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https://sourceware.org/ml/libc-alpha/2014-04/msg00006.html
2014-04-01 Will Newton <will.newton@linaro.org>
[BZ #16629]
* sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
Re-implement to restore registers in user code and avoid
rt_sigreturn system call.
---
sysdeps/unix/sysv/linux/aarch64/setcontext.S | 147 +++++++++++++++++----------
2 files changed, 95 insertions(+), 58 deletions(-)
Index: eglibc-2.19/ports/sysdeps/unix/sysv/linux/aarch64/setcontext.S
===================================================================
--- eglibc-2.19.orig/ports/sysdeps/unix/sysv/linux/aarch64/setcontext.S 2150-05-09 09:36:21.925789000 +0000
+++ eglibc-2.19/ports/sysdeps/unix/sysv/linux/aarch64/setcontext.S 2150-05-09 09:36:48.235789000 +0000
@@ -22,68 +22,105 @@
#include "ucontext_i.h"
#include "ucontext-internal.h"
-/* int setcontext (const ucontext_t *ucp) */
+/* int __setcontext (const ucontext_t *ucp)
- .text
-
-ENTRY(__setcontext)
-
- /* Create a signal frame on the stack:
-
- fp
- lr
- ...
- sp-> rt_sigframe
- */
-
- stp x29, x30, [sp, -16]!
- cfi_adjust_cfa_offset (16)
- cfi_rel_offset (x29, 0)
- cfi_rel_offset (x30, 8)
-
- mov x29, sp
- cfi_def_cfa_register (x29)
-
- /* Allocate space for the sigcontext. */
- mov w3, #((RT_SIGFRAME_SIZE + SP_ALIGN_SIZE) & SP_ALIGN_MASK)
- sub sp, sp, x3
+ Restores the machine context in UCP and thereby resumes execution
+ in that context.
- /* Compute the base address of the ucontext structure. */
- add x1, sp, #RT_SIGFRAME_UCONTEXT
+ This implementation is intended to be used for *synchronous* context
+ switches only. Therefore, it does not have to restore anything
+ other than the PRESERVED state. */
- /* Only ucontext is required in the frame, *copy* it in. */
-
-#if UCONTEXT_SIZE % 16
-#error The implementation of setcontext.S assumes sizeof(ucontext_t) % 16 == 0
-#endif
-
- mov x2, #UCONTEXT_SIZE / 16
-0:
- ldp x3, x4, [x0], #16
- stp x3, x4, [x1], #16
- sub x2, x2, 1
- cbnz x2, 0b
+ .text
- /* rt_sigreturn () -- no arguments, sp points to struct rt_sigframe. */
- mov x8, SYS_ify (rt_sigreturn)
+ENTRY (__setcontext)
+ /* Save a copy of UCP. */
+ mov x9, x0
+
+ /* Set the signal mask with
+ rt_sigprocmask (SIG_SETMASK, mask, NULL, _NSIG/8). */
+ mov x0, #SIG_SETMASK
+ add x1, x9, #UCONTEXT_SIGMASK
+ mov x2, #0
+ mov x3, #_NSIG8
+ mov x8, SYS_ify (rt_sigprocmask)
svc 0
-
- /* Ooops we failed. Recover the stack */
-
- mov sp, x29
- cfi_def_cfa_register (sp)
-
- ldp x29, x30, [sp], 16
- cfi_adjust_cfa_offset (16)
- cfi_restore (x29)
- cfi_restore (x30)
- b C_SYMBOL_NAME(__syscall_error)
-
+ cbz x0, 1f
+ b C_SYMBOL_NAME (__syscall_error)
+1:
+ /* Restore the general purpose registers. */
+ mov x0, x9
+ cfi_def_cfa (x0, 0)
+ cfi_offset (x18, oX0 + 18 * SZREG)
+ cfi_offset (x19, oX0 + 19 * SZREG)
+ cfi_offset (x20, oX0 + 20 * SZREG)
+ cfi_offset (x21, oX0 + 21 * SZREG)
+ cfi_offset (x22, oX0 + 22 * SZREG)
+ cfi_offset (x23, oX0 + 23 * SZREG)
+ cfi_offset (x24, oX0 + 24 * SZREG)
+ cfi_offset (x25, oX0 + 25 * SZREG)
+ cfi_offset (x26, oX0 + 26 * SZREG)
+ cfi_offset (x27, oX0 + 27 * SZREG)
+ cfi_offset (x28, oX0 + 28 * SZREG)
+ cfi_offset (x29, oX0 + 29 * SZREG)
+ cfi_offset (x30, oX0 + 30 * SZREG)
+
+ cfi_offset ( d8, oV0 + 8 * SZVREG)
+ cfi_offset ( d9, oV0 + 9 * SZVREG)
+ cfi_offset (d10, oV0 + 10 * SZVREG)
+ cfi_offset (d11, oV0 + 11 * SZVREG)
+ cfi_offset (d12, oV0 + 12 * SZVREG)
+ cfi_offset (d13, oV0 + 13 * SZVREG)
+ cfi_offset (d14, oV0 + 14 * SZVREG)
+ cfi_offset (d15, oV0 + 15 * SZVREG)
+ ldp x18, x19, [x0, oX0 + 18 * SZREG]
+ ldp x20, x21, [x0, oX0 + 20 * SZREG]
+ ldp x22, x23, [x0, oX0 + 22 * SZREG]
+ ldp x24, x25, [x0, oX0 + 24 * SZREG]
+ ldp x26, x27, [x0, oX0 + 26 * SZREG]
+ ldp x28, x29, [x0, oX0 + 28 * SZREG]
+ ldr x30, [x0, oX0 + 30 * SZREG]
+ ldr x2, [x0, oSP]
+ mov sp, x2
+
+ /* Check for FP SIMD context. */
+ add x2, x0, #oEXTENSION
+
+ mov w3, #(FPSIMD_MAGIC & 0xffff)
+ movk w3, #(FPSIMD_MAGIC >> 16), lsl #16
+ ldr w1, [x2, #oHEAD + oMAGIC]
+ cmp w1, w3
+ b.ne 2f
+
+ /* Restore the FP SIMD context. */
+ add x3, x2, #oV0 + 8 * SZVREG
+ ldp d8, d9, [x3], #2 * SZVREG
+ ldp d10, d11, [x3], #2 * SZVREG
+ ldp d12, d13, [x3], #2 * SZVREG
+ ldp d14, d15, [x3], #2 * SZVREG
+
+ add x3, x2, oFPSR
+
+ ldr w4, [x3]
+ msr fpsr, x4
+
+ ldr w4, [x3, oFPCR - oFPSR]
+ msr fpcr, x4
+
+2:
+ ldr x16, [x0, oPC]
+ /* Restore arg registers. */
+ ldp x2, x3, [x0, oX0 + 2 * SZREG]
+ ldp x4, x5, [x0, oX0 + 4 * SZREG]
+ ldp x6, x7, [x0, oX0 + 6 * SZREG]
+ ldp x0, x1, [x0, oX0 + 0 * SZREG]
+ /* Jump to the new pc value. */
+ br x16
PSEUDO_END (__setcontext)
weak_alias (__setcontext, setcontext)
-ENTRY(__startcontext)
+ENTRY (__startcontext)
mov x0, x19
cbnz x0, __setcontext
-1: b HIDDEN_JUMPTARGET(_exit)
-END(__startcontext)
+1: b HIDDEN_JUMPTARGET (_exit)
+END (__startcontext)
--
1.8.1.4
|
