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RISCV64: Add per-cpu IRQ stacks support
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This patch introduces per-cpu IRQ stacks for RISCV64 to let
"bt" do backtrace on it and 'bt -E' search eframes on it,
and the 'help -m' command displays the addresses of each
per-cpu IRQ stack.

TEST: a vmcore dumped via hacking the handle_irq_event_percpu()
( Why not using lkdtm INT_HW_IRQ_EN EXCEPTION ?
  There is a deadlock[1] in crash_kexec path if use that)

  crash> bt
  PID: 0        TASK: ffffffff8140db00  CPU: 0    COMMAND: "swapper/0"
   #0 [ff20000000003e60] __handle_irq_event_percpu at ffffffff8006462e
   crash-utility#1 [ff20000000003ed0] handle_irq_event_percpu at ffffffff80064702
   crash-utility#2 [ff20000000003ef0] handle_irq_event at ffffffff8006477c
   crash-utility#3 [ff20000000003f20] handle_fasteoi_irq at ffffffff80068664
   crash-utility#4 [ff20000000003f50] generic_handle_domain_irq at ffffffff80063988
   crash-utility#5 [ff20000000003f60] plic_handle_irq at ffffffff8046633e
   crash-utility#6 [ff20000000003fb0] generic_handle_domain_irq at ffffffff80063988
   crash-utility#7 [ff20000000003fc0] riscv_intc_irq at ffffffff80465f8e
   crash-utility#8 [ff20000000003fd0] handle_riscv_irq at ffffffff808361e8
       PC: ffffffff80837314  [default_idle_call+50]
       RA: ffffffff80837310  [default_idle_call+46]
       SP: ffffffff81403da0  CAUSE: 8000000000000009
  epc : ffffffff80837314 ra : ffffffff80837310 sp : ffffffff81403da0
   gp : ffffffff814ef848 tp : ffffffff8140db00 t0 : ff2000000004bb18
   t1 : 0000000000032c73 t2 : ffffffff81200a48 s0 : ffffffff81403db0
   s1 : 0000000000000000 a0 : 0000000000000004 a1 : 0000000000000000
   a2 : ff6000009f1e7000 a3 : 0000000000002304 a4 : ffffffff80c1c2d8
   a5 : 0000000000000000 a6 : ff6000001fe01958 a7 : 00002496ea89dbf1
   s2 : ffffffff814f0220 s3 : 0000000000000001 s4 : 000000000000003f
   s5 : ffffffff814f03d8 s6 : 0000000000000000 s7 : ffffffff814f00d0
   s8 : ffffffff81526f10 s9 : ffffffff80c1d880 s10: 0000000000000000
   s11: 0000000000000001 t3 : 0000000000003392 t4 : 0000000000000000
   t5 : 0000000000000000 t6 : 0000000000000040
   status: 0000000200000120 badaddr: 0000000000000000
    cause: 8000000000000009 orig_a0: ffffffff80837310
  --- <IRQ stack> ---
   crash-utility#9 [ffffffff81403da0] default_idle_call at ffffffff80837314
   crash-utility#10 [ffffffff81403db0] do_idle at ffffffff8004d0a0
   crash-utility#11 [ffffffff81403e40] cpu_startup_entry at ffffffff8004d21e
   crash-utility#12 [ffffffff81403e60] kernel_init at ffffffff8083746a
   crash-utility#13 [ffffffff81403e70] arch_post_acpi_subsys_init at ffffffff80a006d8
   crash-utility#14 [ffffffff81403e80] console_on_rootfs at ffffffff80a00c92
  crash>

  crash> bt -E
  CPU 0 IRQ STACK:
  KERNEL-MODE EXCEPTION FRAME AT: ff20000000003a48
       PC: ffffffff8006462e  [__handle_irq_event_percpu+30]
       RA: ffffffff80064702  [handle_irq_event_percpu+18]
       SP: ff20000000003e60  CAUSE: 000000000000000d
  epc : ffffffff8006462e ra : ffffffff80064702 sp : ff20000000003e60
   gp : ffffffff814ef848 tp : ffffffff8140db00 t0 : 0000000000046600
   t1 : ffffffff80836464 t2 : ffffffff81200a48 s0 : ff20000000003ed0
   s1 : 0000000000000000 a0 : 0000000000000000 a1 : 0000000000000118
   a2 : 0000000000000052 a3 : 0000000000000000 a4 : 0000000000000000
   a5 : 0000000000010001 a6 : ff6000001fe01958 a7 : 00002496ea89dbf1
   s2 : ff60000000941ab0 s3 : ffffffff814a0658 s4 : ff60000000089230
   s5 : ffffffff814a0518 s6 : ffffffff814a0620 s7 : ffffffff80e5f0f8
   s8 : ffffffff80fc50b0 s9 : ffffffff80c1d880 s10: 0000000000000000
   s11: 0000000000000001 t3 : 0000000000003392 t4 : 0000000000000000
   t5 : 0000000000000000 t6 : 0000000000000040
   status: 0000000200000100 badaddr: 0000000000000078
    cause: 000000000000000d orig_a0: ff20000000003ea0

  CPU 1 IRQ STACK: (none found)

  crash>

  crash> help -m
  <snip>
             machspec: ced1e0
          irq_stack_size: 16384
           irq_stacks[0]: ff20000000000000
           irq_stacks[1]: ff20000000008000
  crash>

[1]: https://lore.kernel.org/linux-riscv/[email protected]/

Signed-off-by: Song Shuai <[email protected]>
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@liutgnu
Song Shuai authored and liutgnu committed Dec 1, 2024
1 parent a832e77 commit 0bda73a
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Showing 3 changed files with 198 additions and 12 deletions.
7 changes: 5 additions & 2 deletions defs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3643,6 +3643,8 @@ typedef signed int s32;
#define pmd_index_l5_4k(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
#define pte_index_l5_4k(addr) (((addr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))

/* machdep->flags */
#define KSYMS_START (0x1)
#define VM_L3_4K (0x2)
#define VM_L3_2M (0x4)
#define VM_L3_1G (0x8)
Expand All @@ -3652,6 +3654,7 @@ typedef signed int s32;
#define VM_L5_4K (0x80)
#define VM_L5_2M (0x100)
#define VM_L5_1G (0x200)
#define IRQ_STACKS (0x400)

#define VM_FLAGS (VM_L3_4K | VM_L3_2M | VM_L3_1G | \
VM_L4_4K | VM_L4_2M | VM_L4_1G | \
Expand Down Expand Up @@ -7027,8 +7030,6 @@ struct riscv64_unwind_frame {
ulong pc;
};

#define KSYMS_START (0x1)

struct machine_specific {
ulong phys_base;
ulong page_offset;
Expand Down Expand Up @@ -7058,6 +7059,8 @@ struct machine_specific {
ulong struct_page_size;

struct riscv64_register *crash_task_regs;
ulong irq_stack_size;
ulong *irq_stacks;
};
/* from arch/riscv/include/asm/pgtable-bits.h */
#define _PAGE_PRESENT (machdep->machspec->_page_present)
Expand Down
8 changes: 4 additions & 4 deletions help.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1938,10 +1938,10 @@ char *help_bt[] = {
" fails or the -t option starts too high in the process stack).",
" -l show file and line number of each stack trace text location.",
" -e search the stack for possible kernel and user mode exception frames.",
" -E search the IRQ stacks (x86, x86_64, arm64, and ppc64), and the",
" exception stacks (x86_64) for possible exception frames; all other",
" arguments except for -c will be ignored since this is not a context-",
" sensitive operation.",
" -E search the IRQ stacks (x86, x86_64, arm64, riscv64 and ppc64), and",
" the exception stacks (x86_64) for possible exception frames; all",
" other arguments except for -c will be ignored since this is not a",
" context-sensitive operation.",
" -f display all stack data contained in a frame; this option can be",
" used to determine the arguments passed to each function; on ia64,",
" the argument register contents are dumped.",
Expand Down
195 changes: 189 additions & 6 deletions riscv64.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ static int riscv64_uvtop(struct task_context *tc, ulong vaddr,
static int riscv64_kvtop(struct task_context *tc, ulong kvaddr,
physaddr_t *paddr, int verbose);
static void riscv64_cmd_mach(void);
static void riscv64_irq_stack_init(void);
static void riscv64_stackframe_init(void);
static void riscv64_back_trace_cmd(struct bt_info *bt);
static int riscv64_eframe_search(struct bt_info *bt);
Expand All @@ -54,9 +55,15 @@ static void riscv64_get_va_bits(struct machine_specific *ms);
static void riscv64_get_struct_page_size(struct machine_specific *ms);
static void riscv64_print_exception_frame(struct bt_info *, ulong , int );
static int riscv64_is_kernel_exception_frame(struct bt_info *, ulong );
static int riscv64_on_irq_stack(int , ulong);
static int riscv64_on_process_stack(struct bt_info *, ulong );
static void riscv64_set_process_stack(struct bt_info *);
static void riscv64_set_irq_stack(struct bt_info *);

#define REG_FMT "%016lx"
#define SZ_2G 0x80000000
#define USER_MODE (0)
#define KERNEL_MODE (1)

/*
* Holds registers during the crash.
Expand Down Expand Up @@ -191,11 +198,14 @@ riscv64_verify_symbol(const char *name, ulong value, char type)
void
riscv64_dump_machdep_table(ulong arg)
{
int others = 0;
const struct machine_specific *ms = machdep->machspec;
int others = 0, i = 0;

fprintf(fp, " flags: %lx (", machdep->flags);
if (machdep->flags & KSYMS_START)
fprintf(fp, "%sKSYMS_START", others++ ? "|" : "");
if (machdep->flags & IRQ_STACKS)
fprintf(fp, "%sIRQ_STACKS", others++ ? "|" : "");
fprintf(fp, ")\n");

fprintf(fp, " kvbase: %lx\n", machdep->kvbase);
Expand Down Expand Up @@ -251,6 +261,15 @@ riscv64_dump_machdep_table(ulong arg)
fprintf(fp, " max_physmem_bits: %ld\n", machdep->max_physmem_bits);
fprintf(fp, " sections_per_root: %ld\n", machdep->sections_per_root);
fprintf(fp, " machspec: %lx\n", (ulong)machdep->machspec);
if (machdep->flags & IRQ_STACKS) {
fprintf(fp, " irq_stack_size: %ld\n", ms->irq_stack_size);
for (i = 0; i < kt->cpus; i++)
fprintf(fp, " irq_stacks[%d]: %lx\n",
i, ms->irq_stacks[i]);
} else {
fprintf(fp, " irq_stack_size: (unused)\n");
fprintf(fp, " irq_stacks: (unused)\n");
}
}

static ulong
Expand Down Expand Up @@ -665,6 +684,111 @@ riscv64_display_full_frame(struct bt_info *bt, struct riscv64_unwind_frame *curr
fprintf(fp, "\n");
}

/*
* Gather IRQ stack values.
*/
static void
riscv64_irq_stack_init(void)
{
int i;
struct syment *sp;
struct gnu_request request, *req;
struct machine_specific *ms = machdep->machspec;
ulong p, sz;
req = &request;

if (symbol_exists("irq_stack_ptr") &&
(sp = per_cpu_symbol_search("irq_stack_ptr")) &&
get_symbol_type("irq_stack_ptr", NULL, req)) {
if (CRASHDEBUG(1)) {
fprintf(fp, "irq_stack_ptr: \n");
fprintf(fp, " type: %x, %s\n",
(int)req->typecode,
(req->typecode == TYPE_CODE_PTR) ?
"TYPE_CODE_PTR" : "other");
fprintf(fp, " target_typecode: %x, %s\n",
(int)req->target_typecode,
req->target_typecode == TYPE_CODE_INT ?
"TYPE_CODE_INT" : "other");
fprintf(fp, " target_length: %ld\n",
req->target_length);
fprintf(fp, " length: %ld\n", req->length);
}

if (!(ms->irq_stacks = (ulong *)malloc((size_t)(kt->cpus * sizeof(ulong)))))
error(FATAL, "cannot malloc irq_stack addresses\n");

/*
* find IRQ_STACK_SIZE (i.e. THREAD_SIZE) via thread_union.stack
* or set STACKSIZE() as default.
*/
if (MEMBER_EXISTS("thread_union", "stack")) {
if ((sz = MEMBER_SIZE("thread_union", "stack")) > 0)
ms->irq_stack_size = sz;
} else
ms->irq_stack_size = machdep->stacksize;

machdep->flags |= IRQ_STACKS;

for (i = 0; i < kt->cpus; i++) {
p = kt->__per_cpu_offset[i] + sp->value;
if (CRASHDEBUG(1))
fprintf(fp, " IRQ stack pointer[%d] is %lx\n", i, p);
readmem(p, KVADDR, &(ms->irq_stacks[i]), sizeof(ulong),
"IRQ stack pointer", RETURN_ON_ERROR);
}
}
}

static int
riscv64_on_irq_stack(int cpu, ulong stkptr)
{
struct machine_specific *ms = machdep->machspec;
ulong * stacks = ms->irq_stacks;
ulong stack_size = ms->irq_stack_size;

if ((cpu >= kt->cpus) || (stacks == NULL) || !stack_size)
return FALSE;

if ((stkptr >= stacks[cpu]) &&
(stkptr < (stacks[cpu] + stack_size)))
return TRUE;

return FALSE;
}

static int
riscv64_on_process_stack(struct bt_info *bt, ulong stkptr)
{
ulong stackbase, stacktop;

stackbase = GET_STACKBASE(bt->task);
stacktop = GET_STACKTOP(bt->task);

if ((stkptr >= stackbase) && (stkptr < stacktop))
return TRUE;

return FALSE;
}

static void
riscv64_set_irq_stack(struct bt_info *bt)
{
struct machine_specific *ms = machdep->machspec;

bt->stackbase = ms->irq_stacks[bt->tc->processor];
bt->stacktop = bt->stackbase + ms->irq_stack_size;
alter_stackbuf(bt);
}

static void
riscv64_set_process_stack(struct bt_info *bt)
{
bt->stackbase = GET_STACKBASE(bt->task);
bt->stacktop = GET_STACKTOP(bt->task);
alter_stackbuf(bt);
}

static void
riscv64_stackframe_init(void)
{
Expand Down Expand Up @@ -751,14 +875,19 @@ riscv64_back_trace_cmd(struct bt_info *bt)
{
struct riscv64_unwind_frame current, previous;
struct stackframe curr_frame;
struct riscv64_register * regs;
struct riscv64_register *regs, *irq_regs;
int level = 0;

if (bt->flags & BT_REGS_NOT_FOUND)
return;

regs = (struct riscv64_register *) bt->machdep;

if (riscv64_on_irq_stack(bt->tc->processor, bt->frameptr)) {
riscv64_set_irq_stack(bt);
bt->flags |= BT_IRQSTACK;
}

current.pc = bt->instptr;
current.sp = bt->stkptr;
current.fp = bt->frameptr;
Expand Down Expand Up @@ -813,6 +942,35 @@ riscv64_back_trace_cmd(struct bt_info *bt)
current.fp = previous.fp;
current.sp = previous.sp;

/*
* When backtracing to do_irq(), find the original FP of do_irq()
* and then use the saved pt_regs in process stack to continue
*/
if ((bt->flags & BT_IRQSTACK) &&
!riscv64_on_irq_stack(bt->tc->processor, current.fp)){
if (riscv64_on_process_stack(bt, current.fp)){

frameptr = (struct stackframe *)current.fp - 1;

if (!readmem((ulong)frameptr, KVADDR, &curr_frame,
sizeof(curr_frame), "get do_irq stack frame", RETURN_ON_ERROR))
return;

riscv64_set_process_stack(bt);

irq_regs = (struct riscv64_register *)
&bt->stackbuf[(ulong)(STACK_OFFSET_TYPE(curr_frame.fp))];

current.pc = irq_regs->regs[RISCV64_REGS_EPC];
current.fp = irq_regs->regs[RISCV64_REGS_FP];
current.sp = irq_regs->regs[RISCV64_REGS_SP];

bt->flags &= ~BT_IRQSTACK;
riscv64_print_exception_frame(bt, curr_frame.fp, KERNEL_MODE);
fprintf(fp, "--- <IRQ stack> ---\n");
}
}

if (CRASHDEBUG(8))
fprintf(fp, "next %d pc %#lx sp %#lx fp %lx\n",
level, current.pc, current.sp, current.fp);
Expand Down Expand Up @@ -1423,6 +1581,8 @@ riscv64_init(int when)
case POST_GDB:
machdep->section_size_bits = _SECTION_SIZE_BITS;
machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;

riscv64_irq_stack_init();
riscv64_stackframe_init();
riscv64_page_type_init();

Expand Down Expand Up @@ -1518,9 +1678,6 @@ riscv64_display_regs_from_elf_notes(int cpu, FILE *ofp)
riscv64_dump_pt_regs(regs, ofp, 0);
}

#define USER_MODE (0)
#define KERNEL_MODE (1)

static void
riscv64_print_exception_frame(struct bt_info *bt, ulong ptr, int mode)
{
Expand Down Expand Up @@ -1639,7 +1796,33 @@ static int
riscv64_eframe_search(struct bt_info *bt)
{
ulong ptr;
int count;
int count, c;
struct machine_specific *ms = machdep->machspec;

if (bt->flags & BT_EFRAME_SEARCH2) {
if (!(machdep->flags & IRQ_STACKS))
error(FATAL, "IRQ stacks do not exist in this kernel\n");

for (c = 0; c < kt->cpus; c++) {
if ((bt->flags & BT_CPUMASK) &&
!(NUM_IN_BITMAP(bt->cpumask, c)))
continue;

fprintf(fp, "CPU %d IRQ STACK: ", c);
bt->stackbase = ms->irq_stacks[c];
bt->stacktop = bt->stackbase + ms->irq_stack_size;
alter_stackbuf(bt);

count = riscv64_dump_kernel_eframes(bt);

if (count)
fprintf(fp, "\n");
else
fprintf(fp, "(none found)\n\n");
}

return 0;
}

count = riscv64_dump_kernel_eframes(bt);

Expand Down

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