commit 553b6df07c9b7ab30ed468a6a4374cbdf73d1c0d
Author: Mark Wielaard <mark@klomp.org>
Date: Tue Apr 17 14:36:13 2018 +0200
linux runtime: Add support for new kernel unwind fallback.
In newer kernels dump_trace got replaced by a new unwind infrastructure.
Add a new autoconf-unwind-stack-trace.c to detect whether we can use it.
Extend the runtime/stack.c _stp_stack_print_fallback with a new pt_regs*
argument. Update all callers and add dbug_unwind output to show which
fallback unwinder we are selecting (or if we are just giving up).
Rename the struct unwind_state in unwind.c and unwind.h to uw_state
because the old name now conflicts with the one used in the kernel.
diff --git a/buildrun.cxx b/buildrun.cxx
index 403fa71..59b9e88 100644
--- a/buildrun.cxx
+++ b/buildrun.cxx
@@ -365,6 +365,8 @@ compile_pass (systemtap_session& s)
"STAPCONF_KERNEL_STACKTRACE", NULL);
output_autoconf(s, o, "autoconf-save-stack-trace-no-bp.c",
"STAPCONF_KERNEL_STACKTRACE_NO_BP", NULL);
+ output_autoconf(s, o, "autoconf-unwind-stack-trace.c",
+ "STAPCONF_KERNEL_UNWIND_STACK", NULL);
output_autoconf(s, o, "autoconf-asm-syscall.c",
"STAPCONF_ASM_SYSCALL_H", NULL);
output_autoconf(s, o, "autoconf-ring_buffer-flags.c", "STAPCONF_RING_BUFFER_FLAGS", NULL);
diff --git a/runtime/linux/autoconf-unwind-stack-trace.c b/runtime/linux/autoconf-unwind-stack-trace.c
new file mode 100644
index 0000000..2ec399e
--- /dev/null
+++ b/runtime/linux/autoconf-unwind-stack-trace.c
@@ -0,0 +1,16 @@
+#include <linux/sched.h>
+#include <asm/unwind.h>
+
+void unwind_stack_trace (void)
+{
+ struct unwind_state state;
+ unwind_start (&state, current, 0, 0);
+ while (! unwind_done (&state))
+ {
+ unsigned long addr = unwind_get_return_address (&state);
+ if (addr == 0)
+ break;
+ unwind_next_frame (&state);
+ }
+}
+
diff --git a/runtime/stack.c b/runtime/stack.c
index c9d2c0c..43f98ef 100644
--- a/runtime/stack.c
+++ b/runtime/stack.c
@@ -43,7 +43,11 @@
#include <asm/stacktrace.h>
#endif
-static void _stp_stack_print_fallback(unsigned long, int, int, int);
+#if defined(STAPCONF_KERNEL_UNWIND_STACK)
+#include <asm/unwind.h>
+#endif
+
+static void _stp_stack_print_fallback(unsigned long, struct pt_regs*, int, int, int);
#ifdef STP_USE_DWARF_UNWINDER
#ifdef STAPCONF_LINUX_UACCESS_H
@@ -128,7 +132,7 @@ static const struct stacktrace_ops print_stack_ops = {
};
/* Used for kernel backtrace printing when other mechanisms fail. */
-static void _stp_stack_print_fallback(unsigned long stack,
+static void _stp_stack_print_fallback(unsigned long stack, struct pt_regs *regs,
int sym_flags, int levels, int skip)
{
struct print_stack_data print_data;
@@ -136,20 +140,55 @@ static void _stp_stack_print_fallback(unsigned long stack,
print_data.levels = levels;
print_data.skip = skip;
#if defined(STAPCONF_KERNEL_STACKTRACE)
+ dbug_unwind(1, "fallback kernel stacktrace\n");
dump_trace(current, NULL, (long *)stack, 0, &print_stack_ops,
&print_data);
#else
/* STAPCONF_KERNEL_STACKTRACE_NO_BP */
+ dbug_unwind(1, "fallback kernel stacktrace (no bp)\n");
dump_trace(current, NULL, (long *)stack, &print_stack_ops,
&print_data);
#endif
}
#else
-static void _stp_stack_print_fallback(unsigned long s, int v, int l, int k) {
+#if defined(STAPCONF_KERNEL_UNWIND_STACK)
+static void _stp_stack_print_fallback(unsigned long sp, struct pt_regs *regs,
+ int sym_flags,
+ int levels, int skip) {
+ struct unwind_state state;
+ unwind_start (&state, current, regs, (unsigned long *) sp);
+ dbug_unwind(1, "fallback kernel stacktrace (unwind)\n");
+ while (levels > 0 && ! unwind_done (&state))
+ {
+ if (skip == 0)
+ {
+ unsigned long addr = unwind_get_return_address (&state);
+ /* When we have frame pointers, the unwind addresses can be
+ (mostly) trusted, otherwise it is all guesswork. */
+#ifdef CONFIG_FRAME_POINTER
+ _stp_print_addr(addr, sym_flags, NULL);
+#else
+ _stp_print_addr(addr, sym_flags | _STP_SYM_INEXACT, NULL);
+#endif
+ if (addr == 0)
+ break;
+ levels--;
+ }
+ else
+ {
+ dbug_unwind(1, "skipping frame\n");
+ skip--;
+ }
+ unwind_next_frame(&state);
+ }
+}
+#else /* no new unwind */
+static void _stp_stack_print_fallback(unsigned long s, struct pt_regs *r, int v, int l, int k) {
/* Don't guess, just give up. */
+ dbug_unwind(1, "no fallback kernel stacktrace (giving up)\n");
_stp_print_addr(0, v | _STP_SYM_INEXACT, NULL);
}
-
+#endif /* new unwind */
#endif /* defined(STAPCONF_KERNEL_STACKTRACE) || defined(STAPCONF_KERNEL_STACKTRACE_NO_BP) */
@@ -382,6 +421,7 @@ static void _stp_stack_kernel_print(struct context *c, int sym_flags)
if (l == 0) {
remaining = MAXBACKTRACE - n;
_stp_stack_print_fallback(UNW_SP(&c->uwcontext_kernel.info),
+ &c->uwcontext_kernel.info.regs,
sym_flags, remaining, 0);
break;
} else {
@@ -408,7 +448,7 @@ static void _stp_stack_kernel_print(struct context *c, int sym_flags)
sp = 0;
skip = 5; /* yes, that many framework frames. */
#endif
- _stp_stack_print_fallback(sp, sym_flags,
+ _stp_stack_print_fallback(sp, NULL, sym_flags,
MAXBACKTRACE, skip);
#else
if (sym_flags & _STP_SYM_SYMBOL)
diff --git a/runtime/unwind.c b/runtime/unwind.c
index ec7cd58..3a2d991 100644
--- a/runtime/unwind.c
+++ b/runtime/unwind.c
@@ -235,7 +235,7 @@ static int parse_fde_cie(const u32 *fde, const u32 *cie,
#define REG_STATE state->reg[state->stackDepth]
-static int advance_loc(unsigned long delta, struct unwind_state *state)
+static int advance_loc(unsigned long delta, struct uw_state *state)
{
state->loc += delta * state->codeAlign;
dbug_unwind(1, "state->loc=%lx\n", state->loc);
@@ -244,7 +244,7 @@ static int advance_loc(unsigned long delta, struct unwind_state *state)
/* Set Same or Nowhere rule for register. */
static void set_no_state_rule(uleb128_t reg, enum item_location where,
- struct unwind_state *state)
+ struct uw_state *state)
{
dbug_unwind(1, "reg=%lx, where=%d\n", reg, where);
if (reg < ARRAY_SIZE(REG_STATE.regs)) {
@@ -254,7 +254,7 @@ static void set_no_state_rule(uleb128_t reg, enum item_location where,
/* Memory or Value rule */
static void set_offset_rule(uleb128_t reg, enum item_location where,
- sleb128_t svalue, struct unwind_state *state)
+ sleb128_t svalue, struct uw_state *state)
{
dbug_unwind(1, "reg=%lx, where=%d, svalue=%lx\n", reg, where, svalue);
if (reg < ARRAY_SIZE(REG_STATE.regs)) {
@@ -265,7 +265,7 @@ static void set_offset_rule(uleb128_t reg, enum item_location where,
/* Register rule. */
static void set_register_rule(uleb128_t reg, uleb128_t value,
- struct unwind_state *state)
+ struct uw_state *state)
{
dbug_unwind(1, "reg=%lx, value=%lx\n", reg, value);
if (reg < ARRAY_SIZE(REG_STATE.regs)) {
@@ -277,7 +277,7 @@ static void set_register_rule(uleb128_t reg, uleb128_t value,
/* Expr or ValExpr rule. */
static void set_expr_rule(uleb128_t reg, enum item_location where,
const u8 **expr, const u8 *end,
- struct unwind_state *state)
+ struct uw_state *state)
{
const u8 *const start = *expr;
uleb128_t len = get_uleb128(expr, end);
@@ -296,7 +296,7 @@ static void set_expr_rule(uleb128_t reg, enum item_location where,
#define MAX_CFI 512
static int processCFI(const u8 *start, const u8 *end, unsigned long targetLoc,
- signed ptrType, int user, struct unwind_state *state, int compat_task)
+ signed ptrType, int user, struct uw_state *state, int compat_task)
{
union {
const u8 *p8;
@@ -1169,7 +1169,7 @@ static int unwind_frame(struct unwind_context *context,
unsigned i;
signed ptrType = -1, call_frame = 1;
uleb128_t retAddrReg = 0;
- struct unwind_state *state = &context->state;
+ struct uw_state *state = &context->state;
unsigned long addr;
if (unlikely(table_len == 0)) {
diff --git a/runtime/unwind/unwind.h b/runtime/unwind/unwind.h
index 9d66732..b3ff786 100644
--- a/runtime/unwind/unwind.h
+++ b/runtime/unwind/unwind.h
@@ -492,7 +492,7 @@ struct unwind_reg_state {
unsigned cfa_is_expr:1;
};
-struct unwind_state {
+struct uw_state {
uleb128_t loc;
uleb128_t codeAlign;
sleb128_t dataAlign;
@@ -503,7 +503,7 @@ struct unwind_state {
struct unwind_context {
struct unwind_frame_info info;
- struct unwind_state state;
+ struct uw_state state;
};
static const struct cfa badCFA = { ARRAY_SIZE(reg_info), 1 };
commit 17ee540dd61113fe4f557f191db3480db875cca1
Author: Mark Wielaard <mark@klomp.org>
Date: Wed Apr 18 15:00:24 2018 +0200
Make kernel DWARF unwinder work with ksalr.
The .debug_frame loaded from disk is already relocated against the
expected load offset of the kernel, but the actual static (load)
address might be different (with kaslr). So adjust the startLoc
for that difference when reading any address from the unwind table.
diff --git a/runtime/unwind.c b/runtime/unwind.c
index 3a2d991..4c360d2 100644
--- a/runtime/unwind.c
+++ b/runtime/unwind.c
@@ -724,10 +724,15 @@ adjustStartLoc (unsigned long startLoc,
dbug_unwind(2, "adjustStartLoc=%lx, ptrType=%s, m=%s, s=%s eh=%d\n",
startLoc, _stp_eh_enc_name(ptrType), m->path, s->name, is_ehframe);
if (startLoc == 0
- || strcmp (m->name, "kernel") == 0
|| (strcmp (s->name, ".absolute") == 0 && !is_ehframe))
return startLoc;
+ /* The .debug_frame loaded from disk is already relocated against the
+ expected load offset of the kernel, but the actual static (load)
+ address might be different (with kaslr). */
+ if (strcmp (m->name, "kernel") == 0)
+ return startLoc - s->sec_load_offset + s->static_addr;
+
/* eh_frame data has been loaded in the kernel, so readjust offset. */
if (is_ehframe) {
dbug_unwind(2, "eh_frame=%lx, eh_frame_addr=%lx\n", (unsigned long) m->eh_frame, m->eh_frame_addr);