Module Name: src
Committed By: thorpej
Date: Thu Feb 18 16:29:12 UTC 2021
Modified Files:
src/sys/arch/powerpc/oea: ofw_subr.S
Log Message:
- Tidy up some comments.
- Use correct stack frame linkage everywhere so that if something goes
wrong, we can get a meaningful back trace.
- Use an additional layer of indirection so that, when we're very
early in bootstrap, we can just call OpenFirmware directly, rather
than using our trampoline that saves/restores kernel state.
- Carve out a space for ofwinit() to call into C code to do additional
initialization. (This is not done yet.)
To generate a diff of this commit:
cvs rdiff -u -r1.13 -r1.14 src/sys/arch/powerpc/oea/ofw_subr.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/powerpc/oea/ofw_subr.S
diff -u src/sys/arch/powerpc/oea/ofw_subr.S:1.13 src/sys/arch/powerpc/oea/ofw_subr.S:1.14
--- src/sys/arch/powerpc/oea/ofw_subr.S:1.13 Sat Feb 13 01:48:33 2021
+++ src/sys/arch/powerpc/oea/ofw_subr.S Thu Feb 18 16:29:12 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: ofw_subr.S,v 1.13 2021/02/13 01:48:33 thorpej Exp $ */
+/* $NetBSD: ofw_subr.S,v 1.14 2021/02/18 16:29:12 thorpej Exp $ */
/*
* Copyright (C) 1995, 1996 Wolfgang Solfrank.
@@ -35,25 +35,43 @@
#include "opt_ppcarch.h"
#endif
- .local firmstk
- .globl openfirmware_entry
- .globl ofwmsr
- .local ofwsrsave
- .local OF_buffer
-
+ /* Stack used to call into OpenFirmware. */
.lcomm firmstk,NBPG,16
+
+ /* Buffer used to pass data to/from OpenFirmware. */
.lcomm OF_buffer,NBPG + 36,4
- .comm openfirmware_entry,4,4 /* openfirmware entry point */
- .lcomm ofwsrsave,64,4 /* openfirmware SR savearea */
- .comm ofwmsr,20,4 /* msr & sprg[0-3] used in OF */
- .comm ofwreal_incharge,4,4
+
+ /* The OpenFirmware entry point, provided by OpenFirmware. */
+ .lcomm ofentry,4,4
+
+ /* Entry trampoline used by openfirmware(). */
+ .lcomm oftramp,4,4
+
+ /* OpenFirmware SR save area */
+ .lcomm ofwsrsave,64,4
+
+ /* MSR and SPRG[0-3] used in OpenFirmware */
+ .globl ofwmsr
+ .comm ofwmsr,20,4
/*
* Called by start to save the initial OFW state so we can restore it
* when call back to OFW.
+ *
+ * We expect the registers to be as for the entry point into the kernel:
+ *
+ * %r1 Stack provided by OpenFirmware / boot loader
+ * %r5 OpenFirmware client entry point
+ *
+ * (others -- don't care)
*/
ENTRY_NOPROFILE(ofwinit)
-#ifdef FIRMWORKSBUGS
+ /* Save return address, Push a stack frame. */
+ mflr %r0
+ stw %r0,4(%r1)
+ stwu %r1,-16(%r1)
+
+#ifdef FIRMWORKSBUGS
mfmsr %r0
andi. %r0,%r0,PSL_IR|PSL_DR
beq 1f
@@ -62,25 +80,24 @@ ENTRY_NOPROFILE(ofwinit)
lis %r9,ofwreal_incharge@ha
stw %r8,ofwreal_incharge@l(%r9)
- mflr %r30
bl _C_LABEL(ofwr_init)
- mtlr %r30
1:
#endif
- lis %r8,openfirmware_entry@ha
- stw %r5,openfirmware_entry@l(%r8) /* save client interface handler*/
+ lis %r8,ofentry@ha
+ stw %r5,ofentry@l(%r8) /* save client interface handler */
+
+ /*
+ * Call directly into OpenFirmware until we're ready to use
+ * the trampoline.
+ */
+ lis %r8,oftramp@ha
+ stw %r5,oftramp@l(%r8)
+
+ /* Save the MSR that OpenFirmware is using. */
mfmsr %r0
-/*
- * XXX
- * doing this here instead of later on in ofwoea_initppc() after setting
- * up the console and such makes my PowerBook 3400c hang.
- * Probably just another OF 2.0 weirdness
- */
- /*li %r8,PSL_IP*/
- /*andc %r0,%r0,%r8*/ /* make sure PSL_IP is off */
lis %r9,ofwmsr@ha
- stwu %r0,ofwmsr@l(%r9) /* save initial MSR value */
+ stwu %r0,ofwmsr@l(%r9)
mfsprg0 %r0 /* save SPRGs */
stw %r0,4(%r9)
@@ -96,28 +113,42 @@ ENTRY_NOPROFILE(ofwinit)
lis %r9,_C_LABEL(OF_buf)@ha
stw %r8,_C_LABEL(OF_buf)@l(%r9)
+ /* XXX Do other stuff in C code. */
+
+ /*
+ * Jump off the trampoline for all subsequent calls
+ * into OpenFirmware.
+ */
+ lis %r5,_C_LABEL(openfirmware_trampoline)@ha
+ addi %r5,%r5,_C_LABEL(openfirmware_trampoline)@l
+ lis %r8,oftramp@ha
+ stw %r5,oftramp@l(%r8)
+
+ /* Retrieve LR, pop stack frame. */
+ addi %r1,%r1,16
+ lwz %r0,4(%r1)
+ mtlr %r0
+
blr
/*
- * OpenFirmware entry point
+ * OpenFirmware trampoline. We are already on the OpenFirmware stack.
*/
- .text
-ENTRY(openfirmware)
+ENTRY_NOPROFILE(openfirmware_trampoline)
mflr %r0
stw %r0,4(%r1) /* save return address */
/*
- * Switch to OpenFirmware stack.
+ * Push stack frame and save area:
*
- * -48 == -16 to stack old SP and align, -32 for save area
+ * [SP+8 save area]
+ * [SP+4 slot for saved LR in callee]
+ * [SP+0 saved SP]
*/
- lis %r7,firmstk+NBPG-48@ha
- addi %r7,%r7,firmstk+NBPG-48@l
- stw %r1,32(%r7) /* stash away prev stack pointer */
- mr %r1,%r7
+ stwu %r1,-48(%r1)
- lis %r4,openfirmware_entry@ha /* get firmware entry point */
- lwz %r4,openfirmware_entry@l(%r4)
+ lis %r4,ofentry@ha /* get firmware entry point */
+ lwz %r4,ofentry@l(%r4)
mtlr %r4
mfsprg0 %r5 /* save current sprg0 (curcpu) */
@@ -211,7 +242,31 @@ ENTRY(openfirmware)
lwz %r5,28(%r1)
mtsprg3 %r5
- lwz %r1,32(%r1) /* restore previous stack pointer */
+ addi %r1,%r1,48 /* pop stack frame and save area */
+ lwz %r0,4(%r1) /* return address */
+ mtlr %r0
+ blr
+
+/*
+ * Call into OpenFirmware.
+ */
+ENTRY_NOPROFILE(openfirmware)
+ mflr %r0
+ stw %r0,4(%r1) /* save return address */
+
+ /* Switch to OpenFirmware stack. */
+ lis %r7,firmstk+NBPG-16@ha
+ addi %r7,%r7,firmstk+NBPG-16@l
+ stw %r1,0(%r7) /* stash away prev stack pointer */
+ mr %r1,%r7
+
+ lis %r4,oftramp@ha
+ lwz %r4,oftramp@l(%r4)
+
+ mtctr %r4
+ bctrl
+
+ lwz %r1,0(%r1) /* restore previous stack pointer */
lwz %r0,4(%r1) /* return address */
mtlr %r0
blr
