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powerpc: Emulate non privileged DSCR read and write

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POWER8 allows read and write of the DSCR in userspace. We added
kernel emulation so applications could always use the instructions
regardless of the CPU type.

Unfortunately there are two SPRs for the DSCR and we only added
emulation for the privileged one. Add code to match the non
privileged one.

A simple test was created to verify the fix:

http://ozlabs.org/~anton/junkcode/user_dscr_test.c

Without the patch we get a SIGILL and it passes with the patch.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Anton Blanchard 2013-05-01 20:06:33 +00:00 committed by Benjamin Herrenschmidt
parent 01227a889e
commit 73d2fb758e
2 changed files with 12 additions and 2 deletions
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4
arch/powerpc/include/asm/ppc-opcode.h
View file

@ -115,6 +115,10 @@
#define PPC_INST_MFSPR_DSCR_MASK 0xfc1fffff
#define PPC_INST_MTSPR_DSCR 0x7c1103a6
#define PPC_INST_MTSPR_DSCR_MASK 0xfc1fffff
#define PPC_INST_MFSPR_DSCR_USER 0x7c0302a6
#define PPC_INST_MFSPR_DSCR_USER_MASK 0xfc1fffff
#define PPC_INST_MTSPR_DSCR_USER 0x7c0303a6
#define PPC_INST_MTSPR_DSCR_USER_MASK 0xfc1fffff
#define PPC_INST_SLBFEE 0x7c0007a7
#define PPC_INST_STRING 0x7c00042a

10
arch/powerpc/kernel/traps.c
View file

@ -970,7 +970,10 @@ static int emulate_instruction(struct pt_regs *regs)
#ifdef CONFIG_PPC64
/* Emulate the mfspr rD, DSCR. */
if (((instword & PPC_INST_MFSPR_DSCR_MASK) == PPC_INST_MFSPR_DSCR) &&
if ((((instword & PPC_INST_MFSPR_DSCR_USER_MASK) ==
PPC_INST_MFSPR_DSCR_USER) ||
((instword & PPC_INST_MFSPR_DSCR_MASK) ==
PPC_INST_MFSPR_DSCR)) &&
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mfdscr, regs);
rd = (instword >> 21) & 0x1f;
@ -978,7 +981,10 @@ static int emulate_instruction(struct pt_regs *regs)
return 0;
}
/* Emulate the mtspr DSCR, rD. */
if (((instword & PPC_INST_MTSPR_DSCR_MASK) == PPC_INST_MTSPR_DSCR) &&
if ((((instword & PPC_INST_MTSPR_DSCR_USER_MASK) ==
PPC_INST_MTSPR_DSCR_USER) ||
((instword & PPC_INST_MTSPR_DSCR_MASK) ==
PPC_INST_MTSPR_DSCR)) &&
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mtdscr, regs);
rd = (instword >> 21) & 0x1f;