[PATCH v3 10/16] unistd: Avoid PLT entries with _FORTIFY_SOURCE

[Siddhesh Poyarekar]

On 2023-06-28 04:42, Frédéric Bérat wrote:
> The change is meant to avoid unwanted PLT entries for the read_chk,
> getdomainname_chk and getlogin_r_chk routines when _FORTIFY_SOURCE is set.
> ---
>   debug/getdomainname_chk.c | 1 +
>   debug/read_chk.c          | 1 +
>   include/unistd.h          | 4 ++++
>   login/getlogin_r_chk.c    | 1 +
>   posix/bits/unistd-decl.h  | 6 +++---
>   5 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/debug/getdomainname_chk.c b/debug/getdomainname_chk.c
> index ccea1b2d9e..c0e6c7bd4b 100644
> --- a/debug/getdomainname_chk.c
> +++ b/debug/getdomainname_chk.c
> @@ -26,3 +26,4 @@ __getdomainname_chk (char *buf, size_t buflen, size_t nreal)
>   
>     return getdomainname (buf, buflen);
>   }
> +libc_hidden_builtin_def (__getdomainname_chk)

getdomainname is not a builtin, so perhaps just use libc_hidden_def?  It 
doesn't make a difference in practice, but I reckon we may make a 
distinction in future and this might slip up.

Builtins are defined in gcc sources, see gcc/builtins.def.  As an aside 
though, I wonder if we've ever made this distinction, but that's a QoI 
issue at the moment.

> diff --git a/debug/read_chk.c b/debug/read_chk.c
> index 17588736a1..dfd87206b2 100644
> --- a/debug/read_chk.c
> +++ b/debug/read_chk.c
> @@ -25,3 +25,4 @@ __read_chk (int fd, void *buf, size_t nbytes, size_t buflen)
>   
>     return __read (fd, buf, nbytes);
>   }
> +libc_hidden_builtin_def (__read_chk)

Likewise, not a builtin.

> diff --git a/include/unistd.h b/include/unistd.h
> index b042a485f9..243e52b471 100644
> --- a/include/unistd.h
> +++ b/include/unistd.h
> @@ -32,6 +32,10 @@ libc_hidden_proto (readlinkat)
>   libc_hidden_proto (fsync)
>   libc_hidden_proto (fdatasync)
>   
> +libc_hidden_builtin_proto (__read_chk)
> +libc_hidden_builtin_proto (__getdomainname_chk)
> +libc_hidden_builtin_proto (__getlogin_r_chk)

Likewise, libc_hidden_proto.

> +
>   /* Now define the internal interfaces.  */
>   extern int __access (const char *__name, int __type);
>   libc_hidden_proto (__access)
> diff --git a/login/getlogin_r_chk.c b/login/getlogin_r_chk.c
> index 12a0d12bd4..576567f287 100644
> --- a/login/getlogin_r_chk.c
> +++ b/login/getlogin_r_chk.c
> @@ -26,3 +26,4 @@ __getlogin_r_chk (char *buf, size_t buflen, size_t nreal)
>   
>     return getlogin_r (buf, buflen);
>   }
> +libc_hidden_builtin_def (__getlogin_r_chk)

Likewise.

> diff --git a/posix/bits/unistd-decl.h b/posix/bits/unistd-decl.h
> index 2d0f7a4456..2603039767 100644
> --- a/posix/bits/unistd-decl.h
> +++ b/posix/bits/unistd-decl.h
> @@ -26,7 +26,7 @@
>   extern ssize_t __read_chk (int __fd, void *__buf, size_t __nbytes,
>   			   size_t __buflen)
>        __wur __attr_access ((__write_only__, 2, 3));
> -extern ssize_t __REDIRECT (__read_alias, (int __fd, void *__buf,
> +extern ssize_t __REDIRECT_FORTIFY (__read_alias, (int __fd, void *__buf,
>   						  size_t __nbytes), read)
>        __wur __attr_access ((__write_only__, 2, 3));
>   extern ssize_t __REDIRECT (__read_chk_warn,
> @@ -157,7 +157,7 @@ extern int __REDIRECT_NTH (__ttyname_r_chk_warn,
>   #ifdef __USE_POSIX199506
>   extern int __getlogin_r_chk (char *__buf, size_t __buflen, size_t __nreal)
>        __nonnull ((1)) __attr_access ((__write_only__, 1, 2));
> -extern int __REDIRECT (__getlogin_r_alias, (char *__buf, size_t __buflen),
> +extern int __REDIRECT_FORTIFY (__getlogin_r_alias, (char *__buf, size_t __buflen),
>   		       getlogin_r) __nonnull ((1));
>   extern int __REDIRECT (__getlogin_r_chk_warn,
>   		       (char *__buf, size_t __buflen, size_t __nreal),
> @@ -184,7 +184,7 @@ extern int __REDIRECT_NTH (__gethostname_chk_warn,
>   #if defined __USE_MISC || (defined __USE_XOPEN && !defined __USE_UNIX98)
>   extern int __getdomainname_chk (char *__buf, size_t __buflen, size_t __nreal)
>        __THROW __nonnull ((1)) __wur __attr_access ((__write_only__, 1, 2));
> -extern int __REDIRECT_NTH (__getdomainname_alias, (char *__buf,
> +extern int __REDIRECT_FORTIFY_NTH (__getdomainname_alias, (char *__buf,
>   						   size_t __buflen),
>   			   getdomainname) __nonnull ((1))
>        __wur __attr_access ((__write_only__, 1, 2));