From d12d57dcd872822ad7259dd7976c6a9bc89dee3e Mon Sep 17 00:00:00 2001
From: Ben Gras <ben@minix3.org>
Date: Tue, 21 May 2013 14:57:57 +0200
Subject: [PATCH] arm: recognize instruction fetch pagefault

	. an instruction fetch pagefault generates a prefetch
	  abort exception, this should also be a source of
	  a pagefault event
	. the saved_lr argument to the C exception handler was
	  sometimes an address, sometimes a pointer to that address;
	  the kernel sometimes dereferences it, so it should always be
	  an in-kernel address, never a userspace address. fix in mpx.S
	  makes it always a pointer.
	. move dumping of all processes over serial out of
	  the arch-specific arch_system.c
---
 kernel/arch/earm/exception.c   | 35 ++++++++++++++++++++--------------
 kernel/arch/earm/mpx.S         |  2 +-
 kernel/arch/i386/arch_system.c | 11 -----------
 kernel/proc.c                  | 12 ++++++++++++
 4 files changed, 34 insertions(+), 26 deletions(-)

diff --git a/kernel/arch/earm/exception.c b/kernel/arch/earm/exception.c
index 2a2ca0f14..84b4fe62a 100644
--- a/kernel/arch/earm/exception.c
+++ b/kernel/arch/earm/exception.c
@@ -37,22 +37,15 @@ static void proc_stacktrace_execute(struct proc *whichproc, reg_t v_bp, reg_t pc
 
 static void pagefault( struct proc *pr,
 			reg_t *saved_lr,
-			int is_nested)
+			int is_nested,
+			u32_t pagefault_addr,
+			u32_t pagefault_status)
 {
 	int in_physcopy = 0, in_memset = 0;
 
-	reg_t pagefault_addr, pagefault_status;
 	message m_pagefault;
 	int err;
 
-	pagefault_addr = read_dfar();
-	pagefault_status = read_dfsr();
-
-#if 0
-	printf("kernel: pagefault in pr %d, addr 0x%lx, his ttbr 0x%lx, actual ttbr 0x%lx\n",
-		pr->p_endpoint, pagefault_addr, pr->p_seg.p_ttbr, read_ttbr0());
-#endif
-
 	in_physcopy = (*saved_lr > (vir_bytes) phys_copy) &&
 	   (*saved_lr < (vir_bytes) phys_copy_fault);
 
@@ -61,9 +54,6 @@ static void pagefault( struct proc *pr,
 
 	if((is_nested || iskernelp(pr)) &&
 		catch_pagefaults && (in_physcopy || in_memset)) {
-#if 0
-		printf("pf caught! addr 0x%lx\n", pagefault_addr);
-#endif
 		if (is_nested) {
 			if(in_physcopy) {
 				assert(!in_memset);
@@ -153,6 +143,8 @@ void exception_handler(int is_nested, reg_t *saved_lr, int vector)
 
   ep = &ex_data[vector];
 
+  assert((vir_bytes) saved_lr >= kinfo.vir_kern_start);
+
   /*
    * handle special cases for nested problems as they might be tricky or filter
    * them out quickly if the traps are not nested
@@ -179,7 +171,22 @@ void exception_handler(int is_nested, reg_t *saved_lr, int vector)
   }
 
   if (vector == DATA_ABORT_VECTOR) {
-	pagefault(saved_proc, saved_lr, is_nested);
+	pagefault(saved_proc, saved_lr, is_nested, read_dfar(), read_dfsr());
+	return;
+  }
+
+  if (!is_nested && vector == PREFETCH_ABORT_VECTOR) {
+	reg_t ifar = read_ifar(), ifsr = read_ifsr();
+
+	/* The saved_lr is the instruction we're going to execute after
+	 * the fault is handled; IFAR is the address that pagefaulted
+	 * while fetching the instruction. As far as we know the two
+	 * should be the same, if not this assumption will lead to very
+	 * hard to debug problems (instruction executing being off by one)
+	 * and this assumption needs re-examining, hence the assert.
+	 */
+	assert(*saved_lr == ifar);
+	pagefault(saved_proc, saved_lr, is_nested, ifar, ifsr);
 	return;
   }
 
diff --git a/kernel/arch/earm/mpx.S b/kernel/arch/earm/mpx.S
index 622bc83f9..dba2b8446 100644
--- a/kernel/arch/earm/mpx.S
+++ b/kernel/arch/earm/mpx.S
@@ -83,7 +83,7 @@ ENTRY(\exc_name\()_entry)
 	/* save the pointer to the current process */
 	ldr	fp, [sp]
 	/* save the exception pc (saved lr_user) */
-	ldr	r4, [fp, #PCREG]
+	add	r4, fp, #PCREG
 
 	/* stop user process cycles */
 	mov	r0, fp  /* first param: caller proc ptr */
diff --git a/kernel/arch/i386/arch_system.c b/kernel/arch/i386/arch_system.c
index 2c5e0931e..bb12b0682 100644
--- a/kernel/arch/i386/arch_system.c
+++ b/kernel/arch/i386/arch_system.c
@@ -421,17 +421,6 @@ static void ser_debug(const int c)
 }
 
 #if DEBUG_SERIAL
-void ser_dump_proc()
-{
-	struct proc *pp;
-
-	for (pp= BEG_PROC_ADDR; pp < END_PROC_ADDR; pp++)
-	{
-		if (isemptyp(pp))
-			continue;
-		print_proc_recursive(pp);
-	}
-}
 
 static void ser_dump_vfs()
 {
diff --git a/kernel/proc.c b/kernel/proc.c
index a15039315..e60e55071 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -1894,3 +1894,15 @@ void release_fpu(struct proc * p) {
 	if (*fpu_owner_ptr == p)
 		*fpu_owner_ptr = NULL;
 }
+
+void ser_dump_proc()
+{
+        struct proc *pp;
+
+        for (pp= BEG_PROC_ADDR; pp < END_PROC_ADDR; pp++)
+        {
+                if (isemptyp(pp))
+                        continue;
+                print_proc_recursive(pp);
+        }
+}
-- 
2.44.0