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authorArd Biesheuvel <ardb@kernel.org>2022-11-30 17:37:17 +0100
committerArd Biesheuvel <ardb@kernel.org>2022-12-01 14:48:26 +0100
commit7572ac3c979d4d0fb42d73a72d2608656516ff4f (patch)
tree1f5d452d5b93e3ac525dbaa04ed9106aa9ba4b18
parent9b9eaee9828fe98b030cf43ac50065a54a2f5d52 (diff)
downloadlwn-7572ac3c979d4d0fb42d73a72d2608656516ff4f.tar.gz
lwn-7572ac3c979d4d0fb42d73a72d2608656516ff4f.zip
arm64: efi: Revert "Recover from synchronous exceptions ..."
This reverts commit 23715a26c8d81291, which introduced some code in assembler that manipulates both the ordinary and the shadow call stack pointer in a way that could potentially be taken advantage of. So let's revert it, and do a better job the next time around. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
-rw-r--r--arch/arm64/include/asm/efi.h8
-rw-r--r--arch/arm64/kernel/efi-rt-wrapper.S33
-rw-r--r--arch/arm64/kernel/efi.c26
-rw-r--r--arch/arm64/mm/fault.c4
4 files changed, 2 insertions, 69 deletions
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index d6cf535d8352..439e2bc5d5d8 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -14,16 +14,8 @@
#ifdef CONFIG_EFI
extern void efi_init(void);
-
-bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg);
#else
#define efi_init()
-
-static inline
-bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
-{
- return false;
-}
#endif
int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
diff --git a/arch/arm64/kernel/efi-rt-wrapper.S b/arch/arm64/kernel/efi-rt-wrapper.S
index 67babd5f04c2..75691a2641c1 100644
--- a/arch/arm64/kernel/efi-rt-wrapper.S
+++ b/arch/arm64/kernel/efi-rt-wrapper.S
@@ -6,7 +6,7 @@
#include <linux/linkage.h>
SYM_FUNC_START(__efi_rt_asm_wrapper)
- stp x29, x30, [sp, #-112]!
+ stp x29, x30, [sp, #-32]!
mov x29, sp
/*
@@ -17,20 +17,6 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
stp x1, x18, [sp, #16]
/*
- * Preserve all callee saved registers and record the stack pointer
- * value in a per-CPU variable so we can recover from synchronous
- * exceptions occurring while running the firmware routines.
- */
- stp x19, x20, [sp, #32]
- stp x21, x22, [sp, #48]
- stp x23, x24, [sp, #64]
- stp x25, x26, [sp, #80]
- stp x27, x28, [sp, #96]
-
- adr_this_cpu x8, __efi_rt_asm_recover_sp, x9
- str x29, [x8]
-
- /*
* We are lucky enough that no EFI runtime services take more than
* 5 arguments, so all are passed in registers rather than via the
* stack.
@@ -45,7 +31,7 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
ldp x1, x2, [sp, #16]
cmp x2, x18
- ldp x29, x30, [sp], #112
+ ldp x29, x30, [sp], #32
b.ne 0f
ret
0:
@@ -59,18 +45,3 @@ SYM_FUNC_START(__efi_rt_asm_wrapper)
mov x18, x2
b efi_handle_corrupted_x18 // tail call
SYM_FUNC_END(__efi_rt_asm_wrapper)
-
-SYM_FUNC_START(__efi_rt_asm_recover)
- ldr_this_cpu x8, __efi_rt_asm_recover_sp, x9
- mov sp, x8
-
- ldp x0, x18, [sp, #16]
- ldp x19, x20, [sp, #32]
- ldp x21, x22, [sp, #48]
- ldp x23, x24, [sp, #64]
- ldp x25, x26, [sp, #80]
- ldp x27, x28, [sp, #96]
- ldp x29, x30, [sp], #112
-
- b efi_handle_runtime_exception
-SYM_FUNC_END(__efi_rt_asm_recover)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index ee53f2a0aa03..a908a37f0367 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -9,7 +9,6 @@
#include <linux/efi.h>
#include <linux/init.h>
-#include <linux/percpu.h>
#include <asm/efi.h>
@@ -145,28 +144,3 @@ asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f)
pr_err_ratelimited(FW_BUG "register x18 corrupted by EFI %s\n", f);
return s;
}
-
-asmlinkage DEFINE_PER_CPU(u64, __efi_rt_asm_recover_sp);
-
-asmlinkage efi_status_t __efi_rt_asm_recover(void);
-
-asmlinkage efi_status_t efi_handle_runtime_exception(const char *f)
-{
- pr_err(FW_BUG "Synchronous exception occurred in EFI runtime service %s()\n", f);
- clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
- return EFI_ABORTED;
-}
-
-bool efi_runtime_fixup_exception(struct pt_regs *regs, const char *msg)
-{
- /* Check whether the exception occurred while running the firmware */
- if (current_work() != &efi_rts_work.work || regs->pc >= TASK_SIZE_64)
- return false;
-
- pr_err(FW_BUG "Unable to handle %s in EFI runtime service\n", msg);
- add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
- dump_stack();
-
- regs->pc = (u64)__efi_rt_asm_recover;
- return true;
-}
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 3e9cf9826417..5b391490e045 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -30,7 +30,6 @@
#include <asm/bug.h>
#include <asm/cmpxchg.h>
#include <asm/cpufeature.h>
-#include <asm/efi.h>
#include <asm/exception.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
@@ -392,9 +391,6 @@ static void __do_kernel_fault(unsigned long addr, unsigned long esr,
msg = "paging request";
}
- if (efi_runtime_fixup_exception(regs, msg))
- return;
-
die_kernel_fault(msg, addr, esr, regs);
}