Re: [PATCH 1/2] linux-user: Introduce stubs for ELF AT_BASE_PLATFORM

[Philippe Mathieu-Daudé]

On 1/8/22 22:09, Jiaxun Yang wrote:
> AT_BASE_PLATFORM is a elf auxiliary vector pointing to a string
> to pass some architecture information.

We can be more specific.

"See getauxval(3) man-page."

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>   linux-user/elfload.c | 29 +++++++++++++++++++++++++++--
>   1 file changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index ce902dbd56..e7666c5c60 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1718,6 +1718,10 @@ static inline void init_thread(struct target_pt_regs 
> *regs,
>   
>   #endif /* TARGET_HEXAGON */
>   
> +#ifndef ELF_BASE_PLATFORM
> +#define ELF_BASE_PLATFORM (NULL)
> +#endif
> +
>   #ifndef ELF_PLATFORM
>   #define ELF_PLATFORM (NULL)
>   #endif
> @@ -2148,8 +2152,8 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, 
> int envc,
>       int i;
>       abi_ulong u_rand_bytes;
>       uint8_t k_rand_bytes[16];
> -    abi_ulong u_platform;
> -    const char *k_platform;
> +    abi_ulong u_platform, u_base_platform;
> +    const char *k_platform, *k_base_platform;
>       const int n = sizeof(elf_addr_t);
>   
>       sp = p;
> @@ -2171,6 +2175,22 @@ static abi_ulong create_elf_tables(abi_ulong p, int 
> argc, int envc,
>           }
>       }
>   
> +    u_base_platform = 0;
> +    k_base_platform = ELF_BASE_PLATFORM;
> +    if (k_base_platform) {
> +        size_t len = strlen(k_base_platform) + 1;
> +        if (STACK_GROWS_DOWN) {
> +            sp -= (len + n - 1) & ~(n - 1);
> +            u_base_platform = sp;
> +            /* FIXME - check return value of memcpy_to_target() for failure */
> +            memcpy_to_target(sp, k_base_platform, len);
> +        } else {
> +            memcpy_to_target(sp, k_base_platform, len);
> +            u_base_platform = sp;
> +            sp += len + 1;
> +        }
> +    }
> +
>       u_platform = 0;
>       k_platform = ELF_PLATFORM;
>       if (k_platform) {
> @@ -2212,6 +2232,8 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, 
> int envc,
>       }
>   
>       size = (DLINFO_ITEMS + 1) * 2;
> +    if (k_base_platform)
> +        size += 2;
>       if (k_platform)
>           size += 2;
>   #ifdef DLINFO_ARCH_ITEMS
> @@ -2289,6 +2311,9 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, 
> int envc,
>       NEW_AUX_ENT(AT_HWCAP2, (abi_ulong) ELF_HWCAP2);
>   #endif
>   
> +    if (u_base_platform) {
> +        NEW_AUX_ENT(AT_BASE_PLATFORM, u_base_platform);
> +    }
>       if (u_platform) {
>           NEW_AUX_ENT(AT_PLATFORM, u_platform);
>       }