Upgrade to 4.4.50-rt62

[kvmfornfv.git] / kernel / arch / x86 / boot / compressed / head_32.S

diff --git a/kernel/arch/x86/boot/compressed/head_32.S b/kernel/arch/x86/boot/compressed/head_32.S
index 8ef964d..0256064 100644 (file)
--- a/kernel/arch/x86/boot/compressed/head_32.S
+++ b/kernel/arch/x86/boot/compressed/head_32.S
@@ -31,6 +31,34 @@
 #include <asm/asm-offsets.h>
 #include <asm/bootparam.h>
 
+/*
+ * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
+ * relocation to get the symbol address in PIC.  When the compressed x86
+ * kernel isn't built as PIC, the linker optimizes R_386_GOT32X
+ * relocations to their fixed symbol addresses.  However, when the
+ * compressed x86 kernel is loaded at a different address, it leads
+ * to the following load failure:
+ *
+ *   Failed to allocate space for phdrs
+ *
+ * during the decompression stage.
+ *
+ * If the compressed x86 kernel is relocatable at run-time, it should be
+ * compiled with -fPIE, instead of -fPIC, if possible and should be built as
+ * Position Independent Executable (PIE) so that linker won't optimize
+ * R_386_GOT32X relocation to its fixed symbol address.  Older
+ * linkers generate R_386_32 relocations against locally defined symbols,
+ * _bss, _ebss, _got and _egot, in PIE.  It isn't wrong, just less
+ * optimal than R_386_RELATIVE.  But the x86 kernel fails to properly handle
+ * R_386_32 relocations when relocating the kernel.  To generate
+ * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as
+ * hidden:
+ */
+       .hidden _bss
+       .hidden _ebss
+       .hidden _got
+       .hidden _egot
+
        __HEAD
 ENTRY(startup_32)
 #ifdef CONFIG_EFI_STUB