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authorDavid S. Miller <davem@davemloft.net>2006-01-31 18:34:51 -0800
committerDavid S. Miller <davem@sunset.davemloft.net>2006-03-20 01:11:29 -0800
commit86b818687d4894063ecd1190e54717a0cce8c009 (patch)
treed2951295358502c88f7fe0c02517d729cff4eb9a /include/asm-sparc64/cpudata.h
parent9954863975910a1b9372b7d5006a6cba43bdd288 (diff)
[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 <davem@davemloft.net>
Diffstat (limited to 'include/asm-sparc64/cpudata.h')
-rw-r--r--include/asm-sparc64/cpudata.h19
1 files changed, 12 insertions, 7 deletions
diff --git a/include/asm-sparc64/cpudata.h b/include/asm-sparc64/cpudata.h
index 16d62891383..f83768883e9 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 */