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Further fixes for usermode handling #289

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merged 3 commits into from
Aug 28, 2023
Merged

Further fixes for usermode handling #289

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27f2e11
arch,usermode: fix user stack handling in enter_usermode()
wipawel Aug 27, 2023
fe61963
arch,entry: cleanup: rearrange code
wipawel Aug 27, 2023
2090c8f
arch,entry,usermode: fix user pagetable mappings alignment
wipawel Aug 27, 2023
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87 changes: 46 additions & 41 deletions arch/x86/entry.S
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Original file line number Diff line number Diff line change
Expand Up @@ -92,6 +92,23 @@ ENTRY(asm_interrupt_handler_\sym)
END_FUNC(asm_interrupt_handler_\sym)
.endm

ENTRY(handle_exception)
cld
SAVE_ALL_REGS

mov %_ASM_SP, %_ASM_DI
call do_exception

RESTORE_ALL_REGS

add $8, %_ASM_SP

enter_to_usermode
IRET
END_FUNC(handle_exception)

.align PAGE_SIZE
GLOBAL(exception_handlers)
exception_handler DE X86_EX_DE 0
exception_handler DB X86_EX_DB 0
exception_handler NMI X86_EX_NMI 0
Expand All @@ -114,29 +131,40 @@ exception_handler MC X86_EX_MC 0
exception_handler XM X86_EX_XM 0
exception_handler VE X86_EX_VE 0
exception_handler SE X86_EX_SE 1
GLOBAL(end_exception_handlers)

ENTRY(handle_exception)
cld
SAVE_ALL_REGS

mov %_ASM_SP, %_ASM_DI
call do_exception

RESTORE_ALL_REGS

add $8, %_ASM_SP

enter_to_usermode
IRET
END_FUNC(handle_exception)

GLOBAL(interrupt_handlers)
interrupt_handler timer timer_interrupt_handler
interrupt_handler uart uart_interrupt_handler
interrupt_handler keyboard keyboard_interrupt_handler
#ifdef KTF_ACPICA
interrupt_handler acpi acpi_interrupt_handler
#endif
GLOBAL(end_interrupt_handlers)

.align PAGE_SIZE
ENTRY(syscall_exit)
POPF

/* Save exit code to return value register (AX) */
mov %_ASM_SI, cpu_regs_ax(%_ASM_SP)
RESTORE_ALL_REGS

ret
END_FUNC(syscall_exit)

ENTRY(terminate_user_task)
SWITCH_STACK
POPF

movl $-EFAULT, cpu_regs_ax(%_ASM_SP)
RESTORE_ALL_REGS

ret
END_FUNC(terminate_user_task)

.align PAGE_SIZE
GLOBAL(usermode_helpers)
ENTRY(enter_usermode)
/* FIXME: Add 32-bit support */

Expand All @@ -145,10 +173,9 @@ ENTRY(enter_usermode)
PUSHF

/* Save stack pointer onto per-cpu */
mov %_ASM_SP, %gs:usermode_private
mov %_ASM_DX, %gs:(usermode_private)

/* Move to user stack */
mov %_ASM_DX, %_ASM_SP
syscall_to_usermode
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/* SS + SP */
push $__USER_DS
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Expand All @@ -162,32 +189,9 @@ ENTRY(enter_usermode)
/* CS + IP */
push $__USER_CS
push $usermode_stub

enter_to_usermode
IRET
END_FUNC(enter_usermode)

ENTRY(syscall_exit)
POPF

/* Save exit code to return value register (AX) */
mov %_ASM_SI, cpu_regs_ax(%_ASM_SP)
RESTORE_ALL_REGS

ret
END_FUNC(syscall_exit)

ENTRY(terminate_user_task)
SWITCH_STACK
POPF

movl $-EFAULT, cpu_regs_ax(%_ASM_SP)
RESTORE_ALL_REGS

ret
END_FUNC(terminate_user_task)

.align PAGE_SIZE
ENTRY(syscall_handler_entry)
SAVE_CALLEE_SAVED_REGS
syscall_from_usermode
Expand All @@ -209,6 +213,7 @@ ENTRY(syscall_handler_entry)
RESTORE_CALLEE_SAVED_REGS
SYSRET
END_FUNC(syscall_handler_entry)
GLOBAL(end_usermode_helpers)

SECTION(.text.user, "ax", 16)
ENTRY(usermode_stub)
Expand Down
2 changes: 1 addition & 1 deletion arch/x86/pagetables.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@
#include <spinlock.h>
#include <string.h>

cr3_t cr3;
cr3_t __aligned(PAGE_SIZE) cr3;
cr3_t user_cr3;

static inline const char *dump_pte_flags(char *buf, size_t size, pte_t pte) {
Expand Down
17 changes: 15 additions & 2 deletions common/usermode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,10 @@
#include <processor.h>
#include <usermode.h>

extern char exception_handlers[], end_exception_handlers[];
extern char interrupt_handlers[], end_interrupt_handlers[];
extern char usermode_helpers[], end_usermode_helpers[];

long syscall_handler(long syscall_nr, long arg1, long arg2, long arg3, long arg4,
long arg5) {
switch (syscall_nr) {
Expand Down Expand Up @@ -89,8 +93,17 @@ static void init_syscall(void) {

void init_usermode(percpu_t *percpu) {
vmap_user_4k(&cr3, virt_to_mfn(&cr3), L1_PROT);
vmap_user_4k(&enter_usermode, virt_to_mfn(&enter_usermode), L1_PROT);
vmap_user_4k(&syscall_handler_entry, virt_to_mfn(&syscall_handler_entry), L1_PROT);
vmap_user_4k(&user_cr3, virt_to_mfn(&user_cr3), L1_PROT);

BUG_ON(end_exception_handlers - exception_handlers > (long) PAGE_SIZE);
vmap_user_4k(exception_handlers, virt_to_mfn(exception_handlers), L1_PROT);

BUG_ON(end_interrupt_handlers - interrupt_handlers > (long) PAGE_SIZE);
vmap_user_4k(interrupt_handlers, virt_to_mfn(interrupt_handlers), L1_PROT);

BUG_ON(end_usermode_helpers - usermode_helpers > (long) PAGE_SIZE);
vmap_user_4k(usermode_helpers, virt_to_mfn(usermode_helpers), L1_PROT);

init_syscall();
}

Expand Down