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[PATCH 4.3 131/157] powerpc/module: Handle R_PPC64_ENTRY relocations

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4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ulrich Weigand <ulrich.weigand@de.ibm.com>

commit a61674bdfc7c2bf909c4010699607b62b69b7bec upstream.

GCC 6 will include changes to generated code with -mcmodel=large,
which is used to build kernel modules on powerpc64le.  This was
necessary because the large model is supposed to allow arbitrary
sizes and locations of the code and data sections, but the ELFv2
global entry point prolog still made the unconditional assumption
that the TOC associated with any particular function can be found
within 2 GB of the function entry point:

func:
	addis r2,r12,(.TOC.-func)@ha
	addi  r2,r2,(.TOC.-func)@l
	.localentry func, .-func

To remove this assumption, GCC will now generate instead this global
entry point prolog sequence when using -mcmodel=large:

	.quad .TOC.-func
func:
	.reloc ., R_PPC64_ENTRY
	ld    r2, -8(r12)
	add   r2, r2, r12
	.localentry func, .-func

The new .reloc triggers an optimization in the linker that will
replace this new prolog with the original code (see above) if the
linker determines that the distance between .TOC. and func is in
range after all.

Since this new relocation is now present in module object files,
the kernel module loader is required to handle them too.  This
patch adds support for the new relocation and implements the
same optimization done by the GNU linker.

Signed-off-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/powerpc/include/uapi/asm/elf.h |    2 ++
 arch/powerpc/kernel/module_64.c     |   27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

--- a/arch/powerpc/include/uapi/asm/elf.h
+++ b/arch/powerpc/include/uapi/asm/elf.h
@@ -295,6 +295,8 @@ do {									\
 #define R_PPC64_TLSLD		108
 #define R_PPC64_TOCSAVE		109
 
+#define R_PPC64_ENTRY		118
+
 #define R_PPC64_REL16		249
 #define R_PPC64_REL16_LO	250
 #define R_PPC64_REL16_HI	251
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -635,6 +635,33 @@ int apply_relocate_add(Elf64_Shdr *sechd
 			 */
 			break;
 
+		case R_PPC64_ENTRY:
+			/*
+			 * Optimize ELFv2 large code model entry point if
+			 * the TOC is within 2GB range of current location.
+			 */
+			value = my_r2(sechdrs, me) - (unsigned long)location;
+			if (value + 0x80008000 > 0xffffffff)
+				break;
+			/*
+			 * Check for the large code model prolog sequence:
+		         *	ld r2, ...(r12)
+			 *	add r2, r2, r12
+			 */
+			if ((((uint32_t *)location)[0] & ~0xfffc)
+			    != 0xe84c0000)
+				break;
+			if (((uint32_t *)location)[1] != 0x7c426214)
+				break;
+			/*
+			 * If found, replace it with:
+			 *	addis r2, r12, (.TOC.-func)@ha
+			 *	addi r2, r12, (.TOC.-func)@l
+			 */
+			((uint32_t *)location)[0] = 0x3c4c0000 + PPC_HA(value);
+			((uint32_t *)location)[1] = 0x38420000 + PPC_LO(value);
+			break;
+
 		case R_PPC64_REL16_HA:
 			/* Subtract location pointer */
 			value -= (unsigned long)location;

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[PATCH 4.3 000/157] 4.3.5-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by default on modern CPUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
    Re: [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by  default on modern CPUs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 23:30 +0100
    Re: [PATCH 4.3 001/157] x86 smpboot: Re-enable init_udelay=0 by  default on modern CPUs Donald Parsons <dparsons@brightdsl.net> - 2016-01-27 23:30 +0100
  [PATCH 4.3 052/157] ALSA: seq: Fix race at timer setup and close Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 046/157] ALSA: hda - Add mic mute hotkey quirk for Lenovo ThinkCentre AIO Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 010/157] KVM: svm: unconditionally intercept #DB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 155/157] mn10300: Select CONFIG_HAVE_UID16 to fix build failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 20:10 +0100
  [PATCH 4.3 154/157] fix the regression from "direct-io: Fix negative return from dio read beyond eof" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 126/157] powerpc/opal-irqchip: Fix deadlock introduced by "Fix double endian conversion" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 135/157] arm64: cmpxchg_dbl: fix return value type Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 134/157] arm64: bpf: fix mod-by-zero case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:20 +0100
  [PATCH 4.3 044/157] ALSA: hda - Set SKL+ hda controller power at freeze() and thaw() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 128/157] powerpc: Make value-returning atomics fully ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 157/157] arm64: KVM: Add workaround for Cortex-A57 erratum 834220 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 131/157] powerpc/module: Handle R_PPC64_ENTRY relocations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 129/157] powerpc: Make {cmp}xchg* and their atomic_ versions fully ordered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 133/157] arm64: bpf: fix div-by-zero case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 156/157] arm64: restore bogomips information in /proc/cpuinfo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 147/157] parisc iommu: fix panic due to trying to allocate too large region Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 132/157] recordmcount: arm64: Replace the ignored mcount call into nop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 148/157] HID: wacom: Tie cached HID_DG_CONTACTCOUNT indices to report ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 150/157] HID: core: Avoid uninitialized buffer access Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 149/157] HID: wacom: Expect touch_max touches if HID_DG_CONTACTCOUNT not present Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 130/157] scripts/recordmcount.pl: support data in text section on powerpc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  [PATCH 4.3 153/157] direct-io: Fix negative return from dio read beyond eof Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-01-27 21:30 +0100
  Re: [PATCH 4.3 000/157] 4.3.5-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-01-28 00:30 +0100
  Re: [PATCH 4.3 000/157] 4.3.5-stable review Guenter Roeck <linux@roeck-us.net> - 2016-01-28 03:20 +0100

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