24@huawei.com>
> ---
> arch/powerpc/boot/main.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
> index cae31a6e8f02..50fd7f11b642 100644
> --- a/arch/powerpc/boot/main.c
> +++ b/arch/powerpc/boot/main.c
> @@ -268,7 +268,16 @@ void start(void)
> if (console_ops.close)
> console_ops.close();
>
> +#ifdef CONFIG_PPC64_BOOT_WRAPPER

This kind of need doesn't desserve a #ifdef, see
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation

You can do:


kentry = (kernel_entry_t)(IS_ENABLED(CONFIG_PPC64_BOOT_WRAPPER) ? &vmlinux.addr : vmlinux.addr);


Or, if you prefer something less compact:


if (IS_ENABLED(CONFIG_PPC64_BOOT_WRAPPER))
kentry = (kernel_entry_t) &vmlinux.addr;
else
kentry = (kernel_entry_t) vmlinux.addr;


> + /*
> + * For PPC-elf64abi, the value of a function pointer is the address
> + * of the function descriptor. And the first doubleword of a function
> + * descriptor contains the address of the entry point of the function.
> + */
> + kentry = (kernel_entry_t) &vmlinux.addr;
> +#else
> kentry = (kernel_entry_t) vmlinux.addr;
> +#endif
> if (ft_addr) {
> if(platform_ops.kentry)
> platform_ops.kentry(ft_addr, vmlinux.addr);
>

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