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The following commit(s) were added to refs/heads/master by this push:
new 10b40abecc arm64_task/pthread_start: Convert the C / inline ASM code
to assembly
10b40abecc is described below
commit 10b40abeccf6c61a1dbef79204cf630ab25d4752
Author: Ville Juven <[email protected]>
AuthorDate: Fri Sep 13 13:20:56 2024 +0300
arm64_task/pthread_start: Convert the C / inline ASM code to assembly
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.
---
arch/arm64/src/common/arm64_internal.h | 2 ++
arch/arm64/src/common/arm64_pthread_start.c | 26 ++-----------------------
arch/arm64/src/common/arm64_task_start.c | 26 ++-----------------------
arch/arm64/src/common/arm64_vectors.S | 30 +++++++++++++++++++++++++++++
4 files changed, 36 insertions(+), 48 deletions(-)
diff --git a/arch/arm64/src/common/arm64_internal.h
b/arch/arm64/src/common/arm64_internal.h
index 35e51575bd..19c8b9eb69 100644
--- a/arch/arm64/src/common/arm64_internal.h
+++ b/arch/arm64/src/common/arm64_internal.h
@@ -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 */
diff --git a/arch/arm64/src/common/arm64_pthread_start.c
b/arch/arm64/src/common/arm64_pthread_start.c
index db80db228b..8132884cf8 100644
--- a/arch/arm64/src/common/arm64_pthread_start.c
+++ b/arch/arm64/src/common/arm64_pthread_start.c
@@ -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 */
diff --git a/arch/arm64/src/common/arm64_task_start.c
b/arch/arm64/src/common/arm64_task_start.c
index 5e3501eee6..0d20f693e5 100644
--- a/arch/arm64/src/common/arm64_task_start.c
+++ b/arch/arm64/src/common/arm64_task_start.c
@@ -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 */
diff --git a/arch/arm64/src/common/arm64_vectors.S
b/arch/arm64/src/common/arm64_vectors.S
index 16f75106b2..d2d1e5c95a 100644
--- a/arch/arm64/src/common/arm64_vectors.S
+++ b/arch/arm64/src/common/arm64_vectors.S
@@ -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
*
