[PATCH v2] Add build option to disable usage of scv on powerpc
Raphael M Zinsly
rzinsly@linux.ibm.com
Tue Jun 8 19:35:48 GMT 2021
Hi Matheus,
This patch LGTM.
Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>
On 04/06/2021 10:44, Matheus Castanho via Libc-alpha wrote:
> Commit 68ab82f56690ada86ac1e0c46bad06ba189a10ef added support for the scv
> syscall ABI on powerpc. Since then systems that have kernel and processor
> support started using scv. However adding the proper support for a new syscall
> ABI requires changes to several other projects (e.g. qemu, valgrind, strace,
> kernel), which are gradually receiving support.
>
> Meanwhile, having a way to disable scv on glibc at build time can be useful for
> distros that may encounter conflicts with projects that still do not support the
> scv ABI, buying time until proper support is added.
>
> This commit adds a --disable-scv option that disables scv support and uses sc
> for all syscalls, like before commit 68ab82f56690ada86ac1e0c46bad06ba189a10ef.
> ---
> Changes from v1:
> - Update INSTALL with info about the new configure option
> ---
> INSTALL | 4 ++++
> NEWS | 3 +++
> config.h.in | 3 +++
> configure | 16 ++++++++++++++++
> configure.ac | 8 ++++++++
> manual/install.texi | 4 ++++
> sysdeps/powerpc/powerpc64/sysdep.h | 16 ++++++++--------
> .../unix/sysv/linux/powerpc/powerpc64/clone.S | 14 +++++++++++---
> sysdeps/unix/sysv/linux/powerpc/syscall.S | 2 +-
> sysdeps/unix/sysv/linux/powerpc/sysdep.h | 2 +-
> 10 files changed, 59 insertions(+), 13 deletions(-)
>
> diff --git a/INSTALL b/INSTALL
> index bc761ab98b..56ed01d438 100644
> --- a/INSTALL
> +++ b/INSTALL
> @@ -253,6 +253,10 @@ if 'CFLAGS' is specified it must enable optimization. For example:
> (set glibc.malloc.tcache_count to zero), this option can be used to
> remove it from the build completely.
>
> +'--disable-scv'
> + Disable using 'scv' instruction for syscalls. All syscalls will
> + use 'sc' instead, even if the kernel supports 'scv'. PowerPC only.
> +
> '--build=BUILD-SYSTEM'
> '--host=HOST-SYSTEM'
> These options are for cross-compiling. If you specify both options
> diff --git a/NEWS b/NEWS
> index 1bf3daa502..e0fe9d70f0 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -31,6 +31,9 @@ Major new features:
> __STDC_WANT_IEC_60559_BFP_EXT__, as specified in TS 18661-1, is
> defined, and when _GNU_SOURCE is defined.
>
> +* On powerpc64*, glibc can now be compiled without scv support using the
> + --disable-scv configure option.
> +
> Deprecated and removed features, and other changes affecting compatibility:
>
> * The function pthread_mutex_consistent_np has been deprecated; programs
> diff --git a/config.h.in b/config.h.in
> index dbeb7c6243..8b45a3a61d 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -26,6 +26,9 @@
> /* On powerpc64, define if the compiler supports -mcpu=power10. */
> #undef USE_PPC64_MCPU_POWER10
>
> +/* On powerpc*, define if scv should be used for syscalls (when available). */
> +#undef USE_PPC_SCV
> +
> /* Define if _Unwind_Find_FDE should be exported from glibc. */
> #undef EXPORT_UNWIND_FIND_FDE
>
> diff --git a/configure b/configure
> index 5dde2ba355..c588c90d21 100755
> --- a/configure
> +++ b/configure
> @@ -791,6 +791,7 @@ enable_pt_chown
> enable_tunables
> enable_mathvec
> enable_cet
> +enable_scv
> with_cpu
> '
> ac_precious_vars='build_alias
> @@ -1463,6 +1464,8 @@ Optional Features:
> depends on architecture]
> --enable-cet enable Intel Control-flow Enforcement Technology
> (CET), x86 only
> + --disable-scv syscalls will not use scv instruction, even if the
> + kernel supports it, powerpc only
>
> Optional Packages:
> --with-PACKAGE[=ARG] use PACKAGE [ARG=yes]
> @@ -3776,6 +3779,19 @@ else
> fi
>
>
> +# Check whether --enable-scv was given.
> +if test "${enable_scv+set}" = set; then :
> + enableval=$enable_scv; use_scv=$enableval
> +else
> + use_scv=yes
> +fi
> +
> +
> +if test "$use_scv" != "no"; then :
> + $as_echo "#define USE_PPC_SCV 1" >>confdefs.h
> +
> +fi
> +
> # We keep the original values in `$config_*' and never modify them, so we
> # can write them unchanged into config.make. Everything else uses
> # $machine, $vendor, and $os, and changes them whenever convenient.
> diff --git a/configure.ac b/configure.ac
> index 19051b8ee0..857e237e1b 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -470,6 +470,14 @@ AC_ARG_ENABLE([cet],
> [enable_cet=$enableval],
> [enable_cet=$libc_cv_compiler_default_cet])
>
> +AC_ARG_ENABLE([scv],
> + AC_HELP_STRING([--disable-scv],
> + [syscalls will not use scv instruction, even if the kernel supports it, powerpc only]),
> + [use_scv=$enableval],
> + [use_scv=yes])
> +
> +AS_IF([[test "$use_scv" != "no"]],[AC_DEFINE(USE_PPC_SCV)])
> +
> # We keep the original values in `$config_*' and never modify them, so we
> # can write them unchanged into config.make. Everything else uses
> # $machine, $vendor, and $os, and changes them whenever convenient.
> diff --git a/manual/install.texi b/manual/install.texi
> index f1d858fb78..254a8a9a79 100644
> --- a/manual/install.texi
> +++ b/manual/install.texi
> @@ -282,6 +282,10 @@ this cache can be disabled on a per-application basis using tunables
> (set glibc.malloc.tcache_count to zero), this option can be used to
> remove it from the build completely.
>
> +@item --disable-scv
> +Disable using @code{scv} instruction for syscalls. All syscalls will use
> +@code{sc} instead, even if the kernel supports @code{scv}. PowerPC only.
> +
> @item --build=@var{build-system}
> @itemx --host=@var{host-system}
> These options are for cross-compiling. If you specify both options and
> diff --git a/sysdeps/powerpc/powerpc64/sysdep.h b/sysdeps/powerpc/powerpc64/sysdep.h
> index 1ea4c3b917..589f7c8d18 100644
> --- a/sysdeps/powerpc/powerpc64/sysdep.h
> +++ b/sysdeps/powerpc/powerpc64/sysdep.h
> @@ -306,7 +306,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> beq \JUMPFALSE
> .endm
>
> -#if IS_IN(rtld)
> +#if !defined(USE_PPC_SCV) || IS_IN(rtld)
> # define DO_CALL(syscall) \
> li r0,syscall; \
> DO_CALL_SC
> @@ -323,7 +323,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> b 1f; \
> 0: DO_CALL_SC; \
> 1:
> -#endif /* IS_IN(rtld) */
> +#endif /* !defined(USE_PPC_SCV) || IS_IN(rtld) */
>
> /* DO_CALL_SC and DO_CALL_SCV expect the syscall number to be in r0. */
> #define DO_CALL_SC \
> @@ -378,7 +378,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> .endif
> #endif
>
> -#if IS_IN(rtld)
> +#if !defined(USE_PPC_SCV) || IS_IN(rtld)
> # define PSEUDO_RET \
> RET_SC; \
> TAIL_CALL_SYSCALL_ERROR
> @@ -395,7 +395,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> b 1f; \
> 0: RET_SC; \
> 1: TAIL_CALL_SYSCALL_ERROR
> -#endif
> +#endif /* !defined(USE_PPC_SCV) || IS_IN(rtld) */
>
> #define RET_SCV \
> li r9,-4095; \
> @@ -417,7 +417,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> ENTRY (name); \
> DO_CALL (SYS_ify (syscall_name))
>
> -#if IS_IN(rtld)
> +#if !defined(USE_PPC_SCV) || IS_IN(rtld)
> # define PSEUDO_RET_NOERRNO \
> blr
> #else
> @@ -425,7 +425,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> # define PSEUDO_RET_NOERRNO \
> NVOLREG_RESTORE; \
> blr
> -#endif /* IS_IN(rtld) */
> +#endif /* !defined(USE_PPC_SCV) || IS_IN(rtld) */
>
> #define ret_NOERRNO PSEUDO_RET_NOERRNO
>
> @@ -438,7 +438,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> ENTRY (name); \
> DO_CALL (SYS_ify (syscall_name))
>
> -#if IS_IN(rtld)
> +#if !defined(USE_PPC_SCV) || IS_IN(rtld)
> # define PSEUDO_RET_ERRVAL \
> blr
> #else
> @@ -446,7 +446,7 @@ LT_LABELSUFFIX(name,_name_end): ; \
> # define PSEUDO_RET_ERRVAL \
> NVOLREG_RESTORE; \
> blr
> -#endif /* IS_IN(rtld) */
> +#endif /* !defined(USE_PPC_SCV) || IS_IN(rtld) */
>
> #define ret_ERRVAL PSEUDO_RET_ERRVAL
>
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
> index e9bd8cb960..777ead80b0 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
> @@ -38,11 +38,13 @@ ENTRY (__clone)
> beq- cr0,L(badargs)
>
> /* Save some regs in the "red zone". */
> +#ifdef USE_PPC_SCV
> std r28,-32(r1)
> + cfi_offset(r28,-32)
> +#endif
> std r29,-24(r1)
> std r30,-16(r1)
> std r31,-8(r1)
> - cfi_offset(r28,-32)
> cfi_offset(r29,-24)
> cfi_offset(r30,-16)
> cfi_offset(r31,-8)
> @@ -71,6 +73,7 @@ ENTRY (__clone)
>
> /* Do the call. */
> li r0,SYS_ify(clone)
> +#ifdef USE_PPC_SCV
> CHECK_SCV_SUPPORT r28 0f
> /* This is equivalent to DO_CALL_SCV, but we cannot use the macro here
> because it uses CFI directives and we just called cfi_endproc. */
> @@ -87,6 +90,7 @@ ENTRY (__clone)
> /* When using scv, error is indicated by negative r3. */
> cmpdi cr1,r3,0
> b 1f
> +#endif /* USE_PPC_SCV */
> 0: DO_CALL_SC
>
> /* Check for child process. */
> @@ -119,22 +123,26 @@ L(parent):
> cmpdi cr1,r28,0
>
> /* Parent. Restore registers & return. */
> +#ifdef USE_PPC_SCV
> cfi_offset(r28,-32)
> + ld r28,-32(r1)
> + cfi_restore(r28)
> +#endif
> cfi_offset(r29,-24)
> cfi_offset(r30,-16)
> cfi_offset(r31,-8)
> - ld r28,-32(r1)
> ld r29,-24(r1)
> ld r30,-16(r1)
> ld r31,-8(r1)
> - cfi_restore(r28)
> cfi_restore(r29)
> cfi_restore(r30)
> cfi_restore(r31)
>
> +#ifdef USE_PPC_SCV
> beq cr1,0f
> RET_SCV
> b 1f
> +#endif
> 0: RET_SC
> 1: TAIL_CALL_SYSCALL_ERROR
>
> diff --git a/sysdeps/unix/sysv/linux/powerpc/syscall.S b/sysdeps/unix/sysv/linux/powerpc/syscall.S
> index d6ec87f006..a29652feaf 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/syscall.S
> +++ b/sysdeps/unix/sysv/linux/powerpc/syscall.S
> @@ -25,7 +25,7 @@ ENTRY (syscall)
> mr r6,r7
> mr r7,r8
> mr r8,r9
> -#if !IS_IN(rtld) && (defined(__PPC64__) || defined(__powerpc64__))
> +#if defined(USE_PPC_SCV) && !IS_IN(rtld) && (defined(__PPC64__) || defined(__powerpc64__))
> CHECK_SCV_SUPPORT r9 0f
> DO_CALL_SCV
> RET_SCV
> diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> index 2f31f9177b..4b9d43c636 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> @@ -125,7 +125,7 @@
>
> /* When inside the dynamic loader, the thread pointer may not have been
> initialized yet, so don't check for scv support in that case. */
> -# if !IS_IN(rtld)
> +# if defined(USE_PPC_SCV) && !IS_IN(rtld)
> # undef TRY_SYSCALL_SCV
> # define TRY_SYSCALL_SCV(nr) \
> CHECK_THREAD_POINTER && THREAD_GET_HWCAP() & PPC_FEATURE2_SCV ? \
>
--
Raphael Moreira Zinsly
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