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target/arm: relax permission checks for HWCAP_CPUID registers

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Although technically not visible to userspace the kernel does make
them visible via a trap and emulate ABI. We provide a new permission
mask (PL0U_R) which maps to PL0_R for CONFIG_USER builds and adjust
the minimum permission check accordingly.

Backports commit b5bd7440422bb66deaceb812bb9287a6a3cdf10c from qemu
This commit is contained in:
Alex Bennée 2019-02-15 17:17:58 -05:00 committed by Lioncash
parent 841ac2b3bb
commit 0a51e5055f
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GPG key ID: 4E3C3CC1031BA9C7
2 changed files with 17 additions and 1 deletions
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12
qemu/target/arm/cpu.h
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@ -2168,6 +2168,18 @@ static inline bool cptype_valid(int cptype)
#define PL0_R (0x02 | PL1_R)
#define PL0_W (0x01 | PL1_W)
/*
* For user-mode some registers are accessible to EL0 via a kernel
* trap-and-emulate ABI. In this case we define the read permissions
* as actually being PL0_R. However some bits of any given register
* may still be masked.
*/
#ifdef CONFIG_USER_ONLY
#define PL0U_R PL0_R
#else
#define PL0U_R PL1_R
#endif
#define PL3_RW (PL3_R | PL3_W)
#define PL2_RW (PL2_R | PL2_W)
#define PL1_RW (PL1_R | PL1_W)

6
qemu/target/arm/helper.c
View file

@ -5937,7 +5937,11 @@ void define_one_arm_cp_reg_with_opaque(ARMCPU *cpu,
if (r->state != ARM_CP_STATE_AA32) {
int mask = 0;
switch (r->opc1) {
case 0: case 1: case 2:
case 0:
/* min_EL EL1, but some accessible to EL0 via kernel ABI */
mask = PL0U_R | PL1_RW;
break;
case 1: case 2:
/* min_EL EL1 */
mask = PL1_RW;
break;