[v2,05/11] powerpc64: Add the clone3 wrapper
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Commit Message
It follows the internal signature:
extern int clone3 (struct clone_args *__cl_args, size_t __size,
int (*__func) (void *__arg), void *__arg);
The powerpc64 ABI requires an initial stackframe so the child can
store/restore the TOC. Iit is create prior calling clone3 by
adjusting the stack size (since kernel will compute the stack as
stack plus size).
Checked on powerpc64-linux-gnu (power8, kernel 6.0) and
powerpc64le-linux-gnu (power9, kernel 4.18).
---
.../sysv/linux/powerpc/powerpc64/clone3.S | 152 ++++++++++++++++++
sysdeps/unix/sysv/linux/powerpc/sysdep.h | 1 +
2 files changed, 153 insertions(+)
create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
Comments
On 11/4/22 2:01 PM, Adhemerval Zanella via Libc-alpha wrote:
> It follows the internal signature:
>
> extern int clone3 (struct clone_args *__cl_args, size_t __size,
> int (*__func) (void *__arg), void *__arg);
>
> The powerpc64 ABI requires an initial stackframe so the child can
> store/restore the TOC. Iit is create prior calling clone3 by
trivial nit, s/Iit/It/.
> adjusting the stack size (since kernel will compute the stack as
> stack plus size).
>
> Checked on powerpc64-linux-gnu (power8, kernel 6.0) and
> powerpc64le-linux-gnu (power9, kernel 4.18).
> ---
> .../sysv/linux/powerpc/powerpc64/clone3.S | 152 ++++++++++++++++++
> sysdeps/unix/sysv/linux/powerpc/sysdep.h | 1 +
> 2 files changed, 153 insertions(+)
> create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
>
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
> new file mode 100644
> index 0000000000..0fe2fe91db
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
> @@ -0,0 +1,152 @@
> +/* The clone3 syscall wrapper. Linux/powerpc64 version.
> + Copyright (C) 2022 Free Software Foundation, Inc.
> +
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <sysdep.h>
> +#define _ERRNO_H 1
> +#include <bits/errno.h>
> +
> +/* The userland implementation is:
> + int clone3 (struct clone_args *cl_args, size_t size,
> + int (*func)(void *arg), void *arg);
> +
> + the kernel entry is:
> + int clone3 (struct clone_args *cl_args, size_t size);
> +
> + The parameters are passed in registers from userland:
> + r3: cl_args
> + r4: size
> + r5: func
> + r6: arg */
> +
> + .text
> +ENTRY(__clone3)
> + CALL_MCOUNT 4
> +
> + /* Sanity checks args. */
> + cmpdi cr0, r3, 0
> + cmpdi cr1, r5, 0
> + cror cr0*4+eq, cr1*4+eq, cr0*4+eq
> + beq cr0,L(badargs)
> +
> + /* Save some regs in the "red zone". */
Is there reason to avoid explicitly stacking a frame in here? Also, does
the red zone exist on ELFv1?
> +#ifdef USE_PPC_SCV
> + std r28, -24(r1)
> + cfi_offset (r28, -24)
> +#endif
> + std r29, -16(r1)
> + std r30, -8(r1)
> + cfi_offset (r29, -16)
> + cfi_offset (r30, -8)
> +
> + /* Save fn and args across syscall. */
trivial nit, s/fn/func/ s/args/arg/.
> + mr r30, r5 /* Function in r30. */
> + mr r29, r6 /* Argument in r29. */
> +
> + /* End FDE now, because in the child the unwind info will be
> + wrong. */
> + cfi_endproc
> +
> + /* Setup a minimum stack fram for child. It needs to first calculate
s/fram/frame/.
> + the effective stack address, write the start NULL frame-pointer,
> + and update the frame size in the input cl_args. */
> + ld r7, 40(r3) /* Load stack value. */
> + ld r8, 48(r3) /* Load stack_size value. */
> + li r10, 0
> + add r7, r7, r8 /* Calculate effective stack address. */
> + std r10, -FRAME_MIN_SIZE_PARM(r7)
This is clearing the backchain pointer? Maybe a small comment here.
> + addi r8, r8, -FRAME_MIN_SIZE_PARM
> + std r8, 48(r3)
> +
> + /* Do the system call, the kernel expects:
> + r0: system call numer
> + r3: cl_args
> + r4: size */
> + li r0, SYS_ify(clone3)
> +#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. */
> + mflr r9
> + std r9, FRAME_LR_SAVE(r1)
> + .machine "push"
> + .machine "power9"
> + scv 0
> + .machine "pop"
> + ld r9, FRAME_LR_SAVE(r1)
> + mtlr r9
> +
> + /* When using scv, error is indicated by negative r3. */
With scv an, an error is a value -4095 <= x < 0. This test should be
more specific.
> + cmpdi cr1, r3, 0
> + b 1f
> +#endif
> +0: DO_CALL_SC
> +
> + /* With sc, error is indicated by cr0.SO. */
> + cmpdi cr1, r3, 0
> + crandc cr1*4+eq, cr1*4+eq, cr0*4+so > +
> +1: bne- cr1,L(parent)
> +
> + /* Child, load the function and arguments. */
> + std r2, FRAME_TOC_SAVE(r1)
> + PPC64_LOAD_FUNCPTR r30
> + mr r3, r29
> + bctrl
> + ld r2, FRAME_TOC_SAVE(r1)
> +
> + li r0, SYS_ify(exit)
> + DO_CALL_SC
Minor nit, this should also use scv if supported.
> + /* We won't ever get here but provide a nop so that the linker
> + will insert a toc adjusting stub if necessary. */
> + nop
> +
> +L(badargs):
> + cfi_startproc
> + li r3, EINVAL
> + TAIL_CALL_SYSCALL_ERROR
> +
> +L(parent):
> + /* Check if svc is available. */
s/svc/scv/.
> + cmpdi cr1, r28, 0
> +
> + /* Parent. Restore registers & return. */
> +#ifdef USE_PPC_SCV
> + cfi_offset (r28, -24)
> + ld r28, -24(r1)
> + cfi_restore (r28)
> +#endif
> + cfi_offset (r29,-16)
> + cfi_offset (r30,-8)
> + ld r29, -16(r1)
> + ld r30, -8(r1)
> + cfi_restore (r29)
> + cfi_restore (r30)
> +
> +#ifdef USE_PPC_SCV
> + beq cr1, 0f
> + RET_SCV
> + b 1f
> +#endif
> +0: RET_SC
> +1: TAIL_CALL_SYSCALL_ERROR
> +
> +PSEUDO_END (__clone3)
> +
> +libc_hidden_def (__clone3)
> +weak_alias (__clone3, clone3)
> diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> index 9e44818978..af63b3974b 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
> @@ -214,6 +214,7 @@
> #if defined(__PPC64__) || defined(__powerpc64__)
> #define HAVE_CLOCK_GETRES64_VSYSCALL "__kernel_clock_getres"
> #define HAVE_CLOCK_GETTIME64_VSYSCALL "__kernel_clock_gettime"
> +#define HAVE_CLONE3_WRAPPER 1
> #else
> #define HAVE_CLOCK_GETRES_VSYSCALL "__kernel_clock_getres"
> #define HAVE_CLOCK_GETTIME_VSYSCALL "__kernel_clock_gettime"
On 28/11/22 13:38, Paul E Murphy wrote:
>
>
> On 11/4/22 2:01 PM, Adhemerval Zanella via Libc-alpha wrote:
>> It follows the internal signature:
>>
>> extern int clone3 (struct clone_args *__cl_args, size_t __size,
>> int (*__func) (void *__arg), void *__arg);
>>
>> The powerpc64 ABI requires an initial stackframe so the child can
>> store/restore the TOC. Iit is create prior calling clone3 by
>
> trivial nit, s/Iit/It/.
Ack.
>
>> adjusting the stack size (since kernel will compute the stack as
>> stack plus size).
>>
>> Checked on powerpc64-linux-gnu (power8, kernel 6.0) and
>> powerpc64le-linux-gnu (power9, kernel 4.18).
>> ---
>> .../sysv/linux/powerpc/powerpc64/clone3.S | 152 ++++++++++++++++++
>> sysdeps/unix/sysv/linux/powerpc/sysdep.h | 1 +
>> 2 files changed, 153 insertions(+)
>> create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
>>
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
>> new file mode 100644
>> index 0000000000..0fe2fe91db
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
>> @@ -0,0 +1,152 @@
>> +/* The clone3 syscall wrapper. Linux/powerpc64 version.
>> + Copyright (C) 2022 Free Software Foundation, Inc.
>> +
>> + This file is part of the GNU C Library.
>> +
>> + The GNU C Library is free software; you can redistribute it and/or
>> + modify it under the terms of the GNU Lesser General Public
>> + License as published by the Free Software Foundation; either
>> + version 2.1 of the License, or (at your option) any later version.
>> +
>> + The GNU C Library is distributed in the hope that it will be useful,
>> + but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>> + Lesser General Public License for more details.
>> +
>> + You should have received a copy of the GNU Lesser General Public
>> + License along with the GNU C Library; if not, see
>> + <https://www.gnu.org/licenses/>. */
>> +
>> +#include <sysdep.h>
>> +#define _ERRNO_H 1
>> +#include <bits/errno.h>
>> +
>> +/* The userland implementation is:
>> + int clone3 (struct clone_args *cl_args, size_t size,
>> + int (*func)(void *arg), void *arg);
>> +
>> + the kernel entry is:
>> + int clone3 (struct clone_args *cl_args, size_t size);
>> +
>> + The parameters are passed in registers from userland:
>> + r3: cl_args
>> + r4: size
>> + r5: func
>> + r6: arg */
>> +
>> + .text
>> +ENTRY(__clone3)
>> + CALL_MCOUNT 4
>> +
>> + /* Sanity checks args. */
>> + cmpdi cr0, r3, 0
>> + cmpdi cr1, r5, 0
>> + cror cr0*4+eq, cr1*4+eq, cr0*4+eq
>> + beq cr0,L(badargs)
>> +
>> + /* Save some regs in the "red zone". */
> Is there reason to avoid explicitly stacking a frame in here? Also, does the red zone exist on ELFv1?
>
I don't think so, although it allows to tail call directly to
__syscall_error. I used powerpc64 clone.S as example, which does
something similar.
>> +#ifdef USE_PPC_SCV
>> + std r28, -24(r1)
>> + cfi_offset (r28, -24)
>> +#endif
>> + std r29, -16(r1)
>> + std r30, -8(r1)
>> + cfi_offset (r29, -16)
>> + cfi_offset (r30, -8)
>> +
>> + /* Save fn and args across syscall. */
> trivial nit, s/fn/func/ s/args/arg/.
Ack.
>
>> + mr r30, r5 /* Function in r30. */
>> + mr r29, r6 /* Argument in r29. */
>> +
>> + /* End FDE now, because in the child the unwind info will be
>> + wrong. */
>> + cfi_endproc
>> +
>> + /* Setup a minimum stack fram for child. It needs to first calculate
> s/fram/frame/.
Ack.
>
>> + the effective stack address, write the start NULL frame-pointer,
>> + and update the frame size in the input cl_args. */
>> + ld r7, 40(r3) /* Load stack value. */
>> + ld r8, 48(r3) /* Load stack_size value. */
>> + li r10, 0
>> + add r7, r7, r8 /* Calculate effective stack address. */
>> + std r10, -FRAME_MIN_SIZE_PARM(r7)
> This is clearing the backchain pointer? Maybe a small comment here.
Yes, since this stack will be the initial one. I changed the comment to:
/* Setup a minimum stack frame for child. It needs to first calculate
the effective stack address, write the start empty backchain pointer,
and update the frame size in the input cl_args. */
To make it more clear.
>
>> + addi r8, r8, -FRAME_MIN_SIZE_PARM
>> + std r8, 48(r3)
>> +
>> + /* Do the system call, the kernel expects:
>> + r0: system call numer
>> + r3: cl_args
>> + r4: size */
>> + li r0, SYS_ify(clone3)
>> +#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. */
>> + mflr r9
>> + std r9, FRAME_LR_SAVE(r1)
>> + .machine "push"
>> + .machine "power9"
>> + scv 0
>> + .machine "pop"
>> + ld r9, FRAME_LR_SAVE(r1)
>> + mtlr r9
>> +
>> + /* When using scv, error is indicated by negative r3. */
> With scv an, an error is a value -4095 <= x < 0. This test should be more specific.
Ack, I changed the comment (btw clone.S has the same mistake).
>
>> + cmpdi cr1, r3, 0
>> + b 1f
>> +#endif
>> +0: DO_CALL_SC
>> +
>> + /* With sc, error is indicated by cr0.SO. */
>> + cmpdi cr1, r3, 0
>> + crandc cr1*4+eq, cr1*4+eq, cr0*4+so > +
>> +1: bne- cr1,L(parent)
>> +
>> + /* Child, load the function and arguments. */
>> + std r2, FRAME_TOC_SAVE(r1)
>> + PPC64_LOAD_FUNCPTR r30
>> + mr r3, r29
>> + bctrl
>> + ld r2, FRAME_TOC_SAVE(r1)
>> +
>> + li r0, SYS_ify(exit)
>> + DO_CALL_SC
> Minor nit, this should also use scv if supported.
Ack (btw clone.S also use issues DO_CALL_SC).
>> + /* We won't ever get here but provide a nop so that the linker
>> + will insert a toc adjusting stub if necessary. */
>> + nop
>> +
>> +L(badargs):
>> + cfi_startproc
>> + li r3, EINVAL
>> + TAIL_CALL_SYSCALL_ERROR
>> +
>> +L(parent):
>> + /* Check if svc is available. */
> s/svc/scv/.
Ack.
>
>> + cmpdi cr1, r28, 0
>> +
>> + /* Parent. Restore registers & return. */
>> +#ifdef USE_PPC_SCV
>> + cfi_offset (r28, -24)
>> + ld r28, -24(r1)
>> + cfi_restore (r28)
>> +#endif
>> + cfi_offset (r29,-16)
>> + cfi_offset (r30,-8)
>> + ld r29, -16(r1)
>> + ld r30, -8(r1)
>> + cfi_restore (r29)
>> + cfi_restore (r30)
>> +
>> +#ifdef USE_PPC_SCV
>> + beq cr1, 0f
>> + RET_SCV
>> + b 1f
>> +#endif
>> +0: RET_SC
>> +1: TAIL_CALL_SYSCALL_ERROR
>> +
>> +PSEUDO_END (__clone3)
>> +
>> +libc_hidden_def (__clone3)
>> +weak_alias (__clone3, clone3)
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
>> index 9e44818978..af63b3974b 100644
>> --- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
>> +++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
>> @@ -214,6 +214,7 @@
>> #if defined(__PPC64__) || defined(__powerpc64__)
>> #define HAVE_CLOCK_GETRES64_VSYSCALL "__kernel_clock_getres"
>> #define HAVE_CLOCK_GETTIME64_VSYSCALL "__kernel_clock_gettime"
>> +#define HAVE_CLONE3_WRAPPER 1
>> #else
>> #define HAVE_CLOCK_GETRES_VSYSCALL "__kernel_clock_getres"
>> #define HAVE_CLOCK_GETTIME_VSYSCALL "__kernel_clock_gettime"
new file mode 100644
@@ -0,0 +1,152 @@
+/* The clone3 syscall wrapper. Linux/powerpc64 version.
+ Copyright (C) 2022 Free Software Foundation, Inc.
+
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <sysdep.h>
+#define _ERRNO_H 1
+#include <bits/errno.h>
+
+/* The userland implementation is:
+ int clone3 (struct clone_args *cl_args, size_t size,
+ int (*func)(void *arg), void *arg);
+
+ the kernel entry is:
+ int clone3 (struct clone_args *cl_args, size_t size);
+
+ The parameters are passed in registers from userland:
+ r3: cl_args
+ r4: size
+ r5: func
+ r6: arg */
+
+ .text
+ENTRY(__clone3)
+ CALL_MCOUNT 4
+
+ /* Sanity checks args. */
+ cmpdi cr0, r3, 0
+ cmpdi cr1, r5, 0
+ cror cr0*4+eq, cr1*4+eq, cr0*4+eq
+ beq cr0,L(badargs)
+
+ /* Save some regs in the "red zone". */
+#ifdef USE_PPC_SCV
+ std r28, -24(r1)
+ cfi_offset (r28, -24)
+#endif
+ std r29, -16(r1)
+ std r30, -8(r1)
+ cfi_offset (r29, -16)
+ cfi_offset (r30, -8)
+
+ /* Save fn and args across syscall. */
+ mr r30, r5 /* Function in r30. */
+ mr r29, r6 /* Argument in r29. */
+
+ /* End FDE now, because in the child the unwind info will be
+ wrong. */
+ cfi_endproc
+
+ /* Setup a minimum stack fram for child. It needs to first calculate
+ the effective stack address, write the start NULL frame-pointer,
+ and update the frame size in the input cl_args. */
+ ld r7, 40(r3) /* Load stack value. */
+ ld r8, 48(r3) /* Load stack_size value. */
+ li r10, 0
+ add r7, r7, r8 /* Calculate effective stack address. */
+ std r10, -FRAME_MIN_SIZE_PARM(r7)
+ addi r8, r8, -FRAME_MIN_SIZE_PARM
+ std r8, 48(r3)
+
+ /* Do the system call, the kernel expects:
+ r0: system call numer
+ r3: cl_args
+ r4: size */
+ li r0, SYS_ify(clone3)
+#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. */
+ mflr r9
+ std r9, FRAME_LR_SAVE(r1)
+ .machine "push"
+ .machine "power9"
+ scv 0
+ .machine "pop"
+ ld r9, FRAME_LR_SAVE(r1)
+ mtlr r9
+
+ /* When using scv, error is indicated by negative r3. */
+ cmpdi cr1, r3, 0
+ b 1f
+#endif
+0: DO_CALL_SC
+
+ /* With sc, error is indicated by cr0.SO. */
+ cmpdi cr1, r3, 0
+ crandc cr1*4+eq, cr1*4+eq, cr0*4+so
+
+1: bne- cr1,L(parent)
+
+ /* Child, load the function and arguments. */
+ std r2, FRAME_TOC_SAVE(r1)
+ PPC64_LOAD_FUNCPTR r30
+ mr r3, r29
+ bctrl
+ ld r2, FRAME_TOC_SAVE(r1)
+
+ li r0, SYS_ify(exit)
+ DO_CALL_SC
+ /* We won't ever get here but provide a nop so that the linker
+ will insert a toc adjusting stub if necessary. */
+ nop
+
+L(badargs):
+ cfi_startproc
+ li r3, EINVAL
+ TAIL_CALL_SYSCALL_ERROR
+
+L(parent):
+ /* Check if svc is available. */
+ cmpdi cr1, r28, 0
+
+ /* Parent. Restore registers & return. */
+#ifdef USE_PPC_SCV
+ cfi_offset (r28, -24)
+ ld r28, -24(r1)
+ cfi_restore (r28)
+#endif
+ cfi_offset (r29,-16)
+ cfi_offset (r30,-8)
+ ld r29, -16(r1)
+ ld r30, -8(r1)
+ cfi_restore (r29)
+ cfi_restore (r30)
+
+#ifdef USE_PPC_SCV
+ beq cr1, 0f
+ RET_SCV
+ b 1f
+#endif
+0: RET_SC
+1: TAIL_CALL_SYSCALL_ERROR
+
+PSEUDO_END (__clone3)
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
@@ -214,6 +214,7 @@
#if defined(__PPC64__) || defined(__powerpc64__)
#define HAVE_CLOCK_GETRES64_VSYSCALL "__kernel_clock_getres"
#define HAVE_CLOCK_GETTIME64_VSYSCALL "__kernel_clock_gettime"
+#define HAVE_CLONE3_WRAPPER 1
#else
#define HAVE_CLOCK_GETRES_VSYSCALL "__kernel_clock_getres"
#define HAVE_CLOCK_GETTIME_VSYSCALL "__kernel_clock_gettime"