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xtensa: userspace: align stack before calling syscall handler

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We stuff the 7th argument into stack by moving the stack pointer
before calling syscall handler. The Xtensa ABI says stack must
be 16-byte aligned. So instead of moving stack pointer 4 bytes,
we move 16 bytes (assuming stack has been aligned so far).

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
This commit is contained in:
Daniel Leung 2025-04-02 09:38:38 -07:00 • committed by Benjamin Cabé
commit 7f028e2f6e
1 changed files with 5 additions and 3 deletions
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8
arch/xtensa/core/userspace.S
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@ -179,12 +179,14 @@ _id_ok:
/* Stack frame pointer is the 7th argument to z_mrsh_*()
* as ssf, and must be put on stack to be consumed.
*
* Subtract 16 bytes as stack needs to be 16-byte aligned.
*/
mov a3, a1
addi a1, a1, -4
addi a1, a1, -16
s32i a3, a1, 0
l32i a3, a1, 4
l32i a3, a1, 16
l32i a7, a3, ___xtensa_irq_bsa_t_a3_OFFSET
@ -201,7 +203,7 @@ _id_ok:
* actual the stack frame. So restoration of registers
* can be done properly when finishing syscalls.
*/
addi a1, a1, 4
addi a1, a1, 16
/* copy return value. Lets put it in the top of stack
* because registers will be clobbered in