From 86b818687d4894063ecd1190e54717a0cce8c009 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 31 Jan 2006 18:34:51 -0800 Subject: [PATCH] [SPARC64]: Fix race in LOAD_PER_CPU_BASE() Since we use %g5 itself as a temporary, it can get clobbered if we take an interrupt mid-stream and thus cause end up with the final %g5 value too early as a result of rtrap processing. Set %g5 at the very end, atomically, to avoid this problem. Signed-off-by: David S. Miller --- arch/sparc64/kernel/etrap.S | 4 ++-- arch/sparc64/kernel/rtrap.S | 2 +- arch/sparc64/kernel/winfixup.S | 6 +++--- include/asm-sparc64/cpudata.h | 19 ++++++++++++------- 4 files changed, 18 insertions(+), 13 deletions(-) diff --git a/arch/sparc64/kernel/etrap.S b/arch/sparc64/kernel/etrap.S index db7681017299..d974d18b15be 100644 --- a/arch/sparc64/kernel/etrap.S +++ b/arch/sparc64/kernel/etrap.S @@ -100,7 +100,7 @@ etrap_irq: stx %i7, [%sp + PTREGS_OFF + PT_V9_I7] wrpr %g0, ETRAP_PSTATE2, %pstate mov %l6, %g6 - LOAD_PER_CPU_BASE(%g4, %g3) + LOAD_PER_CPU_BASE(%g4, %g3, %l1) jmpl %l2 + 0x4, %g0 ldx [%g6 + TI_TASK], %g4 @@ -250,7 +250,7 @@ scetrap: stx %i6, [%sp + PTREGS_OFF + PT_V9_I6] mov %l6, %g6 stx %i7, [%sp + PTREGS_OFF + PT_V9_I7] - LOAD_PER_CPU_BASE(%g4, %g3) + LOAD_PER_CPU_BASE(%g4, %g3, %l1) ldx [%g6 + TI_TASK], %g4 done diff --git a/arch/sparc64/kernel/rtrap.S b/arch/sparc64/kernel/rtrap.S index 89794ebdcbcf..64bc03610bc6 100644 --- a/arch/sparc64/kernel/rtrap.S +++ b/arch/sparc64/kernel/rtrap.S @@ -226,7 +226,7 @@ rt_continue: ldx [%sp + PTREGS_OFF + PT_V9_G1], %g1 brz,pt %l3, 1f nop /* Must do this before thread reg is clobbered below. */ - LOAD_PER_CPU_BASE(%g6, %g7) + LOAD_PER_CPU_BASE(%i0, %i1, %i2) 1: ldx [%sp + PTREGS_OFF + PT_V9_G6], %g6 ldx [%sp + PTREGS_OFF + PT_V9_G7], %g7 diff --git a/arch/sparc64/kernel/winfixup.S b/arch/sparc64/kernel/winfixup.S index c0545d089c96..ade991b7d079 100644 --- a/arch/sparc64/kernel/winfixup.S +++ b/arch/sparc64/kernel/winfixup.S @@ -86,7 +86,7 @@ fill_fixup: wrpr %l1, (PSTATE_IE | PSTATE_AG | PSTATE_RMO), %pstate mov %o7, %g6 ldx [%g6 + TI_TASK], %g4 - LOAD_PER_CPU_BASE(%g1, %g2) + LOAD_PER_CPU_BASE(%g1, %g2, %g3) /* This is the same as below, except we handle this a bit special * since we must preserve %l5 and %l6, see comment above. @@ -209,7 +209,7 @@ fill_fixup_mna: wrpr %l1, (PSTATE_IE | PSTATE_AG | PSTATE_RMO), %pstate mov %o7, %g6 ! Get current back. ldx [%g6 + TI_TASK], %g4 ! Finish it. - LOAD_PER_CPU_BASE(%g1, %g2) + LOAD_PER_CPU_BASE(%g1, %g2, %g3) call mem_address_unaligned add %sp, PTREGS_OFF, %o0 @@ -312,7 +312,7 @@ fill_fixup_dax: wrpr %l1, (PSTATE_IE | PSTATE_AG | PSTATE_RMO), %pstate mov %o7, %g6 ! Get current back. ldx [%g6 + TI_TASK], %g4 ! Finish it. - LOAD_PER_CPU_BASE(%g1, %g2) + LOAD_PER_CPU_BASE(%g1, %g2, %g3) call spitfire_data_access_exception add %sp, PTREGS_OFF, %o0 diff --git a/include/asm-sparc64/cpudata.h b/include/asm-sparc64/cpudata.h index 16d628913837..f83768883e98 100644 --- a/include/asm-sparc64/cpudata.h +++ b/include/asm-sparc64/cpudata.h @@ -101,20 +101,25 @@ extern void setup_tba(void); ldx [%g1 + %g6], %g6; /* Given the current thread info pointer in %g6, load the per-cpu - * area base of the current processor into %g5. REG1 and REG2 are + * area base of the current processor into %g5. REG1, REG2, and REG3 are * clobbered. + * + * You absolutely cannot use %g5 as a temporary in this code. The + * reason is that traps can happen during execution, and return from + * trap will load the fully resolved %g5 per-cpu base. This can corrupt + * the calculations done by the macro mid-stream. */ #ifdef CONFIG_SMP -#define LOAD_PER_CPU_BASE(REG1, REG2) \ +#define LOAD_PER_CPU_BASE(REG1, REG2, REG3) \ ldub [%g6 + TI_CPU], REG1; \ - sethi %hi(__per_cpu_shift), %g5; \ + sethi %hi(__per_cpu_shift), REG3; \ sethi %hi(__per_cpu_base), REG2; \ - ldx [%g5 + %lo(__per_cpu_shift)], %g5; \ + ldx [REG3 + %lo(__per_cpu_shift)], REG3; \ ldx [REG2 + %lo(__per_cpu_base)], REG2; \ - sllx REG1, %g5, %g5; \ - add %g5, REG2, %g5; + sllx REG1, REG3, REG3; \ + add REG3, REG2, %g5; #else -#define LOAD_PER_CPU_BASE(REG1, REG2) +#define LOAD_PER_CPU_BASE(REG1, REG2, REG3) #endif #endif /* _SPARC64_CPUDATA_H */ -- 2.39.5