UP systems do not implement all the instructions that SMP systems have,
so in order to boot a SMP kernel on a UP system, we need to rewrite
parts of the kernel.
Do this using an 'alternatives' scheme, where the kernel code and data
is modified prior to initialization to replace the SMP instructions,
thereby rendering the problematical code ineffectual. We use the linker
to generate a list of 32-bit word locations and their replacement values,
and run through these replacements when we detect a UP system.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
We suffer an unfortunate combination of "features" which makes highmem
support on platforms without hardware TLB maintainence broadcast difficult:
- we need kmap_high_get() support for DMA cache coherence
- this requires kmap_high() to take a spinlock with IRQs disabled
- kmap_high() occasionally calls flush_all_zero_pkmaps() to clear
out old mappings
- flush_all_zero_pkmaps() calls flush_tlb_kernel_range(), which
on s/w IPI'd systems eventually calls smp_call_function_many()
- smp_call_function_many() must not be called with IRQs disabled:
WARNING: at kernel/smp.c:380 smp_call_function_many+0xc4/0x240()
Modules linked in:
Backtrace:
[<c00306f0>] (dump_backtrace+0x0/0x108) from [<c0286e6c>] (dump_stack+0x18/0x1c)
r6:c007cd18 r5:c02ff228 r4:0000017c
[<c0286e54>] (dump_stack+0x0/0x1c) from [<c0053e08>] (warn_slowpath_common+0x50/0x80)
[<c0053db8>] (warn_slowpath_common+0x0/0x80) from [<c0053e50>] (warn_slowpath_null+0x18/0x1c)
r7:00000003 r6:00000001 r5:c1ff4000 r4:c035fa34
[<c0053e38>] (warn_slowpath_null+0x0/0x1c) from [<c007cd18>] (smp_call_function_many+0xc4/0x240)
[<c007cc54>] (smp_call_function_many+0x0/0x240) from [<c007cec0>] (smp_call_function+0x2c/0x38)
[<c007ce94>] (smp_call_function+0x0/0x38) from [<c005980c>] (on_each_cpu+0x1c/0x38)
[<c00597f0>] (on_each_cpu+0x0/0x38) from [<c0031788>] (flush_tlb_kernel_range+0x50/0x58)
r6:00000001 r5:00000800 r4:c05f3590
[<c0031738>] (flush_tlb_kernel_range+0x0/0x58) from [<c009c600>] (flush_all_zero_pkmaps+0xc0/0xe8)
[<c009c540>] (flush_all_zero_pkmaps+0x0/0xe8) from [<c009c6b4>] (kmap_high+0x8c/0x1e0)
[<c009c628>] (kmap_high+0x0/0x1e0) from [<c00364a8>] (kmap+0x44/0x5c)
[<c0036464>] (kmap+0x0/0x5c) from [<c0109dfc>] (cramfs_readpage+0x3c/0x194)
[<c0109dc0>] (cramfs_readpage+0x0/0x194) from [<c0090c14>] (__do_page_cache_readahead+0x1f0/0x290)
[<c0090a24>] (__do_page_cache_readahead+0x0/0x290) from [<c0090ce4>] (ra_submit+0x30/0x38)
[<c0090cb4>] (ra_submit+0x0/0x38) from [<c0089384>] (filemap_fault+0x3dc/0x438)
r4:c1819988
[<c0088fa8>] (filemap_fault+0x0/0x438) from [<c009d21c>] (__do_fault+0x58/0x43c)
[<c009d1c4>] (__do_fault+0x0/0x43c) from [<c009e8cc>] (handle_mm_fault+0x104/0x318)
[<c009e7c8>] (handle_mm_fault+0x0/0x318) from [<c0033c98>] (do_page_fault+0x188/0x1e4)
[<c0033b10>] (do_page_fault+0x0/0x1e4) from [<c0033ddc>] (do_translation_fault+0x7c/0x84)
[<c0033d60>] (do_translation_fault+0x0/0x84) from [<c002b474>] (do_DataAbort+0x40/0xa4)
r8:c1ff5e20 r7:c0340120 r6:00000805 r5:c1ff5e54 r4:c03400d0
[<c002b434>] (do_DataAbort+0x0/0xa4) from [<c002bcac>] (__dabt_svc+0x4c/0x60)
...
So we disable highmem support on these systems.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
