ACK: [PATCH] powerpc/64: Fix HMI exception on LE with CONFIG_RELOCATABLE=y

Kleber Souza kleber.souza at canonical.com
Fri Aug 4 08:35:32 UTC 2017


Hi Manoj,

On 07/31/17 17:43, Manoj Iyer wrote:
> Looks like this was acked, but I dont see any update to bugs wrt to fix
> commit etc on the
> bug. https://bugs.launchpad.net/ubuntu-power-systems/+bug/1684054 
> 
> was this fixed-committed ?

The series Status on the Launchpad bug changes to 'Fix Committed' when
the patches are applied on the tree and is on the way to be included on
the next -proposed update.

In the case of this patch, it has been ACK'ed during the first week of
the current SRU cycle and we start applying new patches for the next
cycle not before we approach the end of the current one. So this patch
should be applied today and available on the next proposed kernel update.


Kleber

> 
> On Fri, Jul 21, 2017 at 4:05 AM, Colin Ian King
> <colin.king at canonical.com> wrote:
>> On 20/07/17 00:41, Manoj Iyer wrote:
>>
>>     From: Michael Ellerman <mpe at ellerman.id.au
>>     <mailto:mpe at ellerman.id.au>> Prior to commit 2337d207288f
>>     ("powerpc/64: CONFIG_RELOCATABLE support for hmi interrupts"), the
>>     branch from hmi_exception_early() to hmi_exception_realmode() was
>>     just a bl hmi_exception_realmode, which the linker would turn into
>>     a bl to the local entry point of hmi_exception_realmode. This was
>>     broken when CONFIG_RELOCATABLE=y because hmi_exception_realmode()
>>     is not in the low part of the kernel text that is copied down to
>>     0x0. But in fixing that, we added a new bug on little endian
>>     kernels. Because the branch is now a bctrl when
>>     CONFIG_RELOCATABLE=y, we branch to the global entry point of
>>     hmi_exception_realmode(). The global entry point must be called
>>     with r12 containing the address of hmi_exception_realmode(),
>>     because it uses that value to calculate the TOC value (r2). This
>>     may manifest as a checkstop, because we take a junk value from r12
>>     which came from HSRR1, add a small constant to it and then use
>>     that as the TOC pointer. The HSRR1 value will have 0x9 as the top
>>     nibble, which puts it above RAM and somewhere in MMIO space. Fix
>>     it by changing the BRANCH_LINK_TO_FAR() macro to always use r12 to
>>     load the label we're branching to. This means r12 will be setup
>>     correctly on LE, fixing this bug, and r12 is also volatile across
>>     function calls on BE so it's a good choice anyway. BugLink:
>>     https://launchpad.net/bugs/1684054 Fixes: 2337d207288f
>>     ("powerpc/64: CONFIG_RELOCATABLE support for hmi interrupts")
>>     Reported-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com
>>     <mailto:mahesh at linux.vnet.ibm.com>> Acked-by: Nicholas Piggin
>>     <npiggin at gmail.com <mailto:npiggin at gmail.com>> Signed-off-by:
>>     Michael Ellerman <mpe at ellerman.id.au <mailto:mpe at ellerman.id.au>>
>>     (cherry picked from commit
>>     be5c5e843c4afa1c8397cb740b6032bd4142f32d) Signed-off-by: Manoj
>>     Iyer <manoj.iyer at canonical.com <mailto:manoj.iyer at canonical.com>>
>>     --- arch/powerpc/include/asm/exception-64s.h | 8 ++++----
>>     arch/powerpc/kernel/exceptions-64s.S | 2 +- 2 files changed, 5
>>     insertions(+), 5 deletions(-) diff --git
>>     a/arch/powerpc/include/asm/exception-64s.h
>>     b/arch/powerpc/include/asm/exception-64s.h index
>>     14752eee3d0c..ed3beadd2cc5 100644 ---
>>     a/arch/powerpc/include/asm/exception-64s.h +++
>>     b/arch/powerpc/include/asm/exception-64s.h @@ -236,9 +236,9 @@
>>     END_FTR_SECTION_NESTED(ftr,ftr,943) mtctr reg; \ bctr -#define
>>     BRANCH_LINK_TO_FAR(reg, label) \ - __LOAD_FAR_HANDLER(reg, label);
>>     \ - mtctr reg; \ +#define BRANCH_LINK_TO_FAR(label) \ +
>>     __LOAD_FAR_HANDLER(r12, label); \ + mtctr r12; \ bctrl /* @@
>>     -265,7 +265,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943) #define
>>     BRANCH_TO_COMMON(reg, label) \ b label -#define
>>     BRANCH_LINK_TO_FAR(reg, label) \ +#define
>>     BRANCH_LINK_TO_FAR(label) \ bl label #define BRANCH_TO_KVM(reg,
>>     label) \ diff --git a/arch/powerpc/kernel/exceptions-64s.S
>>     b/arch/powerpc/kernel/exceptions-64s.S index
>>     79318275e507..78456131385d 100644 ---
>>     a/arch/powerpc/kernel/exceptions-64s.S +++
>>     b/arch/powerpc/kernel/exceptions-64s.S @@ -986,7 +986,7 @@
>>     TRAMP_REAL_BEGIN(hmi_exception_early)
>>     EXCEPTION_PROLOG_COMMON_2(PACA_EXGEN)
>>     EXCEPTION_PROLOG_COMMON_3(0xe60) addi r3,r1,STACK_FRAME_OVERHEAD -
>>     BRANCH_LINK_TO_FAR(r4, hmi_exception_realmode) +
>>     BRANCH_LINK_TO_FAR(hmi_exception_realmode) /* Function call ABI */
>>     /* Windup the stack. */ /* Move original HSRR0 and HSRR1 into the
>>     respective regs */ ld r9,_MSR(r1) 
>>
>> Upstream cherry pick and has positive test results. Thanks Manoj.
>> Acked-by: Colin Ian King <colin.king at canonical.com
>> <mailto:colin.king at canonical.com>> 
> 
> 




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