From 618febd6784054eea928d712b7e564558a7cefd5 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Fri, 21 Oct 2005 22:53:26 -0400 Subject: [PATCH] [PARISC] Fix the alloc_slabmgmt panic Fix the alloc_slabmgmt panic Hopefully this should also fix a lot of other intermittent kernel bugs. The problem has been around since 2.6.9-rc2-pa6 when we allowed floating point registers to be used in kernel code. The essence of the problem is that gcc prefers to use floating point for integer divides and multiples. Further, it can rely on the values in the no clobber fp regs being correct across a function call. Unfortunately, our task switch function only saves the integer no clobber registers, not the fp ones, so if gcc makes a function call to any function in the kernel which could sleep, the values it is relying on in any no clobber floating point register may be lost. In the case of alloc_slabmgmt, the value of the page offset is being stored in %fr12 across a call to kmem_getpages(), which sleeps if no pages are available. Thus, the offset can be trashed and the slab code can end up with a completely bogus address leading to corruption. Kudos to Randolph who came up with the program to trip this problem at will and thus allowed it to be tracked and fixed. Signed-off-by: James Bottomley Signed-off-by: Kyle McMartin --- arch/parisc/kernel/entry.S | 2 ++ include/asm-parisc/assembly.h | 40 ++++++++++++++++++++++++++++++++++------ 2 files changed, 36 insertions(+), 6 deletions(-) diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index 0ca4971..166df5b 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -863,6 +863,7 @@ __execve: _switch_to: STREG %r2, -RP_OFFSET(%r30) + callee_save_float callee_save load32 _switch_to_ret, %r2 @@ -879,6 +880,7 @@ _switch_to: _switch_to_ret: mtctl %r0, %cr0 /* Needed for single stepping */ callee_rest + callee_rest_float LDREG -RP_OFFSET(%r30), %r2 bv %r0(%r2) diff --git a/include/asm-parisc/assembly.h b/include/asm-parisc/assembly.h index b24a99e..fb8bc7c 100644 --- a/include/asm-parisc/assembly.h +++ b/include/asm-parisc/assembly.h @@ -21,6 +21,7 @@ #ifndef _PARISC_ASSEMBLY_H #define _PARISC_ASSEMBLY_H +#define CALLEE_FLOAT_FRAME_SIZE 80 #ifdef __LP64__ #define LDREG ldd #define STREG std @@ -30,7 +31,7 @@ #define SHRREG shrd #define RP_OFFSET 16 #define FRAME_SIZE 128 -#define CALLEE_SAVE_FRAME_SIZE 144 +#define CALLEE_REG_FRAME_SIZE 144 #else #define LDREG ldw #define STREG stw @@ -40,8 +41,9 @@ #define SHRREG shr #define RP_OFFSET 20 #define FRAME_SIZE 64 -#define CALLEE_SAVE_FRAME_SIZE 128 +#define CALLEE_REG_FRAME_SIZE 128 #endif +#define CALLEE_SAVE_FRAME_SIZE (CALLEE_REG_FRAME_SIZE + CALLEE_FLOAT_FRAME_SIZE) #ifdef CONFIG_PA20 #define BL b,l @@ -300,9 +302,35 @@ fldd,mb -8(\regs), %fr0 .endm + .macro callee_save_float + fstd,ma %fr12, 8(%r30) + fstd,ma %fr13, 8(%r30) + fstd,ma %fr14, 8(%r30) + fstd,ma %fr15, 8(%r30) + fstd,ma %fr16, 8(%r30) + fstd,ma %fr17, 8(%r30) + fstd,ma %fr18, 8(%r30) + fstd,ma %fr19, 8(%r30) + fstd,ma %fr20, 8(%r30) + fstd,ma %fr21, 8(%r30) + .endm + + .macro callee_rest_float + fldd,mb -8(%r30), %fr21 + fldd,mb -8(%r30), %fr20 + fldd,mb -8(%r30), %fr19 + fldd,mb -8(%r30), %fr18 + fldd,mb -8(%r30), %fr17 + fldd,mb -8(%r30), %fr16 + fldd,mb -8(%r30), %fr15 + fldd,mb -8(%r30), %fr14 + fldd,mb -8(%r30), %fr13 + fldd,mb -8(%r30), %fr12 + .endm + #ifdef __LP64__ .macro callee_save - std,ma %r3, CALLEE_SAVE_FRAME_SIZE(%r30) + std,ma %r3, CALLEE_REG_FRAME_SIZE(%r30) mfctl %cr27, %r3 std %r4, -136(%r30) std %r5, -128(%r30) @@ -340,13 +368,13 @@ ldd -128(%r30), %r5 ldd -136(%r30), %r4 mtctl %r3, %cr27 - ldd,mb -CALLEE_SAVE_FRAME_SIZE(%r30), %r3 + ldd,mb -CALLEE_REG_FRAME_SIZE(%r30), %r3 .endm #else /* ! __LP64__ */ .macro callee_save - stw,ma %r3, CALLEE_SAVE_FRAME_SIZE(%r30) + stw,ma %r3, CALLEE_REG_FRAME_SIZE(%r30) mfctl %cr27, %r3 stw %r4, -124(%r30) stw %r5, -120(%r30) @@ -384,7 +412,7 @@ ldw -120(%r30), %r5 ldw -124(%r30), %r4 mtctl %r3, %cr27 - ldw,mb -CALLEE_SAVE_FRAME_SIZE(%r30), %r3 + ldw,mb -CALLEE_REG_FRAME_SIZE(%r30), %r3 .endm #endif /* ! __LP64__ */ -- 2.7.4