Clean up arm setjmp family.
Bug: 16918359
Change-Id: I9b986bdbdbaefe9d9896a820ee8cfe860adfe5c5
diff --git a/libc/arch-arm/bionic/setjmp.S b/libc/arch-arm/bionic/setjmp.S
index 7bf2aed..6b9c626 100644
--- a/libc/arch-arm/bionic/setjmp.S
+++ b/libc/arch-arm/bionic/setjmp.S
@@ -1,6 +1,3 @@
-/* $OpenBSD: setjmp.S,v 1.2 2004/02/01 05:40:52 drahn Exp $ */
-/* $NetBSD: setjmp.S,v 1.5 2003/04/05 23:08:51 bjh21 Exp $ */
-
/*
* Copyright (c) 1997 Mark Brinicombe
* Copyright (c) 2010 Android Open Source Project.
@@ -36,103 +33,154 @@
#include <private/bionic_asm.h>
#include <machine/setjmp.h>
-#include <machine/cpu-features.h>
-/*
- * C library -- setjmp, longjmp
- *
- * longjmp(a,v)
- * will generate a "return(v)" from the last call to
- * setjmp(a)
- * by restoring registers from the stack.
- * The previous signal state is restored.
- */
+// According to the ARM AAPCS document, we only need to save
+// the following registers:
+//
+// Core r4-r14
+//
+// VFP d8-d15 (see section 5.1.2.1)
+//
+// Registers s16-s31 (d8-d15, q4-q7) must be preserved across subroutine
+// calls; registers s0-s15 (d0-d7, q0-q3) do not need to be preserved
+// (and can be used for passing arguments or returning results in standard
+// procedure-call variants). Registers d16-d31 (q8-q15), if present, do
+// not need to be preserved.
+//
+// FPSCR saved because glibc does.
+
+// The internal structure of a jmp_buf is totally private.
+// Current layout (may change in the future):
+//
+// word name description
+// 0 magic magic number
+// 1 sigmask signal mask (not used with _setjmp / _longjmp)
+// 2 float_base base of float registers (d8 to d15)
+// 18 float_state floating-point status and control register
+// 19 core_base base of core registers (r4 to r14)
+// 30 reserved reserved entries (room to grow)
+// 64
+//
+// NOTE: float_base must be at an even word index, since the
+// FP registers will be loaded/stored with instructions
+// that expect 8-byte alignment.
+
+#define _JB_MAGIC 0
+#define _JB_SIGMASK (_JB_MAGIC+1)
+#define _JB_FLOAT_BASE (_JB_SIGMASK+1)
+#define _JB_FLOAT_STATE (_JB_FLOAT_BASE + (15-8+1)*2)
+#define _JB_CORE_BASE (_JB_FLOAT_STATE+1)
+
+.L_setjmp_magic_signal_mask_n: .word 0x4278f500
+.L_setjmp_magic_signal_mask_y: .word 0x4278f501
ENTRY(setjmp)
- /* Block all signals and retrieve the old signal mask */
- stmfd sp!, {r0, r14}
- .cfi_def_cfa_offset 8
- .cfi_rel_offset r0, 0
- .cfi_rel_offset r14, 4
- mov r0, #0x00000000
-
- bl sigblock
- mov r1, r0
-
- ldmfd sp!, {r0, r14}
- .cfi_def_cfa_offset 0
-
- /* Store signal mask */
- str r1, [r0, #(_JB_SIGMASK * 4)]
-
- ldr r1, .Lsetjmp_magic
- str r1, [r0, #(_JB_MAGIC * 4)]
-
- /* Store core registers */
- add r1, r0, #(_JB_CORE_BASE * 4)
- stmia r1, {r4-r14}
-
- /* Store floating-point registers */
- add r1, r0, #(_JB_FLOAT_BASE * 4)
- vstmia r1, {d8-d15}
- /* Store floating-point state */
- fmrx r1, fpscr
- str r1, [r0, #(_JB_FLOAT_STATE * 4)]
-
- mov r0, #0x00000000
- bx lr
+ mov r1, #1
+ b sigsetjmp
END(setjmp)
-.Lsetjmp_magic:
- .word _JB_MAGIC_SETJMP
+ENTRY(_setjmp)
+ mov r1, #0
+ b sigsetjmp
+END(_setjmp)
+// int sigsetjmp(sigjmp_buf env, int save_signal_mask);
+ENTRY(sigsetjmp)
+ // Do we need to save the signal mask?
+ teq r1, #0
+ ldreq r1, .L_setjmp_magic_signal_mask_n
+ beq 1f
-ENTRY(longjmp)
- ldr r2, .Lsetjmp_magic
- ldr r3, [r0, #(_JB_MAGIC * 4)]
- teq r2, r3
- blne longjmperror
+ // Get current signal mask.
+ stmfd sp!, {r0, r14}
+ .cfi_def_cfa_offset 8
+ .cfi_rel_offset r0, 0
+ .cfi_rel_offset r14, 4
+ mov r0, #0
+ bl sigblock
+ mov r1, r0
+ ldmfd sp!, {r0, r14}
+ .cfi_def_cfa_offset 0
- /* Fetch signal mask */
- ldr r2, [r0, #(_JB_SIGMASK * 4)]
+ // Save signal mask.
+ str r1, [r0, #(_JB_SIGMASK * 4)]
- /* Set signal mask */
- stmfd sp!, {r0, r1, r14}
- .cfi_def_cfa_offset 12
- .cfi_rel_offset r0, 0
- .cfi_rel_offset r1, 4
- .cfi_rel_offset r14, 8
- sub sp, sp, #4 /* align the stack */
- .cfi_adjust_cfa_offset 4
+ ldr r1, .L_setjmp_magic_signal_mask_y
- mov r0, r2
- bl sigsetmask
+1:
+ // Save magic number.
+ str r1, [r0, #(_JB_MAGIC * 4)]
- add sp, sp, #4 /* unalign the stack */
- .cfi_adjust_cfa_offset -4
- ldmfd sp!, {r0, r1, r14}
- .cfi_def_cfa_offset 0
+ // Save core registers.
+ add r1, r0, #(_JB_CORE_BASE * 4)
+ stmia r1, {r4-r14}
- /* Restore floating-point registers */
- add r2, r0, #(_JB_FLOAT_BASE * 4)
- vldmia r2, {d8-d15}
- /* Restore floating-point state */
- ldr r2, [r0, #(_JB_FLOAT_STATE * 4)]
- fmxr fpscr, r2
+ // Save floating-point registers.
+ add r1, r0, #(_JB_FLOAT_BASE * 4)
+ vstmia r1, {d8-d15}
- /* Restore core registers */
- add r2, r0, #(_JB_CORE_BASE * 4)
- ldmia r2, {r4-r14}
+ // Save floating-point state.
+ fmrx r1, fpscr
+ str r1, [r0, #(_JB_FLOAT_STATE * 4)]
- /* Validate sp and r14 */
- teq sp, #0
- teqne r14, #0
- bleq longjmperror
+ mov r0, #0
+ bx lr
+END(sigsetjmp)
- /* Set return value */
- mov r0, r1
- teq r0, #0x00000000
- moveq r0, #0x00000001
- bx lr
- mov r15, r14
-END(longjmp)
+// void siglongjmp(sigjmp_buf env, int value);
+ENTRY(siglongjmp)
+ // Check magic.
+ ldr r3, [r0, #(_JB_MAGIC * 4)]
+ ldr r2, .L_setjmp_magic_signal_mask_n
+ teq r2, r3
+ beq 1f
+ ldr r2, .L_setjmp_magic_signal_mask_y
+ teq r2, r3
+ bne longjmperror
+
+ // Restore signal mask.
+ stmfd sp!, {r0, r1, r14}
+ .cfi_def_cfa_offset 12
+ .cfi_rel_offset r0, 0
+ .cfi_rel_offset r1, 4
+ .cfi_rel_offset r14, 8
+ sub sp, sp, #4 // Align the stack.
+ .cfi_adjust_cfa_offset 4
+
+ ldr r0, [r0, #(_JB_SIGMASK * 4)]
+ bl sigsetmask
+
+ add sp, sp, #4 // Unalign the stack.
+ .cfi_adjust_cfa_offset -4
+ ldmfd sp!, {r0, r1, r14}
+ .cfi_def_cfa_offset 0
+
+1:
+ // Restore floating-point registers.
+ add r2, r0, #(_JB_FLOAT_BASE * 4)
+ vldmia r2, {d8-d15}
+
+ // Restore floating-point state.
+ ldr r2, [r0, #(_JB_FLOAT_STATE * 4)]
+ fmxr fpscr, r2
+
+ // Restore core registers.
+ add r2, r0, #(_JB_CORE_BASE * 4)
+ ldmia r2, {r4-r14}
+
+ // Validate sp and r14.
+ teq sp, #0
+ teqne r14, #0
+ bleq longjmperror
+
+ // Set return value.
+ mov r0, r1
+ teq r0, #0
+ moveq r0, #1
+ bx lr
+END(siglongjmp)
+
+ .globl longjmp
+ .equ longjmp, siglongjmp
+ .globl _longjmp
+ .equ _longjmp, siglongjmp