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From: Richard Earnshaw <rearnsha@sourceware.org> To: newlib-cvs@sourceware.org Subject: [newlib-cygwin] arm: Restrict processor mode change when in hypervisor mode Date: Fri, 3 Mar 2023 13:33:56 +0000 (GMT) [thread overview] Message-ID: <20230303133356.A6FA038582B7@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=1d3d2ba54bf7fb7f47510b70cc71489b293ff60d commit 1d3d2ba54bf7fb7f47510b70cc71489b293ff60d Author: Srinath Parvathaneni <srinath.parvathaneni@arm.com> Date: Fri Mar 3 13:12:18 2023 +0000 arm: Restrict processor mode change when in hypervisor mode If a CPU implements EL2 as its highest exception level then programs using newlib may start in hypervisor mode. In that state it is not trivial to switch into the various EL1 modes to configure the individual exception stacks, so do not try. Diff: --- libgloss/arm/crt0.S | 14 +++++++------- newlib/libc/sys/arm/crt0.S | 14 +++++++------- 2 files changed, 14 insertions(+), 14 deletions(-) diff --git a/libgloss/arm/crt0.S b/libgloss/arm/crt0.S index 79ae1e251..cd1a20d61 100644 --- a/libgloss/arm/crt0.S +++ b/libgloss/arm/crt0.S @@ -122,10 +122,10 @@ * +-----+ <- SP_svc of getting in and out of secure state are not as * | | simple as writing to the CPSR mode bits. * | IRQ | -= 0x2000 - Mode switch via CPSR is not allowed once in -* | | non-privileged mode, so we take care not to enter -* ^ +-----+ <- SP_und "User" to set up its SP, and also skip most -* s | | operations if already in that mode. -* t | UND | -= 0x1000 +* | | non-privileged mode or in hypervisor mode, so we +* ^ +-----+ <- SP_und take care not to enter "User" or "Hypervisor" mode +* s | | to set up its SP, and also skip most operations if +* t | UND | -= 0x1000 already in these modes. * a | | Input parameters: * c +-----+ <- SP_und - sp - Initialized SP * k | | - r2 - May contain SL value from semihosting @@ -150,9 +150,9 @@ /* Following code is compatible for both ARM and Thumb ISA. */ mrs r4, CPSR mov r3, sp /* Save input SP value. */ - /* Test mode bits - in User of all are 0. */ - tst r4, #(CPSR_M_MASK) - /* "eq" means r4 AND #0x0F is 0. */ + ands r1, r4, #(CPSR_M_MASK) + beq .Lskip_cpu_modes + cmp r1, #(CPSR_M_HYP) beq .Lskip_cpu_modes /* FIQ mode, interrupts disabled. */ diff --git a/newlib/libc/sys/arm/crt0.S b/newlib/libc/sys/arm/crt0.S index 121246cfa..90d5be393 100644 --- a/newlib/libc/sys/arm/crt0.S +++ b/newlib/libc/sys/arm/crt0.S @@ -122,10 +122,10 @@ * +-----+ <- SP_svc of getting in and out of secure state are not as * | | simple as writing to the CPSR mode bits. * | IRQ | -= 0x2000 - Mode switch via CPSR is not allowed once in -* | | non-privileged mode, so we take care not to enter -* ^ +-----+ <- SP_und "User" to set up its SP, and also skip most -* s | | operations if already in that mode. -* t | UND | -= 0x1000 +* | | non-privileged mode or in hypervisor mode, so we +* ^ +-----+ <- SP_und take care not to enter "User" or "Hypervisor" mode +* s | | to set up its SP, and also skip most operations if +* t | UND | -= 0x1000 already in these modes. * a | | Input parameters: * c +-----+ <- SP_und - sp - Initialized SP * k | | - r2 - May contain SL value from semihosting @@ -150,9 +150,9 @@ /* Following code is compatible for both ARM and Thumb ISA. */ mrs r4, CPSR mov r3, sp /* Save input SP value. */ - /* Test mode bits - in User of all are 0. */ - tst r4, #(CPSR_M_MASK) - /* "eq" means r4 AND #0x0F is 0. */ + ands r1, r4, #(CPSR_M_MASK) + beq .Lskip_cpu_modes + cmp r1, #(CPSR_M_HYP) beq .Lskip_cpu_modes /* FIQ mode, interrupts disabled. */
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