Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers

Helge Deller
2017-09-19T20:03:57Z

* Helge Deller <deller@gmx.de>:
> On 19.09.2017 04:05, Sergey Senozhatsky wrote:
> >On (09/18/17 20:39), Helge Deller wrote:
> >>I did tried your testcases [on parisc] too.
> ...
> >>and here is "modprobe zram":
> >> printk#7 __UNIQUE_ID_vermagic8+0xb9a4/0xbd04 [zram]
> >> printk#8 __UNIQUE_ID_vermagic8+0xb9a4/0xbd04 [zram]
> >> printk#9 do_one_initcall+0x194/0x290
> >> printk#10 do_one_initcall+0x194/0x290
> >> printk#11 do_one_initcall+0x194/0x290
> >> printk#12 do_one_initcall+0x194/0x290
> >> printk#13 zram_init+0x22c/0x2a0 [zram]
> >> printk#14 zram_init+0x22c/0x2a0 [zram]
> >> printk#15 zram_init+0x22c/0x2a0 [zram]
> >> printk#16 zram_init+0x22c/0x2a0 [zram]
> >>
> >>I wonder why printk#7 and printk#8 don't show "zram_init"...
> >
> >interesting... what does the unpatched kernel show?
>
> Really strange.
> The unpatched kernel shows __UNIQUE_ID_vermagic8+0xb9a4/0xbd04 too.
> The symbol should be known, because later on in printk13 it shows correctly zram_init.
> I'll need to dig deeper into it, but at least the regression is not due
> to your patch.

Sergey, I was wrong with this assumption.

Your implementation of dereference_module_function_descriptor() in
arch/parisc/kernel/module.c is faulty.
mod->arch.fdesc_offset is relative to the base address of the module,
so you need to add to mod->core_layout.base.

Here is the relevant patch to fix this issue (against mainline).
Additionally I compare against mod->arch.fdesc_count instead of
mod->arch.fdesc_max.
Can you please fold it into your patch
[PATCH 4/5] parisc64: Add .opd based function descriptor dereference
for the next round?

Thanks,
Helge

Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c
index f1a7693..ae3e6c5 100644
--- a/arch/parisc/kernel/module.c
+++ b/arch/parisc/kernel/module.c
@@ -66,6 +66,7 @@

#include <asm/pgtable.h>
#include <asm/unwind.h>
+#include <asm/sections.h>

#if 0
#define DEBUGP printk
@@ -954,3 +955,19 @@ void module_arch_cleanup(struct module *mod)
{
deregister_unwind_table(mod);
}
+
+#ifdef CONFIG_64BIT
+unsigned long dereference_module_function_descriptor(struct module *mod,
+ unsigned long addr)
+{
+ unsigned long opd_start = (Elf64_Addr) mod->core_layout.base
+ + mod->arch.fdesc_offset;
+ unsigned long opd_end = opd_start
+ + mod->arch.fdesc_count * sizeof(Elf64_Fdesc);
+
+ if (addr < opd_start || addr >= opd_end)
+ return addr;
+
+ return (unsigned long) dereference_function_descriptor((void *) addr);
+}
+#endif