On 26/02/2024 11.11, Nicholas Piggin wrote:
Add support for backtracing across interrupt stacks, and
add interrupt frame backtrace for unhandled interrupts.
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
lib/powerpc/processor.c | 4 ++-
lib/ppc64/asm/stack.h | 3 +++
lib/ppc64/stack.c | 55 +++++++++++++++++++++++++++++++++++++++++
powerpc/Makefile.ppc64 | 1 +
powerpc/cstart64.S | 7 ++++--
5 files changed, 67 insertions(+), 3 deletions(-)
create mode 100644 lib/ppc64/stack.c
diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
index ad0d95666..114584024 100644
--- a/lib/powerpc/processor.c
+++ b/lib/powerpc/processor.c
@@ -51,7 +51,9 @@ void do_handle_exception(struct pt_regs *regs)
return;
}
- printf("unhandled cpu exception %#lx at NIA:0x%016lx MSR:0x%016lx\n", regs->trap, regs->nip, regs->msr);
+ printf("Unhandled cpu exception %#lx at NIA:0x%016lx MSR:0x%016lx\n",
+ regs->trap, regs->nip, regs->msr);
+ dump_frame_stack((void *)regs->nip, (void *)regs->gpr[1]);
abort();
}
diff --git a/lib/ppc64/asm/stack.h b/lib/ppc64/asm/stack.h
index 9734bbb8f..94fd1021c 100644
--- a/lib/ppc64/asm/stack.h
+++ b/lib/ppc64/asm/stack.h
@@ -5,4 +5,7 @@
#error Do not directly include <asm/stack.h>. Just use <stack.h>.
#endif
+#define HAVE_ARCH_BACKTRACE
+#define HAVE_ARCH_BACKTRACE_FRAME
+
#endif
diff --git a/lib/ppc64/stack.c b/lib/ppc64/stack.c
new file mode 100644
index 000000000..fcb7fa860
--- /dev/null
+++ b/lib/ppc64/stack.c
@@ -0,0 +1,55 @@
+#include <libcflat.h>
+#include <asm/ptrace.h>
+#include <stack.h>
+
+extern char exception_stack_marker[];
+
+int backtrace_frame(const void *frame, const void **return_addrs, int max_depth)
+{
+ static int walking;
+ int depth = 0;
+ const unsigned long *bp = (unsigned long *)frame;
+ void *return_addr;
+
+ asm volatile("" ::: "lr"); /* Force it to save LR */
+
+ if (walking) {
+ printf("RECURSIVE STACK WALK!!!\n");
+ return 0;
+ }
+ walking = 1;
+
+ bp = (unsigned long *)bp[0];
+ return_addr = (void *)bp[2];
+
+ for (depth = 0; bp && depth < max_depth; depth++) {
+ return_addrs[depth] = return_addr;
+ if (return_addrs[depth] == 0)
+ break;
+ if (return_addrs[depth] == exception_stack_marker) {
+ struct pt_regs *regs;
+
+ regs = (void *)bp + STACK_FRAME_OVERHEAD;
+ bp = (unsigned long *)bp[0];
+ /* Represent interrupt frame with vector number */
+ return_addr = (void *)regs->trap;
+ if (depth + 1 < max_depth) {
+ depth++;
+ return_addrs[depth] = return_addr;
+ return_addr = (void *)regs->nip;
+ }
+ } else {
+ bp = (unsigned long *)bp[0];
+ return_addr = (void *)bp[2];
+ }
+ }
+
+ walking = 0;
+ return depth;
+}
+
+int backtrace(const void **return_addrs, int max_depth)
+{
+ return backtrace_frame(__builtin_frame_address(0), return_addrs,
+ max_depth);
+}
diff --git a/powerpc/Makefile.ppc64 b/powerpc/Makefile.ppc64
index b0ed2b104..eb682c226 100644
--- a/powerpc/Makefile.ppc64
+++ b/powerpc/Makefile.ppc64
@@ -17,6 +17,7 @@ cstart.o = $(TEST_DIR)/cstart64.o
reloc.o = $(TEST_DIR)/reloc64.o
OBJDIRS += lib/ppc64
+cflatobjs += lib/ppc64/stack.o
# ppc64 specific tests
tests = $(TEST_DIR)/spapr_vpa.elf
diff --git a/powerpc/cstart64.S b/powerpc/cstart64.S
index 14ab0c6c8..278af84a6 100644
--- a/powerpc/cstart64.S
+++ b/powerpc/cstart64.S
@@ -188,6 +188,7 @@ call_handler:
.endr
mfsprg1 r0
std r0,GPR1(r1)
+ std r0,0(r1)
/* lr, xer, ccr */
@@ -206,12 +207,12 @@ call_handler:
subi r31, r31, 0b - start_text
ld r2, (p_toc_text - start_text)(r31)
- /* FIXME: build stack frame */
-
/* call generic handler */
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_handle_exception
+ .global exception_stack_marker
+exception_stack_marker:
/* restore context */
@@ -321,6 +322,7 @@ handler_trampoline:
/* nip and msr */
mfsrr0 r0
std r0, _NIP(r1)
+ std r0, INT_FRAME_SIZE+16(r1)
So if I got that right, INT_FRAME_SIZE+16 points to the stack frame of the
function that was running before the interrupt handler? Is it such a good
idea to change that here? Please add a comment here explaining this line.
Thanks!
mfsrr1 r0
std r0, _MSR(r1)
@@ -337,6 +339,7 @@ handler_htrampoline:
/* nip and msr */
mfspr r0, SPR_HSRR0
std r0, _NIP(r1)
+ std r0, INT_FRAME_SIZE+16(r1)
dito.
mfspr r0, SPR_HSRR1
std r0, _MSR(r1)
Thomas
