Commit 0a5b288e authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/mce: Prevent severity computation from being instrumented 



Mark all the MCE severity computation logic noinstr and allow
instrumentation when it "calls out".

Fixes

  vmlinux.o: warning: objtool: do_machine_check()+0xc5d: call to mce_severity() leaves .noinstr.text section

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211208111343.8130-7-bp@alien8.de
parent 4fbce464

arch/x86/kernel/cpu/mce/severity.c

+21 −9
Original line number Diff line number Diff line
@@ -263,24 +263,36 @@ static bool is_copy_from_user(struct pt_regs *regs) 
 * distinguish an exception taken in user from from one

 * taken in the kernel.

 */

static int error_context(struct mce *m, struct pt_regs *regs)

static noinstr int error_context(struct mce *m, struct pt_regs *regs)

{

	int fixup_type;

	bool copy_user;



	if ((m->cs & 3) == 3)

		return IN_USER;



	if (!mc_recoverable(m->mcgstatus))

		return IN_KERNEL;



	switch (ex_get_fixup_type(m->ip)) {

	/* Allow instrumentation around external facilities usage. */

	instrumentation_begin();

	fixup_type = ex_get_fixup_type(m->ip);

	copy_user  = is_copy_from_user(regs);

	instrumentation_end();



	switch (fixup_type) {

	case EX_TYPE_UACCESS:

	case EX_TYPE_COPY:

		if (!regs || !is_copy_from_user(regs))

		if (!regs || !copy_user)

			return IN_KERNEL;

		m->kflags |= MCE_IN_KERNEL_COPYIN;

		fallthrough;



	case EX_TYPE_FAULT_MCE_SAFE:

	case EX_TYPE_DEFAULT_MCE_SAFE:

		m->kflags |= MCE_IN_KERNEL_RECOV;

		return IN_KERNEL_RECOV;



	default:

		return IN_KERNEL;

	}
@@ -315,7 +327,7 @@ static int mce_severity_amd_smca(struct mce *m, enum context err_ctx) 
 * See AMD Error Scope Hierarchy table in a newer BKDG. For example

 * 49125_15h_Models_30h-3Fh_BKDG.pdf, section "RAS Features"

 */

static int mce_severity_amd(struct mce *m, struct pt_regs *regs, int tolerant,

static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, int tolerant,

				    char **msg, bool is_excp)

{

	enum context ctx = error_context(m, regs);
@@ -368,7 +380,7 @@ static int mce_severity_amd(struct mce *m, struct pt_regs *regs, int tolerant, 
	return MCE_KEEP_SEVERITY;

}



static int mce_severity_intel(struct mce *m, struct pt_regs *regs,

static noinstr int mce_severity_intel(struct mce *m, struct pt_regs *regs,

				      int tolerant, char **msg, bool is_excp)

{

	enum exception excp = (is_excp ? EXCP_CONTEXT : NO_EXCP);
@@ -405,7 +417,7 @@ static int mce_severity_intel(struct mce *m, struct pt_regs *regs, 
	}

}



int mce_severity(struct mce *m, struct pt_regs *regs, int tolerant, char **msg,

int noinstr mce_severity(struct mce *m, struct pt_regs *regs, int tolerant, char **msg,

			 bool is_excp)

{

	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||