Commit 7f163573 authored by shechenglong's avatar shechenglong Committed by Will Deacon
Browse files

arm64: proton-pack: Fix hard lockup due to print in scheduler context 



Relocate the printk() calls from spectre_v4_mitigations_off() and
spectre_v2_mitigations_off() into setup_system_capabilities() function,
preventing hard lockups caused by printk calls in scheduler context:

  | _raw_spin_lock_nested+168
  | ttwu_queue+180 （rq_lock(rq, &rf); 2nd acquiring the rq->__lock）
  | try_to_wake_up+548
  | wake_up_process+32
  | __up+88
  | up+100
  | __up_console_sem+96
  | console_unlock+696
  | vprintk_emit+428
  | vprintk_default+64
  | vprintk_func+220
  | printk+104
  | spectre_v4_enable_task_mitigation+344
  | __switch_to+100
  | __schedule+1028 (rq_lock(rq, &rf); 1st acquiring the rq->__lock)
  | schedule_idle+48
  | do_idle+388
  | cpu_startup_entry+44
  | secondary_start_kernel+352

Suggested-by: default avatarMark Rutland <mark.rutland@arm.com>
Suggested-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Suggested-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarshechenglong <shechenglong@xfusion.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 62e72463

arch/arm64/include/asm/spectre.h

+1 −0
Original line number Diff line number Diff line
@@ -117,6 +117,7 @@ void spectre_bhb_patch_wa3(struct alt_instr *alt, 
			   __le32 *origptr, __le32 *updptr, int nr_inst);

void spectre_bhb_patch_clearbhb(struct alt_instr *alt,

				__le32 *origptr, __le32 *updptr, int nr_inst);

void spectre_print_disabled_mitigations(void);



#endif	/* __ASSEMBLY__ */

#endif	/* __ASM_SPECTRE_H */

arch/arm64/kernel/cpufeature.c

+6 −0
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ 
#include <asm/vectors.h>

#include <asm/virt.h>



#include <asm/spectre.h>

/* Kernel representation of AT_HWCAP and AT_HWCAP2 */

static DECLARE_BITMAP(elf_hwcap, MAX_CPU_FEATURES) __read_mostly;
@@ -3875,6 +3876,11 @@ static void __init setup_system_capabilities(void) 
	 */

	if (system_uses_ttbr0_pan())

		pr_info("emulated: Privileged Access Never (PAN) using TTBR0_EL1 switching\n");



	/*

	 * Report Spectre mitigations status.

	 */

	spectre_print_disabled_mitigations();

}



void __init setup_system_features(void)

arch/arm64/kernel/proton-pack.c

+18 −15
Original line number Diff line number Diff line
@@ -91,12 +91,7 @@ early_param("nospectre_v2", parse_spectre_v2_param); 


static bool spectre_v2_mitigations_off(void)

{

	bool ret = __nospectre_v2 || cpu_mitigations_off();



	if (ret)

		pr_info_once("spectre-v2 mitigation disabled by command line option\n");



	return ret;

	return __nospectre_v2 || cpu_mitigations_off();

}



static const char *get_bhb_affected_string(enum mitigation_state bhb_state)
@@ -421,13 +416,8 @@ early_param("ssbd", parse_spectre_v4_param); 
 */

static bool spectre_v4_mitigations_off(void)

{

	bool ret = cpu_mitigations_off() ||

	return cpu_mitigations_off() ||

	       __spectre_v4_policy == SPECTRE_V4_POLICY_MITIGATION_DISABLED;



	if (ret)

		pr_info_once("spectre-v4 mitigation disabled by command-line option\n");



	return ret;

}



/* Do we need to toggle the mitigation state on entry to/exit from the kernel? */
@@ -1042,8 +1032,6 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry) 


	if (arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE) {

		/* No point mitigating Spectre-BHB alone. */

	} else if (cpu_mitigations_off() || __nospectre_bhb) {

		pr_info_once("spectre-bhb mitigation disabled by command line option\n");

	} else if (supports_ecbhb(SCOPE_LOCAL_CPU)) {

		state = SPECTRE_MITIGATED;

		set_bit(BHB_HW, &system_bhb_mitigations);
@@ -1197,3 +1185,18 @@ void unpriv_ebpf_notify(int new_state) 
		pr_err("WARNING: %s", EBPF_WARN);

}

#endif



void spectre_print_disabled_mitigations(void)

{

	/* Keep a single copy of the common message suffix to avoid duplication. */

	const char *spectre_disabled_suffix = "mitigation disabled by command-line option\n";



	if (spectre_v2_mitigations_off())

		pr_info("spectre-v2 %s", spectre_disabled_suffix);



	if (spectre_v4_mitigations_off())

		pr_info("spectre-v4 %s", spectre_disabled_suffix);



	if (__nospectre_bhb || cpu_mitigations_off())

		pr_info("spectre-bhb %s", spectre_disabled_suffix);

}