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parisc: Fix and improve kernel stack unwinding

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This patchset fixes and improves stack unwinding a lot:
1. Show backward stack traces with up to 30 callsites
2. Add callinfo to ENTRY_CFI() such that every assembler function will get an
   entry in the unwind table
3. Use constants instead of numbers in call_on_stack()
4. Do not depend on CONFIG_KALLSYMS to generate backtraces.
5. Speed up backtrace generation

Make sure you have this patch to GNU as installed:
https://sourceware.org/ml/binutils/2018-07/msg00474.html
Without this patch, unwind info in the kernel is often wrong for various
functions.

Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Helge Deller
2018-08-05 00:03:29 +02:00
parent 3b885ac1dc
commit c8921d72e3
10 changed files with 88 additions and 232 deletions
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89
arch/parisc/kernel/unwind.c
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@ -13,7 +13,6 @@
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kallsyms.h>
#include <linux/sort.h>
#include <linux/uaccess.h>
@ -117,7 +116,8 @@ unwind_table_init(struct unwind_table *table, const char *name,
for (; start <= end; start++) {
if (start < end &&
start->region_end > (start+1)->region_start) {
printk("WARNING: Out of order unwind entry! %p and %p\n", start, start+1);
pr_warn("Out of order unwind entry! %px and %px\n",
start, start+1);
}
start->region_start += base_addr;
@ -203,26 +203,61 @@ int __init unwind_init(void)
return 0;
}
#ifdef CONFIG_64BIT
#define get_func_addr(fptr) fptr[2]
#else
#define get_func_addr(fptr) fptr[0]
#endif
static int unwind_special(struct unwind_frame_info *info, unsigned long pc, int frame_size)
{
extern void handle_interruption(int, struct pt_regs *);
static unsigned long *hi = (unsigned long *)&handle_interruption;
/*
* We have to use void * instead of a function pointer, because
* function pointers aren't a pointer to the function on 64-bit.
* Make them const so the compiler knows they live in .text
*/
extern void * const handle_interruption;
extern void * const ret_from_kernel_thread;
extern void * const syscall_exit;
extern void * const intr_return;
extern void * const _switch_to_ret;
#ifdef CONFIG_IRQSTACKS
extern void * const call_on_stack;
#endif /* CONFIG_IRQSTACKS */
if (pc == get_func_addr(hi)) {
if (pc == (unsigned long) &handle_interruption) {
struct pt_regs *regs = (struct pt_regs *)(info->sp - frame_size - PT_SZ_ALGN);
dbg("Unwinding through handle_interruption()\n");
info->prev_sp = regs->gr[30];
info->prev_ip = regs->iaoq[0];
return 1;
}
if (pc == (unsigned long) &ret_from_kernel_thread ||
pc == (unsigned long) &syscall_exit) {
info->prev_sp = info->prev_ip = 0;
return 1;
}
if (pc == (unsigned long) &intr_return) {
struct pt_regs *regs;
dbg("Found intr_return()\n");
regs = (struct pt_regs *)(info->sp - PT_SZ_ALGN);
info->prev_sp = regs->gr[30];
info->prev_ip = regs->iaoq[0];
info->rp = regs->gr[2];
return 1;
}
if (pc == (unsigned long) &_switch_to_ret) {
info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
return 1;
}
#ifdef CONFIG_IRQSTACKS
if (pc == (unsigned long) &call_on_stack) {
info->prev_sp = *(unsigned long *)(info->sp - FRAME_SIZE - REG_SZ);
info->prev_ip = *(unsigned long *)(info->sp - FRAME_SIZE - RP_OFFSET);
return 1;
}
#endif
return 0;
}
@ -238,34 +273,8 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
if (e == NULL) {
unsigned long sp;
dbg("Cannot find unwind entry for 0x%lx; forced unwinding\n", info->ip);
#ifdef CONFIG_KALLSYMS
/* Handle some frequent special cases.... */
{
char symname[KSYM_NAME_LEN];
char *modname;
kallsyms_lookup(info->ip, NULL, NULL, &modname,
symname);
dbg("info->ip = 0x%lx, name = %s\n", info->ip, symname);
if (strcmp(symname, "_switch_to_ret") == 0) {
info->prev_sp = info->sp - CALLEE_SAVE_FRAME_SIZE;
info->prev_ip = *(unsigned long *)(info->prev_sp - RP_OFFSET);
dbg("_switch_to_ret @ %lx - setting "
"prev_sp=%lx prev_ip=%lx\n",
info->ip, info->prev_sp,
info->prev_ip);
return;
} else if (strcmp(symname, "ret_from_kernel_thread") == 0 ||
strcmp(symname, "syscall_exit") == 0) {
info->prev_ip = info->prev_sp = 0;
return;
}
}
#endif
dbg("Cannot find unwind entry for %pS; forced unwinding\n",
(void *) info->ip);
/* Since we are doing the unwinding blind, we don't know if
we are adjusting the stack correctly or extracting the rp