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AArch32: Add support for HLT to Mixed Mode models 

The Semihosting v2 protocol requires us to output the Armv8-a HLT instruction
when in mixed mode (SEMIHOST_V2_MIXED_MODE), however it also requires this to
be done for Armv7-a and earlier architectures.

The HLT instruction is defined in the undefined encoding space for older
architectures but simulators such as QEMU already trap on it [1] for all
architectures and is a requirement for semihosting v2 [2].

Unfortunately the GAS restricts the use of HLT to Armv8-a which requires us to
use the instruction encodings we want directly in crt0.

This patch does this, I have not updated newlib/libc/* as that is quite out of
date already.  A proper sync is needed in order to get things back in sync.

A different patch for this would be best.

[1] 19a6e31c9d
[2] https://developer.arm.com/docs/100863/latest/the-semihosting-interface
This commit is contained in:
Tamar Christina 2019-02-06 11:27:12 +00:00 committed by Corinna Vinschen
parent 3956ddd9bf
commit 6d6a623e7d
2 changed files with 13 additions and 7 deletions
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6
libgloss/arm/crt0.S
View File

@ -116,10 +116,10 @@
bkpt AngelSWI
#elif defined(__thumb2__)
/* We are in thumb mode for startup on armv7 architectures. */
AngelSWIAsm AngelSWI
AngelSWIAsm (AngelSWI)
#else
/* We are always in ARM mode for startup on pre armv7 archs. */
AngelSWIAsm AngelSWI_ARM
AngelSWIAsm (AngelSWI_ARM)
#endif
ldr r0, .LC0 /* point at values read */
@ -297,7 +297,7 @@ __change_mode:
#else
movs r0, #AngelSWI_Reason_GetCmdLine
ldr r1, .LC30 /* Space for command line */
AngelSWIAsm AngelSWI
AngelSWIAsm (AngelSWI)
ldr r1, .LC30
ldr r1, [r1]
#endif

14
libgloss/arm/swi.h
View File

@ -31,9 +31,9 @@
/* Now the SWI numbers and reason codes for RDI (Angel) monitors. */
#if defined (SEMIHOST_V2) && defined (SEMIHOST_V2_MIXED_MODE)
#define AngelSWI_ARM 0xF000 /* HLT A32. */
#define AngelSWI_ARM 0xE10F0070 /* HLT #0xF000 A32. */
#ifdef __thumb__
#define AngelSWI 0x3C /* HLT T32. */
#define AngelSWI 0xBABC /* HLT #0x3c T32. */
#else /* __thumb__. */
#define AngelSWI AngelSWI_ARM
#endif /* __thumb__. */
@ -49,10 +49,16 @@
/* For thumb only architectures use the BKPT instruction instead of SWI. */
#ifdef THUMB_VXM
#define AngelSWIInsn "bkpt"
#define AngelSWIAsm bkpt
#define AngelSWIAsm(IMM) bkpt IMM
#elif defined (SEMIHOST_V2) && defined (SEMIHOST_V2_MIXED_MODE)
/* This is actually encoding the HLT instruction, however we don't have
support for this in older assemblers. So we have to encode the
instruction manually. */
#define AngelSWIInsn ".inst"
#define AngelSWIAsm(IMM) .inst IMM
#else
#define AngelSWIInsn "swi"
#define AngelSWIAsm swi
#define AngelSWIAsm(IMM) swi IMM
#endif
/* The reason codes: */