mips: FIx clone3 implementation (BZ 31325)
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Commit Message
For o32 we need to setup a minimal stack frame to allow cprestore
on __thread_start_clone3 (which instruct the linker to save the
gp for PIC). Also, there is no guarantee by kABI that $8 will be
preserved after syscall execution, so we need to save it on the
provided stack.
Checked on mipsel-linux-gnu.
Reported-by: Khem Raj <raj.khem@gmail.com>
---
sysdeps/unix/sysv/linux/mips/clone3.S | 32 ++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 5 deletions(-)
Comments
On Thu, Feb 1, 2024 at 9:41 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> For o32 we need to setup a minimal stack frame to allow cprestore
> on __thread_start_clone3 (which instruct the linker to save the
> gp for PIC). Also, there is no guarantee by kABI that $8 will be
> preserved after syscall execution, so we need to save it on the
> provided stack.
>
> Checked on mipsel-linux-gnu.
works ok on yocto reference mips ( Big-endian ) ( mips-linux-gnu )
Tested-by: Khem Raj <raj.khem@gmail.com>
>
> Reported-by: Khem Raj <raj.khem@gmail.com>
> ---
> sysdeps/unix/sysv/linux/mips/clone3.S | 32 ++++++++++++++++++++++-----
> 1 file changed, 27 insertions(+), 5 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/mips/clone3.S b/sysdeps/unix/sysv/linux/mips/clone3.S
> index e9fec2fa47..481b8ae963 100644
> --- a/sysdeps/unix/sysv/linux/mips/clone3.S
> +++ b/sysdeps/unix/sysv/linux/mips/clone3.S
> @@ -37,11 +37,6 @@
>
> .text
> .set nomips16
> -#if _MIPS_SIM == _ABIO32
> -# define EXTRA_LOCALS 1
> -#else
> -# define EXTRA_LOCALS 0
> -#endif
> #define FRAMESZ ((NARGSAVE*SZREG)+ALSZ)&ALMASK
> GPOFF= FRAMESZ-(1*SZREG)
> NESTED(__clone3, SZREG, sp)
> @@ -68,8 +63,31 @@ NESTED(__clone3, SZREG, sp)
> beqz a0, L(error) /* No NULL cl_args pointer. */
> beqz a2, L(error) /* No NULL function pointer. */
>
> +#if _MIPS_SIM == _ABIO32
> + /* Both stack and stack_size on clone_args are defined as uint64_t, and
> + there is no need to handle values larger than to 32 bits for o32. */
> +# if __BYTE_ORDER == __BIG_ENDIAN
> +# define CL_STACKPOINTER_OFFSET 44
> +# define CL_STACKSIZE_OFFSET 52
> +# else
> +# define CL_STACKPOINTER_OFFSET 40
> +# define CL_STACKSIZE_OFFSET 48
> +# endif
> +
> + /* For o32 we need to setup a minimal stack frame to allow cprestore
> + on __thread_start_clone3. Also there is no guarantee by kABI that
> + $8 will be preserved after syscall execution (so we need to save it
> + on the provided stack). */
> + lw t0, CL_STACKPOINTER_OFFSET(a0) /* Load the stack pointer. */
> + lw t1, CL_STACKSIZE_OFFSET(a0) /* Load the stack_size. */
> + addiu t1, -32 /* Update the stack size. */
> + addu t2, t1, t0 /* Calculate the thread stack. */
> + sw a3, 0(t2) /* Save argument pointer. */
> + sw t1, CL_STACKSIZE_OFFSET(a0) /* Save the new stack size. */
> +#else
> move $8, a3 /* a3 is set to 0/1 for syscall success/error
> while a4/$8 is returned unmodified. */
> +#endif
>
> /* Do the system call, the kernel expects:
> v0: system call number
> @@ -125,7 +143,11 @@ L(thread_start_clone3):
>
> /* Restore the arg for user's function. */
> move t9, a2 /* Function pointer. */
> +#if _MIPS_SIM == _ABIO32
> + PTR_L a0, 0(sp)
> +#else
> move a0, $8 /* Argument pointer. */
> +#endif
>
> /* Call the user's function. */
> jal t9
> --
> 2.34.1
>
On 01/02/24 21:06, Khem Raj wrote:
> On Thu, Feb 1, 2024 at 9:41 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>> For o32 we need to setup a minimal stack frame to allow cprestore
>> on __thread_start_clone3 (which instruct the linker to save the
>> gp for PIC). Also, there is no guarantee by kABI that $8 will be
>> preserved after syscall execution, so we need to save it on the
>> provided stack.
>>
>> Checked on mipsel-linux-gnu.
>
> works ok on yocto reference mips ( Big-endian ) ( mips-linux-gnu )
>
> Tested-by: Khem Raj <raj.khem@gmail.com>
Thanks, I will install it.
@@ -37,11 +37,6 @@
.text
.set nomips16
-#if _MIPS_SIM == _ABIO32
-# define EXTRA_LOCALS 1
-#else
-# define EXTRA_LOCALS 0
-#endif
#define FRAMESZ ((NARGSAVE*SZREG)+ALSZ)&ALMASK
GPOFF= FRAMESZ-(1*SZREG)
NESTED(__clone3, SZREG, sp)
@@ -68,8 +63,31 @@ NESTED(__clone3, SZREG, sp)
beqz a0, L(error) /* No NULL cl_args pointer. */
beqz a2, L(error) /* No NULL function pointer. */
+#if _MIPS_SIM == _ABIO32
+ /* Both stack and stack_size on clone_args are defined as uint64_t, and
+ there is no need to handle values larger than to 32 bits for o32. */
+# if __BYTE_ORDER == __BIG_ENDIAN
+# define CL_STACKPOINTER_OFFSET 44
+# define CL_STACKSIZE_OFFSET 52
+# else
+# define CL_STACKPOINTER_OFFSET 40
+# define CL_STACKSIZE_OFFSET 48
+# endif
+
+ /* For o32 we need to setup a minimal stack frame to allow cprestore
+ on __thread_start_clone3. Also there is no guarantee by kABI that
+ $8 will be preserved after syscall execution (so we need to save it
+ on the provided stack). */
+ lw t0, CL_STACKPOINTER_OFFSET(a0) /* Load the stack pointer. */
+ lw t1, CL_STACKSIZE_OFFSET(a0) /* Load the stack_size. */
+ addiu t1, -32 /* Update the stack size. */
+ addu t2, t1, t0 /* Calculate the thread stack. */
+ sw a3, 0(t2) /* Save argument pointer. */
+ sw t1, CL_STACKSIZE_OFFSET(a0) /* Save the new stack size. */
+#else
move $8, a3 /* a3 is set to 0/1 for syscall success/error
while a4/$8 is returned unmodified. */
+#endif
/* Do the system call, the kernel expects:
v0: system call number
@@ -125,7 +143,11 @@ L(thread_start_clone3):
/* Restore the arg for user's function. */
move t9, a2 /* Function pointer. */
+#if _MIPS_SIM == _ABIO32
+ PTR_L a0, 0(sp)
+#else
move a0, $8 /* Argument pointer. */
+#endif
/* Call the user's function. */
jal t9