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Christophe Leroy a58cbed683 powerpc/traps: Declare unrecoverable_exception() as __noreturn
unrecoverable_exception() is never expected to return, most callers
have an infiniteloop in case it returns.

Ensure it really never returns by terminating it with a BUG(), and
declare it __no_return.

It always GCC to really simplify functions calling it. In the exemple
below, it avoids the stack frame in the likely fast path and avoids
code duplication for the exit.

With this patch:

	00000348 <interrupt_exit_kernel_prepare>:
	 348:	81 43 00 84 	lwz     r10,132(r3)
	 34c:	71 48 00 02 	andi.   r8,r10,2
	 350:	41 82 00 2c 	beq     37c <interrupt_exit_kernel_prepare+0x34>
	 354:	71 4a 40 00 	andi.   r10,r10,16384
	 358:	40 82 00 20 	bne     378 <interrupt_exit_kernel_prepare+0x30>
	 35c:	80 62 00 70 	lwz     r3,112(r2)
	 360:	74 63 00 01 	andis.  r3,r3,1
	 364:	40 82 00 28 	bne     38c <interrupt_exit_kernel_prepare+0x44>
	 368:	7d 40 00 a6 	mfmsr   r10
	 36c:	7c 11 13 a6 	mtspr   81,r0
	 370:	7c 12 13 a6 	mtspr   82,r0
	 374:	4e 80 00 20 	blr
	 378:	48 00 00 00 	b       378 <interrupt_exit_kernel_prepare+0x30>
	 37c:	94 21 ff f0 	stwu    r1,-16(r1)
	 380:	7c 08 02 a6 	mflr    r0
	 384:	90 01 00 14 	stw     r0,20(r1)
	 388:	48 00 00 01 	bl      388 <interrupt_exit_kernel_prepare+0x40>
				388: R_PPC_REL24	unrecoverable_exception
	 38c:	38 e2 00 70 	addi    r7,r2,112
	 390:	3d 00 00 01 	lis     r8,1
	 394:	7c c0 38 28 	lwarx   r6,0,r7
	 398:	7c c6 40 78 	andc    r6,r6,r8
	 39c:	7c c0 39 2d 	stwcx.  r6,0,r7
	 3a0:	40 a2 ff f4 	bne     394 <interrupt_exit_kernel_prepare+0x4c>
	 3a4:	38 60 00 01 	li      r3,1
	 3a8:	4b ff ff c0 	b       368 <interrupt_exit_kernel_prepare+0x20>

Without this patch:

	00000348 <interrupt_exit_kernel_prepare>:
	 348:	94 21 ff f0 	stwu    r1,-16(r1)
	 34c:	93 e1 00 0c 	stw     r31,12(r1)
	 350:	7c 7f 1b 78 	mr      r31,r3
	 354:	81 23 00 84 	lwz     r9,132(r3)
	 358:	71 2a 00 02 	andi.   r10,r9,2
	 35c:	41 82 00 34 	beq     390 <interrupt_exit_kernel_prepare+0x48>
	 360:	71 29 40 00 	andi.   r9,r9,16384
	 364:	40 82 00 28 	bne     38c <interrupt_exit_kernel_prepare+0x44>
	 368:	80 62 00 70 	lwz     r3,112(r2)
	 36c:	74 63 00 01 	andis.  r3,r3,1
	 370:	40 82 00 3c 	bne     3ac <interrupt_exit_kernel_prepare+0x64>
	 374:	7d 20 00 a6 	mfmsr   r9
	 378:	7c 11 13 a6 	mtspr   81,r0
	 37c:	7c 12 13 a6 	mtspr   82,r0
	 380:	83 e1 00 0c 	lwz     r31,12(r1)
	 384:	38 21 00 10 	addi    r1,r1,16
	 388:	4e 80 00 20 	blr
	 38c:	48 00 00 00 	b       38c <interrupt_exit_kernel_prepare+0x44>
	 390:	7c 08 02 a6 	mflr    r0
	 394:	90 01 00 14 	stw     r0,20(r1)
	 398:	48 00 00 01 	bl      398 <interrupt_exit_kernel_prepare+0x50>
				398: R_PPC_REL24	unrecoverable_exception
	 39c:	80 01 00 14 	lwz     r0,20(r1)
	 3a0:	81 3f 00 84 	lwz     r9,132(r31)
	 3a4:	7c 08 03 a6 	mtlr    r0
	 3a8:	4b ff ff b8 	b       360 <interrupt_exit_kernel_prepare+0x18>
	 3ac:	39 02 00 70 	addi    r8,r2,112
	 3b0:	3d 40 00 01 	lis     r10,1
	 3b4:	7c e0 40 28 	lwarx   r7,0,r8
	 3b8:	7c e7 50 78 	andc    r7,r7,r10
	 3bc:	7c e0 41 2d 	stwcx.  r7,0,r8
	 3c0:	40 a2 ff f4 	bne     3b4 <interrupt_exit_kernel_prepare+0x6c>
	 3c4:	38 60 00 01 	li      r3,1
	 3c8:	4b ff ff ac 	b       374 <interrupt_exit_kernel_prepare+0x2c>

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1e883e9d93fdb256853d1434c8ad77c257349b2d.1615552866.git.christophe.leroy@csgroup.eu
2021-03-29 13:22:02 +11:00
arch powerpc/traps: Declare unrecoverable_exception() as __noreturn 2021-03-29 13:22:02 +11:00
block block: Discard page cache of zone reset target range 2021-03-11 11:49:25 -07:00
certs certs: Replace K{U,G}IDT_INIT() with GLOBAL_ROOT_{U,G}ID 2021-01-21 16:16:10 +00:00
crypto crypto: mips/poly1305 - enable for all MIPS processors 2021-03-08 11:52:17 +01:00
Documentation A set of irqchip updates: 2021-03-14 13:33:33 -07:00
drivers cxl: don't manipulate the mm.mm_users field directly 2021-03-29 12:52:24 +11:00
fs Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
include A set of irqchip updates: 2021-03-14 13:33:33 -07:00
init Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel prctl: fix PR_SET_MM_AUXV kernel stack leak 2021-03-14 14:33:27 -07:00
lib kasan: fix KASAN_STACK dependency for HW_TAGS 2021-03-13 11:27:31 -08:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
net NFS Client Bugfixes for Linux 5.10-rc3 2021-03-12 14:19:35 -08:00
samples Merge git://git.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2021-03-09 17:15:56 -08:00
scripts kbuild: fix ld-version.sh to not be affected by locale 2021-03-13 11:12:13 +09:00
security Revert 95ebabde38 ("capabilities: Don't allow writing ambiguous v3 file capabilities") 2021-03-12 15:27:14 -06:00
sound ALSA: hda/hdmi: Cancel pending works before suspend 2021-03-10 12:52:01 +01:00
tools selftests/powerpc: Fix L1D flushing tests for Power10 2021-03-24 14:09:29 +11:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS treewide: Miguel has moved 2021-02-26 09:41:03 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2021-03-14 12:23:34 -07:00
Makefile Linux 5.12-rc3 2021-03-14 14:41:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.