libc: arm: fix setjmp abi non-conformance

As per the arm Procedure Call Standard for the Arm Architecture
section 6.1.2 [1], VFP registers s16-s31 (d8-d15, q4-q7) must be
preserved across subroutine calls.

The current setjmp/longjmp implementations preserve only the core
registers, with the jump buffer size too small to store the required
co-processor registers.

In accordance with the C Library ABI for the Arm Architecture
section 6.11 [2], this patch sets _JBTYPE to long long adjusting
_JBLEN to 20.

It also emits vfp load/store instructions depending on architectural
support, predicated at compile time on ACLE feature-test macros.

[1] https://github.com/ARM-software/abi-aa/blob/main/aapcs32/aapcs32.rst
[2] https://github.com/ARM-software/abi-aa/blob/main/clibabi32/clibabi32.rst

COPYING.NEWLIB

@@ -762,7 +762,7 @@ SUCH DAMAGE.
 
 (35) - Arm Ltd
 
- Copyright (c) 2009-2018 Arm Ltd
+ Copyright (c) 2009-2022 Arm Ltd
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without

newlib/libc/include/machine/setjmp.h

@@ -12,9 +12,13 @@ _BEGIN_STD_C
 #if defined(__arm__) || defined(__thumb__)
 /*
  * All callee preserved registers:
- * v1 - v7, fp, ip, sp, lr, f4, f5, f6, f7
+ *  core registers:
+ *   r4 - r10, fp, sp, lr
+ *  VFP registers (architectural support dependent):
+ *   d8 - d15
  */
-#define _JBLEN 23
+#define _JBLEN 20
+#define _JBTYPE long long
 #endif
 
 #if defined(__aarch64__)

newlib/libc/machine/arm/setjmp.S

@@ -27,34 +27,34 @@
    The interworking scheme expects functions to use a BX instruction
    to return control to their parent.  Since we need this code to work
    in both interworked and non-interworked environments as well as with
-   older processors which do not have the BX instruction we do the 
+   older processors which do not have the BX instruction we do the
    following:
 	Test the return address.
 	If the bottom bit is clear perform an "old style" function exit.
 	(We know that we are in ARM mode and returning to an ARM mode caller).
 	Otherwise use the BX instruction to perform the function exit.
 
-   We know that we will never attempt to perform the BX instruction on 
+   We know that we will never attempt to perform the BX instruction on
-   an older processor, because that kind of processor will never be 
+   an older processor, because that kind of processor will never be
-   interworked, and a return address with the bottom bit set will never 
+   interworked, and a return address with the bottom bit set will never
    be generated.
 
    In addition, we do not actually assemble the BX instruction as this would
    require us to tell the assembler that the processor is an ARM7TDMI and
    it would store this information in the binary.  We want this binary to be
    able to be linked with binaries compiled for older processors however, so
-   we do not want such information stored there.  
+   we do not want such information stored there.
 
    If we are running using the APCS-26 convention however, then we never
-   test the bottom bit, because this is part of the processor status.  
+   test the bottom bit, because this is part of the processor status.
-   Instead we just do a normal return, since we know that we cannot be 
+   Instead we just do a normal return, since we know that we cannot be
    returning to a Thumb caller - the Thumb does not support APCS-26.
-	
+
-   Function entry is much simpler.  If we are compiling for the Thumb we 
+   Function entry is much simpler.  If we are compiling for the Thumb we
    just switch into ARM mode and then drop through into the rest of the
    function.  The function exit code will take care of the restore to
    Thumb mode.
-   
+
    For Thumb-2 do everything in Thumb mode.  */
 
 	.syntax unified
@@ -115,15 +115,15 @@ SYM (longjmp):
 #else
 #define RET	tst		lr, #1; \
 	        moveq		pc, lr ; \
-.word           0xe12fff1e	/* bx lr */
+.inst           0xe12fff1e	/* bx lr */
 #endif
 
 #ifdef __thumb2__
-.macro COND where when 
+.macro COND where when
 	i\where	\when
 .endm
 #else
-.macro COND where when 
+.macro COND where when
 .endm
 #endif
 
@@ -140,7 +140,7 @@ SYM (longjmp):
 .macro PROLOGUE name
 	.code 16
 	bx	pc
-	nop	
+	nop
 	.code 32
 SYM (.arm_start_of.\name):
 .endm
@@ -149,7 +149,7 @@ SYM (.arm_start_of.\name):
 .macro PROLOGUE name
 .endm
 #endif
-	
+
 .macro FUNC_START name
 	.text
 	.align 2
@@ -164,61 +164,65 @@ SYM (\name):
 	RET
 	SIZE (\name)
 .endm
-	
+
 /* --------------------------------------------------------------------
-                 int setjmp (jmp_buf); 
+                 int setjmp (jmp_buf);
    -------------------------------------------------------------------- */
-	
+
 	FUNC_START setjmp
 
 	/* Save all the callee-preserved registers into the jump buffer.  */
 #ifdef __thumb2__
 	mov		ip, sp
-	stmea		a1!, { v1-v7, fp, ip, lr }
+	stmia		r0!, { r4-r10, fp, ip, lr }
 #else
-	stmea		a1!, { v1-v7, fp, ip, sp, lr }
+	stmia		r0!, { r4-r10, fp, sp, lr }
 #endif
-	
+#if defined __ARM_FP || defined __ARM_FEATURE_MVE
+	vstm		r0, { d8-d15 }
+#endif
+
 #if 0	/* Simulator does not cope with FP instructions yet.  */
 #ifndef __SOFTFP__
 	/* Save the floating point registers.  */
 	sfmea		f4, 4, [a1]
 #endif
-#endif		
+#endif
 	/* When setting up the jump buffer return 0.  */
-	mov		a1, #0
+	mov		r0, #0
 
 	FUNC_END setjmp
-	
+
 /* --------------------------------------------------------------------
 		volatile void longjmp (jmp_buf, int);
    -------------------------------------------------------------------- */
-	
+
 	FUNC_START longjmp
 
 	/* If we have stack extension code it ought to be handled here.  */
-	
+
 	/* Restore the registers, retrieving the state when setjmp() was called.  */
 #ifdef __thumb2__
-	ldmfd		a1!, { v1-v7, fp, ip, lr }
+	ldmia		r0!, { r4-r10, fp, ip, lr }
 	mov		sp, ip
 #else
-	ldmfd		a1!, { v1-v7, fp, ip, sp, lr }
+	ldmia		r0!, { r4-r10, fp, sp, lr }
 #endif
-	
+#if defined __ARM_FP || defined __ARM_FEATURE_MVE
+	vldm		r0, { d8-d15 }
+#endif
+
 #if 0	/* Simulator does not cope with FP instructions yet.  */
 #ifndef __SOFTFP__
 	/* Restore floating point registers as well.  */
 	lfmfd		f4, 4, [a1]
 #endif
-#endif	
-	/* Put the return value into the integer result register.
-	   But if it is zero then return 1 instead.  */	
-	movs		a1, a2
-#ifdef __thumb2__
-	it		eq
 #endif
-	moveq		a1, #1
+	/* Put the return value into the integer result register.
+	   But if it is zero then return 1 instead.  */
+	movs		r0, r1
+	it		eq
+	moveq		r0, #1
 
 	FUNC_END longjmp
 #endif