x86/e820/32: Fix e820_search_gap() error handling on x86-32

GCC correctly points out that on 32-bit kernels, e820_search_gap()
not finding a start now leads to pci_mem_start ('gapstart') being set to an
uninitialized value:

  arch/x86/kernel/e820.c: In function 'e820_setup_gap':
  arch/x86/kernel/e820.c:641:16: error: 'gapstart' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This restores the behavior from before this cleanup:

  b4ed1d15b453 ("x86/e820: Make e820_search_gap() static and remove unused variables")

... defaulting to address 0x10000000 if nothing was found.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Fixes: b4ed1d15b453 ("x86/e820: Make e820_search_gap() static and remove unused variables")
Link: http://lkml.kernel.org/r/20170111144926.695369-1-arnd@arndb.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 46f2afd3577a0ef254be5ed1cced68edeeff02a2..b2bbad6ebe4d8c5c822965134ea1daf4a6fe8adc 100644 (file)
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -626,14 +626,16 @@ __init void e820_setup_gap(void)
        gapsize = 0x400000;
        found  = e820_search_gap(&gapstart, &gapsize);
 
-#ifdef CONFIG_X86_64
        if (!found) {
+#ifdef CONFIG_X86_64
                gapstart = (max_pfn << PAGE_SHIFT) + 1024*1024;
                printk(KERN_ERR
        "e820: cannot find a gap in the 32bit address range\n"
        "e820: PCI devices with unassigned 32bit BARs may break!\n");
-       }
+#else
+               gapstart = 0x10000000;
 #endif
+       }
 
        /*
         * e820_reserve_resources_late protect stolen RAM already