581141cb4b
This path isn't obvious. It looks as if the kernel will be taking three args from the user stack, but it only takes one from there. Signed-off-by: Albert Cahalan <acahalan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
120 lines
3.6 KiB
ArmAsm
120 lines
3.6 KiB
ArmAsm
/*
|
|
* Code for the vsyscall page. This version uses the sysenter instruction.
|
|
*
|
|
* NOTE:
|
|
* 1) __kernel_vsyscall _must_ be first in this page.
|
|
* 2) there are alignment constraints on this stub, see vsyscall-sigreturn.S
|
|
* for details.
|
|
*/
|
|
|
|
/*
|
|
* The caller puts arg2 in %ecx, which gets pushed. The kernel will use
|
|
* %ecx itself for arg2. The pushing is because the sysexit instruction
|
|
* (found in entry.S) requires that we clobber %ecx with the desired %esp.
|
|
* User code might expect that %ecx is unclobbered though, as it would be
|
|
* for returning via the iret instruction, so we must push and pop.
|
|
*
|
|
* The caller puts arg3 in %edx, which the sysexit instruction requires
|
|
* for %eip. Thus, exactly as for arg2, we must push and pop.
|
|
*
|
|
* Arg6 is different. The caller puts arg6 in %ebp. Since the sysenter
|
|
* instruction clobbers %esp, the user's %esp won't even survive entry
|
|
* into the kernel. We store %esp in %ebp. Code in entry.S must fetch
|
|
* arg6 from the stack.
|
|
*/
|
|
.text
|
|
.globl __kernel_vsyscall
|
|
.type __kernel_vsyscall,@function
|
|
__kernel_vsyscall:
|
|
.LSTART_vsyscall:
|
|
push %ecx
|
|
.Lpush_ecx:
|
|
push %edx
|
|
.Lpush_edx:
|
|
push %ebp
|
|
.Lenter_kernel:
|
|
movl %esp,%ebp
|
|
sysenter
|
|
|
|
/* 7: align return point with nop's to make disassembly easier */
|
|
.space 7,0x90
|
|
|
|
/* 14: System call restart point is here! (SYSENTER_RETURN - 2) */
|
|
jmp .Lenter_kernel
|
|
/* 16: System call normal return point is here! */
|
|
.globl SYSENTER_RETURN /* Symbol used by entry.S. */
|
|
SYSENTER_RETURN:
|
|
pop %ebp
|
|
.Lpop_ebp:
|
|
pop %edx
|
|
.Lpop_edx:
|
|
pop %ecx
|
|
.Lpop_ecx:
|
|
ret
|
|
.LEND_vsyscall:
|
|
.size __kernel_vsyscall,.-.LSTART_vsyscall
|
|
.previous
|
|
|
|
.section .eh_frame,"a",@progbits
|
|
.LSTARTFRAMEDLSI:
|
|
.long .LENDCIEDLSI-.LSTARTCIEDLSI
|
|
.LSTARTCIEDLSI:
|
|
.long 0 /* CIE ID */
|
|
.byte 1 /* Version number */
|
|
.string "zR" /* NUL-terminated augmentation string */
|
|
.uleb128 1 /* Code alignment factor */
|
|
.sleb128 -4 /* Data alignment factor */
|
|
.byte 8 /* Return address register column */
|
|
.uleb128 1 /* Augmentation value length */
|
|
.byte 0x1b /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
|
|
.byte 0x0c /* DW_CFA_def_cfa */
|
|
.uleb128 4
|
|
.uleb128 4
|
|
.byte 0x88 /* DW_CFA_offset, column 0x8 */
|
|
.uleb128 1
|
|
.align 4
|
|
.LENDCIEDLSI:
|
|
.long .LENDFDEDLSI-.LSTARTFDEDLSI /* Length FDE */
|
|
.LSTARTFDEDLSI:
|
|
.long .LSTARTFDEDLSI-.LSTARTFRAMEDLSI /* CIE pointer */
|
|
.long .LSTART_vsyscall-. /* PC-relative start address */
|
|
.long .LEND_vsyscall-.LSTART_vsyscall
|
|
.uleb128 0
|
|
/* What follows are the instructions for the table generation.
|
|
We have to record all changes of the stack pointer. */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lpush_ecx-.LSTART_vsyscall
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x08 /* RA at offset 8 now */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lpush_edx-.Lpush_ecx
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x0c /* RA at offset 12 now */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lenter_kernel-.Lpush_edx
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x10 /* RA at offset 16 now */
|
|
.byte 0x85, 0x04 /* DW_CFA_offset %ebp -16 */
|
|
/* Finally the epilogue. */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lpop_ebp-.Lenter_kernel
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x0c /* RA at offset 12 now */
|
|
.byte 0xc5 /* DW_CFA_restore %ebp */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lpop_edx-.Lpop_ebp
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x08 /* RA at offset 8 now */
|
|
.byte 0x04 /* DW_CFA_advance_loc4 */
|
|
.long .Lpop_ecx-.Lpop_edx
|
|
.byte 0x0e /* DW_CFA_def_cfa_offset */
|
|
.byte 0x04 /* RA at offset 4 now */
|
|
.align 4
|
|
.LENDFDEDLSI:
|
|
.previous
|
|
|
|
/*
|
|
* Get the common code for the sigreturn entry points.
|
|
*/
|
|
#include "vsyscall-sigreturn.S"
|