src/nsexec: fix stack pointer alignment exception

When test g/317 or g/318 on ARM server, we got a kernel exception:

kernel: nsexec[8203]: SP Alignment exception: pc=00000000004010a0 sp=00000000005200e8

nsexec gives an unaligned child stack address to clone() system call sometimes. For making sure it's always aligned, use "__attribute__((aligned))" extension of GCC (Thanks this suggestion from Eric sandeen).

Signed-off-by Zorro Lang <[email protected]>

---
 src/nsexec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

src/nsexec.c +0 -0

index f033b1a4..205dd081 100644

src/nsexec.c +0 -0

 int
 main(int argc, char *argv[])

Signature · 6 lines

2.13.5

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When test g/317 or g/318 on ARM server, we got a kernel exception:

kernel: nsexec[8203]: SP Alignment exception: pc=00000000004010a0 sp=00000000005200e8

nsexec gives an unaligned child stack address to clone() system call sometimes. For making sure it's always aligned, use "__attribute__((aligned))" extension of GCC (Thanks this suggestion from Eric sandeen).

Signed-off-by Zorro Lang <[email protected]>

---
 src/nsexec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

src/nsexec.c +0 -0

index f033b1a4..205dd081 100644

src/nsexec.c +0 -0

 int
 main(int argc, char *argv[])

Quoted 22 lines · Zorro Lang

When test g/317 or g/318 on ARM server, we got a kernel exception:

kernel: nsexec[8203]: SP Alignment exception: pc=00000000004010a0 sp=00000000005200e8

nsexec gives an unaligned child stack address to clone() system call sometimes. For making sure it's always aligned, use "__attribute__((aligned))" extension of GCC (Thanks this suggestion from Eric sandeen).

Signed-off-by Zorro Lang <[email protected]>

---
 src/nsexec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

src/nsexec.c +0 -0

index f033b1a4..205dd081 100644
@@ -138,7 +138,8 @@ childFunc(void *arg)
 
 #define STACK_SIZE (1024 * 1024)
 

src/nsexec.c childFunc(void *arg) · line 142

Quoted 3 lines

src/nsexec.c +2 -1

-static char child_stack[STACK_SIZE];    /* Space for child's stack */
+/* Space for child's stack */
+static char __attribute__((aligned)) child_stack[STACK_SIZE];

Does it matter if the __attribute__ goes before or after
the array name (child_stack[])? I can't quite tell from reading i.e.
https://gcc.gnu.org/onlinedocs/gcc-3.1/gcc/Variable-Attributes.html#Variable%20Attributes
if it does, though most examples I see have the __attribute__ after the variable name, i.e.

src/nsexec.c childFunc(void *arg) · line 143

Quoted 2 lines

src/nsexec.c +0 -0

 short array[3] __attribute__ ((aligned));

in the URL above.

-Eric

Quoted 4 lines

src/nsexec.c +0 -0

 int
 main(int argc, char *argv[])