parisc: Fix backtrace on PA-RISC (be24a897) · Commits · 戴 / test

This patch fixes backtrace on PA-RISC There were several problems: 1) The code that decodes instructions handles instructions that subtract from the stack pointer incorrectly. If the instruction subtracts the number X from the stack pointer the code increases the frame size by (0x100000000-X). This results in invalid accesses to memory and recursive page faults. 2) Because gcc reorders blocks, handling instructions that subtract from the frame pointer is incorrect. For example, this function int f(int a) { if (__builtin_expect(a, 1)) return a; g(); return a; } is compiled in such a way, that the code that decreases the stack pointer for the first "return a" is placed before the code for "g" call. If we recognize this decrement, we mistakenly believe that the frame size for the "g" call is zero. To fix problems 1) and 2), the patch doesn't recognize instructions that decrease the stack pointer at all. To further safeguard the unwind code against nonsense values, we don't allow frame size larger than Total_frame_size. 3) The backtrace is not locked. If stack dump races with module unload, invalid table can be accessed. This patch adds a spinlock when processing module tables. Note, that for correct backtrace, you need recent binutils. Binutils 2.18 from Debian 5 produce garbage unwind tables. Binutils 2.21 work better (it sometimes forgets function frames, but at least it doesn't generate garbage). Signed-off-by:

Mikulas Patocka <mpatocka@redhat.com> Signed-off-by:

Helge Deller <deller@gmx.de>

arch/parisc/kernel/unwind.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -75,7 +75,10 @@ find_unwind_entry(unsigned long addr)
		if (addr >= kernel_unwind_table.start &&
		addr <= kernel_unwind_table.end)
		e = find_unwind_entry_in_table(&kernel_unwind_table, addr);
		else
		else {
		unsigned long flags;

		spin_lock_irqsave(&unwind_lock, flags);
		list_for_each_entry(table, &unwind_tables, list) {
		if (addr >= table->start &&
		addr <= table->end)
		@@ -86,6 +89,8 @@ find_unwind_entry(unsigned long addr)
		break;
		}
		}
		spin_unlock_irqrestore(&unwind_lock, flags);
		}

		return e;
		}
		@@ -303,18 +308,16 @@ static void unwind_frame_regs(struct unwind_frame_info *info)

		insn = (unsigned int )npc;

		if ((insn & 0xffffc000) == 0x37de0000 \|\|
		(insn & 0xffe00000) == 0x6fc00000) {
		if ((insn & 0xffffc001) == 0x37de0000 \|\|
		(insn & 0xffe00001) == 0x6fc00000) {
		/* ldo X(sp), sp, or stwm X,D(sp) */
		frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
		((insn & 0x3fff) >> 1);
		frame_size += (insn & 0x3fff) >> 1;
		dbg("analyzing func @ %lx, insn=%08x @ "
		"%lx, frame_size = %ld\n", info->ip,
		insn, npc, frame_size);
		} else if ((insn & 0xffe00008) == 0x73c00008) {
		} else if ((insn & 0xffe00009) == 0x73c00008) {
		/* std,ma X,D(sp) */
		frame_size += (insn & 0x1 ? -1 << 13 : 0) \|
		(((insn >> 4) & 0x3ff) << 3);
		frame_size += ((insn >> 4) & 0x3ff) << 3;
		dbg("analyzing func @ %lx, insn=%08x @ "
		"%lx, frame_size = %ld\n", info->ip,
		insn, npc, frame_size);
		@@ -333,6 +336,9 @@ static void unwind_frame_regs(struct unwind_frame_info *info)
		}
		}

		if (frame_size > e->Total_frame_size << 3)
		frame_size = e->Total_frame_size << 3;

		if (!unwind_special(info, e->region_start, frame_size)) {
		info->prev_sp = info->sp - frame_size;
		if (e->Millicode)

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