[patch 0/3] [KEXEC] Use generic elf code on ia64

[patch 0/3] [KEXEC] Use generic elf code on ia64

[Simon Horman]

Hi,

the following series of three patches changes ia64 to use
the generic elf note creation code. I previously posted it as
a single patch, and have broken it up on Nanhai Zou's suggestion
in order to make it easier to review.

-- 

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

[patch 1/3] Add kdump_elf_core_copy_regs()

[Simon Horman]

Facilitate using crash_save_cpu() on ia64 by adding
kdump_elf_core_copy_regs(). By default kdump_elf_core_copy_regs() is just
defined to be elf_core_copy_regs(), which is what crash_save_cpu()
previously used. ia64 (and other architectures) are able to define their
own implementations as needed.

Signed-off-by: Simon Horman <horms@verge.net.au>

--- 
* This patch applies on top of the note size calculation patch
  that can be found in mm and at
  http://lists.linux-foundation.org/pipermail/fastboot/2007-April/006792.html

  Porting this patch to not require that one is quite trivial.
  I can supply a port or a thread containing both patches if it helps.

 linux-2.6/include/linux/kexec.h |    5 +++++
 linux-2.6/kernel/kexec.c        |    2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

Index: linux-2.6/include/linux/kexec.h
=================================--- linux-2.6.orig/include/linux/kexec.h	2007-05-08 17:49:35.000000000 +0900
+++ linux-2.6/include/linux/kexec.h	2007-05-08 17:49:51.000000000 +0900
@@ -128,6 +128,11 @@ extern struct kimage *kexec_crash_image;
 #define kexec_flush_icache_page(page)
 #endif
 
+#ifndef kexec_elf_core_copy_regs
+#define kexec_elf_core_copy_regs(elfregs, regs) \
+	elf_core_copy_regs(elfregs, regs)
+#endif
+
 #define KEXEC_ON_CRASH  0x00000001
 #define KEXEC_ARCH_MASK 0xffff0000
 
Index: linux-2.6/kernel/kexec.c
=================================--- linux-2.6.orig/kernel/kexec.c	2007-05-08 17:49:35.000000000 +0900
+++ linux-2.6/kernel/kexec.c	2007-05-08 17:49:51.000000000 +0900
@@ -1117,7 +1117,7 @@ void crash_save_cpu(struct pt_regs *regs
 		return;
 	memset(&prstatus, 0, sizeof(prstatus));
 	prstatus.pr_pid = current->pid;
-	elf_core_copy_regs(&prstatus.pr_reg, regs);
+	kexec_elf_core_copy_regs(&prstatus.pr_reg, regs);
 	buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS,
 		      	      &prstatus, sizeof(prstatus));
 	final_note(buf);

-- 

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

[patch 2/3] Use per-cpu elf_prstatus

[Simon Horman]

Use a pre-allocated per-cpu variable for saving the cpu registers, as per
the IA64 specific code. This is in order to reduce possible stack
contention at crash-time as per the inline comment.

A following patch will update ia64 to use crash_save_cpu() rather
than its own re-implementation of the routine.

Signed-off-by: Simon Horman <horms@verge.net.au>

--- 
 linux-2.6/kernel/kexec.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

Index: linux-2.6/kernel/kexec.c
=================================--- linux-2.6.orig/kernel/kexec.c	2007-05-08 18:08:50.000000000 +0900
+++ linux-2.6/kernel/kexec.c	2007-05-08 18:22:45.000000000 +0900
@@ -1097,9 +1097,18 @@ static void final_note(u32 *buf)
 	memcpy(buf, &note, sizeof(note));
 }
 
+/*
+ * There is some concern that on architectures where struct elf_prstatus is
+ * large, such as IA64, having elf_prstatus on the stack in
+ * crash_save_cpu() could cause problems given that this function
+ * is run after a kernel crash has occured. To aleviate this problem
+ * a pre-allocated per-cpu value is used instead.
+ */
+static DEFINE_PER_CPU(struct elf_prstatus, elf_prstatus);
+
 void crash_save_cpu(struct pt_regs *regs, int cpu)
 {
-	struct elf_prstatus prstatus;
+	struct elf_prstatus *prstatus;
 	u32 *buf;
 
 	if ((cpu < 0) || (cpu >= NR_CPUS))
@@ -1115,11 +1124,12 @@ void crash_save_cpu(struct pt_regs *regs
 	buf = (u32*)per_cpu_ptr(crash_notes, cpu);
 	if (!buf)
 		return;
-	memset(&prstatus, 0, sizeof(prstatus));
-	prstatus.pr_pid = current->pid;
-	kexec_elf_core_copy_regs(&prstatus.pr_reg, regs);
+	prstatus = &per_cpu(elf_prstatus, cpu);
+	memset(prstatus, 0, sizeof(struct elf_prstatus));
+	prstatus->pr_pid = current->pid;
+	kexec_elf_core_copy_regs(&(prstatus->pr_reg), regs);
 	buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS,
-		      	      &prstatus, sizeof(prstatus));
+			      prstatus, sizeof(struct elf_prstatus));
 	final_note(buf);
 }
 

-- 

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

[patch 3/3] Use generic elf code on ia64

[Simon Horman]

Make use of the generic implementation of crash_save_cpu().

The code appears to work, however as the place where the registers
are captured has changed natrually some of their values have also changed.
This makes looking for problems by comparing the new and old output a
little tricky.

Signed-off-by: Simon Horman <horms@verge.net.au>

--- 
* This patch applies on top of the note size calculation patch
  that can be found in mm and at
  http://lists.linux-foundation.org/pipermail/fastboot/2007-April/006792.html

  Porting this patch to not require that one is quite trivial.
  I can supply a port or a thread containing both patches if it helps.

* Update
  Diff against include/asm-ia64/kexec.h instead of include/asm/kexec.h
  Ooops!

* Updated crash_save_cpu() to use a per-cpu variable for the registers.
  As requested by Nanhai Zou

* Added CC: kexec@lists.infradead.org, which is the new place for kexec
  discussion.

* Split per-cpu prstatus and kdump_elf_core_copy_regs() macro changes
  into two separate patches

 linux-2.6/arch/ia64/kernel/crash.c         |   46 +---------------------------
 linux-2.6/arch/ia64/kernel/machine_kexec.c |    2 -
 linux-2.6/include/asm-ia64/kexec.h         |    7 +++-
 3 files changed, 10 insertions(+), 45 deletions(-)

Index: linux-2.6/arch/ia64/kernel/crash.c
=================================--- linux-2.6.orig/arch/ia64/kernel/crash.c	2007-04-25 17:31:54.000000000 +0900
+++ linux-2.6/arch/ia64/kernel/crash.c	2007-04-25 17:31:55.000000000 +0900
@@ -25,44 +25,11 @@ static atomic_t kdump_cpu_frozen;
 atomic_t kdump_in_progress;
 static int kdump_on_init = 1;
 
-static inline Elf64_Word
-*append_elf_note(Elf64_Word *buf, char *name, unsigned type, void *data,
-		size_t data_len)
-{
-	struct elf_note *note = (struct elf_note *)buf;
-	note->n_namesz = strlen(name) + 1;
-	note->n_descsz = data_len;
-	note->n_type   = type;
-	buf += (sizeof(*note) + 3)/4;
-	memcpy(buf, name, note->n_namesz);
-	buf += (note->n_namesz + 3)/4;
-	memcpy(buf, data, data_len);
-	buf += (data_len + 3)/4;
-	return buf;
-}
-
-static void
-final_note(void *buf)
-{
-	memset(buf, 0, sizeof(struct elf_note));
-}
-
-extern void ia64_dump_cpu_regs(void *);
-
-static DEFINE_PER_CPU(struct elf_prstatus, elf_prstatus);
-
 void
-crash_save_this_cpu(void)
+ia64_kexec_elf_core_copy_regs(elf_gregset_t *elfregs, struct pt_regs *regs)
 {
-	void *buf;
 	unsigned long cfm, sof, sol;
-
-	int cpu = smp_processor_id();
-	struct elf_prstatus *prstatus = &per_cpu(elf_prstatus, cpu);
-
-	elf_greg_t *dst = (elf_greg_t *)&(prstatus->pr_reg);
-	memset(prstatus, 0, sizeof(*prstatus));
-	prstatus->pr_pid = current->pid;
+	elf_greg_t *dst = (elf_greg_t *)elfregs;
 
 	ia64_dump_cpu_regs(dst);
 	cfm = dst[43];
@@ -70,13 +37,6 @@ crash_save_this_cpu(void)
 	sof = cfm & 0x7f;
 	dst[46] = (unsigned long)ia64_rse_skip_regs((unsigned long *)dst[46],
 			sof - sol);
-
-	buf = (u64 *) per_cpu_ptr(crash_notes, cpu);
-	if (!buf)
-		return;
-	buf = append_elf_note(buf, KEXEC_CORE_NOTE_NAME, NT_PRSTATUS, prstatus,
-			sizeof(*prstatus));
-	final_note(buf);
 }
 
 #ifdef CONFIG_SMP
@@ -134,7 +94,7 @@ kdump_cpu_freeze(struct unw_frame_info *
 	int cpuid;
 	local_irq_disable();
 	cpuid = smp_processor_id();
-	crash_save_this_cpu();
+	crash_save_cpu(NULL, smp_processor_id());
 	current->thread.ksp = (__u64)info->sw - 16;
 	atomic_inc(&kdump_cpu_frozen);
 	kdump_status[cpuid] = 1;
Index: linux-2.6/include/asm-ia64/kexec.h
=================================--- linux-2.6.orig/include/asm-ia64/kexec.h	2007-04-25 17:31:54.000000000 +0900
+++ linux-2.6/include/asm-ia64/kexec.h	2007-04-25 17:31:55.000000000 +0900
@@ -19,6 +19,9 @@
                 flush_icache_range(page_addr, page_addr + PAGE_SIZE); \
         } while(0)
 
+#define kexec_elf_core_copy_regs(elfregs, regs) \
+	ia64_kexec_elf_core_copy_regs(elfregs, regs)
+
 extern struct kimage *ia64_kimage;
 extern const unsigned int relocate_new_kernel_size;
 extern void relocate_new_kernel(unsigned long, unsigned long,
@@ -32,7 +35,9 @@ extern struct resource boot_param_res;
 extern void kdump_smp_send_stop(void);
 extern void kdump_smp_send_init(void);
 extern void kexec_disable_iosapic(void);
-extern void crash_save_this_cpu(void);
+extern void ia64_dump_cpu_regs(void *);
+extern void ia64_kexec_elf_core_copy_regs(elf_gregset_t *elfregs,
+					  struct pt_regs *regs);
 struct rsvd_region;
 extern unsigned long kdump_find_rsvd_region(unsigned long size,
 		struct rsvd_region *rsvd_regions, int n);
Index: linux-2.6/arch/ia64/kernel/machine_kexec.c
=================================--- linux-2.6.orig/arch/ia64/kernel/machine_kexec.c	2007-04-25 17:31:54.000000000 +0900
+++ linux-2.6/arch/ia64/kernel/machine_kexec.c	2007-04-25 17:31:55.000000000 +0900
@@ -84,7 +84,7 @@ static void ia64_machine_kexec(struct un
 
 	BUG_ON(!image);
 	if (image->type = KEXEC_TYPE_CRASH) {
-		crash_save_this_cpu();
+		crash_save_cpu(NULL, smp_processor_id());
 		current->thread.ksp = (__u64)info->sw - 16;
 	}
 

-- 

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/