linux-kernel - [PATCH] powerpc/32s: fix BATs setting with CONFIG_STRICT_KERNEL

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Message-Id: <3a21c6f19637847e6ed080186a834ede619f3849.1556528569.git.christophe.leroy@c-s.fr>
Date:   Mon, 29 Apr 2019 09:08:09 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Serge Belyshev <belyshev@...ni.sinp.msu.ru>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        stable@...r.kernel.org
Subject: [PATCH] powerpc/32s: fix BATs setting with CONFIG_STRICT_KERNEL_RWX

Serge reported some crashes with CONFIG_STRICT_KERNEL_RWX enabled
on a book3s32 machine.

Analysis shows two issues:
- BATs addresses and sizes are not properly aligned.
- There is a gap between the last address covered by BATs and the
first address covered by pages.

Memory mapped with DBATs:
0: 0xc0000000-0xc07fffff 0x00000000 Kernel RO coherent
1: 0xc0800000-0xc0bfffff 0x00800000 Kernel RO coherent
2: 0xc0c00000-0xc13fffff 0x00c00000 Kernel RW coherent
3: 0xc1400000-0xc23fffff 0x01400000 Kernel RW coherent
4: 0xc2400000-0xc43fffff 0x02400000 Kernel RW coherent
5: 0xc4400000-0xc83fffff 0x04400000 Kernel RW coherent
6: 0xc8400000-0xd03fffff 0x08400000 Kernel RW coherent
7: 0xd0400000-0xe03fffff 0x10400000 Kernel RW coherent

Memory mapped with pages:
0xe1000000-0xefffffff  0x21000000       240M        rw       present           dirty  accessed

This patch fixes both issues. With the patch, we get the following
which is as expected:

Memory mapped with DBATs:
0: 0xc0000000-0xc07fffff 0x00000000 Kernel RO coherent
1: 0xc0800000-0xc0bfffff 0x00800000 Kernel RO coherent
2: 0xc0c00000-0xc0ffffff 0x00c00000 Kernel RW coherent
3: 0xc1000000-0xc1ffffff 0x01000000 Kernel RW coherent
4: 0xc2000000-0xc3ffffff 0x02000000 Kernel RW coherent
5: 0xc4000000-0xc7ffffff 0x04000000 Kernel RW coherent
6: 0xc8000000-0xcfffffff 0x08000000 Kernel RW coherent
7: 0xd0000000-0xdfffffff 0x10000000 Kernel RW coherent

Memory mapped with pages:
0xe0000000-0xefffffff  0x20000000       256M        rw       present           dirty  accessed

Reported-by: Serge Belyshev <belyshev@...ni.sinp.msu.ru>
Fixes: 63b2bc619565 ("powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX")
Cc: stable@...r.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/mm/ppc_mmu_32.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/mm/ppc_mmu_32.c b/arch/powerpc/mm/ppc_mmu_32.c
index bf1de3ca39bc..37cf2af98f6a 100644
--- a/arch/powerpc/mm/ppc_mmu_32.c
+++ b/arch/powerpc/mm/ppc_mmu_32.c
@@ -101,7 +101,7 @@ static int find_free_bat(void)
 static unsigned int block_size(unsigned long base, unsigned long top)
 {
 	unsigned int max_size = (cpu_has_feature(CPU_FTR_601) ? 8 : 256) << 20;
-	unsigned int base_shift = (fls(base) - 1) & 31;
+	unsigned int base_shift = (ffs(base) - 1) & 31;
 	unsigned int block_shift = (fls(top - base) - 1) & 31;
 
 	return min3(max_size, 1U << base_shift, 1U << block_shift);
@@ -157,7 +157,7 @@ static unsigned long __init __mmu_mapin_ram(unsigned long base, unsigned long to
 
 unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 {
-	int done;
+	unsigned long done;
 	unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
 
 	if (__map_without_bats) {
@@ -169,10 +169,10 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 		return __mmu_mapin_ram(base, top);
 
 	done = __mmu_mapin_ram(base, border);
-	if (done != border - base)
+	if (done != border)
 		return done;
 
-	return done + __mmu_mapin_ram(border, top);
+	return __mmu_mapin_ram(border, top);
 }
 
 void mmu_mark_initmem_nx(void)
-- 
2.13.3