sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

arm64_task/pthread_start: Convert the C / inline ASM code to assembly

Browse Source 
The aforementioned functions can/will fail if the C compiler decides
to use the stack for the incoming entrypt/etc. parameters.

Fix this issue by converting the jump to user part into pure assembly,
ensuring the stack is NOT used for the parameters.
This commit is contained in:
Ville Juven 2024-09-13 13:20:56 +03:00 committed by Xiang Xiao
parent 09ab135d2f
commit 10b40abecc
4 changed files with 36 additions and 48 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm64/src/common/arm64_internal.h
View File

@ -270,6 +270,8 @@ EXTERN uint8_t g_idle_topstack[]; /* End+1 of heap */
****************************************************************************/
void arm64_new_task(struct tcb_s *tak_new);
void arm64_jump_to_user(uint64_t entry, uint64_t x0, uint64_t x1,
uint64_t *regs) noreturn_function;
/* Low level initialization provided by chip logic */

26
arch/arm64/src/common/arm64_pthread_start.c
View File

@ -68,12 +68,6 @@
void up_pthread_start(pthread_trampoline_t startup,
pthread_startroutine_t entrypt, pthread_addr_t arg)
{
uint64_t *regs = this_task()->xcp.initregs;
/* This must be performed atomically, the C-section ends upon user entry */
enter_critical_section();
/* Set up to enter the user-space pthread start-up function in
* unprivileged mode. We need:
*
@ -83,24 +77,8 @@ void up_pthread_start(pthread_trampoline_t startup,
* SPSR = user mode
*/
regs[REG_ELR] = (uint64_t)startup;
regs[REG_X0] = (uint64_t)entrypt;
regs[REG_X1] = (uint64_t)arg;
regs[REG_SPSR] = (regs[REG_SPSR] & ~SPSR_MODE_MASK) | SPSR_MODE_EL0T;
/* Fully unwind the kernel stack and drop to user space */
asm
(
"mov x0, %0\n" /* Get context registers */
"mov sp, x0\n" /* Stack pointer = context */
"b arm64_exit_exception\n"
:
: "r" (regs)
: "x0", "memory"
);
PANIC();
arm64_jump_to_user((uint64_t)startup, (uint64_t)entrypt, (uint64_t)arg,
this_task()->xcp.initregs);
}
#endif /* !CONFIG_BUILD_FLAT && __KERNEL__ && !CONFIG_DISABLE_PTHREAD */

26
arch/arm64/src/common/arm64_task_start.c
View File

@ -65,12 +65,6 @@
void up_task_start(main_t taskentry, int argc, char *argv[])
{
uint64_t *regs = this_task()->xcp.initregs;
/* This must be performed atomically, the C-section ends upon user entry */
enter_critical_section();
/* Set up to return to the user-space _start function in
* unprivileged mode. We need:
*
@ -80,24 +74,8 @@ void up_task_start(main_t taskentry, int argc, char *argv[])
* SPSR = user mode
*/
regs[REG_ELR] = (uint64_t)taskentry;
regs[REG_X0] = (uint64_t)argc;
regs[REG_X1] = (uint64_t)argv;
regs[REG_SPSR] = (regs[REG_SPSR] & ~SPSR_MODE_MASK) | SPSR_MODE_EL0T;
/* Fully unwind the kernel stack and drop to user space */
asm
(
"mov x0, %0\n" /* Get context registers */
"mov sp, x0\n" /* Stack pointer = context */
"b arm64_exit_exception\n"
:
: "r" (regs)
: "x0", "memory"
);
PANIC();
arm64_jump_to_user((uint64_t)taskentry, (uint64_t)argc, (uint64_t)argv,
this_task()->xcp.initregs);
}
#endif /* !CONFIG_BUILD_FLAT */

30
arch/arm64/src/common/arm64_vectors.S
View File

@ -156,6 +156,36 @@ restore_new:
ret
/****************************************************************************
* Function: arm64_jump_to_user
*
* Description:
* Routine to jump to user space, called when a user process is started and
* the kernel is ready to give control to the user task in user space.
*
* arm64_jump_to_user(entry, x0, x1, regs)
* entry: process entry point
* x0: parameter 0 for process
* x1: parameter 1 for process
* regs: integer register save area to use
*
****************************************************************************/
#ifndef CONFIG_BUILD_FLAT
GTEXT(arm64_jump_to_user)
SECTION_FUNC(text, arm64_jump_to_user)
msr daifset, #IRQ_DAIF_MASK
mov sp, x3
str x0, [sp, #8 * REG_ELR]
str x1, [sp, #8 * REG_X0]
str x2, [sp, #8 * REG_X1]
mrs x0, spsr_el1
and x0, x0, #~SPSR_MODE_MASK
#orr x0, x0, #SPSR_MODE_EL0T # EL0T=0x00, out of range for orr
str x0, [sp, #8 * REG_SPSR]
b arm64_exit_exception
#endif
/****************************************************************************
* Function: arm64_sync_exc
*