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arch: arm: userspace: adapt assembly code for Cortex-M Baseline

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In this commit we implement the assembly functions in userspace.S
- z_arm_userspace_enter()
- z_arm_do_syscall()
- z_arch_user_string_nlen()
for ARMv6-M and ARMv8-M Baseline architecture. We "inline" the
implementation for Baseline, along with the Mainline (ARMv7-M)
implementation, i.e. we rework only what is required to build
for Baseline Cortex-M.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2019-10-11 13:10:38 +02:00 • committed by Kumar Gala
commit cfe1b1de1a
1 changed files with 209 additions and 0 deletions
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209
arch/arm/core/userspace.S
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@ -50,9 +50,20 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
/* prepare to set stack to privileged stack */
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* move p1 to ip */
mov ip, r1
ldr r1, =_thread_offset_to_priv_stack_start
ldr r0, [r0, r1] /* priv stack ptr */
ldr r1, =CONFIG_PRIVILEGED_STACK_SIZE
add r0, r0, r1
/* Restore p1 from ip */
mov r1, ip
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
ldr r0, [r0, #_thread_offset_to_priv_stack_start] /* priv stack ptr */
ldr ip, =CONFIG_PRIVILEGED_STACK_SIZE
add r0, r0, ip
#endif
/* store current stack pointer to ip
* the current stack pointer is needed to retrieve
@ -73,7 +84,12 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
/* push args to stack */
push {r1,r2,r3,lr}
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
mov r1, ip
push {r0,r1}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
push {r0,ip}
#endif
/* Re-program dynamic memory map.
*
@ -93,6 +109,16 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
ldr r0, [r0, #_kernel_offset_to_current]
bl z_arm_configure_dynamic_mpu_regions
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
pop {r0,r3}
/* load up stack info from user stack */
ldr r0, [r3]
ldr r3, [r3, #4]
mov ip, r3
push {r0,r3}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
pop {r0,ip}
/* load up stack info from user stack */
@ -100,6 +126,7 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
ldr ip, [ip, #4]
push {r0,ip}
#endif
/* clear the user stack area to clean out privileged data */
/* from right past the guard right up to the end */
@ -111,7 +138,12 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
#endif
bl memset
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
pop {r0, r1}
mov ip, r1
#elif (defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE))
pop {r0,ip}
#endif
/* r0 contains user stack start, ip contains user stack size */
add r0, r0, ip /* calculate top of stack */
@ -121,8 +153,17 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
mov r3, #0
msr PSPLIM, r3
#endif
/* pop remaining arguments from stack before switching stacks */
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* Use r4 to pop lr, then restore r4 */
mov ip, r4
pop {r1,r2,r3,r4}
mov lr, r4
mov r4, ip
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
pop {r1,r2,r3,lr}
#endif
/* set stack to user stack */
msr PSP, r0
@ -145,6 +186,21 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
#endif /* CONFIG_EXECUTION_BENCHMARKING */
/* change processor mode to unprivileged */
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
push {r0, r1, r2, r3}
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
ldr r1, =_thread_offset_to_mode
ldr r1, [r0, r1]
movs r2, #1
orrs r1, r1, r2
mrs r3, CONTROL
orrs r3, r3, r2
mov ip, r3
/* Store (unprivileged) mode in thread's mode state variable */
ldr r2, =_thread_offset_to_mode
str r1, [r0, r2]
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
push {r0, r1}
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
@ -154,6 +210,7 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
orrs ip, ip, #1
/* Store (unprivileged) mode in thread's mode state variable */
str r1, [r0, #_thread_offset_to_mode]
#endif
dsb
msr CONTROL, ip
@ -162,10 +219,21 @@ SECTION_FUNC(TEXT,z_arm_userspace_enter)
* instructions with the previous privilege.
*/
isb
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
pop {r0, r1, r2, r3}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
pop {r0, r1}
#endif
/* jump to z_thread_entry entry */
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
push {r0, r1}
ldr r0, =z_thread_entry
mov ip, r0
pop {r0, r1}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
ldr ip, =z_thread_entry
#endif
bx ip
/**
@ -197,6 +265,30 @@ SECTION_FUNC(TEXT, z_arm_do_syscall)
msr PSPLIM, ip
#endif
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* save current stack pointer (user stack) */
mov ip, sp
/* temporarily push to user stack */
push {r0,r1}
/* setup privileged stack */
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
adds r0, r0, #_thread_offset_to_priv_stack_start
ldr r0, [r0] /* priv stack ptr */
ldr r1, =CONFIG_PRIVILEGED_STACK_SIZE
add r0, r1
/* Store current SP and LR at the beginning of the priv stack */
subs r0, #8
mov r1, ip
str r1, [r0, #0]
mov r1, lr
str r1, [r0, #4]
mov ip, r0
/* Restore user stack and original r0, r1 */
pop {r0, r1}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
/* setup privileged stack */
ldr ip, =_kernel
ldr ip, [ip, #_kernel_offset_to_current]
@ -207,6 +299,7 @@ SECTION_FUNC(TEXT, z_arm_do_syscall)
subs ip, #8
str sp, [ip, #0]
str lr, [ip, #4]
#endif
/* switch to privileged stack */
msr PSP, ip
@ -224,6 +317,54 @@ SECTION_FUNC(TEXT, z_arm_do_syscall)
* r6 contains call_id
* r8 contains original LR
*/
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* save r0, r1 to ip, lr */
mov ip, r0
mov lr, r1
ldr r0, =K_SYSCALL_BAD
cmp r6, r0
bne valid_syscall
/* BAD SYSCALL path */
/* fixup stack frame on the privileged stack, adding ssf */
mov r1, sp
push {r4,r5}
/* ssf is present in r1 (sp) */
push {r1,lr}
/* restore r0, r1 */
mov r0, ip
mov r1, lr
b dispatch_syscall
valid_syscall:
/* push args to complete stack frame */
push {r4,r5}
dispatch_syscall:
/* original r0 is saved in ip */
ldr r0, =_k_syscall_table
lsls r6, #2
add r0, r6
ldr r0, [r0] /* load table address */
/* swap ip and r0, restore r1 from lr */
mov r1, ip
mov ip, r0
mov r0, r1
mov r1, lr
/* execute function from dispatch table */
blx ip
/* restore LR
* r0 holds the return value and needs to be preserved
*/
mov ip, r0
mov r0, sp
adds r0, #12
ldr r0, [r0]
mov lr, r0
/* Restore r0 */
mov r0, ip
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
ldr ip, =K_SYSCALL_BAD
cmp r6, ip
bne valid_syscall
@ -248,6 +389,7 @@ dispatch_syscall:
/* restore LR */
ldr lr, [sp,#12]
#endif
#if defined(CONFIG_BUILTIN_STACK_GUARD)
/* clear stack limit (stack protection not required in user mode) */
@ -255,11 +397,39 @@ dispatch_syscall:
msr PSPLIM, r3
#endif
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* set stack back to unprivileged stack */
mov ip, r0
mov r0, sp
ldr r0, [r0,#8]
msr PSP, r0
/* Restore r0 */
mov r0, ip
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
/* set stack back to unprivileged stack */
ldr ip, [sp,#8]
msr PSP, ip
#endif
push {r0, r1}
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
push {r2, r3}
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
ldr r2, =_thread_offset_to_mode
ldr r1, [r0, r2]
movs r3, #1
orrs r1, r1, r3
/* Store (unprivileged) mode in thread's mode state variable */
str r1, [r0, r2]
dsb
/* drop privileges by setting bit 0 in CONTROL */
mrs r2, CONTROL
orrs r2, r2, r3
msr CONTROL, r2
pop {r2, r3}
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
ldr r0, =_kernel
ldr r0, [r0, #_kernel_offset_to_current]
ldr r1, [r0, #_thread_offset_to_mode]
@ -271,6 +441,7 @@ dispatch_syscall:
mrs ip, CONTROL
orrs ip, ip, #1
msr CONTROL, ip
#endif
/* ISB is not strictly necessary here (stack pointer is not being
* touched), but it's recommended to avoid executing pre-fetched
@ -279,6 +450,33 @@ dispatch_syscall:
isb
pop {r0, r1}
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
/* Zero out volatile (caller-saved) registers so as to not leak state from
* kernel mode. The C calling convention for the syscall handler will
* restore the others to original values.
*/
movs r2, #0
movs r3, #0
/*
* return back to original function that called SVC, add 1 to force thumb
* mode
*/
/* Save return value temporarily to ip */
mov ip, r0
mov r0, r8
movs r1, #1
orrs r0, r0, r1
/* swap ip, r0 */
mov r1, ip
mov ip, r0
mov r0, r1
movs r1, #0
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
/* Zero out volatile (caller-saved) registers so as to not leak state from
* kernel mode. The C calling convention for the syscall handler will
* restore the others to original values.
@ -293,6 +491,8 @@ dispatch_syscall:
*/
mov ip, r8
orrs ip, ip, #1
#endif
bx ip
@ -303,7 +503,11 @@ SECTION_FUNC(TEXT, z_arch_user_string_nlen)
push {r0, r1, r2, r4, r5, lr}
/* sp+4 is error value, init to -1 */
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
ldr r3, =-1
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
mov.w r3, #-1
#endif
str r3, [sp, #4]
/* Perform string length calculation */
@ -315,7 +519,12 @@ z_arch_user_string_nlen_fault_start:
ldrb r5, [r0, r3]
z_arch_user_string_nlen_fault_end:
#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
cmp r5, #0
beq strlen_done
#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
cbz r5, strlen_done
#endif
cmp r3, r1
beq.n strlen_done