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Message-ID: <b90a6bcb-22c4-e500-2586-d54cd881e02e@ghiti.fr>
Date:   Sun, 6 Jun 2021 09:23:45 +0200
From:   Alex Ghiti <alex@...ti.fr>
To:     Jisheng Zhang <jszhang3@...l.ustc.edu.cn>,
        Nathan Chancellor <nathan@...nel.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] riscv: mm: init: Consolidate vars, functions

Hi Jisheng,

Le 4/06/2021 à 19:09, Jisheng Zhang a écrit :
> On Thu, 3 Jun 2021 19:54:18 +0800
> Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
> 
>> On Thu, 3 Jun 2021 08:27:14 +0800
>> Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
>>
>>> On Wed, 2 Jun 2021 12:54:40 -0700
>>> Nathan Chancellor <nathan@...nel.org> wrote:
>>>    
>>>> On Wed, Jun 02, 2021 at 11:58:51PM +0800, Jisheng Zhang wrote:
>>>>> On Wed, 2 Jun 2021 23:12:26 +0800
>>>>> Jisheng Zhang <jszhang3@...l.ustc.edu.cn> wrote:
>>>>>        
>>>>>> On Tue, 1 Jun 2021 13:21:05 -0700
>>>>>> Nathan Chancellor <nathan@...nel.org> wrote:
>>>>>>        
>>>>>>> Hi Jisheng,
>>>>>>
>>>>>> Hi Nathan,
>>>>>>        
>>>>>>>
>>>>>>> On Sun, May 16, 2021 at 09:15:56PM +0800, Jisheng Zhang wrote:
>>>>>>>> From: Jisheng Zhang <jszhang@...nel.org>
>>>>>>>>
>>>>>>>> Consolidate the following items in init.c
>>>>>>>>
>>>>>>>> Staticize global vars as much as possible;
>>>>>>>> Add __initdata mark if the global var isn't needed after init
>>>>>>>> Add __init mark if the func isn't needed after init
>>>>>>>> Add __ro_after_init if the global var is read only after init
>>>>>>>>
>>>>>>>> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
>>>>>>>> ---
>>>>>>>>   arch/riscv/include/asm/set_memory.h |  2 +-
>>>>>>>>   arch/riscv/mm/init.c                | 36 +++++++++++++++--------------
>>>>>>>>   2 files changed, 20 insertions(+), 18 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
>>>>>>>> index 086f757e8ba3..9d4d455726d4 100644
>>>>>>>> --- a/arch/riscv/include/asm/set_memory.h
>>>>>>>> +++ b/arch/riscv/include/asm/set_memory.h
>>>>>>>> @@ -27,7 +27,7 @@ static inline int set_memory_rw_nx(unsigned long addr, int numpages) { return 0;
>>>>>>>>   #endif
>>>>>>>>   
>>>>>>>>   #if defined(CONFIG_64BIT) && defined(CONFIG_STRICT_KERNEL_RWX)
>>>>>>>> -void protect_kernel_linear_mapping_text_rodata(void);
>>>>>>>> +void __init protect_kernel_linear_mapping_text_rodata(void);
>>>>>>>>   #else
>>>>>>>>   static inline void protect_kernel_linear_mapping_text_rodata(void) {}
>>>>>>>>   #endif
>>>>>>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>>>>>>> index 4c4c92ce0bb8..eac2d5c27b3e 100644
>>>>>>>> --- a/arch/riscv/mm/init.c
>>>>>>>> +++ b/arch/riscv/mm/init.c
>>>>>>>> @@ -53,7 +53,7 @@ struct pt_alloc_ops {
>>>>>>>>   #endif
>>>>>>>>   };
>>>>>>>>   
>>>>>>>> -static phys_addr_t dma32_phys_limit __ro_after_init;
>>>>>>>> +static phys_addr_t dma32_phys_limit __initdata;
>>>>>>>>   
>>>>>>>>   static void __init zone_sizes_init(void)
>>>>>>>>   {
>>>>>>>> @@ -184,7 +184,7 @@ extern char _sdata[], _edata[];
>>>>>>>>   #endif /* CONFIG_XIP_KERNEL */
>>>>>>>>   
>>>>>>>>   #ifdef CONFIG_MMU
>>>>>>>> -static struct pt_alloc_ops _pt_ops __ro_after_init;
>>>>>>>> +static struct pt_alloc_ops _pt_ops __initdata;
>>>>>>>>   
>>>>>>>>   #ifdef CONFIG_XIP_KERNEL
>>>>>>>>   #define pt_ops (*(struct pt_alloc_ops *)XIP_FIXUP(&_pt_ops))
>>>>>>>> @@ -200,13 +200,13 @@ EXPORT_SYMBOL(va_pa_offset);
>>>>>>>>   #endif
>>>>>>>>   /* Offset between kernel mapping virtual address and kernel load address */
>>>>>>>>   #ifdef CONFIG_64BIT
>>>>>>>> -unsigned long va_kernel_pa_offset;
>>>>>>>> +unsigned long va_kernel_pa_offset __ro_after_init;
>>>>>>>>   EXPORT_SYMBOL(va_kernel_pa_offset);
>>>>>>>>   #endif
>>>>>>>>   #ifdef CONFIG_XIP_KERNEL
>>>>>>>>   #define va_kernel_pa_offset    (*((unsigned long *)XIP_FIXUP(&va_kernel_pa_offset)))
>>>>>>>>   #endif
>>>>>>>> -unsigned long va_kernel_xip_pa_offset;
>>>>>>>> +unsigned long va_kernel_xip_pa_offset __ro_after_init;
>>>>>>>>   EXPORT_SYMBOL(va_kernel_xip_pa_offset);
>>>>>>>>   #ifdef CONFIG_XIP_KERNEL
>>>>>>>>   #define va_kernel_xip_pa_offset        (*((unsigned long *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
>>>>>>>> @@ -216,7 +216,7 @@ EXPORT_SYMBOL(pfn_base);
>>>>>>>>   
>>>>>>>>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>>>>>>>>   pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>>>>>>>> -pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>>>>>>>> +static pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>>>>>>>>   
>>>>>>>>   pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>>>>>>>>   
>>>>>>>> @@ -253,7 +253,7 @@ static inline pte_t *__init get_pte_virt_fixmap(phys_addr_t pa)
>>>>>>>>   	return (pte_t *)set_fixmap_offset(FIX_PTE, pa);
>>>>>>>>   }
>>>>>>>>   
>>>>>>>> -static inline pte_t *get_pte_virt_late(phys_addr_t pa)
>>>>>>>> +static inline pte_t *__init get_pte_virt_late(phys_addr_t pa)
>>>>>>>>   {
>>>>>>>>   	return (pte_t *) __va(pa);
>>>>>>>>   }
>>>>>>>> @@ -272,7 +272,7 @@ static inline phys_addr_t __init alloc_pte_fixmap(uintptr_t va)
>>>>>>>>   	return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>>>>>>>>   }
>>>>>>>>   
>>>>>>>> -static phys_addr_t alloc_pte_late(uintptr_t va)
>>>>>>>> +static phys_addr_t __init alloc_pte_late(uintptr_t va)
>>>>>>>>   {
>>>>>>>>   	unsigned long vaddr;
>>>>>>>>   
>>>>>>>> @@ -296,10 +296,10 @@ static void __init create_pte_mapping(pte_t *ptep,
>>>>>>>>   
>>>>>>>>   #ifndef __PAGETABLE_PMD_FOLDED
>>>>>>>>   
>>>>>>>> -pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>>>>>>> -pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>>>>>>> -pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>>>>>>> -pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>>>>>>> +static pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>>>>>>> +static pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>>>>>>> +static pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>>>>>>> +static pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>>>>>>>   
>>>>>>>>   #ifdef CONFIG_XIP_KERNEL
>>>>>>>>   #define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
>>>>>>>> @@ -319,7 +319,7 @@ static pmd_t *__init get_pmd_virt_fixmap(phys_addr_t pa)
>>>>>>>>   	return (pmd_t *)set_fixmap_offset(FIX_PMD, pa);
>>>>>>>>   }
>>>>>>>>   
>>>>>>>> -static pmd_t *get_pmd_virt_late(phys_addr_t pa)
>>>>>>>> +static pmd_t *__init get_pmd_virt_late(phys_addr_t pa)
>>>>>>>>   {
>>>>>>>>   	return (pmd_t *) __va(pa);
>>>>>>>>   }
>>>>>>>> @@ -336,7 +336,7 @@ static phys_addr_t __init alloc_pmd_fixmap(uintptr_t va)
>>>>>>>>   	return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
>>>>>>>>   }
>>>>>>>>   
>>>>>>>> -static phys_addr_t alloc_pmd_late(uintptr_t va)
>>>>>>>> +static phys_addr_t __init alloc_pmd_late(uintptr_t va)
>>>>>>>>   {
>>>>>>>>   	unsigned long vaddr;
>>>>>>>>   
>>>>>>>> @@ -454,14 +454,16 @@ asmlinkage void __init __copy_data(void)
>>>>>>>>   #error "setup_vm() is called from head.S before relocate so it should not use absolute addressing."
>>>>>>>>   #endif
>>>>>>>>   
>>>>>>>> -uintptr_t load_pa, load_sz;
>>>>>>>> +static uintptr_t load_pa __initdata;
>>>>>>>
>>>>>>> Making load_pa static causing clang built kernels to no longer boot,
>>>>>>> hanging after just a few lines of output in the console:
>>>>>>>
>>>>>>> https://github.com/ClangBuiltLinux/continuous-integration2/runs/2717606254?check_suite_focus=true
>>>>>>>
>>>>>>> I am not sure why that would make a difference nor why GCC is okay with
>>>>>>> it. If it is a clang bug, it appears to be there for a while, given that
>>>>>>> it reproduces back to clang-11.
>>>>>>
>>>>>> I can reproduce the issue. Here are my findindings:
>>>>>>
>>>>>> * gcc + binutils can't reproduce it
>>>>>> * clang + llvm-utils + ias can reproduce it
>>>>>> * clang + binutils can reproduce it
>>>>
>>>> Yes, this seems like something strictly related to clang so that is what
>>>> I have been testing with.
>>>>      
>>>>>> All below tests are done with clang + binutils.
>>>>>>
>>>>>> Then I applied below modification:
>>>>>>
>>>>>> -static uintptr_t load_pa __initdata;
>>>>>> +uintptr_t load_pa __initdata;
>>>>>>
>>>>>> I got below panic log:
>>>>>> [    0.015418] Unable to handle kernel paging request at virtual address fffffffffffffff9
>>>>>> [    0.016432] Oops [#1]
>>>>>> [    0.016679] Modules linked in:
>>>>>> [    0.017103] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.13.0-rc1+ #5
>>>>>> [    0.017711] Hardware name: riscv-virtio,qemu (DT)
>>>>>> [    0.018201] epc : trace_hardirqs_on+0x60/0xb2
>>>>>> [    0.018582]  ra : restore_all+0xe/0x66
>>>>>> [    0.018879] epc : ffffffff800cb09a ra : ffffffff800027b8 sp : ffffffff80c03dd0
>>>>>> [    0.019376]  gp : ffffffff80d001c8 tp : ffffffff80c0c180 t0 : 0000000000000020
>>>>>> [    0.019870]  t1 : ffffffff80006e40 t2 : ffffffff800d2e0a s0 : ffffffff80c03e00
>>>>>> [    0.020346]  s1 : 0000000000000001 a0 : 0000000000000001 a1 : 0000000000000001
>>>>>> [    0.020800]  a2 : 0000000000000001 a3 : 0000000000000000 a4 : 0000000000000000
>>>>>> [    0.021243]  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000054494d45
>>>>>> [    0.021717]  s2 : ffffffff800027b8 s3 : ffffffff80d35968 s4 : ffffffff8061e1d8
>>>>>> [    0.022179]  s5 : ffffffff80c0c180 s6 : ffffffe000e34b50 s7 : 00000000800130f0
>>>>>> [    0.022674]  s8 : 000000000000007f s9 : 0000000080012010 s10: 0000000000000000
>>>>>> [    0.023176]  s11: 0000000000000000 t3 : ffffffff80d00108 t4 : ffffffff80006e40
>>>>>> [    0.023693]  t5 : ffffffff80006e40 t6 : ffffffff800d2e0a
>>>>>> [    0.024153] status: 0000000000000100 badaddr: fffffffffffffff9 cause: 000000000000000d
>>>>>> [    0.025367] Call Trace:
>>>>>> [    0.025749] [<ffffffff800cb09a>] trace_hardirqs_on+0x60/0xb2
>>>>>> [    0.026402] [<ffffffff800027b8>] restore_all+0xe/0x66
>>>>>> [    0.027261] Unable to handle kernel paging request at virtual address fffffffffffffffa
>>>>>> [    0.027827] Oops [#2]
>>>>>> [    0.028013] Modules linked in:
>>>>>> [    0.028321] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G      D           5.13.0-rc1+ #5
>>>>>> [    0.028839] Hardware name: riscv-virtio,qemu (DT)
>>>>>> [    0.029166] epc : trace_hardirqs_on+0x60/0xb2
>>>>>> [    0.029505]  ra : restore_all+0xe/0x66
>>>>>> [    0.029785] epc : ffffffff800cb09a ra : ffffffff800027b8 sp : ffffffff80c03a80
>>>>>> [    0.030266]  gp : ffffffff80d001c8 tp : ffffffff80c0c180 t0 : 0000000000000020
>>>>>> [    0.030748]  t1 : ffffffff80006e40 t2 : ffffffff800d2e0a s0 : ffffffff80c03ab0
>>>>>> [    0.031227]  s1 : 0000000000000001 a0 : 0000000000000002 a1 : 0000000000000002
>>>>>> [    0.031717]  a2 : 0000000000000001 a3 : 0000000000000000 a4 : 0000000000000000
>>>>>> [    0.032199]  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000054494d45
>>>>>> [    0.032680]  s2 : ffffffff800027b8 s3 : ffffffff80d35968 s4 : ffffffff8061e1d8
>>>>>> [    0.033160]  s5 : ffffffff80c0c180 s6 : ffffffe000e34b50 s7 : 00000000800130f0
>>>>>> [    0.033642]  s8 : 000000000000007f s9 : 0000000080012010 s10: 0000000000000000
>>>>>> [    0.034123]  s11: 0000000000000000 t3 : ffffffff80d00108 t4 : ffffffff80006e40
>>>>>> [    0.034601]  t5 : ffffffff80006e40 t6 : ffffffff800d2e0a
>>>>>> [    0.034965] status: 0000000000000100 badaddr: fffffffffffffffa cause: 000000000000000d
>>>>>> [    0.035492] Call Trace:
>>>>>> [    0.035682] [<ffffffff800cb09a>] trace_hardirqs_on+0x60/0xb2
>>>>>> [    0.036077] [<ffffffff800027b8>] restore_all+0xe/0x66
>>>>>> [    0.036545] ---[ end trace 7f4fbff09d927668 ]---
>>>>>> [    0.037188] Kernel panic - not syncing: Attempted to kill the idle task!
>>>>>> [    0.038107] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
>>>>>>
>>>>>> Then I checked 5.13-rc1, above panic log can be reproduced too. So the issue
>>>>>> should exist there for a while. I never tried clang with riscv, did you remember
>>>>>> which last commit or version clang works, I may try to bisect.
>>>> V> >
>>>>>
>>>>> More findings:
>>>>>
>>>>> *The above panic issue can also be seen from 5.12-rc2. If disable FTRACE, then
>>>>> the panic disappears, kernel can boot
>>>>>
>>>>> *so I retested riscv next tree w/ FTRACE disabled, kernel can boot w/ below
>>>>> modification:
>>>>
>>>> Yeah, I do not enable CONFIG_FTRACE because it is not enabled in
>>>> ARCH=riscv defconfig by default.
>>>>      
>>>>> -static uintptr_t load_pa __initdata;
>>>>> +uintptr_t load_pa __initdata;
>>>>>
>>>>> This is a weird issue. Any clue is appreciated.
>>>>
>>>> Unfortunately, this is outside of my realm of expertise, as I am
>>>> unfamiliar with RISC-V at this level. Maybe Palmer has some ideas. I
>>>> would think that changing this variable to static would be fine given
>>>> that the symbol is only used in this translation unit but clearly not. I
>>>> have attempted to debug this in gdb but that does not really get me
>>>> anywhere: I cannot break on start_kernel() for whatever reason and the
>>>> kernel never gets to my breakpoint in setup_vm().
>>>>
>>>> I did decide to through a BUG() around arch/riscv/mm/init.c to see
>>>> exactly which statement causes everything to hang. I landed on:
>>>>
>>>> csr_write(CSR_SATP, PFN_DOWN(__pa_symbol(swapper_pg_dir)) | SATP_MODE);
>>>>
>>>> in setup_vm_final(). No idea how that is relevant to this.
>>>>
>>>> Some people in the ClangBuiltLinux bi-weekly meeting today pointed out
>>>> that since load_pa is assigned to the linker defined symbol _start,
>>>> there could be some optimization that goes awry here. I have keyed that
>>>
>>> Thanks for the inspiration. Below patch fixes the hang issue, but I didn't
>>> go through all necessary WRITE_ONCE convertions.
>>>
>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>> index ae32f78207f0..fa9336a2583f 100644
>>> --- a/arch/riscv/mm/init.c
>>> +++ b/arch/riscv/mm/init.c
>>> @@ -504,7 +504,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>   
>>>          va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
>>>   #else
>>> -       load_pa = (uintptr_t)(&_start);
>>> +       WRITE_ONCE(load_pa, (uintptr_t)(&_start));
>>>          load_sz = (uintptr_t)(&_end) - load_pa;
>>>   #endif
>>>    
>>
>> I think I found the root cause, but I dunno whether this is clang bug or
>> we need WRITE_ONCE patch.
>> W/O WRITE_ONCE, the setup_vm() is compiled to
>>
>> ffffffff8040472a <setup_vm>:
>> ffffffff8040472a:       1101                    addi    sp,sp,-32
>> ffffffff8040472c:       ec06                    sd      ra,24(sp)
>> ffffffff8040472e:       e822                    sd      s0,16(sp)
>> ffffffff80404730:       e426                    sd      s1,8(sp)
>> ffffffff80404732:       e04a                    sd      s2,0(sp)
>> ffffffff80404734:       1000                    addi    s0,sp,32
>> ffffffff80404736:       892a                    mv      s2,a0
>> ffffffff80404738:       001fd517                auipc   a0,0x1fd
>> ffffffff8040473c:       8c850513                addi    a0,a0,-1848 # ffffffff80601000 <load_pa>
>> ffffffff80404740:       4585                    li      a1,1
>> ffffffff80404742:       00b50023                sb      a1,0(a0)     // BUG!
>> ffffffff80404746:       001fd517                auipc   a0,0x1fd
>> ffffffff8040474a:       8c250513                addi    a0,a0,-1854 # ffffffff80601008 <load_sz>
>> ffffffff8040474e:       00b50023                sb      a1,0(a0)     // BUG!
>> ffffffff80404752:       ffbfc517                auipc   a0,0xffbfc
>> ffffffff80404756:       8ae50513                addi    a0,a0,-1874 # ffffffff80000000 <_start>
>> ffffffff8040475a:       55fd                    li      a1,-1
>> ffffffff8040475c:       02559613                slli    a2,a1,0x25
>> ffffffff80404760:       83018593                addi    a1,gp,-2000 # ffffffff80ca6428 <kernel_virt_addr>
>> ffffffff80404764:       618c                    ld      a1,0(a1)
>> ffffffff80404766:       8e09                    sub     a2,a2,a0
>> ...
>>
>> It seems load_pa and load_sz are stored with 1, this is obviously not what the
>> code expected.
>>
>>
>> W/ WRITE_ONCE, the setup_vm() is compiled to:
>>
>> ffffffff8040472a <setup_vm>:
>> ffffffff8040472a:       1101                    addi    sp,sp,-32
>> ffffffff8040472c:       ec06                    sd      ra,24(sp)
>> ffffffff8040472e:       e822                    sd      s0,16(sp)
>> ffffffff80404730:       e426                    sd      s1,8(sp)
>> ffffffff80404732:       e04a                    sd      s2,0(sp)
>> ffffffff80404734:       1000                    addi    s0,sp,32
>> ffffffff80404736:       892a                    mv      s2,a0
>> ffffffff80404738:       001fd597                auipc   a1,0x1fd
>> ffffffff8040473c:       8c858593                addi    a1,a1,-1848 # ffffffff80601000 <load_pa>
>> ffffffff80404740:       ffbfc517                auipc   a0,0xffbfc
>> ffffffff80404744:       8c050513                addi    a0,a0,-1856 # ffffffff80000000 <_start>
>> ffffffff80404748:       e188                    sd      a0,0(a1)
>> ffffffff8040474a:       001fd597                auipc   a1,0x1fd
>> ffffffff8040474e:       8be58593                addi    a1,a1,-1858 # ffffffff80601008 <load_sz>
>> ffffffff80404752:       4605                    li      a2,1
>> ffffffff80404754:       00c58023                sb      a2,0(a1)
>> ffffffff80404758:       55fd                    li      a1,-1
>> ffffffff8040475a:       02559613                slli    a2,a1,0x25
>> ffffffff8040475e:       83018593                addi    a1,gp,-2000 # ffffffff80ca6428 <kernel_virt_addr>
>> ffffffff80404762:       618c                    ld      a1,0(a1)
>> ffffffff80404764G       8e09                    sub     a2,a2,a0
>> ...
>>
>> This is what the code expected.
> 
> This issue can also be solved by avoiding global vars: load_pa and load_sz.
> 
> Hi Alexandre,
> 
> IMHO, the load_pa and load_sz can be removed, I have one patch to remove
> them, it works. I'm not sure whether will the two vars be used in your
> future patches?
> 

More or less, I want to move all the address conversion macros to inline 
functions as suggested by Christoph, and there I will need load_sz and 
load_pa. But I'm not sure it is really necessary.

Anyway, that would "solve" this issue, but I think we all agree the real 
problem should be solved at clang level.


> Thanks in advance,
> Jisheng
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
> 

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