On Fri, Nov 23, 2012 at 10:27:51AM +0400, Alexander Shiyan wrote:
On Fri, Nov 23, 2012 at 07:40:30AM +0400, Alexander Shiyan wrote: [...]
static unsigned long no_fiq_insn; +static int got_no_fiq_insn; @@ -78,11 +79,14 @@ void show_fiq_list(struct seq_file *p, int prec) void set_fiq_handler(void *start, unsigned int length) { -#if defined(CONFIG_CPU_USE_DOMAINS)
- memcpy((void *)0xffff001c, start, length);
-#else
- memcpy(vectors_page + 0x1c, start, length);
- unsigned long *addr = (void *)0xffff001c;
+#ifndef CONFIG_CPU_USE_DOMAINS
- addr = vectors_page + 0x1c;
#endif
- if (!cmpxchg(&got_no_fiq_insn, 0, 1))
no_fiq_insn = *addr;- memcpy(addr, start, length); flush_icache_range(0xffff001c, 0xffff001c + length); if (!vectors_high()) flush_icache_range(0x1c, 0x1c + length);
@@ -126,8 +130,3 @@ EXPORT_SYMBOL(__set_fiq_regs); /* defined in fiqasm.S */
-void __init init_FIQ(void) -{
- no_fiq_insn = *(unsigned long *)0xffff001c;
it seems that this is wrong. In this case we have an uninitialized variable and sequential call claim_fiq and release_fiq could be fatal. FIXME please.
Um... I don't think I understand, can you please elaborate?
OK, I'll try to explain it. At the end of the release_fiq function we have a call fiq_op. For the default handler - is a fiq_def_op function, and we call this function with the option "relinquish = 0", i.e. we want to restore old fiq_handler. But if we do not call set_fiq_handler never before, we will have an uninitialized no_fiq_insn variable.
It should not matter when or in what order anyone calls the set_fiq_handler(), since it stores "no FIQ instruction" into no_fiq_insn at its first invocation:
if (!cmpxchg(&got_no_fiq_insn, 0, 1)) no_fiq_insn = *addr;
If we never called set_fiq_handler() before, during release_fiq() we'll:
1. Copy the initial instruction from the vector page to 'no_fiq_insn'; 2. Copy the initial instruction from 'no_fiq_insn' to the vector page;
So no_fiq_insn gets initialized, then we just instantly write the same value back.
Thanks, Anton.