How do I write a given address to a register using inline assembly
0
I have the following statement:
asm volatile("ldr r0, =0x10000");
Instead of writing 0x10000 I want to write a parameter so it will look like this:
uint32_t addr = 0x20000;
asm volatile("ldr r0, =addr");
how can I manage to do it?
i am using ARM processor.
I want to do this:
At the end I want to do this:
asm volatile("ldr r0, =0x10000");
asm volatile("ldr r0, [r0]");
asm volatile("mov sp, r0");
same for pc
thanks.
c arm inline-assembly
asked Nov 12 at 10:04
Vlad Shlimovich
162
add a comment |
0
I have the following statement:
asm volatile("ldr r0, =0x10000");
Instead of writing 0x10000 I want to write a parameter so it will look like this:
uint32_t addr = 0x20000;
asm volatile("ldr r0, =addr");
how can I manage to do it?
i am using ARM processor.
I want to do this:
At the end I want to do this:
asm volatile("ldr r0, =0x10000");
asm volatile("ldr r0, [r0]");
asm volatile("mov sp, r0");
same for pc
thanks.
c arm inline-assembly
asked Nov 12 at 10:04
Vlad Shlimovich
162
4
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
3
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generallyldris redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.
– Matteo Italia
Nov 12 at 10:14
add a comment |
0
0
0
I have the following statement:
asm volatile("ldr r0, =0x10000");
Instead of writing 0x10000 I want to write a parameter so it will look like this:
uint32_t addr = 0x20000;
asm volatile("ldr r0, =addr");
how can I manage to do it?
i am using ARM processor.
I want to do this:
At the end I want to do this:
asm volatile("ldr r0, =0x10000");
asm volatile("ldr r0, [r0]");
asm volatile("mov sp, r0");
same for pc
thanks.
c arm inline-assembly
asked Nov 12 at 10:04
Vlad Shlimovich
162
I have the following statement:
asm volatile("ldr r0, =0x10000");
Instead of writing 0x10000 I want to write a parameter so it will look like this:
uint32_t addr = 0x20000;
asm volatile("ldr r0, =addr");
how can I manage to do it?
i am using ARM processor.
I want to do this:
At the end I want to do this:
asm volatile("ldr r0, =0x10000");
asm volatile("ldr r0, [r0]");
asm volatile("mov sp, r0");
same for pc
thanks.
c arm inline-assembly
c arm inline-assembly
asked Nov 12 at 10:04
Vlad Shlimovich
162
asked Nov 12 at 10:04
Vlad Shlimovich
162
edited Nov 12 at 14:06
asked Nov 12 at 10:04
Vlad Shlimovich
162
asked Nov 12 at 10:04
Vlad Shlimovich
162
asked Nov 12 at 10:04
Vlad Shlimovich
162
162
4
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
3
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generallyldris redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.
– Matteo Italia
Nov 12 at 10:14
add a comment |
4
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
3
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generallyldris redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.
– Matteo Italia
Nov 12 at 10:14
4
4
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
3
3
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generally
ldr is redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.– Matteo Italia
Nov 12 at 10:14
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generally
ldr is redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.– Matteo Italia
Nov 12 at 10:14
add a comment |
1 Answer
1
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0
gcc is quite capable of generating those instructions so you can do:
void** p = 0x10000;
register void* sp asm("sp") = *p;
__asm__ __volatile__("" : : "r" (sp) : "memory");
Note it's dangerous to mess with sp so make sure you know what you are doing.
To load pc you will indeed need to use a mov such as:
void** p = 0x10000;
__asm__ __volatile__("mov pc, %0" : : "r" (*p) : "memory");
__builtin_unreachable();
answered Nov 12 at 11:14
Jester
46.3k34581
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
add a comment |
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
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active
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votes
0
gcc is quite capable of generating those instructions so you can do:
void** p = 0x10000;
register void* sp asm("sp") = *p;
__asm__ __volatile__("" : : "r" (sp) : "memory");
Note it's dangerous to mess with sp so make sure you know what you are doing.
To load pc you will indeed need to use a mov such as:
void** p = 0x10000;
__asm__ __volatile__("mov pc, %0" : : "r" (*p) : "memory");
__builtin_unreachable();
answered Nov 12 at 11:14
Jester
46.3k34581
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
add a comment |
0
gcc is quite capable of generating those instructions so you can do:
void** p = 0x10000;
register void* sp asm("sp") = *p;
__asm__ __volatile__("" : : "r" (sp) : "memory");
Note it's dangerous to mess with sp so make sure you know what you are doing.
To load pc you will indeed need to use a mov such as:
void** p = 0x10000;
__asm__ __volatile__("mov pc, %0" : : "r" (*p) : "memory");
__builtin_unreachable();
answered Nov 12 at 11:14
Jester
46.3k34581
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
add a comment |
0
0
0
gcc is quite capable of generating those instructions so you can do:
void** p = 0x10000;
register void* sp asm("sp") = *p;
__asm__ __volatile__("" : : "r" (sp) : "memory");
Note it's dangerous to mess with sp so make sure you know what you are doing.
To load pc you will indeed need to use a mov such as:
void** p = 0x10000;
__asm__ __volatile__("mov pc, %0" : : "r" (*p) : "memory");
__builtin_unreachable();
answered Nov 12 at 11:14
Jester
46.3k34581
gcc is quite capable of generating those instructions so you can do:
void** p = 0x10000;
register void* sp asm("sp") = *p;
__asm__ __volatile__("" : : "r" (sp) : "memory");
Note it's dangerous to mess with sp so make sure you know what you are doing.
To load pc you will indeed need to use a mov such as:
void** p = 0x10000;
__asm__ __volatile__("mov pc, %0" : : "r" (*p) : "memory");
__builtin_unreachable();
answered Nov 12 at 11:14
Jester
46.3k34581
edited Nov 12 at 14:23
answered Nov 12 at 11:14
Jester
46.3k34581
answered Nov 12 at 11:14
Jester
46.3k34581
answered Nov 12 at 11:14
Jester
46.3k34581
46.3k34581
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
add a comment |
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
hi, how I can do the same with pc?
– Vlad Shlimovich
Nov 12 at 12:50
add a comment |
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4
That depends on your compiler. What compiler are you using?
– Some programmer dude
Nov 12 at 10:06
3
BTW it doesn't make much sense to just write to a register in the middle of some C code, you are either going to mess up the code generated by the compiler (if you don't specify the clobber list) or just have it overwritten immediately after. If instead this is to prepare data for another assembly instruction, they should both be in the same assembly block, and generally
ldris redundant in extended asm if you specify your constraints/clobber lists correctly correctly. You should really provide some more context about what you are doing.– Matteo Italia
Nov 12 at 10:14