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authorMark Brown <broonie@kernel.org>2024-12-14 02:12:06 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2024-12-20 14:12:04 +0000
commit926e862058978a8f81872845715d67ad21c30f65 (patch)
tree55f88204b611ebf0468f93f902e01bf7b245c984 /arch/arm64
parentce03573a1917532da06057da9f8e74a2ee9e2ac9 (diff)
downloadlwn-926e862058978a8f81872845715d67ad21c30f65.tar.gz
lwn-926e862058978a8f81872845715d67ad21c30f65.zip
arm64/signal: Silence sparse warning storing GCSPR_EL0
We are seeing a sparse warning in gcs_restore_signal(): arch/arm64/kernel/signal.c:1054:9: sparse: sparse: cast removes address space '__user' of expression when storing the final GCSPR_EL0 value back into the register, caused by the fact that write_sysreg_s() casts the value it writes to a u64 which sparse sees as discarding the __userness of the pointer. Avoid this by treating the address as an integer, casting to a pointer only when using it to write to userspace. While we're at it also inline gcs_signal_cap_valid() into it's one user and make equivalent updates to gcs_signal_entry(). Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202412082005.OBJ0BbWs-lkp@intel.com/ Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20241214-arm64-gcs-signal-sparse-v3-1-5e8d18fffc0c@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/signal.c35
1 files changed, 15 insertions, 20 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 37e24f1bd227..99ea26d400ff 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -36,15 +36,8 @@
#include <asm/traps.h>
#include <asm/vdso.h>
-#ifdef CONFIG_ARM64_GCS
#define GCS_SIGNAL_CAP(addr) (((unsigned long)addr) & GCS_CAP_ADDR_MASK)
-static bool gcs_signal_cap_valid(u64 addr, u64 val)
-{
- return val == GCS_SIGNAL_CAP(addr);
-}
-#endif
-
/*
* Do a signal return; undo the signal stack. These are aligned to 128-bit.
*/
@@ -1062,8 +1055,7 @@ static int restore_sigframe(struct pt_regs *regs,
#ifdef CONFIG_ARM64_GCS
static int gcs_restore_signal(void)
{
- unsigned long __user *gcspr_el0;
- u64 cap;
+ u64 gcspr_el0, cap;
int ret;
if (!system_supports_gcs())
@@ -1072,7 +1064,7 @@ static int gcs_restore_signal(void)
if (!(current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE))
return 0;
- gcspr_el0 = (unsigned long __user *)read_sysreg_s(SYS_GCSPR_EL0);
+ gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
/*
* Ensure that any changes to the GCS done via GCS operations
@@ -1087,22 +1079,23 @@ static int gcs_restore_signal(void)
* then faults will be generated on GCS operations - the main
* concern is to protect GCS pages.
*/
- ret = copy_from_user(&cap, gcspr_el0, sizeof(cap));
+ ret = copy_from_user(&cap, (unsigned long __user *)gcspr_el0,
+ sizeof(cap));
if (ret)
return -EFAULT;
/*
* Check that the cap is the actual GCS before replacing it.
*/
- if (!gcs_signal_cap_valid((u64)gcspr_el0, cap))
+ if (cap != GCS_SIGNAL_CAP(gcspr_el0))
return -EINVAL;
/* Invalidate the token to prevent reuse */
- put_user_gcs(0, (__user void*)gcspr_el0, &ret);
+ put_user_gcs(0, (unsigned long __user *)gcspr_el0, &ret);
if (ret != 0)
return -EFAULT;
- write_sysreg_s(gcspr_el0 + 1, SYS_GCSPR_EL0);
+ write_sysreg_s(gcspr_el0 + 8, SYS_GCSPR_EL0);
return 0;
}
@@ -1421,7 +1414,7 @@ static int get_sigframe(struct rt_sigframe_user_layout *user,
static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
{
- unsigned long __user *gcspr_el0;
+ u64 gcspr_el0;
int ret = 0;
if (!system_supports_gcs())
@@ -1434,18 +1427,20 @@ static int gcs_signal_entry(__sigrestore_t sigtramp, struct ksignal *ksig)
* We are entering a signal handler, current register state is
* active.
*/
- gcspr_el0 = (unsigned long __user *)read_sysreg_s(SYS_GCSPR_EL0);
+ gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0);
/*
* Push a cap and the GCS entry for the trampoline onto the GCS.
*/
- put_user_gcs((unsigned long)sigtramp, gcspr_el0 - 2, &ret);
- put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 1), gcspr_el0 - 1, &ret);
+ put_user_gcs((unsigned long)sigtramp,
+ (unsigned long __user *)(gcspr_el0 - 16), &ret);
+ put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 8),
+ (unsigned long __user *)(gcspr_el0 - 8), &ret);
if (ret != 0)
return ret;
- gcspr_el0 -= 2;
- write_sysreg_s((unsigned long)gcspr_el0, SYS_GCSPR_EL0);
+ gcspr_el0 -= 16;
+ write_sysreg_s(gcspr_el0, SYS_GCSPR_EL0);
return 0;
}