[PATCH 3/6] x86_64: Collect register values on exception frame

[HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>]

KDUMP, NETDUMP and DISKDUMP all saves register values for active tasks onto
exception frame at kernel crash. This patch implements the logic to collect the
register values by retrieving EFRAME information from back_trace()'s output.

Signed-off-by: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
---
 src/libgcore/gcore_x86.c |   67 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 67 insertions(+), 0 deletions(-)

diff --git a/src/libgcore/gcore_x86.c b/src/libgcore/gcore_x86.c
index 377df6d..29fe808 100644
--- a/src/libgcore/gcore_x86.c
+++ b/src/libgcore/gcore_x86.c
@@ -1354,6 +1354,64 @@ static ulong gcore_x86_64_get_cpu__pda_oldrsp(int cpu)
 	return oldrsp;
 }
 
+static int
+gcore_find_regs_from_bt_output(FILE *output, char *buf, size_t bufsize)
+{
+	while (fgets(buf, bufsize, output))
+		if (strncmp(buf, "    RIP:", 8) == 0)
+			return TRUE;
+
+	return FALSE;
+}
+
+static int
+gcore_get_regs_from_bt_output(FILE *output, struct pt_regs *regs)
+{
+	char buf[BUFSIZE];
+
+	if (gcore_find_regs_from_bt_output(output, buf, BUFSIZE) == FALSE)
+		return FALSE;
+
+	sscanf(buf, "    RIP: %016lx  RSP: %016lx  RFLAGS: %08lx\n",
+	       &regs->rip, &regs->rsp, &regs->eflags);
+	fscanf(output, "    RAX: %016lx  RBX: %016lx  RCX: %016lx\n",
+	       &regs->rax, &regs->rbx, &regs->rcx);
+	fscanf(output, "    RDX: %016lx  RSI: %016lx  RDI: %016lx\n",
+	       &regs->rdx, &regs->rsi, &regs->rdi);
+	fscanf(output, "    RBP: %016lx   R8: %016lx   R9: %016lx\n",
+	       &regs->rbp, &regs->r8, &regs->r9);
+	fscanf(output, "    R10: %016lx  R11: %016lx  R12: %016lx\n",
+	       &regs->r10, &regs->r11, &regs->r12);
+	fscanf(output, "    R13: %016lx  R14: %016lx  R15: %016lx\n",
+	       &regs->r13, &regs->r14, &regs->r15);
+	fscanf(output, "    ORIG_RAX: %016lx  CS: %04lx  SS: %04lx\n",
+	       &regs->orig_rax, &regs->cs, &regs->ss);
+
+	return TRUE;
+}
+
+static int
+gcore_get_regs_from_eframe(struct task_context *tc, struct pt_regs *regs)
+{
+	int ret;
+	struct bt_info bt;
+
+	BZERO(&bt, sizeof(struct bt_info));
+	bt.stackbuf = NULL;
+	bt.tc = tc;
+	bt.task = tc->task;
+	bt.stackbase = GET_STACKBASE(tc->task);
+	bt.stacktop = GET_STACKTOP(tc->task);
+
+	open_tmpfile();
+	back_trace(&bt);
+	rewind(pc->tmpfile);
+	ret = gcore_get_regs_from_bt_output(pc->tmpfile, regs);
+	close_tmpfile();
+
+	return ret;
+}
+
 static int get_active_regs(struct task_context *target,
 			   struct user_regs_struct *regs)
 {
@@ -1363,6 +1421,15 @@ static int get_active_regs(struct task_context *target,
 		return TRUE;
 	}
 
+	if (gcore_get_regs_from_eframe(target, (struct pt_regs *)regs)) {
+		/*
+		 * EFRAME contains CS and SS only. Here collects the
+		 * remaining part of segment registers.
+		 */
+		restore_segment_registers(target->task, regs);
+		return TRUE;
+	}
+
 	return FALSE;
 }
 
-- 
1.7.4


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