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Koen Kooi
646ff9d602
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com>
71 lines
2.8 KiB
Diff
71 lines
2.8 KiB
Diff
From 5c6f8c50fe40cec7015a6bfa9762bf76d52211d6 Mon Sep 17 00:00:00 2001
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From: Steffen Rumler <steffen.rumler.ext@nsn.com>
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Date: Wed, 6 Jun 2012 16:37:17 +0200
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Subject: [PATCH 07/67] powerpc: Fix kernel panic during kernel module load
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commit 3c75296562f43e6fbc6cddd3de948a7b3e4e9bcf upstream.
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This fixes a problem which can causes kernel oopses while loading
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a kernel module.
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According to the PowerPC EABI specification, GPR r11 is assigned
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the dedicated function to point to the previous stack frame.
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In the powerpc-specific kernel module loader, do_plt_call()
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(in arch/powerpc/kernel/module_32.c), GPR r11 is also used
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to generate trampoline code.
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This combination crashes the kernel, in the case where the compiler
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chooses to use a helper function for saving GPRs on entry, and the
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module loader has placed the .init.text section far away from the
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.text section, meaning that it has to generate a trampoline for
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functions in the .init.text section to call the GPR save helper.
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Because the trampoline trashes r11, references to the stack frame
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using r11 can cause an oops.
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The fix just uses GPR r12 instead of GPR r11 for generating the
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trampoline code. According to the statements from Freescale, this is
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safe from an EABI perspective.
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I've tested the fix for kernel 2.6.33 on MPC8541.
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Signed-off-by: Steffen Rumler <steffen.rumler.ext@nsn.com>
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[paulus@samba.org: reworded the description]
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Signed-off-by: Paul Mackerras <paulus@samba.org>
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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arch/powerpc/kernel/module_32.c | 11 +++++------
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1 file changed, 5 insertions(+), 6 deletions(-)
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diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
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index 0b6d796..2e3200c 100644
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--- a/arch/powerpc/kernel/module_32.c
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+++ b/arch/powerpc/kernel/module_32.c
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@@ -176,8 +176,8 @@ int module_frob_arch_sections(Elf32_Ehdr *hdr,
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static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
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{
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- if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
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- && entry->jump[1] == 0x396b0000 + (val & 0xffff))
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+ if (entry->jump[0] == 0x3d800000 + ((val + 0x8000) >> 16)
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+ && entry->jump[1] == 0x398c0000 + (val & 0xffff))
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return 1;
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return 0;
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}
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@@ -204,10 +204,9 @@ static uint32_t do_plt_call(void *location,
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entry++;
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}
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- /* Stolen from Paul Mackerras as well... */
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- entry->jump[0] = 0x3d600000+((val+0x8000)>>16); /* lis r11,sym@ha */
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- entry->jump[1] = 0x396b0000 + (val&0xffff); /* addi r11,r11,sym@l*/
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- entry->jump[2] = 0x7d6903a6; /* mtctr r11 */
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+ entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
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+ entry->jump[1] = 0x398c0000 + (val&0xffff); /* addi r12,r12,sym@l*/
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+ entry->jump[2] = 0x7d8903a6; /* mtctr r12 */
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entry->jump[3] = 0x4e800420; /* bctr */
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DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
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--
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1.7.9.5
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