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carlocaioneNicolas Pitre
carlocaione
authored and
Nicolas Pitre
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aarch64: userspace: Implement syscalls
This patch adds the code managing the syscalls. The privileged stack is setup before jumping into the real syscall. Signed-off-by: Carlo Caione <ccaione@baylibre.com>
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8 files changed

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‎arch/arm/core/aarch64/Kconfig‎

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Original file line numberDiff line numberDiff line change
@@ -64,6 +64,9 @@ config AARCH64_IMAGE_HEADER
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This option enables standard ARM64 boot image header used by Linux
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and understood by loaders such as u-boot on Xen xl tool.
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config PRIVILEGED_STACK_SIZE
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default 4096
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if CPU_CORTEX_A
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config ARMV8_A_NS

‎arch/arm/core/aarch64/switch.S‎

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@@ -111,6 +111,11 @@ SECTION_FUNC(TEXT, z_arm64_sync_exc)
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cmp x1, #_SVC_CALL_RUNTIME_EXCEPT
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beq oops
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#ifdef CONFIG_USERSPACE
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cmp x1, #_SVC_CALL_SYSTEM_CALL
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beq z_arm64_do_syscall
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#endif
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#ifdef CONFIG_IRQ_OFFLOAD
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cmp x1, #_SVC_CALL_IRQ_OFFLOAD
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beq offload

‎arch/arm/core/aarch64/thread.c‎

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Original file line numberDiff line numberDiff line change
@@ -54,6 +54,7 @@ void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
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}
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pInitCtx->tpidrro_el0 = 0x0;
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thread->arch.priv_stack_start = 0;
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#else
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pInitCtx->elr = (uint64_t)z_thread_entry;
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#endif
@@ -82,6 +83,9 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
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z_arch_esf_t *pInitCtx;
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uintptr_t stack_ptr;
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/* Setup the private stack */
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_current->arch.priv_stack_start = (uint64_t)(_current->stack_obj);
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/* Reset the stack pointer to the base discarding any old context */
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stack_ptr = Z_STACK_PTR_ALIGN(_current->stack_info.start +
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_current->stack_info.size -

‎arch/arm/core/aarch64/userspace.S‎

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Original file line numberDiff line numberDiff line change
@@ -85,6 +85,61 @@ abv_fail:
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mov x0, #-1
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ret
8787

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/*
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* System call entry point.
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*/
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GTEXT(z_arm64_do_syscall)
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SECTION_FUNC(TEXT, z_arm64_do_syscall)
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/* Recover the syscall parameters from the ESF */
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ldp x0, x1, [sp, ___esf_t_x0_x1_OFFSET]
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ldp x2, x3, [sp, ___esf_t_x2_x3_OFFSET]
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ldp x4, x5, [sp, ___esf_t_x4_x5_OFFSET]
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/* Recover the syscall ID */
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ldr x8, [sp, ___esf_t_x8_x9_OFFSET]
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/* Check whether the ID is valid */
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ldr x9, =K_SYSCALL_LIMIT
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cmp x8, x9
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blo valid_syscall_id
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ldr x8, =K_SYSCALL_BAD
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valid_syscall_id:
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ldr x9, =_k_syscall_table
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ldr x9, [x9, x8, lsl #3]
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/* Recover the privileged stack */
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#ifdef CONFIG_SMP
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get_cpu x10, x8
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ldr x10, [x10, #___cpu_t_current_OFFSET]
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#else
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ldr x10, =_kernel
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ldr x10, [x10, #_kernel_offset_to_current]
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#endif
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ldr x10, [x10, #_thread_offset_to_priv_stack_start]
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add x10, x10, #CONFIG_PRIVILEGED_STACK_SIZE
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/* Save the original SP on the privileged stack */
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mov x11, sp
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mov sp, x10
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str x11, [sp, #-16]!
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/* Jump into the syscall */
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msr daifclr, #(DAIFSET_IRQ_BIT)
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blr x9
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msr daifset, #(DAIFSET_IRQ_BIT)
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/* Restore the original SP containing the ESF */
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ldr x11, [sp], #16
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mov sp, x11
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/* Save the return value into the ESF */
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str x0, [sp, ___esf_t_x0_x1_OFFSET]
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/* Return from exception */
141+
b z_arm64_exit_exc
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88143
/*
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* Routine to jump into userspace
90145
*

‎arch/arm/core/offsets/offsets_aarch64.c‎

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Original file line numberDiff line numberDiff line change
@@ -29,6 +29,10 @@
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#include <kernel_arch_data.h>
3030
#include <kernel_offsets.h>
3131

32+
#ifdef CONFIG_USERSPACE
33+
GEN_OFFSET_SYM(_thread_arch_t, priv_stack_start);
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#endif
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3236
GEN_NAMED_OFFSET_SYM(_callee_saved_t, x19, x19_x20);
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GEN_NAMED_OFFSET_SYM(_callee_saved_t, x21, x21_x22);
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GEN_NAMED_OFFSET_SYM(_callee_saved_t, x23, x23_x24);

‎arch/arm/include/aarch64/offsets_short_arch.h‎

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Original file line numberDiff line numberDiff line change
@@ -9,4 +9,9 @@
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1010
#include <offsets.h>
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12+
#ifdef CONFIG_USERSPACE
13+
#define _thread_offset_to_priv_stack_start \
14+
(___thread_t_arch_OFFSET + ___thread_arch_t_priv_stack_start_OFFSET)
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#endif
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1217
#endif /* ZEPHYR_ARCH_ARM_INCLUDE_AARCH64_OFFSETS_SHORT_ARCH_H_ */

‎include/arch/arm/aarch64/syscall.h‎

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Original file line numberDiff line numberDiff line change
@@ -19,6 +19,7 @@
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#define _SVC_CALL_CONTEXT_SWITCH 0
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#define _SVC_CALL_IRQ_OFFLOAD 1
2121
#define _SVC_CALL_RUNTIME_EXCEPT 2
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#define _SVC_CALL_SYSTEM_CALL 3
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2324
#ifdef CONFIG_USERSPACE
2425
#ifndef _ASMLANGUAGE
@@ -31,6 +32,137 @@
3132
extern "C" {
3233
#endif
3334

35+
/*
36+
* Syscall invocation macros. arm-specific machine constraints used to ensure
37+
* args land in the proper registers.
38+
*/
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static inline uintptr_t arch_syscall_invoke6(uintptr_t arg1, uintptr_t arg2,
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uintptr_t arg3, uintptr_t arg4,
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uintptr_t arg5, uintptr_t arg6,
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uintptr_t call_id)
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{
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register uint64_t ret __asm__("x0") = arg1;
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register uint64_t r1 __asm__("x1") = arg2;
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register uint64_t r2 __asm__("x2") = arg3;
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register uint64_t r3 __asm__("x3") = arg4;
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register uint64_t r4 __asm__("x4") = arg5;
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register uint64_t r5 __asm__("x5") = arg6;
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register uint64_t r8 __asm__("x8") = call_id;
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__asm__ volatile("svc %[svid]\n"
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: "=r"(ret)
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: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
55+
"r" (ret), "r" (r1), "r" (r2), "r" (r3),
56+
"r" (r4), "r" (r5), "r" (r8)
57+
: "memory");
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return ret;
60+
}
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62+
static inline uintptr_t arch_syscall_invoke5(uintptr_t arg1, uintptr_t arg2,
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uintptr_t arg3, uintptr_t arg4,
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uintptr_t arg5,
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uintptr_t call_id)
66+
{
67+
register uint64_t ret __asm__("x0") = arg1;
68+
register uint64_t r1 __asm__("x1") = arg2;
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register uint64_t r2 __asm__("x2") = arg3;
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register uint64_t r3 __asm__("x3") = arg4;
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register uint64_t r4 __asm__("x4") = arg5;
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register uint64_t r8 __asm__("x8") = call_id;
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__asm__ volatile("svc %[svid]\n"
75+
: "=r"(ret)
76+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
77+
"r" (ret), "r" (r1), "r" (r2), "r" (r3),
78+
"r" (r4), "r" (r8)
79+
: "memory");
80+
81+
return ret;
82+
}
83+
84+
static inline uintptr_t arch_syscall_invoke4(uintptr_t arg1, uintptr_t arg2,
85+
uintptr_t arg3, uintptr_t arg4,
86+
uintptr_t call_id)
87+
{
88+
register uint64_t ret __asm__("x0") = arg1;
89+
register uint64_t r1 __asm__("x1") = arg2;
90+
register uint64_t r2 __asm__("x2") = arg3;
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register uint64_t r3 __asm__("x3") = arg4;
92+
register uint64_t r8 __asm__("x8") = call_id;
93+
94+
__asm__ volatile("svc %[svid]\n"
95+
: "=r"(ret)
96+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
97+
"r" (ret), "r" (r1), "r" (r2), "r" (r3),
98+
"r" (r8)
99+
: "memory");
100+
101+
return ret;
102+
}
103+
104+
static inline uintptr_t arch_syscall_invoke3(uintptr_t arg1, uintptr_t arg2,
105+
uintptr_t arg3,
106+
uintptr_t call_id)
107+
{
108+
register uint64_t ret __asm__("x0") = arg1;
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register uint64_t r1 __asm__("x1") = arg2;
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register uint64_t r2 __asm__("x2") = arg3;
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register uint64_t r8 __asm__("x8") = call_id;
112+
113+
__asm__ volatile("svc %[svid]\n"
114+
: "=r"(ret)
115+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
116+
"r" (ret), "r" (r1), "r" (r2), "r" (r8)
117+
: "memory");
118+
119+
return ret;
120+
}
121+
122+
static inline uintptr_t arch_syscall_invoke2(uintptr_t arg1, uintptr_t arg2,
123+
uintptr_t call_id)
124+
{
125+
register uint64_t ret __asm__("x0") = arg1;
126+
register uint64_t r1 __asm__("x1") = arg2;
127+
register uint64_t r8 __asm__("x8") = call_id;
128+
129+
__asm__ volatile("svc %[svid]\n"
130+
: "=r"(ret)
131+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
132+
"r" (ret), "r" (r1), "r" (r8)
133+
: "memory");
134+
135+
return ret;
136+
}
137+
138+
static inline uintptr_t arch_syscall_invoke1(uintptr_t arg1,
139+
uintptr_t call_id)
140+
{
141+
register uint64_t ret __asm__("x0") = arg1;
142+
register uint64_t r8 __asm__("x8") = call_id;
143+
144+
__asm__ volatile("svc %[svid]\n"
145+
: "=r"(ret)
146+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
147+
"r" (ret), "r" (r8)
148+
: "memory");
149+
return ret;
150+
}
151+
152+
static inline uintptr_t arch_syscall_invoke0(uintptr_t call_id)
153+
{
154+
register uint64_t ret __asm__("x0");
155+
register uint64_t r8 __asm__("x8") = call_id;
156+
157+
__asm__ volatile("svc %[svid]\n"
158+
: "=r"(ret)
159+
: [svid] "i" (_SVC_CALL_SYSTEM_CALL),
160+
"r" (ret), "r" (r8)
161+
: "memory");
162+
163+
return ret;
164+
}
165+
34166
static inline bool arch_is_user_context(void)
35167
{
36168
uint64_t tpidrro_el0;

‎include/arch/arm/aarch64/thread.h‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -40,7 +40,9 @@ struct _callee_saved {
4040
typedef struct _callee_saved _callee_saved_t;
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4242
struct _thread_arch {
43-
/* empty */
43+
#ifdef CONFIG_USERSPACE
44+
uint64_t priv_stack_start;
45+
#endif
4446
};
4547

4648
typedef struct _thread_arch _thread_arch_t;

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